Dead batteries - with odd charging circuitry
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- Опубліковано 6 лют 2025
- This is entirely my fault. I bought a mini chainsaw to make a video about, but as I'd featured another variant at that time I held off and ended up storing the unit and its batteries for about three years. When I rediscovered it I found that both batteries were damaged beyond recovery by over-discharge. Usually if the cells have dipped just below about 2.5V they can be gently eased up to 3V and then charged fully. But these ones have suffered long term discharge damage to at least one cell in each pack, causing rogue self discharge.
When a cell does not maintain its voltage after charging (allowing for a slight settling of voltage) then it's time to let it self discharge completely and recycle it. The losing of charge usually indicates a damaged separator between the electrode layers.
Odd circuitry though. They seem to have gone a different charging direction than usual, with the charge MOSFET drive being level shifted to switch a MOSFET on the other supply rail.
I'd guess that the charge MOSFET output is active at all times, except when an end of charge state is detected, by one of the cells in the battery reaching 4.2V.
The moral of this story is to ensure that all power tool batteries are given a top-up charge every so often. Especially the ones that don't get used for long periods of time.
If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:- www.bigclive.c...
This also keeps the channel independent of UA-cam's algorithm quirks, allowing it to be a bit more dangerous and naughty.
#ElectronicsCreators
It’s always good when a chainsaw does not cost an arm and a leg.
I see what you said there 😂😂😂😂
thats always good unless you are a naturist and trim the wrong wood.
That is when you _want_ it to fail.
Oh, NUTS! The Chainsaw stopped working!
That's some good cutting humor!
This completely defeats the fun of gardening !😂
One of the occupational hazards of being a hoarder, things break whist they are not being used.
yes, its a shame when you think ooh I have a tool for that and the battery's flat and wont take a charge. I guess its an excuse to buy another. 👍👍
@@dcallan812 One can never have enough batteries.
Whilst
That's like Gandma's old '89 Buick when she said "Of course it will run. Nobody has used it for the past 10 years. It's just been sitting in the garage since Grandpa left it there."
@@robinbrowne5419 Ouch! It will need some TLC, Grandma. 🤣😂
That voice needs to be reading the 10pm news, "theres a slight problem in Gaza", "one moment pleaze"....thanks Clive, very informative as normal......best regards
The tone of his recordings are something to behold.
One UA-camr had a large collection of old cell phones, carefully stored. Because you can't remove the battery, he found a lot of them had discharged and the batteries swollen, damaging the cases.
ua-cam.com/video/OfM0GqsIB6c/v-deo.html
When I saw the thumbnail I thought you were going to go full AvE and open the battery with the chainsaw.
HA, same here.
Going full Meathook ab0rti0n
Going beyond the X-ray.
Has AvE stopped posting videos cus I've not seen any notifications from him 😂
"DO IT"
-Emperor Palpatine
I bought one of those modules to convert an old Ni-Cad batt pack to Li-Io. Works great at keeping each cell charged - better than the old system, which had no current limit when charging. Every problem batt pack I've opened typically has one bad cell, while the rest are fine. So many good batts end up in the waste bin. If they made it easier to access and replace the cells, there'd be less waste but I'd image manufacturers don't want that.
I 100% agree with you. Would be nice if they didn't hardwire the battery cells in.
I agree in theory but the issue with lithium cells is that if you don't hardwire them in, you either use:
1) springs/tabs which aren't super secure and under high vibration situations or drops, small shakeups of the cells at high SoC can result in arcing which isn't healthy for the contact point or cell itself and will result in higher resistance and therefore higher temperatures (believe me the mOhms add up with these things, especially in powertool packs)
2) a system of clamps that puts the cells under pressure, which may not be good for them long term. They're far more robust than the pouch cells, but they weren't really designed to take load like that
The reality is that spotwelding the cells is not only the cheapest and fastest, but also likely the safest way to pack them
@@crumpus5815 While spot welding is cheap and fast, an enclosed battery compartment is the best alternative. Lots of devices use these without any problems.
Hmm ... a thought just occurred to me. Why are the batteries attached directly to a device? Why not have the battery separate (attached to your belt, perhaps) with a cable running from it to the device. Yeah, sounds just like a power cord but I can see some advantages here. Easier to swap devices - just plug them into the same battery pack. And easy to swap out packs. Could also swap to a power cord if the batteries aren't performing. Best of both worlds.
You do get heavy duty tools with a separate belt mounted battery pack.
Many big hardware stores have battery recycling programmes that, I'd assume, would actually recycle the batteries and extract the good cells. There are businesses that sell reconditioned name-brand powertool batteries, but for these no-name batteries they're only good for some cheap cells.
Interesting and thanks Big Clive. I finally broke down and got one of these little saws when it was $30 and I have to say I'm totally impressed. It will chop through a 4" limb easily. I think it must have been a few years ago seeing your video that has kept that on my wish list for such a long time.
This has prompted me to make sure all my batteries are topped off. Thank you.
Topping them up is not a good idea for storage. They like to sit at about 40%, if they are not in use for a long while.
@@dr.robertnick9599 Dangerous information Robert.
Storing at 40% SoC is ideal for individual cells but when you're storing a battery pack with a BMS that may have quiescent current draw it's best to store them fully charged, preferably in a cold place. This gives you the maximum dormancy period without danger of loss. If you can keep a strict regimen of cycling them once every x months then yes, 40% SoC is ideal for battery packs with BMS also.
Better battery packs have extremely low quiescent current draw. I can (and do) store my Bosch 18v batteries in a 4 degree fridge at around 50% SoC and only check them annually (and they don't seem to lose charge). However cheaper batteries such as this one can have quite a high quiescent current draw and will need topping off / cycling / using every 3 months or less. For cheap packs I fully charge them, use them in a tool to drain about 5% of their capacity, then store. It seems to work best.
Cheers.
@@dr.robertnick9599 Isn't it like 3.85v - 3.9v being the ideal storage voltage? At least that is what I store my salvaged vape batteries at...
@@dr.robertnick9599 I think you're right though for some reason I've had 80% as the ideal storage charge. Not sure and the voltage thing too.
Incredible breakdown of battery safety and circuitry! Your explanation on lithium cell maintenance is eye-opening. thanks
Bot
I really appreciate your breakdowns and your painstaking analysis.
Had that with a replacement laptop pack. First one was 7V8, for a 3 series pack, so was returned and replaced. Second was 9V, but was in undervoltage lock out. So a small bit of work with a 1mm drill bit to get a pair of holes to the end of the pack, and a charge at 1A for a few minutes to raise the voltage up to 11V, and the pack decided it was happy again, and started to charge. After 12 hours it was still at 77% capacity, but fully charged, so it took a few cycles of full to near flat to get the charge controller to agree with the battery, and bring it back up to 100% again.
Rather than recycle the whole pack, remove the good cells and reuse them as a USB power pack. They won't get too stressed in this mode of operation and you get to re-use rather than just recycle them all.
The main concern is whether internal damage has occurred.
@@bigclivedotcomname brand 3.7v cells are charged to -12v and dead shorted as two of the tests, and must not explode or catch fire to pass. Something extreme like that anyway.
I think li-ion cells are most dangerous if either punctured or overheat & unable to puff up if lipo (creates a thermal runaway like situation?).
@@davadoff To be clear, that test requires that they don't catastrophically fail, but certainly doesn't require that they work afterwards 😅
IIRC the main concern is that the main result of internal damage due to overdischarge is internal shorts, which will kill the cell if they are small, but can also be a very bad day if those shorts are just enough to start failing at a higher voltage. If he's confident that the other cell groups didn't get pulled down too low then they may be ok, but realistically they aren't that expensive so it's probably not worth the risk.
@@davadoff Just a couple points, tests like you described are done on a small number of li-on products through a production run and can't guarantee any individual item as a battery as much as confirm outcome of process. But like you referenced, name brands "quality" manufacturers generally hold a standard... but who do you think made the batteries for an item like this with such a low overall cost to purchase? And your a bit off with the problems you listed. Heat yeah, is a problem but gas is not a cause but a consequence. Problematic temperature that destroys a cell is caused by another cell going into thermal-runaway from the biggest and most common problem with these batteries, being damage or condition caused during charging. These batteries need very specific charging requirements that are almost always neglected because of cost efficiency determined by calculated risk assessment by manufacturers. Reputable companies don't neglect safety but they make chargers that are optimised to the habits of users so to get best performance and life from a battery and not for what is actually optimal if the human equation was removed. Cheap dodgy companies skimp on everything that's not mandated by law!
Physical damage is absolutely a cause of a failure or development of failure, but not a statistical cause of significant note. Li-on batteries should be stored at about 60% charge and not discharged under 10% or charged over 90% and optimal input should be done by a complex system with limits set on the individual capacity and trimed during charging to follow the "curve" between those limits relative to state of charge! This is not the sort of finicky factor people want to pay for or bother with, so tradeoffs are made and consequences occur!
I recently purchased an American made Hart battery-operated drill and was furious to find the battery was dead and that buying a new one for $60+ was no guarantee.
The fun part of the story is I hooked it up directly to 12v (a bit dangerous), and I was able to "jump" the battery and get it going again. I did try less voltage first with no luck.
I bought a similar one. Very impressed , managed not to kill myself , 10 foot up a ladder trying to cut down Ivy. I keep any tool batteries out of the house in a locked box as they could be go up in smoke at some point. I also never leave any batteries charging unattended. May be I am too Elf and safety conscious but working in the energy industry since I was 18 and I am now 56 , I think that is where it comes from.. All the best Alex.
Makita uses the 3rd pin as a signalling pin to the tool (as well as for charging). The 3rd pin is held high for power-good and brought low for power-off. I have a vid on my channel about this if you're interested.
I have been playing with tool batteries for a little while now. All brands from recycling places. The reverse charged cells almost always will self discharge. But in your case with one bad pair then I would just replace those two bad cells with two good cells of a higher capacity than the other cells in the pack.
This has worked quite well. I separate out and test each cell independently just to make sure. Charge them all. Check voltages over time. Anything with self discharge is junk, no question. It never "clears".
Was waiting for you too pull an AVE. i miss his old bolter stuff
I used to watch him all the time but found my interests changing as time went on. I'm not a tool jockey and some of his humor goes over my head.
Fascinating battery pack analysis! I know what you mean about energy density, it's quite amazing. My Ryobi strimmer lasted for the duration of clearing my whole overgrown garden, on one charge.
I have had lithium batteries down extremely low but never saw one actually go negative charge!
I think they can only go negative when they're in series and other cells are shunting current through them.
its so slight negative it may just be the meters accuracy
Ive notice its very common in non-rechargeable standard lithium batteries as well as a load being necessary when testing... lithium chemistry is just generally problematic it seems. Lol
What a coincidence, Clive. Earlier this year, I had call to do some pruning and, rather than do it by hand (my handsaw had gone a bit wonky), I thought "why not try one of those el cheapo Chinese chainsaws from eBay that Clive mentioned some time ago". So I bought one and it would not hold a charge. At first, I thought it was the charger since it looked very cheap and was very light.
So I swapped the charger with a compatible one that I knew worked. No luck.
I then opened up the battery pack and tried testing it. I couldn't spot any faults on the circuit board. And testing the batteries didn't reveal anything.
Rather than waste time arguing with the vendor and returning it, I bought another one instead from a different vendor.
The original battery was labeled "Power Share" and "24V Lithium". So I looked around for one that used a similar battery (I figured I could open it up and compare them).
So I found one that included a spare battery and bought that. When it arrived, I found the battery mounts weren't exactly compatible. But the batteries charged, at least.
I opened one of them up and the circuit board was completely different. I also found these boards were sold on eBay but I couldn't find one that looked the same.
Thanks Clive, excellent and practical tip to keep batteries charged. Also if possible rotation to keep them all active.
Clive made a video 7 years ago titled "Are over-discharged lithium cells safe?" that provides a lot more information on safe discharge thresholds, and it seems that anything not negative is OK (and they may even tolerate a little bit of reverse charging.)
What explains the "common wisdom" about low-voltage cells being unsafe to charge is that if you find a reverse or deeply discharged cell in a pack, it became that way because it had already developed an internal short, and not because it was deeply discharged. It's cause and effect reversed.
The fact that a lot of single-cell charge ICs, from reputable manufacturers, will do a trickle charge is evidence that low (but not reverse) voltage lion cells are not in itself a real hazard. They certainly wouldn't have that feature if it was!
Interesting board 2x👍
The warning about discharging batteries before recycling made me think of a local shop that have a "bin" for dead batteries. People just throw out batteries but this thing is right next to the tills that could be really bad if one of the cells "went off"
Problems with 'elf and safe tea'.
Our Lowe's is like that. Just piling all the batteries in a big plastic bin. I hope they have a pie dish handy.
i was given a dead makita 18v 4ah pack. i opened it up and 1 of the banks had reversed voltage. i used one of those little pcb chargers that takes a day or 2 to charge the 2 batteries up. i think ive seen similar things on your channel. i might have given them a surge to start with using techniques seen on a yt video. anyway, i got a genuine-looking pcb from china and installed it. it has died again after 2 years of use. a worthwhile learning experiment.
I'd be interested in seeing you try your hand at battery-pack rebuilding? Get some new cells and return these packs to operation!
It's a good thing to do and if you live near a TESCO they have a battery dumping bin. So I keep an eye out for packs in there as they are free !
Thanks
Thanks. Much appreciated.
"Incredible breakdown of battery safety and circuitry! Your explanation on lithium cell maintenance is eye-opening. Thanks for the valuable info!"
Hello Bot
Yeah, quite a few comments from different accounts with identical wording.
2AM....14:21... It's on except when it's off. 😂😂😂
5:50 Don't top them up but charge them to around 40%. It's the best percentage when you're not using it for a few months. The -0.9V cell is in sleep mode. This happens when a cell gets below 2.5V after which you should just discard it.
I tried recovering some 7yr old cells, 0v cells to be clear and It seems like 4/6 are coming back, i used some 10/30 ma to charge them
If all else fails and the cells don't respond, drill a smallish hole through the center of the Positive cap and push the Reset/wake-up button that is hidden right beneath it. 🤣🤣🤣
NOTE....It is of the utmost importance that I must mention, this is one of the most effective means of validating natural selection.
@@wayneselby5415 That is the vent button, no?
@@NIGHTDREADEDI can't say I know what it's called, but if that is the name of it, then yes. All I know is when a cell over heats, the expansion /internal pressure, mechanically breaks contact disabling the cell. To mention IMO, with all lithium batteries (LTO being an exception) are something else. The marvels of creation are highly underestimated in regard to their sheer power and ability to fuck shit up. I've done a lot of PJs and projects using reclaimed cells and yes I have learnt to respect them. My most favourite saying, most things in life are like farts, if you have to force it, it's going to be shit.
If it does not want to work, rather let it be because it will fight back. The possible costs are not worth saving a couple cells. The cells that do comply teamed with the correct protection and prevention, ie. BMS, fuses etc, by all means, go for it. I'm a firm believer in the reuse of everything. Only within reason.✌️
@@wayneselby5415 you forgot to mention that the Cell must be fully charged for the button to be accessible
We found an old Bosch electric screwdriver at work that uses those 10.8V batteries (now sold under the incorrect name of "12V"), and it still had a charge on the battery for quite some time even though it had been sitting unused for years. I picked up a modern version for myself and charged up the old battery, and it's still going fine. I'm not inclined to pull it apart, but I probably should at least measure the pack voltage at full charge and make sure they're not self-discharging. A new battery is certainly worthwhile compared to buying a whole new tool, battery and charger.
Thanks for the tip not to leave lithium tool batteries in the flat state after use, very interesting. I've had a couple of lithium tool batteries go weak and weird, it's entirely possible I left them flat for a while in my ignorance.
Now you have been told !
It's the same with hybrid cars and EVs.
It's not just the capacity of the entire battery pack. It's the Delta in voltage! As soon the cells have a difference in voltage in the 10th of a Volt or more it's the beginning of the end.
Good battery management systems are able to charge "around" the defect cell/block. Others are "blind" and charge all alike.
First you get a malfunction code. If you ignore and delete it again and again you risk A BIG BANG! That's what happened with my Toyota Prius II. The BANG was like a handgrenade in the trunk. 🤦♂️
Aftermarket repair-services collect new and old hybrid modules, disassemble them, re-condition each single one by supervised charging and discharging cycles. After a final charge the re-assemble the modules by making sure the max. difference in voltage of ALL of them is not much more than 0.01 V. The hybrid akku is then again usable for several years for a fraction of the costs.
Ah yes, the big bang of the cells pressure release going off!
Must have startled the crap out of you. I've seen those go off, but not in person.
Dam I would have thought car manufacturers would be that careless to not have individual cell monitoring with charge/discharge ability to keep all the cells at the same voltage. That just dangerous. Even my rc cars from 15+ years ago I had alarms for when a cell dropped undervoltage and I would balance charge every time due to seeing what happens when lipo cells go wrong
@@HootMaRoot You can read the block voltage in Toyota Hybrids. I don't know how much information is free or blocked in the vehicles of other manufacturers.
The described method of disassembling and re-arranging cells and blocks applies to a guy in Poland who buys and sells hybrid batteries of Toyota.
His name is "hybridrep" and he travels all over Poland and Germany. He comes to you and changes the defect battery of your Toyota Hybrid in front of your door to a recycled one. It costs half of the price that Toyota wants for a new one.
@@volvo09 Yes, I was shocked by the BANG!
It happened at 11 pm on a street in the middle of nowhere, I wore just light clothes, it was just above freezepoint with snowy rain, the car was loaded up to the roof and I didn't have money in my pocket. At least my cellphone was operational.
Can you imagine how stinky a 214 V and 50 to 100 A short-circuit is inside the car? 🤮 It smells like a dozen burnt Chinese computers. 😂
Have a chinise one too. The original battery was too weak, it shout down with cutting modest branches, so i 3d printed an adapter to use a Parkside battery, a couple of spade connectors and some wire and it's done.
As I commented elsewhere, just be very careful using Parkside batteries as they have no FET to turn them off when the voltage drops too low.
I submit that lithium cells, for all their power and efficiency, are not the right choice for something that is only used occasionally. Then they are likely to discharge and become unusable. If you are a professional gardener, lithium cells would be suitable for a portable tool you use often, but for an amateur, when the tool may lie unused for months, the power pack is likely to fail unless you leave it plugged in all the time - which is a waste of a socket.
I personally think NiMh is still a very good battery technology. It is simpeler that Li-Ion / Li-Po because you don't need protection boards and NiMh cells are just pain safer. Ideal for the occasional usage. Although remember to charge your battery packs before usage.
@Frankhe78 the worst thing about nimh cells is, before you use them/charge them you are best discharging them before you charge them as only topping up nimh can cause you to loose some capacity. Meaning the already low capacity of nimh gets so much worse over time
@@HootMaRoot It really depends on what you want and what you need. Li-ion an LiPo have their advantages and disadvantages. One disadvantage of Lithium technology is that they wear when you store them at the maximum voltage. LiFePO4 has less wear and no thermal runaway.
all my battery packs are numbered so none of them get a chance to hide down the back of the cupboard hoping i will forget about them. its not foolproof but it helps.
@@Frankhe78 it's probably my early/mid teens and having nimh batteries in my rc cars that I have such distain for nimh. And when lifepo4 and lipo pouches became very affordable 20 years ago not so much these days. Giving so much more capacity being able to run more powerful items and not needing half as much care to keep them in tiptop condition
That MOSFET in the charging circuit is indeed a P-channel and full marks for drawing the symbol correctly but you've drawn it upside down. The Source should go to the charger and the Drain to the battery. That way the internal diode is not forward biased and the 2M resistor is across the Gate-Source to turn it off. MOSFETs are canny devices which can often be used upside down. They don't care which way up they are as long as the gate is biased correctly relative to the source.
Edit - I spuriously said the 2M resistor was across the Drain-Source, it should of course have been Gate-Source.
Just to clarify, this MOSFET is not really being used upside down, it's the schematic that is what I would consider drawn upside down. The charger line is the most positive voltage and is therefore connected to the Source and would normally be shown above the battery line, hence with the MOSFET shown the other way up. However there are situations where MOSFETs are genuinely used upside down ie with the positive supply connected to the Drain on a P-Channel type, an example being synchronous rectifiers.
I remember your first video, I went online after and bought one straight away, thankfully it came with a spare chain, the first one was blunt after I cut down a hardwood tree.
I've been using DeWalt buzz guns for years. I bought 4 genuine replacement batteries every one the case broke before the battery. I then tried cheaper copy's I've had around 15 now with mixed results most of them have survived for a reasonable period and the case has broken others have had faults and broke straight away. I've still got most of them and intend to use them again for what exactly hasn't come to me yet.
Unwritten safety rules #345: "Don't stand on the chainsaw."
I remember the comment about security radios... The guards scabby radio with the battery pack held together with tape lasted the longest (as the battery was constantly exercised) & the manager's pristine radio lasted no time at all as it festered unused in a drawer.
If nothing else, the chains are probably fully interchangeable, so you can saw away happily for longer before you need to re-sharpen them. The extendable pole-mount versions (e.g. Ryobi) are really handy for heavy - duty pruning of the larger trees. Just make sure you're out of the way when the branch detaches 🙂
You don't have kids or other trained monkeys for those types of maintenance jobs?! 🤔😉😊
@@theoztreecrasher2647 I just noticed your moniker! :-D Well, some of us actually enjoy "heavier duty" gardening (which is handy living out in the sticks!)
The chains come in various sizes (4" and 6" seem to be the most common) so you should check for the correct size when buying spares or swapping. They are very cheap, though, but the price reflects the quality.
A regular chainsaw has a protection switch/break on the hand guard.
My mains eletric chainsaw has similar. It cuts power when pulled back and I have to bump it forward to make it go.
It is that large black paddle sticking out the top.
The paddle is just a guard. No switch.
There's a number of businesses in my country that take old battery packs, dismantle them and charge and test each cell, then retest after a month and sell the good cells and, at a much cheaper price, sell ok (but not perfect) cells. I have used them to repack batteries (even for electric bikes) and they work perfectly.
Cell monitoring is so easy, I don't know why all battery packs don't have a balanced charging system.
Yep, all sorts of things go on, no doubt. I've also seen people soldering wires direct to the terminals of an Alkaline PP3..
@@thephilpott2194 Don't be so arrogant. There's nothing wrong with using cells that have more than 80% of their life left. We're not all so absurdly rich as you and can afford to waste our money and the World's resources; do you replace the battery in your meter every time you use it? How can you compare reusing perfectly fine cells (ones that have been left for a month, then had the voltage checked _and_ load tested) to soldering wires to a battery? Some of us do have good quality spot welders and the skills to use them and warrant our work (we would also stop anyone from soldering batteries). None of the repacked batteries has been returned within the 12 month warranty. No wonder UK is stuffed.
A nailgun battery test video may be neat. With appropriate protection, take some cells at various voltages, and stick a nail through them. Depending on ESR and charge state, this can vary from 'gets a bit warm' to 'loud roar of flame and vents 90% of the contents of the battery'
I've replaced dead cells on many lithium battery packs. Takes time but usually works great. Just make sure you discharge cells before the major operation.
Could probably make one battery out of the cells of the two. Use the fancy Lithium charger to test the cells and pick the best 10? Edit: DeWalt doesn't actually have any on-board electronics. IIRC, there's a small balancing PCB with no ICs, but there's no protection of any kind -- it's all built into the tool or charger. I actually like that, because it means no dead batteries from quiescent draw, but one does have to be more careful with non-DeWalt uses.
The second transistor is most likely used the control the high current charge FET as the IC can't drive the outputpin controlling the FET all the way to the positive terminal. If it can't do this the voltage on the gate-source of the power fet will never got yo zero and the FET won't fully turn off. This is a common problem with driving high side FETs and this arangement is quite common when switching with p-channel high side FETs.
nice to see a pack that draws from the whole bank and not just one cell, causing an imbalance. With no balance cct. Only thing to add is not to fully charge your battery if you are topping it off. they prefer to sit at 3.7 to 3.8 V
I've never come across any that power the BMS from one cell - that sounds particularly nasty!
The rectifier diode across the output is a necessity when you connect those battery packs in series. When one of the BMS in the series connections turns off, the other batteries will put a negative voltage to its terminals and fry it. The diode limits the negative potential to a safe level so that the BMS won't get fried.
Einhell battery chainsaw with 2X20V batteries in series, has similarly diodes on battery connectors. Maybe, those batteries don't have those safety diodes or to be on safe side those are on battery connectors aswell.
@@Tegelane5 if it is explictly made to be series connected, it may have integrated diodes. I killed a battery pack once that was not made for series connection and the water kettle drew a little too much current for one of the BMS to like and poof it went up in smoke. This was before i learnt about the antiparallel diodes and added those to all of my circuits where protected batteries are connected in series.
I got a couple of battery powerewd devices (an impact gun and a handheld "pressure" washer that was more of an electrified supersoaker than a washer!) from "over there" and they came with similar batteries, the cells were about as well-balanced as the tory budget, couldn't get the things to charge to the right voltage and stay there and so they died fast, so opened them up, and, well, a couple cells had charged way over 4.2v, and others stayed under 4v, ended up using the USB TP4056 boards to recharge the cells individually and it seemed to work, though I've not used the tools since so dunno if they've died again...
Interesting I always thought they charged the cells separately for balancing purposes.
Nice video!
Nope, most (at least) just dump charge through a shunt resistance from the fully charged cells and then continue to force current through the string until they (try to) pull the low cells up. That's why your charger will often show quite a few more mAhrs going into a lipo than the battery pack is rated for. Not a good sign!
I have the exact same one. It says "Untimaty" on the case. I love that thing it's so cheap but I love it. Also all the other Chinese tools like the hedge trimmer share the same battery!
@5:55 [timer]You do mean 80%, right? I thought the optimum storage level for lithium
ion batteries was around 3.7-3.8 volts. Max being 4.2V (not for storage but a safe level to have them at when you go to use (discharge) them.)
Nominal (working) voltage is 3.7v store at 3v and charge to 4.2. Anything below 2.5v is dubious but you might trickle it and get lucky if its a good brand.
@@andymouse So store at 3V. Interesting. Yes, I agree that even 2.8V, would cause me alarm. Thanks!
Great video Clive thank you and very well explained thank you 😊
A resistor, in this case 330k, in parallel with the NTC will make the resistance vs temperature curve more liniar. This "trick" is often used in thermometers/thermostats, instead of fx. implementing the liniarity in software.
Not sure if thats the reason it is used in this application, as I could imagine thye just need a threshold temperature.
I'm normally not "in to" chain saws, but those two are really cute, and looks even smaller in your big hands 🙂
What construction were the Cvcx 100nF capacitors with the 1k0 resistors used to sense cell voltage? If they were ceramic monobloc then the 1k0 would prevent a leaky layer from fusing / self-healing, and so would progressively increase the parasitic drain on those cells.
I did ponder if a leaky capacitor was an issue, but these are very low value, so less of a risk.
Hey Clive, just dropping in on the video because I was wondering if you'd thought about looking at any heat not burn tobacco devices because I'd be interested to know exactly how they work.
Cheers
Some use a heater that allows you to pull hot air over the plant material to vaporise the oils. Others for resinous concentrate use a heated ceramic cup.
Even the cell at 1.4v is recoverable. The cell with -0.09v is toast.
ah yes the zombie hand chopper is back
I can remember having to wait a week, or two, before I could go into town to buy a battery for my Legos.
Yeah cut your loses Clive, make one good one from the two, and two spares for your pocket soldering iron.
ah the Zombie Chopper I bought one on your recommendation its an Orange one of course I took down some branches off some pine trees it did very well I'm going to use it tomorrow I will be needing it for Halloween
I have a Vax OnePWR pack which had some sort of thermal fuse trip causing it to never be chargeable ever again as the battery has some 'smart' charging circuitry. I rebalanced the cells manually but it still wouldn't charge. The packs are about £80 new - there's some very small print saying (words to the effect of) 'wait 15 minutes after using the battery fully to let it cool down', presumably due to the current draw heating them up too much.
Replacements under warranty due to failure are a common issue with them. Shame the bad design and thermal management causes so much e-waste. I would have thought it better to have used a thermal probe to throttle back the charging rate then ramp it up as the cells cooled.
Thank you Clive, will do.
That middle... middle right connector related to temperature sensor. You can fool some original makitas with a 10k resistor. Similar trick works for Dewalt / Black and Decker / Porter Cable / stanley. I didn't try other brands.
I wonder if it could slightly extend their (off charger) life if they had some sort of mechanism for charging the lowest cell with the highest cell at a certain critical level.
Yeah they actually do! That's why each battery has it's own wire as well as being connected to the other cells by the nickel strip. It's called a balance charge system and it's not an option as far as I'm concerned, and there are many nuances that li-on cells require to perform well and function as a battery and not an ignition source, but unfortunately (and to my absolute disbelief!!) many if not most companies only provide what's required by law and not by reality of what maximizes the safety of the battery. Almost all battery fires occur because of damage or condition caused during charging. Relative to the number of li-on products available, very few come with adequate charging devices or instructions for safe care of something that would NOT HAVE BEEN ALLOWED on the market because of its potential danger back in the days when the carpeted floor in every shop was littered with cigarette butts, you could ride unprotected and unrestrained in the tray of a vehicle on the freeway and burn portable petroleum fuel heaters in any building for cooking or heating. You can't take a bottle of water or a phone with a broken screen on a plane but it's ok for everyone to have 1 to 5 of these well known potential bombs, on their person when boarding a plane!
@@mrgoodman6620 Ah, I looked it up. I've only ever seen passive balancing systems but it looks like there are active systems that will do exactly what I asked.
IMO they should be the standard especially for packs that go in tools and are going to be worked hard when worked.
@@LanceThumping Yes 100% agree!
I've scavenged old laptop batteries and extracted perfectly good, if ancient, cells. Usually panny-Bs and even some panny-As. They work perfectly well in mild-mannered flashlights and such. Most packs I've seen are nS2P, so typically one pair will be hosed and take down the entire string, but the others will be fine. Got an analysing charger, just give them a few cycles to see how they fare, and make sure they don't get too hot when charging (too-high R). Goldmine...
Have you looked into reviving old NI-CAD batteries? I found that you can revive them by blasting them with high current and recharging them with higher voltages
A short term fix for older NiCd cells with internal shorts forming was to jolt them with high current to blow the whiskers away, but it's a last resort and definitely not suited to lithium cells.
I have one of those mini chainsaws & just re-batteried the two packs with high current Aliexpress cells whilst also doubling the capacity. Liitokala genuine cells are very good.
what is rechatgeble bateri "memory"
do y heve too do a charge /discharg cicle
Why don't you just replace the faulty cells?
To do that properly requires a proper cell spot welder.
Perhaps you could design a battery alarm system, a simple universal clip on that monitors voltage with an alarm for a charge reminder
you can by them cheap for drones and you can vary the low volt alarm within a nice range.
Like the very occasional chirp from a smoke alarm - that has you wandering around the hut like a stunned mullet trying to work out what it is/where it is coming from?! 😱😵💫😈
@@theoztreecrasher2647 Oh hell !! been there
I fondly remember the orange zombie-chopper....
Common wisdom is to store lithium cells at about 60% charge level to keep them from degrading while in storage due to lithium being a very active material. Having said that, does this hasten the pack's demise since time passes faster than what we think and then end up having to re-appropriate the working cells and components for projects like yet another garden light or something similar! 😆
I salvaged four dead 18650's from a laptop battery, they were really low if not dead dead. I have a charger that trickle charges and they came back up fine. In fact one is in a torch. It did take over 24 hours though. But I kept a close eye on them, and made sure they didn;t start generating heat.
I used to have an 18650 powered desk fan and would frequency forget to turn it off and regularly discharged cells to 0v.
I did that to some cells 10x and the capacity loss was surprisingly low, but they were not at that level for more than a few days.
Junk old 900mah batteries would degrade to 700ish after that kind of repeated abuse.
15:25 nce4435 is a p-type mosfet. There is a small mistake on schematic.
"this mosfet is always in the on state... except when its off" yup, sounds about right! it's a shame we cant get battery packs with easily replaceable 18650s.
you say let it self discharge.... how long would that take to self discharge, or is there a quick discharge method?
It would depend on the level of internal self discharging. You can also add a resistor or string of LED lights across a single cell.
Your hand healed rather nice!
Theres hope of making one decent pack out of the two?
So without back-to-back MOSFETs, it can disable the output if the pack voltage gets too low but not if it gets too high? Because of the body diode.
Yeah, you can't prevent it being charged, which can be bad if the cells become unbalanced and one is overcharged without the charger being able to tell because all it knows about is the overall voltage. Lidl Parkside ones have no FETs at all but use the data connection to tell chargers or tools to stop.
I've seen those cheap chain saws and they scare the heck out of me. I wonder how many folks have lost appendages with them.
Did you consider replacing that dead cell or couple of cells in the best package? The others seemed ok...
It's cheaper to get a new pack complete with a different tool, and just salvage the recoverable cells from the old one.
If you are safely discharging them how would you recommend doing that? 1-10k resistor between positive and negative until dead?
A 1K resistor would take a while across a single cell, but would work.
Hey @Clive: can you tell us why some shaded pole fan motors have the pairs of copper loops separate, and some are cross welded together at the back. I can't find any explanations of this, and most suppliers don't mention it and only picture the front of the motors, that always look like the loops are parallel and separate. :/ Cheers. (y)
I'm not sure why. The cross welding might just be for ease of manufacturing, the two on a common pole may be to increase the effect with a manageable wire size, and it's possible that where they are staggered, it may be to create two phase shifts.
Clive, I’ve got some 1.2 NiMh batteries that won’t charge in a lidl smart charger. Is there any trick to revive them?
Yes. If the voltage is too low it can't detect they're there. If you put them in a dumb charger it will raise the voltage to the point they can be detected.
I’m 99.9% sure Clive made a video on how to make a USB NiMH trickle charger.
5v and a current limiting resistor to give a few milliamps should bring the NiMH cell back to life.
@@davadoff Sometimes you need more than that - the dreaded dendrite shorts the cell out and you have to burn it away!
@@matthewmarks6951 Hook up your DC arc welder and give the cell terminals a tap? 🤔😜😱
if you can get your hands on Liitokala chargers eg. Lii-PL400, they are smart enough to trickle charge the dead battery into life. Found out myself after wasting many batteries to stupid Energizer charger with similar problem as you are having.
It's interesting how batteries handle being drained entirely. We've had car batteries come right back to life after sitting dead all night, but you look at a lithium cell wrong and it'll explode. Coworker's alternator went out and only found out the moment he pulled into his parking spot when the battery ran out of juice. Old charger we kept in the crib has the jumpstart option of dumping 100+ amps. Gave him enough charge to go back home and get it fixed over the weekend. Meanwhile the charger I use for my longboard batteries top out at 3 amps and I heard the popping sound of the plastic wrapping giving out as one of the cells started to expand.
What happened to the battery warning light?
@@matthewmarks6951 honestly don't know. I noticed it didnt have a battery gauge, but I suppose it should have at least warned him it was low.
There are some interesting videos showing useful service life from lead acid batteries being completely reverse charged.
They might work with makita battery's, The PCB's look like how the early makita 18v packs looked, the top plastic part is exacly the same.
And there's your danger of not keeping the cells topped up - if you leave them for long periods of time, they self discharge, and due to it being a series pack, it can even go into reverse bias on the weakest cells. Personally I'd have salvaged all but the reverse-biased cells because even at relatively low voltages the cells can be recovered.
I've had laptop battery packs at a very low voltage (under 1.5V) where the cells have recovered to over 2Ah each.
I was hoping to see you recell it with some decent cells to keep it alive :)
Also @Clive, I'm typing on a 'Cosmo Communicator' with the back hanging off as I can't get another battery for it and it swells up. Could you give a tutorial, maybe, on how to buy standard cells from China, and fit in old devices in place of end of line battery packs? I'm sure that a lot of people would like to know how to do this. (y)
are these Worx battery ? i bought a makita adapter for works, is it risky to deplete the worx in a makita device?
It depends on whether the battery low voltage shutoff is in the tool or battery.
There is no BMS in standard DeWALT 18/20v batteries but there is a PCB. Clones often skip the PCB and they seem to work but they certainly look like they do a bit more than just temperature monitoring. That said, I don’t think there is a parasitic draw. I wouldn’t be surprised if DeWALT FlexVolt batteries had a parasitic draw tho’ since they look a lot more complicated inside.
So, did you fix the batteries by replacing the cells?
No. I removed the good cells and got another tool with compatible batteries.
Is there anyway your average Jo can discharge a cell safely without any particular specialist equipment? I recycle my batteries at Aldi but would discharge if safer.
You can connect a suitable load or just a resistor and check the voltage for when it is low (about 2.5V or less for a cell.)
Could reuse, just swap out the bad batteries, be interesting to see if there are any direct connections to those batteries as they could be draining into the nearest component
I think it'll be the cell that gives up the ghost first when the battery as a whole is over-discharged.
Very interesting. Thnaks!
Just what I need for trimming kindling into pleasing shapes for our woodstove. ;*[}
You may think so, but personally I've found that often someone, more in the position of observer than stakeholder and generally unqualified to assert their opinion is the one that gets the final say.
Then there's the "first thing that comes to mind" natural tendency of people. So your in the house, the fire needs more wood, you grab the pocket pruner, over excitedly trimming away with all the focus that a new novelty gets, with the motor whiring away, you don't quite make out what someone just said but they yell your name brining your attention to the sawdust that was thrown in fair quantity onto a hot surface and is now smoking like crazy so you jump up and fan away the smoke but to late the smoke detector got all it needed to squawk like a Karen! All good you'll know next time... so what? Well when this little story moment gets out, the majority of people that get wind of it are going to hear.. You started a CHAINSAW in the house and were waving it around yelling and screaming at people! LOL funny until it causes the authorities to believe your a dangerous threat ... we'll go back to where it's funny coz my related experience gets dark from this point LOL
Cheers for the tip! I just paused and put my electric secateurs on charge, having not used them for over a year! By the way, if you haven't tried them, please do. You won't need to use a mini chainsaw very often, and they are so quiet! Best to keep one hand behind your back or in a heavy mitten though. Just in case. You wouldn't notice till a finger was already on the ground!
Here in the area I live, there's a hard rubbish scheme where you can put things out the front of your house for collection. I have a job where I attend houses being vacated to do final meter readings for the natural gas so I see all these hard rubbish piles.
I have a ridiculous collection of rechargeable lithium batteries and packs as a result, as well as chargers for them. rechargeable Vacuum cleaners are excellent sources for these things.
It’s ok Clive, it’s approaching 2oclock in the morning me watching you 😂
I've a few 1500mAh vape cells, the only one which slowly went flat in storage was the one i'd linked up to a generic TP4056 board (our old friend quiescent current drain)
The parasitic draw was only on the center cells. You could recycle those cells, and use the remaining ones to rebuild a functional battery pack.
The risk is the other cells are often overcharged because of the dead cells in the middle. It sounds like this circuit has a protection preventing that though.
How interesting, and no profanity. You earned a sub, thanks.
How many "disposable" batteries would it take to sub out the cells in one of the depleted battery packs?
While it might be viable to swap in a parallel array of scavenged cells, it might be a bit tricky to fit in.