Відео

Thanks! Yes the ambient temperature may affect the results slightly, I don’t think it would be significant however. Most of the warming inside the battery case will still come from the cell heating film. It was only around 10 degrees in the workshop that day too. There are definitely better ways to implement this and some good suggestions in the comments above. I feel the same as you however, if you install and maintain your battery space correctly then direct heating isn’t needed and if that’s the case, why take the risk of damaging the battery?

Sorry for slow reply. The on/off switch isn’t mandatory - you can just leave it on permanently and use a battery isolator to shut it down (although this will mean you lose the low power hibernation function). Alternatively, we sell a switch extension kit for £50. We would replace the switch with a waterproof port, and supply a 2m cable (can be longer if needed) with a switch on the end. So all you’d do is screw the switch cable to the battery and then install the switch somewhere else 👍

Noted, thanks for feedback. There are subtitles available on the video if needed 👍

Yes, it’s a chemical reaction so it’s going to warm up when discharging anyway. And as this is the same across all cells, the heating effect will be evenly distributed - unlike the self heated batteries which only heat certain areas

Yep if you can maintain temperature of the battery compartment then that works well. Most people in Europe just install in living space of the van so it’s going to be warm enough anyway.

Not sure how else we could have done it but happy to hear your ideas 🙂

@@roamerbatteries perform the test while the battery is in the freezer. It would be more representative of real life conditions.

Yes there are heat pads that go between the cells, apparently the brand we tested uses these on some of their larger batteries. This still isn't ideal however especially when heat is only applied on one side of the cell, temp sensors are located externally and a single temp sensor is used to control low temperature charging - this is still going to lead to uneven heat distribution. The batteries that don't allow the temperature that drop below the set point are a different design and have their own issues (they can discharge the pack unless you have a constant source of charging). If you're overlanding in the UK then just maintain it properly by ensuring it is stored at above 50% state of charge, and if its ever too cold then you'll always have enough energy to discharge and warm it up

@ The Sun Fun Kit I have ( and just recently built ) the BMS monitors temperature and switches on and off the heating pads if it sees temp below a set temp that you can adjust in the software on your phone or tablet. It would automatically stop the battery getting too cold which makes putting the battery in a deep freeze experiment a bit meaningless in most cases. I guess it depends on your application BUT a battery for arctic conditions to be sat at -25 for months isn’t really what most consumers need. If I’m say overlanding in Norway for a two week stretch then stopping the battery getting too cold overnight will be beneficial as I can then recharge as I drive again in the morning. I agree that the heating isn’t the ideal design for say EVE 314 MB31 cells however I’ll do some basic testing to see what the current draw is and how well the pads work in real world conditions.

While that does sound like an improvement on other models, our concerns go further than simply where heat film is placed. The use of large prismatic cells (up to 7cm thick and weighing 5kg) makes this incredibly difficult to get right. Better temp placement and wrapping all cells would be a great start but really I think this is only practical if using small cylindrical cells. To be clear, we have not made any suggestion of specific brands and don’t intend to. This is not a name and shame exercise, we just want to highlight our concerns with the way this is implemented. Hopefully this is taken on board and improvements are made. At the very least, I would hope that additional testing and certification is provided to demonstrate that this is fit for purpose, until then we do not intend to install cell heaters in our batteries. I know we’ll always get some flak for posting this but honestly this is not about pushing our products. The XTREME range is a niche product and we currently only sell in bulk

@@roamerbatteries "makes this incredibly difficult to get right" nah, any design engineer worth their salt would arrive at a working solution. All a larger mass does is slow the process down, a process that occurs anyway in the environments these batteries are in. Lets ignore the Fogstar, or other, battery lack of charge inhibit.... Can you be specific about what you feel is a safety issue with heating prismatic cells in general? Is it because you believe the heat output is a constant?

@@robfodder5575 Yes you're right, a vertically integrated company with design engineers would almost certainly work out a solution. And I would expect any solution to be safety tested and certified too, I believe that is the bare minimum standard required. It is interesting that other than Battleborn (who use cylindrical cells) there are no premium self-heating batteries on the market. Of all the companies that have the resources to design, manufacture and test a self-heating battery - none of them actually do. Regarding safety, I have concerns about the uneven heat distribution which is more difficult when using large prismatic cells due to their size (5kg each) and shape (no gaps between as you would see with cylindrical cells). You can see from the thermal image that the heat distribution is not even across the cells. The increased voltage on cells 2 and 3 is also clear evidence of different temperatures. The way this is currently implemented means that the prismatic cells (or parts of the cell) are being charged faster than they should be for their current temperature and this will therefore lead to lithium plating on the cells. It is widely accepted that lithium plating lowers the temperature required for thermal runaway of lithium cells and that in severe cases, the dendrites can breach the separator layer leading to short circuits. I'm not suggesting that self-heating batteries are suddenly going to combust but I believe that the way this is currently implemented in budget LiFePO4 batteries creates an elevated safety risk and I would like to see this tested and certified before it is sold as a mass market product.

@@roamerbatteries "none of them actually do" - That doesn't mean its not viable, how many companies have gone under due to lack of innovation. I see this all the time and infact its one of the reasons I can put food on the table (companies paying for tech to be developed to get ahead of the competition WRT new features). You may find they dont do it simply because they are mostly in markets where it doesn't matter or there simply isn't the demand for it. WRT safety concerns, yeah fair point if those manufactures, at the very least, dont update the limits in the BMS embedded software.

@@robfodder5575 Yes thats true. I'm not saying it can't be done - it certainly can. Whether they will spend the extra money on developing, testing and certifying it is another question. The Roamer BMS has a heating circuit and we could develop some custom firmware to make this work better. I personally see self-heating as a hammer in search of a nail however, I spend every winter in the Alps and have never had an issue with cold temperature charging. It's installed correctly and I maintain the temperature above 10 degrees constantly while we're away (the diesel heater runs pretty much continuously on a thermostat). And for those people that are installing under the bonnet or an outside locker then self-heating isn't the right solution anyway as it'll be constantly cycling the heating circuit - this is the use case we had in mind when we created the XTREME (although this is now mostly used for industrial applications)

Yes there are some very simple ways to improve the design, for example moving one sensor between the cells and waiting till all sensors show above 5 degrees. The test started at minus 12 which is going to be a rare situation in the UK but not unheard of. And these batteries are used all the world. I think there’s scientific value in testing with various cell sizes and at various starting temperatures but the principle is going to be the same. The problem is caused by the heaters forcing the pack to warm up too quickly, leading to uneven heat distribution. There are leisure batteries out there which maintain temperature above a set point and this is standard on grid scale batteries. These solve the problems highlighted in this video but they are much less common because permanent heating will drain the battery (the tested battery only uses heat energy when charging so it will stay frozen until plugged in)

it really coms down to time if you need 2h to start charging its not much use is it

That would be cool. If you have Victron chargers and a Cerbo then it is also possible to program charge rates by temperature (using DVCC feature), that’s something we’re playing with now. I’m not sure if needs to be that complicated however, as long as low temp protection is in place and you have enough power to run an external space heater (to warm it slowly) then there’s no need for heaters at all. Cell heaters are ‘solving’ a problem that doesn’t exist for the vast majority of people

@@roamerbatteries The closer to an automotive application and the north pole you are, the more important it is. :P

Yes I agree it can be improved and I sincerely hope that this video leads to affected brands making changes in their products. I think problems will persist however, using big prismatic cells wrapped in heat film is always going to be difficult. The examples I’ve seen where it seems to works well are Battleborn and Tesla who both use cylindrical cells and have a much more advanced heating arrangement. And actually I don’t think heating is needed at all for this use case, if you install and maintain correctly then your batteries should never get below zero or if they do then you can warm them slowly over a period of a few hours - no need to try and hack the process. I did have some concerns about publishing content that appears to put competitor products down, that’s not our usual style or mindset. However, this is a possible safety concern so I feel it needed to be called out. Hopefully other independent reviewers carry out their own tests going forwards

@@roamerbatteries I understand the BMS in the video seems to be setup wrong but I'm just not buying this is an issue for prismatic cells in the way you seem to be suggesting (yet also saying some people have done it right? edit: ignore, I see how tesla do it...). What's the thermal conductivity of a prismatic cell? All that's need is an algorithm, a couple of sensors and the solution would be fine. You seem to be suggesting that heat won't propagate, that it won't work, but it will, it just needs to be managed and managed slowly. I've got too much on to spend more than 5 mins on this but just done some heat propagation calcs using thermal conductivity 0.2W/m (assuming the cell is an EVE cell) and arrived at 2 hours from 0 degrees and closer to 3 hours from -10 degrees i.e. the battery has been allowed to be completely frozen and needs to be warmed up safely to be charged.

@@robfodder5575Thanks for this. Very helpful suggestions and I agree, there are probably some pretty simple ways to improve this. Maybe start by relocating temp sensors, making sure heating is distributed evenly and also as you suggest, slowing it down (or introducing a delay) so that all cells warm up completely before charging is enabled. I hope improvements are made here, it’s in the interest of all manufacturers for safety to improve. I would personally want to see more testing and certification of cell heating before this is seen as being fit for purpose however

Yes it’s possible but tricky as most BMS have no way of limiting charge current, control is either on or off. If you have Victron chargers and a Cerbo GX you can program this externally with Node Red.

Battleborn use small cylindrical cells so this is not the same issue. I expect the internal engineering is significantly better too. Yes you’re correct, self heating batteries are only designed to recover a frozen battery. There are other options out there that include a maintenance heaters to keep overall pack temperature above a set point. There are also low temperature cells such as the Roamer XTREME battery that can be charged at -30 without any heating at all

The temperature threshold required for thermal runaway in a LiFePO4 cell is much higher than you’d ever see in reality. The BMS will shut down the battery way before this point

We explain what we mean by A+ in the video. Not sure what you mean by A123systems are CATL, these are two separate companies?

One that's very popular, and indicative of what is available on the market...?

@@fitmydashcam Which one is it? Fogstar?

We can’t confirm the brand, sorry. It wouldn’t be fair to them without giving them a chance to respond. Also, I have concerns over ALL self-heating batteries that use heat film wrapped around prismatic cells that is activated while charging, it is not specific to this one battery. As mentioned in the video, there are good examples of self heating out there. And there are simple ways this can be improved (relocate temp sensor etc) but wrapping big prismatic this way is always going to lead to uneven heat distribution

The effect is the same, its just quicker... the outside of the cell pack is warmed up by the heaters but the inside stays frozen. If you're using the battery then the chemical reaction will warm it up, yes. But if you're using it in a camper then its not going to get cold anyway so the heaters wouldnt be needed.

January-March above 60N, you will more than likely experience -18 or lower :P

@@rkan2 we do

Yep. A good start would be to put a temp sensor between the cells. Also a good idea to program the BMS so that it only starts charging when all sensors are above zero

the problem with more heating matts is where to locate the sensors and with prism cells they are just have to much mass to relay on temp sensors alone and adding delay means a long time without charging

@@OskarHartmannsson you are 100% right. An 15kw Solar battery has a weight of 110kg / 220lbs - takes some hours to heat in case you don‘t use 1.21 GW to heat. Insulating would help a little and using solar you have some hours a day..

@@OskarHartmannsson Yes true but really, if its installed correctly then dropping below zero should be a very rare occurrence. So waiting a few hours is not a big deal - you can just let it warm up naturally, there's no need to try and speed it up using cell heaters and as we've shown then this can cause more problems than it solves. If its likely to drop below zero regularly then this type of self-heating is pointless anyway, you would need something that can maintain temperatures constantly.

You are correct sir.

It was only a small battery or I’d have gone full Turkey! 😂

🙌

Yep, we finally got around to doing a proper test 😊

Thanks David!

No need for an isolator to the Multiplus. It has a power switch on the unit itself and you can also turn it on/off using the Cerbo screen. Most people leave the main power switch on and use the Cerbo to control it. The Blue Sea switch is only used as a battery isolator 👍

Thanks!

Unfortunately not… the whole layout is different so would basically mean replacing everything except the cell pack 😢

The active balancer is part of the Roamer BMS so is not available separately, sorry. There’s lots of good balancers out there however

The 12mm bolts are usually long enough for two big lugs but if not, no problem swapping for 16mm M10 bolts. Any stainless steel hex bolts will work, choose A2 steel for campervan use or A4 steel for marine. And you’ll want M10 washer and spring rings too. I wouldn’t use post extenders, that just adds unnecessary resistance.

Thanks Rio!

Thank you is much, that means a lot.

There’s a few reasons for the copper busbar… one, it’s solid copper rather than the standard aluminium braid cable so less resistance and lower losses. It’s correctly rated for the max load by the way, calculated using UK regs. The flat surface also creates a better connection with the BMS and battery terminals… again less resistance, less voltage drop and reduced chance of a hot spot. You do NOT want that on your cell terminals! Finally, it’s a solid piece of copper from one end to the other (as opposed to than a ring terminal crimped to a cable, then crimped again to another terminal at the other end). Less connections, lower resistance and fewer points of failure. Of course the downside is it costs substantially more than cable but it’s carrying a serious amount of current so it’s worth it 👍

@@roamerbatteriesthis is good to see I've always been slightly worried what was going on inside when I draw high currents

Really interesting video Steve - when I originally discovered Roamer it was the quality and the 250A BMS which drove my decision (oh and it fit in the space I has available perfectly). I believe I have the original (First series 460Ah) which had an amazing spec for the time and is serving me well to date, the magic you want with tech where it all just works for me. What’s the difference between the first, S2 and the S3? I’ve seen slightly different behaviour at times compared to mine when helping people so was interested. All the best, David 👍

⁠@@LeisureBitHi David, lots of little upgrades on the SMART3. The build quality shown in the video is what you get now… cell brackets, busbars etc are all new for SMART3. Cells are now traceable which gives consistency and confidence in quality. We updated firmware and short circuit protection to fix a couple of niggly BMS issues so that now works perfectly. We also added an independent Active Balancer which has eliminated problems with cell balance caused by using the battery incorrectly. Makes it much more forgiving of poor charge profiles - campervans will often have lead acid only chargers fitted and will be in storage for long periods. Active Balancing sorts this out, we never get issues now. Will also extend useful life by ensuring you always get max capacity from the cells. So its incremental improvements but added together mean batteries are very consistent and reliable. Returns have dropped to almost zero, everything now just works and we expect batteries to have a much longer useful life👌

@@carmadme I’ve seen a few hotspots at high amps due to cheap cables and poor terminal connections… you do NOT want that happening inside a lithium battery.

The LiFePO4 chemistry is the same. During charging, lithium ions from the cathode are embedded into compounds with layered structures in in the negative anode material. Conventional LiFePO4 batteries cannot be charged at low temperature because the ionic conductivity of the electrolyte is reduced which interferes with the intercalation of the ions in the anode material. This leads to lithium plating, a process where Lithium ions are reduced to metallic lithium instead of intercalating into the anode. The Roamer Xtreme cells use a special negative anode with large crystal plane spacing and a specially modulated -80℃ non-condensing electrolyte which is conducive to the process of lithium ion intercalation at low temperatures.

Hello Mwadi! Great to have you along :)