Arduino Battery Internal Resistance Meter
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- Опубліковано 21 лип 2024
- Arduino Battery Internal Resistance Meter
In this video we put together an internal resistance meter using an Arduino Nano, a couple of 10R power resisters, a transistor, and an OLED display. The internal resistance of a battery is one way of determining the health of a battery. As a battery ages, and the chemistry wears out, the resistance increases. This causes lower performance and a marked increase in battery temperature under load.
On way to measure the internal resistance is using the voltage drop method. We take two readings of the battery voltage, one unloaded, and one with a moderate load. We can calculate the current from each of these reading using Ohm's Law. Knowing the V1(unloaded) and V2(loaded) as well as the I1 & I2, we can calculate the internal resistance using the formula Ir = V1-V2/I2-I1.
You can learn more about this at Battery University: batteryuniversity.com/learn/ar...
Julian Ilett also has an excellent video on the subject: • Building a Battery (Ce...
All of my sketches are available here: www.dropbox.com/sh/m6c40pu99f...
.96" I2C OLED display: www.ebay.com/itm/1Pcs-0-96-I2C...
10W10R Ceramic Power Resistor: www.ebay.com/itm/5-PIECES-Cera...
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Please watch: "Diodes: The basic building block of all digital circuits"
• Diodes: The basic buil...
~-~~-~~~-~~-~ - Розваги
I was happy to find this post since I am going to build the same project. As I was watching it and trying to reverse engineer the project I have discovered an issue. It explains why the v2 reading was slightly higher than v1 making the math require the *-1 addition to the formula. This issue also makes the final result inaccurate.
I have drawn out the schematic and he wired it incorrectly. He didn't wire a complete current path for the battery under test. The positive pin from the battery splits and the two lines are routed to the load resistors. One is wired to the 1000 Ohm unloaded current path resistor, and the other wire goes to the junction of the two 10 Ohm power resistors. On the other end of these parallel power resistors, they are directed to the switching transistor. He incorrectly has it going to the Emitter pin of this NPN transistor (2N4401). Then the Collector pin is connected to the other end of the 1KOhm resistor and that's where it ends. There is no path to ground, so these two points are basically floating around the battery's positive potential. Instead of having the Arduino's sense point "vIn" (pin A0) connected to the battery's + lead, it is connected to this floating-point which makes the Arduino the only path to ground (which is essentially zero). So when the sketch starts the voltage is nearly the full potential of the battery at rest. When the ON switch is pressed and the transistor turns ON, this sense point now has two parallel paths to the battery's positive lead thus bringing "vIn" measurement up slightly. this creates a negative IR reading making the *-1 addition to the sketch necessary.
It's an easy fix, reverse the Emitter and Collector leads, move the wire connected to A0 and plug it into the ground rail. Add an additional wire, connecting it from A0 to the battery positive lead and remove the *-1 part from the sketch. I think placing a short delay to let the current stabilize when the additional current path is activated might be necessary for stability and accuracy.
Do you have a schematic please?
Nice video, always handy to have an internal resistance meter for batteries.
I came here after watching Grett Scott's video "Is it Time to Replace your Batteries? Here is how you can find out!". I knew I had to search and see if someone created an internal resistance meter using Arduino and of course, there's an awesome guy who explains everything and shares his code!
I was wondering if this is considered AC internal resistance or DC internal resistance? Thank you!
a really nice project. have been looking for such a project for a long time. is an additional voltage divider sufficient to test 12V batteries? I'm also currently looking for a project to measure the impedance and length of a cable using a 1Mhz TTL delay. Have you already tried this with an Arduino?
Very nice, man! Thank you for sharing.
Hi, you should combine this with the battery charging video.
Looks like an awesome project to embark upon. Uh, any idea where I might find your schematic ? Tks
Are you please able to provide a schematic? Many thanks.
Hello there I find your channel interesting and learn full and I watched this video and give you a👍 thumbs up. But may u ask if you have a schematic of it I want to build a setup permanently to test all my lipo / Li-ion battery's and can I use it for example with a 3 or 4s lipo to messure the internal resistance as I build a Lot of packs for my planes Qaudcopters etc. Thank you in advance for your reply and keep us learning 😁
That’s awesome! Thanks for sharing ❤
Have you compared the Value with real tester?
Great video but I don't understand on protoboard circuit connection.
Could you add a link of this circuit connection image ?I was download ino file for software but I have not schema
Thanks
Hi can you share circuit diagram for this IR Testing
This is a great project.. I'll have to try it out.
I don't know much about the metalband resistors though- I have some that I pulled from a TV which are labled MPC722 3.3ΩJ
and I am wondering if you might tell me what the J stands for?
en.wikipedia.org/wiki/Resistor#Industrial_type_designation
If Wikipedia's to be believed, the J is a mil spec designation for tolerance. So it's 3.3 ohms with a 5% tolerance. So the true resistor value could be between 3.135 ohms or 3.47ohms.
hey thanks alot!
I did end up finding the datasheet and it shows the tolerence.. but did not explain it with the J marking, so this helps alot.
You're welcome. Honestly when I was in college, i don't even think we covered those letter designations. If we did, it was in passing. Most of the stuff i've run across since then is usually 10% tolerance and that's good enough for most applications. Now for this project, i'm assuming Learnelectronics is using 5% or 10% tolerance. You can get them as small as .001% but they're super expensive.
Gray, A = 0.05%
Violet, B = 0.1%
Blue, C = 0.25%
Green, D = 0.5%
Brown, F = 1.0%
Red, G = 2.0%
Gold, J = 5.0%
Silver, K = 10%
No color or band, M = 20%
any suggestions for measuring internal temperature of batteries?
Hi there like the project do you have a diagram of the circuit ?
thanks
easyeda.com/editor#id=4a9ed8aa79dd4612b87cb86aa8f6da1b
.
I think i got it right.....
Can you please provide schematics thank you
Is this capacity tester or resistance tester
i am confuse please can you explain
I want to make, can you share the schematic how build the circuit
Thanks
This tests the "Internal Resistance" of the battery. It does not test the "Capacity" of the battery. As batteries go bad, the Internal Resistance increases.
How the hell V1 unloaded battery voltage can be lower than V2 loaded? Battery voltage should drop once you connect resistor. I'm getting this correctly, V2 is battery voltage with resistor connected to battery?
I cant't get it to work. Readings are jumping to much like 50-100%.
looks good, but keep in mind that power resistors usually have a tolerance of 10%, and in the sketch you just assume that the parallel resistance is 5Ω. If that's not exactly, all your measurements are fucked up ;)
and don't forget that a BJT Resistor can act as a variable resistor which also messes with the measurement. A P-Channel mosfet would be a better choice. Then you have the same ground (no Transistor between power resistor and ground) and the measurements are also more accurate.
👍 Thanks Sir..
Can anyone share schematic please....
Hello, I see an issue on you screen, as the loaded batteries have a higher voltage than when unloaded. How it that possible ?
It's called magic science :)
Good point. It may be that he should put a 1 second delay in the Setup routine, before capturing the voltage. When initially started, the voltage from the USB may be drained for a second or two.
shout-out
ELEN3017
Haha
EYY!!
the first 18650 isn't 0.012 Ω, it's probably around 0.025 Ω ...that thing is not precise
EDIT:
also 13:15 you said li-po.. it's Li-ion actually...
if you used a 1ohm 1% current sensing resistor the values would be more precise..
even better a 0.5ohm, with a draw time of 100ms.
also you wouldn't need that 1k resistor because unloaded current would be 0 always..
I think it's even higher, like 0.06 or 0.08. For a fake battery even 0.025 is too low.
He would see it if he tried the same battery twice.
You should leave the load on for longer. Don't think it's that precise
a schematic would have been simpler
Howdy? What took you so long and too laboriously explained could be easily and better explained with a schematic diagram. I have seen other UA-cam Uploaders use this style of better presentation, doing this in their video: "HERE'S THE SCHEMATIC DIAGRAM (superimposed on the video) and THIS IS HOW IT LOOKS AS I HAVE ASSEMBLED IT". Your explanation made you point to circuit parts which we already know - sort of insulting our intelligence - like showing us what a Nano is, an Oled, high wattage resistors, etc. And in the end your wiring explanation was just as fussed up because, for one thing, it did not answer what that 979 ohm resistor is doing there. Don't get sore at this negative comment...just aiming for improved presentation later on from your channel. But as for your project, it is very good. The OPUS, the IMAX B6 (chinese clone) and a few more brand name chargers give the cell internal resistance but we don't know the science behind them...and these devices measure INTERNAL RESISTANCE now and 15 seconds later, using the same cell, give out a completely different INTERNAL RESISTANCE making one conclude that their measurement is LOUSY. Your project is based on SOLID SCIENCE THAT WE SEE AND UNDERSTAND AND WE SEE WORKING. Thanks a lot, Sir.
i dont think you can load test a battery in half a second, 10 seconds maybe
You'd be wrong in that thought process.
id be happy for you to prove me wrong with a video etc ?
@@kermets You don't need a video. Voltage drop divided by current equals resistance. Subtract the resistance of your leads and you are left with internal resistance of the battery.
All the commercial battery load testers I have used for my jobs had a load test time of about 5 - 15 seconds . your formula is correct but not accurate....
@@kermets I probably misspoke, here. I thought we were just discussing IR, since that's what the video is about. I agree, it should probably be ran for more than a second for a load test, but the initial voltage drop due to IR is a good enough test. You usually instantly know whether a battery is good or not the instant the load is applied.