Lithium Battery Protection Circuit Experiments - Self Discharge Measurements? and more!

This was one I was actually curious about, so decided to film the experiments. TLDR - protection board pulls ~4uA from the battery at all times. Cutout was 2.9V Over current was
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[@wadefallin]

Been waiting for this video. I have many lithium powered batteris that I want to use in miscellaneous projects but I was always confused about the protection circuit, particurily in regards to charging protection. Thanks for the video Kevin !

[@hertzkot]

Thank you for sharing your knowledge - respect to you always!

[@zaprodk]

Kevin, can you show what the quiescent current draw by the protection circuit is after the cell has been disconnected. Like what's the lifespan of a discharged cell before the protection destroys the cell by taking it under 2.5V unloaded.

[@jeuf37]

Yes, I also wondered about this case

[@Mr.Leeroy]

It shouldn't kill the battery. The circuit should stop draining power after cutout until you jumpstart it with external voltage (charger) again. Recently, I disassembled some original batteries from Nokia and Sony Ericsson pushbutton phones (you can guess how long they have been discharged, years for sure) and found out that cells were far from dead. So I recharged them with lab PSU and sure enough, they still got like half of capacity and barely self-discharge. Still works on BT audio module with ~20mA current draw, lasts as long as you expect from the remaining capacity, even if you do not use it for long periods of time. But, I'm sure there are plenty of examples of cheap horrible protection PCBs with quiescent current present even after cut out.

[@Kevindarrah]

I measure just a couple nA at 2.9V like it's not even there - basically 0

[@rocoroco15]

Hi Kevin, just found out about this subject while I was experimenting with you TrigBoard V8 - Very useful and hard to get information!

[@WistrelChianti]

Thanks that really is interesting especially the actual high current cut off level. About the discharge cut off, I've experienced this myself with a protected battery and found it kills the voltage down to something relatively low. However this was only until I disconnected and reconnected, then it bounced back. Worth nothing though the cut off occurred under a heavier load (so more sag) whereas on reconnect it was idling with little current draw so probably the voltage back over the low cutoff threshold

[@devluz]

Very interesting. One of these things I always wondered about but too lazy to check.

[@radius.indrawan]

this is a very useful information. thank you for sharing it. 👍🙂

[@MiniLuv-1984]

Very useful to know - thanks Kevin. I noticed your PC interface for v and a which brought up a question, what would be good to monitor sixteen cells in series and record V say every second or faster?

[@syaduinotech3681]

Thanks for sharing sir. One question, is the protection circuit you shows here are similar with most of the protection on the lipo, or there are some differences, I mean the IC use? Thanks sir.. good sharing

[@ClaytonDarwin]

Thanks. I've wondered about that, but never tested it. I guessed it had to be fairly low.

[@hermanvanwoensel]

Kevin, you should measure the current draw of the protection board at the nominal 3.7V. Not at 4.2V. That would be more close to reality, I think. Thanks for the video!

[@Kevindarrah]

good point - 3.87uA at 3.7V and 3.67uA at 3V

[@Nono-hk3is]

Is the protection circuit based n a dw01a? Are those still the most commonly used protection ICs for building into batteries?

[@MrJohnnaz]

Can you do a video on what a charger should have for battery's with a bms. I guess what I'm trying to say is how sophisticated does the charger have to be if the battery pack has a proper BMS. I would like to build a high power (20A) charger for a 3S 80AH battery.

[@hurzelgnurk]

Funny coincidence , I received a delivery of very similiar looking protection circuits today.

[@nastypokernastypoker]

Hi Kevin. What software / power supply do you use? Looks like a cool interface.

[@iantcroft]

Would be good if you could inform us of what protection circuit you are using, what chips etc.

[@Digital-Dan]

Wouldn't the overcurrent thing work differently with a real battery supplying the voltage instead of your power supply?

[@changeagent228]

Battery capacity differs significantly when drawing high current with some cells only offering 65% of rated capacity. I always use discharge charts to make sure I match a known cell type to my intended load.

[@user-qf6yt3id3w]

Seems like there's a market for a microcurrent version of the protection circuit.

[@Kevindarrah]

yea, I bet I could design something!

[@PaulHuininken]

Good video. Thank you

[@uncertainfuture8707]

Nice!

[@GeorgeGraves]

What hardware/software are you using to measure the current? Looks great. Never mind - found it. qoitech

[@Kevindarrah]

yea Otii is a nice tool - little expensive but I use it everyday

[@crazyDIYguy]

I used a super old random lithium cellphone battery in my multimeter years ago, I use the meter almost everyday and it's never needed charging, just keeps powering.🤷‍♂️😆