Great post. I am a programmer and that influenced my decisions about charging. I wanted the charge system to be visible and the various components to be separate. The Chargery is expensive but very fast with nice display of information. It slows down as it approaches the target voltage, etc. I plan to use it for other boards too. I was really surprised at how hard it was to find a 12s charger! Seems like such a no brainer.
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Jehu’s pattern is:
- don’t charge to full (saves cycle life, and don’t need to be precise about termination)
- bottom balance occasionally (only if needed) – when pack is near 0%, cells should be in balance and not over discharged
- don’t stress the cells out with close to max discharge (which tends to unbalance cells)
- for normal charge, don’t balance charge. Just bulk charge to something like 90%.
Even if we don’t do as he does, it’s useful to think about it.
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It’s the same simple design as I have, so yes, it will have the same passive drain issues. I wonder if the multiplexer would really work though. I looked at the datasheet and didn’t understand it (that’s what usually happens to me with datasheets 
). I’ll try again after I have slept on it.
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Solid post. Thanks for sharing all of your research with this community.
I would really like to try 1.3 if you ever release the firmware.
I was planning on getting one of these smart bms anyway. but being able to check cell voltages without opening an app on my phone would be really nice.
Also its not android only, there is an iphone app. Not sure the app name now though, a user on here told me about it a while ago. Might be “Xiaoxiang BMS” its $1usd.
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Thanks @janpom great post. I’ve wasted an enormous amount of time with google on this topic.
I believe these guys are the OEM
The 60a version comes with aluminum top and bottom plate. The 20a/30a only have fets on top, and only has aluminum top plate. Bottom is fish paper. I like the physical protection of the 60a, and it’s not that much more money.
They have a bigger version that can do more discharge, up to 100a. Oh and I see a bunch of new looking stuff with RS385, RS232, Can, SMbus. CAN would mean possible METR compatibility via vesc, like dbms?
There’s also this
https://www.speedict.com/product-page/neptune-15
Expensive (used to be cheaper) and the ES thread showed some concern for accuracy.
And this
https://www.energusps.com/shop/product/tiny-bms-s516-150a-750a-36
Also expensive, fairly well proven I think.
Connectors, @oriol360 showed us using a VGA port (15 pins) for balance and charge leads – fine if you’re doing low current.
I’ve also got m hands on a few of these types of thing
https://www.ebay.com/itm/1Pc-Military-14-Pin-Twist-Male-Female-Connector-Plug/151106903634
Comes in many sizes and shapes.
Balance charger for 10s/12s not a dual where you have to break the series connection, there’s the Chargery ($$$) and
https://www.amazon.com/EVPEAK-1350W-Charger-Battery-Screen/dp/B01D4PORJW
The EVPEAK comes with the 12s breakout board. The company claims they have a 10s board for purchase but won’t actually sell you one.
I think you can also use two 6s chargers if you use 2 different PSUs with the dc ground lifted.
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if you zoom in on my board you can see my voltage meters. they’re literally HobbyKing voltage testers hooked up to a switch. so i can see individual voltages at a flick of a switch
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I like simple solutions like that. Can you turn them off, though?
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There was also that cell checker that I think @Nowind used. Can’t remember what the problem was with it. I think his was called mttec or something similar, but looked like the Chargery BS12.
up is off and down is on. the checker only does the front packs and the other checker does the back packs so i can quickly locate a problem.
each checker cycles like this:
switch on "5Ce (5 cell), Total voltage (eg 21v bc its only measuring 5 cells) c1, (voltage), c2 (voltage), c3, (voltage), c4, (voltage), c5 (voltage)… and then it repeats. switches off
(went over the top but idc)
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Are you sure it’s actually turning off tho? I’ve had a similar checker and even after disconnecting the gnd pin it would still be on just the screen would dim slightly. In order to turn it off I had to disconnect the first 2-3 pins
yeah its dead off
i got the lights completely out to check and nup nothing at all
If the switch only cuts off the ground wire, there’s likely still some passive drain even when it’s off. It’s probably small enough not to be a problem. I’m still curious to know how much it is (if anything at all). I have the same checker at home. I’ll do some measuring on it.
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Fantastic post - just getting round to this part of my build so really useful info!! Cheers
I just had a look at the bms modules and there doesn’t seem to be a 12s liion on the website, however it can be found on AliExpress for reasonably cheap
The product offer is a bit confusing. The 12S is only available for lifepo4 batteries. I’m not sure why. The BMS can definitely be configured for 12S li-ion.
Anyone got any experience with one of these?
￡87.26 17%OFF | 300A 8S 12S 24S Cell Lithium Battery Protection Board Smart Display Balance BMS Coulomb Meter lifepo4 Lipo li-ion APP Bluetooth
My build is 12s 12ah 50c max discharge - 2 x 6s lipo - dual maytech 6374s sealed with focbox unity - and wondered if this is going to be suitable? Rated higher than I need but price difference is negligible so may as well over-spec.
Any disadvantages or is this the ideal solution for charging and battery protection in my case?
Extremely grateful for any advice!
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Thanks @deucesdown for the additional information. Very useful! I added some bits to the original post. Will do more updates later when I have more time.