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Old 05-15-2021, 11:37 AM   #5 (permalink)
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Join Date: Sep 2012
Location: Victoria, BC
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Firefly EV - '98 Pontiac Firefly EV
90 day: 107.65 mpg (US)

Little Boy Blue - '05 Toyota Echo
90 day: 33.35 mpg (US)

BlueZ - '19 Nissan 370Z Sport
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This is the type I used:

AliExpress BMS

As you can see here on my battery:

And I was pleasantly surprised with it. Meaning it did what it was supposed to...shut off on over-discharge, shut off charging when hitting full voltage, etc.

I like the "Common Port" or "Same Port" just behaves like any old battery that way. Not sure what the point of having them separate is...just makes for headaches.

As always when scoping out a BMS:
  • Make sure it's for the right battery chemistry.
  • Look very closely at the cut-off voltages. (some cheap ones wont shut off until 4.35V or higher)
  • Make sure you have plenty of headroom for it's rated current.
  • Decided if you want common port or not.
  • Check that it at least top-balances.
  • Bench test the dang thing before you put it permanently in to service. (Had a couple of faulty ones)

That being said, I end up spending $20-30 on average for something half decent. I have a fancy, blue-tooth, programmable one that ran me like $125 waiting to go in to service, but that was a special case...

Oh, and if you're building it from a mish-mash of cells of uncertain health, you can throw in an active balancer for another $15+ (price varies by cell count). I thought I was going to need one with the pack I built above, but I cycled it and every parallel string stayed at the same voltage throughout....despite some of the cells being previously well used. (Thumbs up to Samsung for the quality of their cells!)

PS: No, you won't bother the controller...pretty sure the controller I pulled out of the E300 had the same current ratings as the E200. (MonsterScooterParts shows the same part numbers)

PPS: If you go for Lead, as you noticed, the 10AH won't need the 7ah (which you can sometimes find the same dimensions as a 9ah, but be careful as you can find 9ah with the same dimensions as the 10ah).

PPPS: Variable controllers are like $15 and throttles for $5-10. (I have a 48V 500W one if I ever get bored of running it at 24v)

Last edited by Stubby79; 05-15-2021 at 11:46 AM..
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