BMS Parasitic power

DIY Builds Battery Builds
#1

Thus far all of my charging/balancing has been off-board with a smart charger, but in my latest build I’m including a n LLT BMS.

But then I ran across this:

Which didn’t really conclude that the BMS killed the batteries, but in general, if I remove the BT adapter, can I expect zero parasitic discharge with the BMS?

If not I’m thinking of setting up a charge connector such that the positive-most lead of the balance leads would only be connected when the charger is plugged in (using a 4-pin connector with 2 of the pins shorted to let the charge through.

Good idea? Bad idea? I store the boards all winter and would prefer not to have to pay attention to them.

Thanks,

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#2

Zero? No.
But you could check the specs for your BMS on their web site: https://www.lithiumbatterypcb.com/

If there are no other electronics connected and the BMS is wired and working properly, it should only draw a small amount of current. IIRC, roughly about what a single cell in good condition self-discharges at, perhaps 50uA.

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#3

Just pull out the balancing harness before you store. Much simpler than disabling the BT and unless I’m mistaken, the bms is powered by the harness and accordingly, that will mean your parasitic draw is neglible. Even leaving it plugged in, in my experience it’s still negligible but if u wanna set it and forget it…

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#4

It shouldn’t be necessary to take your battery apart to put a skate in the closet.

#5

Minimum maintenance, long term storage is a reasonable goal here. Bricking an entire pack would suck

#6

I guess it’s all a matter of how the BMS is built. It would be really easy to route the GND pack wire through the charge port so that it’s disconnected when not charging, but if the BMS is using the red and black balance wires to get its power then that won’t help. I suppose I could poke around until I find out where it gets its power.

Does anyone have a schematic of these things?

Thanks,

#7

I may be mistaken but I believe they changed the LTT Bms recently and added an on/off plug with wire leads provided. I haven’t used it but you might be able to wire it up to an external switch to power it off when you want to store for long periods.

#8

The switch function only controls the discharge

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#9

I’m having very little luck getting the LLT app on my phone to connect to the BMS on my board. It connected once and showed me all the voltage values but every time since it doesn’t find the BT device.

Is there a trick to this? Has anyone figured out the exact voodoo necessary to get a reliable connection?

Thanks,

#10

Oh ok so it’s useless. Good to know

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