Help, something is draining my pack

ESK8 Electronics
1

So some time ago I took my spud out for a spin… but for some reason it wouldn’t fire up.

Went back and found out that my 10S2P had been completely drained… 0.3V per cell left… At that time I thought perhaps my BMS was busted.

So I replaced it with a new 10S2P and new BMS and monitored it. For some reason, the pack was still slowly draining at about 0.5V per day. So I thought maybe it was my anti-spark switch (electricskateboard repair), I swapped that to a brand new flipsky smart anti-spark switch and the same thing is happening, 0.5V draining off each day.

I tried leaving the pack unplugged and voltage was stable, I also tried connecting it to a different VESC and it started to drain slowly again.

Any ideas what the hell is going on?

Thanks in advance! Erv.

2

maybe you could post a pic of your internals?

very strange indeed

3

Bad bms? Maybe, or short? Weird

4

what kind of bms?

which vesc?

my suspicion in on the anti-spark switch. not sure if possible, but if you replaced that with a loop key, i’d bet money the slow drain will be gone.

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@banjaxxed I think the instance when the pack got drained to zero in a matter of a few days might have been BMS issue. But I have since changed to BMS.

@thisguyhere

It’s the cheap waterproof red colour one from China.

VESC is hobbyking 4.12 and flipsky dual 4.2… both still drain slowly. As does new BMS.

I have it now transplanted to another enclosure with an antispark I know works… voltage is stable…

Now what I don’t get is why two brand new antispark from different manufactures would have the same problem… Is it something I did?

This is in no way a high powered board… Single 6374 on 10S…

My current option is to change to a loopkey but that means having to open a larger hole in the enclosure… And also the hassle of a loopkey…

I measured both antispark outputs when the switch was off and both exhibited a small less than 1V leak… WTH…

6

Transferred battery and BMS to another deck with an antispark I know doesn’t leak… Voltage stable again…

So basically I have 2 brand new antisparks which are leaking… Why did this happen?

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Interesting find! So who knows the answer?

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Antisparks:

  1. Meassure what resistance the the FETs show when off. (Should be Mega Ohm or “overload”)
  2. Meassure on “OUT” terminals with battery connected, if you have any active output.
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this would be better answered by an electrical engineer, but here goes.

antispark switches uses mosFET(s) in the open position to complete the circuit. the gate that determines on / off is the thinnest filament and could allow the tiniest amount of current despite it being in the off position:

image

that’s my guess. please tell me how i’m wrong. i’d actually like to know as well.

anyway, this is why i never use antispark switches that have this tradition design.

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Lets say the off state is 1Mohm. You’ll have a “tiny current” of 0.0042mA(10s). So…from full to empty would be…2000+ years something for a 10Ah battery?

Lol hang on, let me get a calculator.

calculator said 27 years, few zeros wrong xD

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How I measure the FET resistance?

As for the OUT terminals I connected a 4S battery, when the switch is off one anti-spark shows 0.2V, the other 0.5V… I’m pretty sure this is not supposed to happen…

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Yes it should be negligible in real world terms… but I’m seeing my pack being drained noticeably…

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I tried every combination to weed out the problem, pretty sure it’s the anti-sparks leaking… and somehow both of them (from different manufacturers) are exhibiting the same problem…

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just meassure between source and drain, nothing connected.

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Across the positive terminal both problematic switches show zero ohms… it’s completely pass thru…

Across ground, one of them was OL.

The other was weird. When I first measured it read 5Mohms… Then after I probed it more it went over limit…

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Gave up… 100% sure both my almost brand new antisparks are the cause of the leaks.

Have since gone back to the primitive but proven XT90 loopkey… no more antisparks for me…

IMG20190221164250

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