Estimation of battery drain by BMS

Hi there,

While spending my winter in Marocco surfing(and riding an Exway Flex on mainly pretty bad roads, still better then nothing), I am waiting for the police to return my Hurricane at some point. And here’s my question:

I had the board taken away from me three months ago. It had around 85% battery left at that point. The (original 708?wh) battery has a different BMS (LLT) built in, and I am wondering how much the BMS will drain the battery on average… So, approximately how much juice should be left by now in the battery? Is there a chance it is still fine, just in case I get my baby Back?

Cheers

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LLT list the estimated power draw in the product specs on their website

Thanks, think I found the number: 300uA. So basically - nothing, right?

Run the numbers….

300uA for one hour removes 300uAh of charge from the pack.
That is 300uAh x 24 hours x 30 days = 0.216Ah per month lost.

But the cells have their own internal self-discharge too. Depending on their condition it could be 50uA per cell or much, much higher. Let’s call it 100uA per cell.

The Hurricane has a 4P pack? That would be 400uA more self-discharge and 400uAh x 24 hours x 30 days = 0.288Ah more lost from the pack per month.

Total loss per month (rough optimistic estimate) = 0.216Ah + 0.288Ah = 504mAh

So for three months of storage that would be about 1500mAh lost. This could be verrrry far off depending on the condition of the cells and their actual leakage rate. It would also depend on any other electronics in your board that could be drawing current.

So hopefully your board is still okay and I hope you get it back soon. :slightly_smiling_face:

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Temprature is a huge varient too. Store the pack in a -3 garage and you can kill it in a month from low charge

Much appreciated, thanks for stopping by :slightly_smiling_face:. My gut told me that I am fine, but it’s sooo much better to have a rough calc. Now I just gotta hope that the police storage room is not as cold as it is in my imagination. But still, my precious board is in the hands of the Sheriffff, so good luck to me.

Changing countries anyway, there’s no fun in avoiding the ‘bad’ cops all the time (and not working out all the time. Fun two years though).

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I’ve had the opposite experience.
Most cells are rated down to -20°C for storage and their self-discharge rate slows down a lot at lower temperatures.

High temperatures really zap a pack though and really speeds up the self-discharge.

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If it is attached to a heated building or inside a heated building then I’d guess it is at least 50 f in the storage room. But that is just a guess based on my own experiences in poorly insulated apartments and buildings during winter storms. The worst was during a super bad arctic storm when the power cut out for over two hours. The building ended up somewhere in the 40s, but it was one of those buildings where they do the bare minimum insulation wise.

Also I wonder if they did kill the battery due to taking it and then neglecting proper storage if there is anything you can do to get them to pay for their negligence/ the damage that they caused to the board. :thinking:

I guess at the moment I would be happy just having the board returned within the next 1-2 months, the cells should be fine, as calculated. It’s a bit a luck of the draw here in Germany, some people had their esk8’s returned within 2 to 3 months, some never saw their boards again and were fined on top.

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I have a 10s3p p42A pack with an ltt bms, i noticed it takes +/- 1% per week

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…makes it the perfect rule of thumb.

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Ah yea you’re right its the other way around. I guess its a pretty big fire risk to store at 30 too, ive seen sheds on fire because an ebike was kept in them under the California sun…

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That’s something that’s never made sense to me.
Vaping devices have caught fire in hot cars, you mention the sheds, but cells don’t go into thermal runaway (and catch fire) until they hit at least 130°C and that’s for LiPo’s. Other chemistries can get up over 250°C before bad things happen.

I keep thinking it’s the electronics or something else that’s the problem and which eventually fails and causes the cells to catch fire.

I guess it doesn’t really matter what the cause actually is though, Heat = Bad. :slightly_smiling_face:

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Shitty chinese cells with a poorly made battery, I’d bet on a hot day (35c+) the inside of a shed could easily be 60+, inside the battery hotter… If someone puts a battery on charge and leaves it I can see how it happens