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Struck

KS14S Stops charging before 100%

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1 hour ago, Struck said:

Hello to everybody and thanks for keeping here with me :p

Finally decided to open the battery pack and measure voltages across.

There are exactly 0V between V7 and V8, all the other dV read 4,18V

So two dead cells...

1 hour ago, Struck said:

My shop promised to have somebody experienced in batteries to take a look at it, but apparently that expertise is not coming.

"Normally" in europe guarantee on li ion cells/battery packs is limited to 6 month?

1 hour ago, Struck said:

Any suggestions on how to proceed? Should I buy two lgebmj11865 (which I think is the cell being used here) and take it to a shop?

If you have an e-bike/battery (repair) shop they could replace this two dead cells and rewrap the pack.

1 hour ago, Struck said:

Can I test somehow if the BMS is at fault? A problem similar to what @Tadas had.

Your board seems fine so far - all components seem fine and no signs of mechanical or thermal abuse?

You'll see once the cells are replaced. Could not think of "easy" tests but visual inspection.

Maybe the repair shop has the equipment and knowledge to test the BMS accordingly?

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4 hours ago, Chriull said:

Your board seems fine so far - all components seem fine and no signs of mechanical or thermal abuse?

I agree, after a second thought, what you see there is a direct connection between the cells and the voltmeter, so 0V is a problem of the cells there are no BMS components in between, if the BMS has a problem we can't check it now. But no visual signs of it.

I will contact some shops. A new pack is way too expensive for what it looks like just a two cell problem.

Thanks,

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A dead pair of cells is a somewhat common issue, a faulty BMS not so much. I'd expect that replacing the cells would make the pack functional again.

15 hours ago, Struck said:

A new pack is way too expensive for what it looks like just a two cell problem.

That's what has led me to learn and to replace the individual cells a few times now. Seems such a waste to throw away 30 decent cells and a BMS!

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What kind of shop? What they did needs quite a bit of specific knowledge. Thanks for the follow-up.

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2 hours ago, Struck said:

I finally went to a shop, and they did a marvelous job (in less than 24h). Replaced the faulty cells, checked if the BMS was damaged (was not), and now I am super happy with my refurbished battery 🥳🥳🥳🥳🥳

Thanks to all! I learned a lot during this process!!

49€

What...? They replaced faulty cells in a pack for 49€?! If someone asked me to do it for 49€, I wouldn’t even bother to laugh at the offer, despite having done it three times for my own packs already!

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The place is called eptv, in Barcelona. They have a warehouse devoted to fixing all kind of personal electric transport vehicles (I was quite impressed at the size, the inventory and the number of workers when I visited them personally), and one of the workers is specialized in batteries.

Most of the team ride euc's, and I met them because of this.

 

9 hours ago, mrelwood said:

What...? They replaced faulty cells in a pack for 49€?! If someone asked me to do it for 49€, I wouldn’t even bother to laugh at the offer, despite having done it three times for my own packs already!

So, not enough for you?

I see in your profile that you are from Finland. You can't compare our wages, etc, to the ones in Finland. I know that two cells might have been 10-15€ in raw materials, and then you add 30 something for less than one hour of work. Seems reasonable. Also, worth noting that the two faulty were at the edge, easily accessible.

 

Cheers!

Edited by Struck

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1 hour ago, Struck said:

So, not enough for you?

There is so much work and risks included, that if someone did that kind of work in Finland, it might’ve cost 200€.

Great that you got a cheap fix for your wheel! What a wonderful company though, fixing only e-transporters! I’d love to work in a place like that.

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On 10/11/2019 at 10:48 AM, Struck said:

I see in your profile that you are from Finland. You can't compare our wages, etc, to the ones in Finland. I know that two cells might have been 10-15€ in raw materials, and then you add 30 something for less than one hour of work. Seems reasonable. Also, worth noting that the two faulty were at the edge, easily accessible.

I hope they double-checked that the problem was not associated with cell control circuit. Because there is a chance that faulty cells are the result, not the culprit. There is a transistor that is shunting the cells with paralell resistance to balance them. It's possible that this transistor is always active, so both cells will be continuously discharged with small current. Small, but enough to completely discharge these two cells with time and unbalance the whole battery.

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