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My KS16S unicycle doesn't charge more than 80%


Augus
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Hello friends,

I have a problem with my KS16S unicycle. Although the charger change to green and the Charge Doctor indicates 67'2v, in the application it is charged at 79%, and with a 62.9V voltage.
When both batteries are removed and measured, shows a 62.1V voltage.
I have tried with a second motherboard that I have spare, and it happens the same.
What do you think it can be?
Thank you

 

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Edited by Augus
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You're sure you turned off charge limiting threshold on the charge doctor (bottom red alternating display shows "- - -", not "X.XXA" (for default dnA setting) or "XX.XV" (for upV), or similar)?

The wheel also doesn't come up to the full ~67.7V when charging full without charge doctor?

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Take the charge doctor off and charge it for a long time.  It might be that over time a significant imbalance between the cells has occurred.  Have you balanced the cells recently?  The Charge Doctor is reading a dumb voltage, i.e. from the + and - on the charge port. But the App is getting smart data from the wheel.  What this is, who knows?  BTW have you range tested it to see if your range agrees with one of the voltages?

 

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29 minutes ago, Augus said:

It's the same without Charge Doctor. I usually charge at 100%, do not use usually Charge Doctor.

I answered you on Facebook already...as said there,  probably one cell is defect in one of the four Serial packs. As all four packs MUST have the same voltage, the BMS prevents the other three packs also from charging higher.

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9 minutes ago, Augus said:

And isn't it weird that it happened with both batteries at the same time?, doesn't it orient this more to BMS problem?

Thats exaclty how it should work!

When one cell is defect on only one pack, this one Serial cell block determines the voltage of the complete battery pack ….

So even if only one cell in one pack is defect...the other pack also does not get to higher voltage. Thats very important, as parallel packs Always Need to have same voltage.

 

And btw. A BMS is sitting on each battery pack...and those BMS's of the two battery packs are connected...exactly for that Purpose...

 

Edited by US69
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Do you have a multimeter? Measure the output voltage from the charger and the battery voltages... it's also possible that the voltage measurement on the board is out of whack and reporting wrong values.

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1 minute ago, esaj said:

Do you have a multimeter? Measure the output voltage from the charger and the battery voltages... it's also possible that the voltage measurement on the board is out of whack and reporting wrong values.

@Augus

That what esaj says is also possible...As the charging on a 16S runs over the board and the board has a Kind of voltage meter…

I have ruled that out, because you said you checked that with your second/spare board, too,  and that it is the same Kind of bad on both boards. So both bpoards being off is the same low probability as having both battery/BMS's defect :-(

 

What got me to think that one (or more) cell failed,  is that the voltage of 62,9Volt goes nearly exactly with having one Cell of 4,2 Volt missing.

 

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I've tried with two chargers and two boards. Now I'm charging the batteries directly from the charger. One does not load more, and the other looks like it is loading more... wait to see if it loads to 67'2V.

Edited by Augus
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4 minutes ago, Augus said:

The second battery has charged up to 66'1V. The other one up to 62'3V. I think both batteries are deteriorated.

No, idont think so!

66,1 is quite normal...after that voltage the charging will go higher only, very,very  slow (as balancing starts in the pack!)

So the one pack with 62,3 has one or two defect cell...this voltage difference is just to high!

 

When cells get worse over the Lifetime, they should still charge up to 4,2 (or at least nearly there)….What gets worse over Lifetime is the "mah" ...Watthours the cells can store get worse

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1 minute ago, Augus said:

My question now arises that it is worth more, if I repair the battery considering that it has 6000Km and can start to fail more cells in a short time, or buy new battery.

6000km on a 840wh battery is nearly Nothing....

lets assume with one full charge you got (only) 50km...that would mean, that you have About 100-120 full charge cycles done.

If you assume 80km for a -complete full- charge that even means that only About 75 full charge cycles where done.

That is not very much. Those cells are announced for having a life of 300-500 cycles before they get down to 75-80% capacity.

 

Question is if you can Change the defect cells in the pack yourself?! If so, it is definitly worth repairing. I guess a battery professional wouldn't repair the pack anyway, because of mixing up cells...

 

Another Thing is: A new -serious cells- 420wh pack unfortunatly is pretty expensive. Expect it to be About 300Euro :-(

 

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