Kalkhoff Battery not charging

Tintaglia

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May 23, 2007
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Hi, we bought a 2011 Kalkhoff Agattu recently which was honestly advertised with a faulty battery. However, on getting it home it has some charge (2 lights) and powers the bike but it won't take any charge. If you press and hold the button it shows 5 lights so we're hopeful it might not be completely knackered. It is showing 25.3 volts (8ah battery) but that doesn't increase after charging, nor do the lights show when you put it on the charger (we've tried 2 different chargers that are working fine with other batteries). Has anyone come across this before or have any idea why it won't charge?
 

nemesis

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I had two batteries of this type in 2011 and 2012 and had the same problems,the only cure was a new one taken care of with warranty.Not sure if they are still available.
 
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Tintaglia

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May 23, 2007
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Thanks for the reply. This is what we were expecting, we do have another battery, it was just the fact that it was showing all 5 lights on the battery condition test that made us wonder if it was fixable before we got rid of it.
 
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LeighPing

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Thanks for the reply. This is what we were expecting, we do have another battery, it was just the fact that it was showing all 5 lights on the battery condition test that made us wonder if it was fixable before we got rid of it.
I just replaced a laptop battery and charger. I was about to throw the old one away when I noticed that all 5 lights came on when I pressed the test button.
Charged it fully and tried it on it's own. It lasted 3 minutes. Sometimes, I guess, they're just done for. :)
 
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Nealh

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It might be scrap but before binning it, open it up and put a dvm across the bms Jst/ ribbon connection to see what the cell strings measure. It may be that one cell group is out of balance and is below the lvc which is why it won't charge. 25.3v suggests an average 3.61v per cell string if its 7s battery, however if one is low say 3.1v or less then it won't charge, however you may be able to tease it to slow/trickle charge up to the other string levels then the battery will or should charge if it's ok.
To charge a low cell string you will need a charger that will slow charge at about 0.2 - 0.5 amps to start with.
 

Tintaglia

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May 23, 2007
80
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Thanks Nealh, might investigate further today. We've never opened up one of these cases, is there a right way to do it or anything to watch out for (opening the lafree cases often manages to pull off the wiring for the leds :-(
Also do you think it would still show all 5 condition lights if one cell string was low? That's really the only reason we're persevering with it but maybe it isn't a reliable indicator of the condition of the battery.
 

flecc

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Oct 25, 2006
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Here's a photo of what's inside the Kalkhoff-BMZ batteries of that age. Yours might not be exactly identical since they varied according to capacity:

Kalkhoff BMZ Battery.jpg
 

Nealh

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Go gently and tease the casing apart being careful usually prevents any overt tugging or pulling of wires. generally their is enough play with any wiring other wise building them would be a total pain.
If not sure how to measure the cell string voltages show us a pic of your bms connection and we can help.
 

Tintaglia

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May 23, 2007
80
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Nr. Newquay, Cornwall
Okay, this is as far as we've got and not really sure how to dismantle it further, it doesn't look anything like Flecc's picture at this stage. We've checked for blown fuses and wires off but there is nothing obvious.
It is a beautifully assembled battery, it makes the NimH/NiCad batteries we've worked on before look like they were put together in someones back room! It is also immaculate in there and looks like brand new.

Thanks for all your help so far :)

P1040975.JPG P1040978.JPG
 
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Danidl

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Okay, this is as far as we've got and not really sure how to dismantle it further, it doesn't look anything like Flecc's picture at this stage. We've checked for blown fuses and wires off but there is nothing obvious.
It is a beautifully assembled battery, it makes the NimH/NiCad batteries we've worked on before look like they were put together in someones back room! It is also immaculate in there and looks like brand new.

Thanks for all your help so far :)

View attachment 18282 View attachment 18283
Excellent photos. The black rectangles with 3 pins are the power transistors , used for the Bat management system. , Putting one lead of your dmm on voltage scale, to the negative terminals of the battery pack and the other lead to the same pin of each of these transistors in turn you should see a step increase in voltage of the same amount . If one of these is way off, then you have identified the problem bank of cells.
 

Nealh

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Can you see a flat connector block anywhere on the bms with several thin wires that route back tot the battery as they are usually the balance wires.
 
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All the mosfets are in parallel, so that's not the way to test it.

Do you see the six silver wires coming from the edge into the PCB, marked V1, V2.... V6? They're the sense wires. Put yout black probe on the black ground and then measure the voltage on each of those wires. The seventh cell should be the red positive wire from the cell-pack, which we have as 25.3v. Post the 6 readings here and then we can see what's wrong.
 
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Danidl

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All the mosfets are in parallel, so that's not the way to test it.

Do you see the six silver wires coming from the edge into the PCB, marked V1, V2.... V6? They're the sense wires. Put yout black probe on the black ground and then measure the voltage on each of those wires. The seventh cell should be the red positive wire from the cell-pack, which we have as 25.3v. Post the 6 readings here and then we can see what's wrong.
... God bless your eyesight!
 
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Nealh

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All the mosfets are in parallel, so that's not the way to test it.

Do you see the six silver wires coming from the edge into the PCB, marked V1, V2.... V6? They're the sense wires. Put yout black probe on the black ground and then measure the voltage on each of those wires. The seventh cell should be the red positive wire from the cell-pack, which we have as 25.3v. Post the 6 readings here and then we can see what's wrong.
The maestro at work :cool:.
 
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Tintaglia

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May 23, 2007
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Thanks for the replies, sorry about the delay replying, only just got home. That test gives an interesting set of results, starting at the top left by the red wires and going round anticlockwise I get: 18v, 10.8v, 3.5v, 7.2v, 14.4v and 21.7v and still a total voltage of 25.3
They sound like pretty random readings, I hope they mean something to one of you :)
 

Danidl

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Thanks for the replies, sorry about the delay replying, only just got home. That test gives an interesting set of results, starting at the top left by the red wires and going round anticlockwise I get: 18v, 10.8v, 3.5v, 7.2v, 14.4v and 21.7v and still a total voltage of 25.3
They sound like pretty random readings, I hope they mean something to one of you :)
.. well they do the sequence is 0 3.5, 7.2,10.8,14.4,18.0,21.7 and 25.3 indicating that each voltage is 3.5 to 3.6 V higher than the preceding one. Are these supposed to be lithium ion cells and a total supply voltage of 26 V 29 V nominal? If so they are at the lower level of discharge and if the pack was charging, they should rise up to 4.1v per tier.
Is it possible to attach the charger to this opened assembly and then measure these same voltages while on charge?
 
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Tintaglia

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May 23, 2007
80
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Nr. Newquay, Cornwall
I've taken the readings again connected to two different chargers and they are all identical to when it isn't on charge. To confirm it is an 8ah 25.2v Kalkhoff lithium ion battery which is showing 2 charge lights and 5 battery condition lights.