TimReynolds

Just to close out this thread and advise anyone with similar symptoms, it was the charger that was faulty. I had to start changing hardware at some point and the charger was the cheaper item, plus the battery, from my investigations, looked reasonably OK. So, ordered a new charger and the battery went straight on charge and took about 8 hours to fill. Thanks for the technical help above, it is much appreciated!

I would agree but when I first took the bike on, earlier this year, the battery was fully charged, right to the top. I didn't check the internal battery voltages at that point but they must have been ~3.5 to ~3.6V. However, the battery didn't charge then, when put on the charger. I ran it down to 4 LED's, thinking it needed to be a bit discharged to take any current but nada. Now, 9 months later, the battery's dead flat and still won't charge, hence I think the problem is with the electronics somewhere rather than the cell chain...... I can try charging the whole chain of cells but I fear it won't make much difference.

My thoughts entirely. I mapped out the layout of the batteries and how the 50 cells were strapped (a string of 10 sets of 5 cells in parallel). I read the voltages of each set of 5, they were within 0.1V, between 2.8 and 2.9V. Just to be sure, I used my bench power supply to bring them all up to exactly the same voltage. Put them on the charger - nothing. The battery was fully charged when I got the bike, but has never recharged since I've had it. The vendor must have had the charger working though..... Sadly, my bench power supply only goes up to 32V, so I can't directly trickle charge the batteries - unless I split them in two. So what's the betting? Duff charger or duff BMS board? Both seem to be working individually, just not together. Charger is £69, battery is 333 Euros from Germany.

OK, have done the test. With the R pin strapped to 0V, 42V appears for about a second, then disappears. Charger LED goes briefly red, then green when 42V has gone. Same test done at charger XLR connector, same result. I then tried to mock up a load with three 12V, 21W bulbs, connected in series. My calculations say that these should draw about 2A from the supply. The result was that the bulbs flash, the 42V appearing and disappearing in rhythm and the charger LED flashing red and green. I've opened the battery and checked the direct charge port 10k resistance is there - it is. It looks to me like the charger is probably working, just confused about a static, resistive load. I think the battery or BMS is SNAFU. Any idea how the cells are organised or where to measure voltages?

Hi dlwest, thanks for your reply! The charger is the original one, supplied with the bike. I've tried charging through the side port and using the cradle, same result - a brief flicker of the battery LEDs then all extinguished, charger LED remains green, nothing else happens. I'll have the battery apart and see if the pull downs, especially the 10k is O/C, that might be the problem. At the moment, the battery is almost dead flat, I should be able to check the cell voltages to see if there are any noticeably duff ones. Thanks again!

Ah, it's not a Bosch motor or battery system, it's the infamous Impulse system that predated Bosch.....

Interesting.... Does this bike use CAN bus to communicate between processors??

I have recently bought a 2012/2013 Kalkhoff Agattu C11 Impulse Premium. I know there are potential mechanical issues with these Impulse motors but that side of the bike seems to be fine and it rides really well with plenty of power assistance, not surprising really, as it shows only a little over 500 miles total use since new. It has been completely unused since 2019. In all respects, the bike is just like it came out of the showroom! The battery was showing 100% full and 100% capacity when I brought it home, although I have no idea when it was last charged. I have done a few test rides, probably 10 miles with some steep hills, battery content had dropped by 1 LED so I put the battery on the charging cradle - there was a brief flicker of the battery LEDs when I connected it but the green light stayed on the charger. I left it for a couple of hours but nothing happened, the content level stayed at 4 LEDs, i.e. the battery is not being charged. Repeated this with the charger directly connected to the battery - same result. I have checked the battery externally with a meter, the pins are un-numbered but referring to the charger cradle as pin 1 on the right, 1-2 is 36.4V, 1-3 is 2.8V, 1-4 is 2.8V and 1-5 is 0V. I also checked the cradle with a meter; 1-2 is 0V, 1-5 is 4.8V ( there are only three pins on the cradle). I think the charger is supposed to handshake with the BMS in the battery and then initiate charging - is that the flicker of the battery LEDs? Looks like the handshake is failing. If so, why? Duff cell? If there is a failing cell or group of cells, wouldn't the battery performance be affected? The battery seems to be doing its job OK. I've seen mention on this forum of a thermal fuse on the BMS board, is that a possibility? Or a duff BMS board? What should my next troubleshooting move be? Dismantle the battery to check the cells or cell groups? Does anyone have map of the access points to test these? Thanks for taking the trouble to read this, any help would be welcome!