Battery issue !!!

[Nealh]

My 15ah Woosh 09 battery (actually Samsung 29e cells so 14.5ah to be correct) seems to be declining after just 14 months of use, noticeably the range seems to have tailed off to about nearly half and the charge in the last 2-3 months has been declining to 41v max the charger going from red to green and finishing its charge.
This morning before going out for xmas dinner etc, I opened up the casing to check battery cell readings from the JST connection block expecting to find a poor group and the following was recorded that surprised me a bit.
Cell block Block voltage Accumulative voltage
1. 4.1 4.1
2. 4.1 8.2
3. 4.1 12.3
4. 4.1 16.4
5. 4.1 20.5
6. 4.1 24.6
7. 4.1 28.7
8 4.1 32.8
9. 4.1 36.9
10. 4.1 41

Before I went out I was going to put it back together but pulled a switch wire off the BMS so decided to leave it for later. Back at home late evening I resoldered the loose wire and reconnected the JST to the BMS and bolted it back together, on a whim I plugged the charger back in and got a red charge light for about 35 mins checking the voltage the reading was 41.7v. To me it appears that the BMS was not charging past 41v and as can be seen balancing is not an issue, so me disconnecting and reconnecting the BMS seem to have resulted in the charge going up. I'm not totally convinced that the battery will get me near the range I am expecting but will have to see what happens on the next run and charge.
If I can get one is to change the 20a BMS with a higher 28a one or so, as all my controllers in use with the 09 are 18 or 20a and wonder if they are trying to draw higher peak rates then 20a and thus causing an issue.

 

[Nealh]

This does appear to seem to have happened Trex , I was going to charge each cell block manually to 4.2v but will see if a reset of the BMS has occurred with the next charge.

Reply to Trex's post which has now disappeared.

 

[Nealh]

The Battery after charging to 41.7v settled down over night and bled back to 41.1v so it appears that the cells are very uniformly balanced but have depreciated in capacity, I have also charged each cell group individually to 42v but again have all bled back to 41v so the battery has lost some useful life of about 25% when I compare the usable range. Another 09 type used alternately with this one is also a little down on range and appears to have lost 10-15% of its range charging to 41.4v, currently I am charging the cell groups individually as well to see what happens, both batteries are of the same age with the serial no's only being 3 apart one ending in 03678 and the other 03681.

 

[anotherkiwi]

How many km have you done with them over those 14 months?

 

[trex]

100% capacity corresponds roughly to 10V (from 41.5V to 31.5V or 42V to 32V), I think your battery has lost 0.6V at the moment. The problem may be at the other end, your controller may cut out before 31.5V. You will need to check the voltage again when it starts cutting out. A brand new battery will need about 600WH to recharge (including loss in the charger) from completely flat to completely full. If you have an energy meter, it's worth checking how many WHs are needed to charge yours back to full. If it's not completely flat, you can extrapolate, for example charging from 34V to 41V (7V out of 10V) will need 520WH for a new battery.

 

[Nealh]

How many km have you done with them over those 14 months?

Approx 3200 km, they seemed fine until I used them with the GSM unrestricted and this seems to have knocked the stuffing out of them a bit, I now can't rely on them a the mo to go on along ride with the BBS mtb as the cold will hurt the mileage to much so will see what happens after spring. The GSM will be run on 10s lipo from now.

 

[Nealh]

100% capacity corresponds roughly to 10V (from 41.5V to 31.5V or 42V to 32V), I think your battery has lost 0.6V at the moment. The problem may be at the other end, your controller may cut out before 31.5V. You will need to check the voltage again when it starts cutting out. A brand new battery will need about 600WH to recharge (including loss in the charger) from completely flat to completely full. If you have an energy meter, it's worth checking how many WHs are needed to charge yours back to full. If it's not completely flat, you can extrapolate, for example charging from 34V to 41V (7V out of 10V) will need 520WH for a new battery.

I would never expect them to go down to go down to 31.5 v the bms cuts off at about 34.5 v. Using them below 34v I feel would be even more detrimental to their usage and this is borne out with my bike lights using 18650's there power at 35v is really on the limit and brightness fades very quickly after this. Mileage wise I am getting 26 out of one and 36 - 38 maybe out of the other but that is cold weather miles at the mo so not to bad for aging cells and these are being used nearly every day.

 

[anotherkiwi]

Approx 3200 km, they seemed fine until I used them with the GSM unrestricted and this seems to have knocked the stuffing out of them a bit.

OK so it is an issue of hitting max Amps a little too often. I am pretty set on the GSMoon for my next build but will be running it restricted to 25 kph and 18 Amp peak. My current vote is for a shrink wrap Li-ion 20 A battery pack in a pannier bag.