Battery Advice

[denwyn]

We have owned couple of Wisper 705 t bikes from new since 05/2017. One has the heavier duty battery, the other the standard. While the heavier duty battery is fine, I’ve noticed the standard one doesn’t seem to charge fully anymore, I’ve swapped the charger over and it’s the same with either. Do I take it the battery is on its way out. If so is there anyone who replaces the cells etc, or am I looking at having to buy another battery. We’re both self isolating with this conovid19 scare, and getting out in the country really stops us going stir crazy being stuck in the house.
Any help appreciated.

 

[denwyn]

Oh and the bikes have only done about 400 miles, always kept indoors, batteries charged regularly.

 

[Woosh]

the best thing for batteries is to get used as frequently as possible and they shouldn't be repaired, cells shouldn't be replaced unless it's a simple change of fuse or the BMS module inside.

 

[sjpt]

Try Jimmy (I never have, but well recommended) for recell of what sounds like a dying battery.

E-Bike Batteries

E-Bike Batteries

bga-reworking.co.uk

Contact him and he will tell you the options (may well have changed over the last few days!).

One reason for short life might be that you kept the battery fully charged too much; that isn't an issue often highlighted in e-bike manuals (if you had one at all). If it is not to be used for more than a few days it should be kept well under full charge. Too late to do much about that now, but might help looking forward.

 

[denwyn]

We were told when we bought the bikes to keep the battery charged. We never charged it after every ride, only usually when it was half discharged, never done a lot of miles just short trips, 8 mile max, bikes rarely used in winter. I will look into getting it re-celled, but will have to take into account postage is around £33 to send it. I may ask the shop we bought the bikes off if they have new batteries in stock, although there after service is very slow. Maybe its worth buying a new one direct from Wisper

 

[Amoto65]

Maybe its worth buying a new one direct from Wisper

That is probably your best bet.

 

[Nealh]

What does the voltage read form the discharge pins after charging ?
If it is less then 4.14v then likely it has a balance issue, it doesn't necessarily men the cells are shot.

It is possible the smaller battery is unbalanced so once a cell group reaches 4.2v the BMS takes ages to balance it up properly. The job of the BMS is to balance cell groups which aren't widely out of balance it uses about 60-100ma to carry this out and typically cell groups need to be within 0.01 - 0.02v.
What you can do is leave the battery somewhere safe for 3 or 4 days to see if it will balance the Green charged light will always remain green.

Even 0.01v difference can take about 10hrs to balance out once the main 2a charge has taken place.

 

[Nealh]

With batteries management is key so is use, only charge them up before a ride (up to 12 hrs before is fine). After a ride check the SOC (voltage) and if it is between 36 -39v then leave them at that charge until you need them again, If below 36v charge them up for about 40 - 60 mins to raise the SOC. If they aren't being used much check the SOC on a monthly basis and if need be just charge them for 10 or 15mins to top up any charge.