Battery Issues

[Ceowulf]

Hello everyone,

I've had a Cyclotricity Revolver now for a little under 1 year and for the most part it has been great. No real problems aside from the usual bike maintenence of brake, gears and such....aside from batteries...

First time it happened was around 2 months after I bought it, LED display and bike just lost power, battery still had plenty of charge and was showing 4/5 green lights on it's inbuilt meter when I pressed the button. Got home and charged it, charger acted normal, was red for an hour or so and turned to green indicating it was fully charged. Put it back on the bike and after a few seconds the bike was just cutting out and going dead. So I checked the voltage myself on the battery with a meter and it was only showing 31.2v when it should be fully charge. Presumably the bike was cutting out with any load on it because it just wasn't getting enough volts.

Cyclotricity were great about it, replaced the battery within a couple of days and I was back up and running... for two weeks, then the exact same thing happened again! So back to cyclotricity to explain the whole situation and they agreed to send out another battery, took a little longer this time, a week or two to get the new battery along with a new charger incase that was causing any problems. After that everything has been perfect again up until now.

Fortunately I'm still just inside warranty but the exact same thing as the other times has just happened again. Have I just been really unlucky with batteries? Could something else on the bike be causing the exact same problem to occur on multiple batteries? This would be getting awfully expensive if I wasn't inside warranty and having to replace these batteries at full cost myself, which will be the case if it happens again.

- The battery is showing 31.2v right off the charge, and switched on.
- The charger itself showing an output of 41.9v.
- The charger also seems to be charging, first being red and then changing to green. (Though now it's just green as it's fully charged, or atleast acts like it is)
- Lights/Indicator on the battery itself show it's fully charged when the button is pressed, until I try to use it on the bike and it cuts out, then it has no lights.

Thanks!

 

[Deleted member 4366]

Do you often run your battery completely flat?

 

[Ceowulf]

Never, aside from once or twice when I first got them as Cyclotricity advised it should be done, not that I'm convinced it has much benefit.

Always charge after everytime I go out, usually not even below 50%.

Also used quite often, battery is never left sitting for long periods without use, occassional week at most.

 

[Deleted member 4366]

It looks to me like the BMS is shutting off charging for whatever reason. I have a bottle battery like that, so probably a BMS fault.

If the battery was out of warranty, I'd short out the charging FET so that it's on all the time. Then, initially and maybe every couple of months, check the cell voltages are nicely balanced. There's a bit of a risk in doing that because you would over-charge a cell if it was out of balance. In the worst case it could cause a fire, though unlikely.

 

[CycloTricity]

Dear Ceowulf,

Thanks for pointing this post out to me by email earlier (I have a bad habit of drifting away from Pedelecs from time to time, so it's nice to be dragged back in ).

Sorry for the hassle with the battery, I know you must be nervous now that the warranty is soon up. But please rest assured we'll support you in one way or another as we're aware of the history of this case. (Even if the warranty is over, it's worth getting in touch if you have issues, we always try to work something out).

Having said that, I'm not convinced it's the same problem that you experienced in the past now reading the symptoms you mentioned. I believe one of the switch wires might have merely come loose. If that happens, the circuitry will only give an output of 31V as that is the case when the battery is switched off. The LED indicators will stop working and the charger will stay green, which matches with your description.
An easy way to verify this is to take a voltage reading once when the battery is on, and another reading when the battery is off. If both read 31V, chances are the switch is simply not connected and needs to be soldered back on. It's a simple fix, you can do this yourself if you are happy to do so, or you can by all means send us the battery and we'll do it for you.

Hope this helps.

Regards,
Rami