This info is great, thanks very much. I am well up for trying to find out more about what has happened. It will take me a couple of days to get hold of a meter and find a bit of time but would really appreciate the support.To explain more once the battery hits lvc or one cell group hits lvc the bms will cut power. At 40.6v it likely means one or two cells groups are out of balance so one/they are likely only charging to 3.5 or 3.6v each whilst the others are reaching 4.2v, the bms only balance voltages that are close so with in 0.01v.
So in use the cells will equally drop in voltage, whilst the weak/low group say is 3.6v and when it hits lvc say at 3.2v the others will be at 3.8v.
A battery is only as good as the weakest cell group.
Hi Bikes4Two, thanks for this. I will also look at the condition of the joints when I take the battery apart. I hope you did find the problem and you continue with no issuesFor what it may be worth, I'm going to throw in my 6-penny's worth:
The point I'm driving at is that my failure symptoms were not much different to those experience by the OP and in my case it was down to dry joints on the BMS.
- My rig is a TSDZ2 250w with a VLCD6 display (no voltage readout, just fairly useless charge indicator bars) and a 36v 10Ah bottle battery
- After about 900 miles of use, I had the odd power shut down
- Faffed around a bit trying to determine if it was a controller or battery issue
- After some time, I thought I'd found the problem which was the on/off switch in the base of the bottle battery but I was able to live with this as if the battery didn't power up, by simply removing the battery from the battery cage, it would power up and mostly stay that way - new switch ordered and so far so good
- And then my range dropped and I ended up cycling home a couple of times without any assistance- arh!.
- More checks and I realised that at times the battery was not fully charging with the voltage only getting to around 37.5v ish
- Time for drastic action and a battery strip-down and to cut a long story short I stripped out the BMS (a circular jobby located in the top of the battery) and inspected it only to find 5 dry joints
- 2 off them were for the on/off switch plug-in socket(the switch closes and puts a short across these two pins which in turn enables the BMS discharge function).
- another two were for the battery thermistor/temperature side of things
- and the 5th dry joint was the BMS -B connect point (negative battery potential) used to power the BMS- I re-wetted these joints and all the others too and shorted together the two pins for the on/off switch (I'm still suspicious of that switch).
- The battery took a full charge and on checking each cell group, the voltages were within 0.01v of each other.
- One test ride so far and more later this week. (update 25Jan - the 35 miler this morning was without issue - woop woop!)
Just saying
Use the meter set to DC 20v.
Find two needles or a pair of arduino pc pins, starting with the Black wire b-/0v and the one next door cell group #1 place a needle/pin in each female pin hole, probe the outer side of the needles for voltage and write it down as a #1.
Next move the first needle/pin from Black to the second White wire, apply the probes in the same way & write down the reading for #2.
Continue doing the same process all the way along the connector until you have ten voltage readings, then list them for us to see.