Battery Vehicle Society

What is the cut off voltage for your charging? My cells turn off the charger when the cells get to 4.04 volts.

How many hours in total had your van been charging for?

Over 4 Volts??
I think your last comment should go to Lithium cells catch fire.

I got as far as 3.338V before I unplugged it and went to sleep. I'm charging a 90kWh pack at 2kW! That was starting from 3.200V after 12 hrs. For testing purposes I have the alarm set at 3.340V and the cut-off set at 3.350V - HiPower recommended that the max cut-off be 3.85V which I will use only when I'm planning a long trip.

LiFePO4 has a lower max voltage than LiCo or LiMn which were 4.2V last time I looked. Beemer might be trying to scare you

Some numbers:

timpootle wrote:Beemer might be trying to scare you

Point taken. I ass-u-me'd LiFePo4's. Apologies.

Only one small thing. LiCo and LiMn's keep on accepting a Voltage/charge linearly until they bubble. Unlike Tim's that rise in Voltage from 3.45V with little current going in.

Cobalt and manganese are more flammable battery chemistries. They generally use the same electrolyte. BMS!

I'm sorry. seen too many battery fires.

This is a link to the batteries in my car

http://3xe-electric-cars.com/lithium-batteries-lifepo4-lifeypo4/winston-battery/winston-battery-160ah-lifepo4-lithium-battery-detail

If you can get the battery spec to open, you will see the recommended max voltage to charge is 4.00 volts. In my car the charge terminates at 102 volts - so for 25 cells that is 4.08 volts per cell. The BMS does a great job of keeping the cells in line towards the end of the charge ( I have been sad enough to watch it and sample cell voltages ).

My pack voltage is around 76 volts under full load from a full charge, obviously going down as the pack depleates. I have noticed that if I dont put the car on for a charge overnight, the following day the voltage will sag below 70 volts under full load, so I always have my car plugged in over night so I have full batteries in the morning.

When I broke the BMS and it went in for repair I was advised that one of the cells in the pack was weaker than the rest and that I should think about getting it changed - of course for a nice fee !!! I was told that they converted some of the cars with a 32 cell pack - taking the controller up to it's maximum working voltage, and they said that the cars had much better performance. I am tempted to get this done to my car.

[quote="mattcarr"]This is a link to the batteries in my car

http://3xe-electric-cars.com/lithium-batteries-lifepo4-lifeypo4/winston-battery/winston-battery-160ah-lifepo4-lithium-battery-detail

They are great guys - located in Wroclaw / Poland I know them. Imported of course from China.

Winston battery is no more.
Sinopoly is the same firm but now make them in black and a smaller form factor. Like the CALB topic I've just wrote earlier.

As your bms top balances please don't go near bottom charge. If you do the first weakest cell will hit 0V and the others will force it into reverse on your drive load. That means instant cell death. It will then heat up mad hot and blow. The rest I'll leave to you because its like spraying petrol around in a combustion engine after that.

I dont think there is any chance of me going totally flat as the BMS also plays it's role there as well. When the car gets to 25% SOC it then limits the car to 30mph which helps reduce the overall current draw, and when it gets to 15% SOC the car is then limited to 15mph - I have done this just to test and it works !!. They do say to make sure the batteries are put on charge within 20 minutes of getting to 25% SOC to prolong their life. My car is 3 years old soon and has covered almost 12k miles and as far as I can tell the battery pack is doing well. I hope to get several more years worth of driving out of the car before the pack needs replacing.

If things stay in the middle and never over stress those batteries they could outlive you to any mileage and I hope they do.

First big outing to the Bevob meet in Bristol was aborted when the "diode" warning light came on around Junction 16 of the M6. Turning the ignition off and on was enough to clear it, but I got scared of venturing so far from home and turned around there and then. The warning did not recur all the way home.

Some more numbers for your delectation:


The second-last line is interesting - 120Wh/mile. I am guessing the A56 through Sale must be more downhill than it looks.
Seems to be averaging 300Wh/mile on the motorway. I still need to know how much capacity the battery really has before estimating total range. I never did reach my test cutoff voltage of 3.5Vmax before I set off. That 102.1kWh starting figure represents about 3.42Vmax