Battery Vehicle Society

I will try it again with .1mS timing when I have finished wiring the car. I have done some hardware changes in my system. Instead of the LCD display for the master I am using an ASUS EEE PC. I have connected the serial output that normally goes to the SV2000 chip to an RS232 chip (Max232) then to a ...

That was only using one slave, should that cause a timing issue?

I wasn't able to get the software running on my system with the 0.1mS pulse width. Changed it back to 1mS and all worked fine.

I had a look at the pulses with a cro and it looks like the bus capacitance was too much to accurately detect a 100uS pulse.

I am in favour of relaying the slave and master boards with a proper ground plane surrounding the components. This greatly reduces EMC issues with boards. I can do it if you like, at no cost. I just need the original layout files.

Do you have historical data for that cell? Was it showing signs of being weaker than the rest of the pack?

Maybe if we can isolate the preliminary signs of failure we can do something about it. Unless of course it is a manufacturing problem.

Yes I think bottom balancing will have to be a planned event. You can probably work out fairly accurately how long it will take to balance the strongest cell by logging the SOC of each cell. It is then a matter of taking the car off the road for the total time it takes for the balance + the charge. ...

Good points made from you both. As you said there is a fair bit of evidence that regular balancing is not required. I think I will rem out the top balancing part of the code and just use the bms as a monitor. If and when I get to see any real unbalance at the bottom of a discharge cycle I will try a...

So when the charger goes from constant current to constant voltage stage the charger current is still above what can effectively be bypassed with the load resistor. This will allow the voltage of those cells that are being bypassed to continue climbing, presumably to the point where the AbsMaxCellVo...

I am not advocating removing the need for a cell voltage monitoring system. If you look at Jack's blog he is also now saying that a voltage only monitoring system is not effective in determining the SOC of a pack. However the method of balancing cells using shunt balancing during charging does not m...

The idea of bottom balancing is that all of your cells reach bottom at about the same time so you are less likely to get stronger cells killing the weaker ones. The bottom balancing idea can still be done with your design. It would mean doing a balance at a time when you know all of the cells are ap...