Battery Vehicle Society

trying to figure out why one of the cells is staying so much lower than the other cells. it's actually 9 cells in parallel so it seems weird that one cell would affect it so much...but as i'm charging it the cell is only just barely coming up, while the others all came up pretty fast. i'm wondering if maybe the bms for that cell is skewed somehow...cause it's reading about 240mV lower than the other cells. but it's been getting worse over time. i guess i'll just have to pull all the cells out and figure out which of the nine is the bad pack.

unless anyone has a better idea

Is the load led on for that cell?

Is the load resistor hot to the touch even if load led is off?

Does the load resistor have any voltage across it when load led is off?

When you say one cell i assume you mean one block of 9 cells in parallel which appears as one cell to the BMS.

Reprogram the slave for that cell.

Check all the other components for that cell/slave.

What is the pitch between the contacts for the jumpers on the master board? I'm assuming 2.54mm. I'm trying to upgrade the jumpers to Molex Microfit connectors when everything is tested and wanted to check the pitch with you.

that's what i've been using. it's .1" which comes out to 2.54mm.

Hi,

I and others have taken over from Dan & Josh with the electric race car at Newcastle University. The learning curve has been epic but have thoroughly enjoyed learning about BMS's. We are at the point of been ready to test the BMS but are currently waiting for the SV2000 chips from America. We have to get it working fully by 19th October in order to design the new car (a deadline set by the University). I was wondering if anyone had any SV2000 chips that we can either buy or replace when we get the ones from America. This will hopefully give us an extra week to get it running.

On another note, we left a slave board connected to the batteries but not connected to the masterboard. The slave board got really hot. Should this of been ok and would there have been a difference if it was connected to the masterboard? What I don't understand is that surely it is the same as the car being turned off.

Thanks

The slave board should not get hot.

The 2w load resistors will get hot if a cell is bypassing current.

I don't think I have any spare SV2000 chips.

Please post some decent resolution pics of the BMS setup and battery connections etc

I don't have any SV2000 chips either. The Tellymate does the same thing but is not supported in the current master software. It could be made to work but will need some coding and hacking, not ideal when you have a deadline.

You need to find out what is getting hot on the slave. Bad solder joints can sometimes cause a load resistor to turn on, but don't leave the slaves connected to the pack until you find out why they are getting hot and are fully tested.

Thanks for the advice guys I will look into it and let you know. I will try and get plenty of pictures as well. Out of curiosity is the BMS still being developed further by yourselves or are you happy with what you've got?

We are still developing it.

I have two versions running for several years without issue.

One based on original picaxe chips has run for four years
One based on plain pic chips has run for over two years

I find I have a day free on Wednesday 17th October when i could come up if reqd.

Discuss it with your team and let me know asap.
I see some discussion also taking place on the BVS forum as well.

The pictures I asked for will help a will help a lot.

I have e-mailed Dorian who contacted me earlier.

Peter

Hi,

I believe Dorians email covered most of your last post. We are having one other problem regarding programming the PIC's. The cheap Asian PIC programmer has decided to stop working (voltage low error when trying to write to chip). So we bought a proper pickit 2 programmer but doesn't attach to the zero insertion force part of it. We see on the internet people programming them through a breadboard. How have you programmed yours and any hints and tips for us?

Thanks
Chris