Battery Vehicle Society

Sounds like you have been a bit unlucky. looks same and should work. Not same vendor so could just be a dud! Are you happy with the 12V supply for it. Do you get the blue screen?

Their spec on the input voltage is 12 volts +/- 10% which seems too tight to operate in an automobile. However, I was powering it from a regulated 12 volt supply.

No, I don't get the blue screen. That is how I originally knew something was wrong. I put a meter across the two power leads and it shows an open circuit.

They say they have shipped me a second unit but I am waiting to confirm via a tracking number.

Rick

I suspect some Chinese soldering and a wire off inside unit

That is my guess also but I wanted to see if they will send me a replacement before I open it up and start checking their work.

Well I have this working on the bench with my 50 cells pack. Couple of glitches in that test software I posted a few days ago I'll update it in next day or so when I've finished testing.

I've learnt a few things.

I measured all my cells first with DMM all at 3.33 or 3.34V

Master was reading high due to the feeble 10k pull down resistor R8 on the master board. This meant the Master Bus pulse decayed slowly elongating the high period causing a higher voltage to be returned. I have changed that to 510R for a much better cut off. I suggest those using the serial comms also change this resistor. It may well help at 4800 baud.

Sending the CellVoltage variable as discussed gives reasonable results but the Master does give some variation of upto 75mv on received values. I suspect that is due to individual clock speed and timing variations between the 50 picaxe chips. I hadn't considered this.

However when I multiplied pulse length x 10 and transmitted that the error was down to the theoretical limit for the BMS about 25mv. So that seems OK.

Transmission error detection works fine as I pulled the jumper on a couple of slaves and it told me straight away which slave had a problem.

So to crank up the transmission speed I could go back to the sending half the data routine, which would half the length of the pulse.

I could also store the data as before in the Picaxe RAM whilst executing a simple loop however this limits the number of cells to 128.

With the new software the numbers of cells is now limited to 255, but could be unlimited if reqd. Hmm?

retepsnikrep wrote:However when I multiplied pulse length x 10 and transmitted that the error was down to the theoretical limit for the BMS about 25mv. So that seems OK.

So to crank up the transmission speed I could go back to the sending half the data routine, which would half the length of the pulse.

Peter,

Maybe try other multipliers beside 10x to cut pulse length. Find the smallest multiplier that still gives reasonable accuracy. It may only need 2x or 3x, but trial and error will tell what works best.

Greg

I'm going to leave it as is at the minute it still manages to do 50 cells per second so I'm happy enough. Using x10 multiplier means the data still makes sense in debug mode as well. 3.60V becomes 360 or x10 = 3600

Works OK in car until I start it then get an Over V error need to look at that in next few days. Had enough for today.

Master is not crashing due to spikes like it was before in the Insight which is good, but I am getting over V alarm so have to look at that with scope. I can see it cycling round cells OK thanks to the slave Leds. So some progress must have cured some interference. I've arranged it so I can get at it all now anyway to tweak the Master.

I also have a spare slave I can put in an accesible position as fake cell 51 for testing. Powered by a variable psu I can test the over/under V Master response etc. It doesn't actually form part of the high voltage chain just the data chain.

Hi Peter,
I have bought some clip on ferrites to use on the data cables (cat5) on my BMS. Perhaps these would offer extra protection for your insight interference problem?
These are identical to mine but I got them at £1 each
Item number: 250456860850
Just wish I could clear up my mechanical backlog and get properly into the BMS
Got the Zivan though

Keep at it Dillond! Thanks for the ferrite advice but I think it is sorted now.

Here is the latest Master software. It's been extensively re-worked.

www.solarvan.co.uk/bms/MASTER_SERIAL_04 ... 00BAUD.txt

It has been greatly simplified and adapted for the LM335 Analog Temp sensors it should work OK. Just waiting for my LM335 chips to arrive tomorrow to test that part.

I saved over 1000 bytes by removing lots of rubbish!

Now only using about 1500 bytes of a possible 4000.

Hopefully it is a bit easier to follow as well now.

I may well start on Master Board MK2 soon to incorporate the changes I have done for the masses.

It will feature I2C & Analog temp sensor inputs for a start.

Any not too hard aditional features reqd.

retepsnikrep wrote:Any not too hard additional features reqd.

How about a motor rpm input. A software routine could be added that prevents the motor from over-revving.