Old BMS General Thread

[boelle]

so far i only miss d1 and r2... every thing else should be in place

now i only need to tell the damn program what walues each component has

latest version atached... use the pcb123 from sunstone.com

hmm.. how do i attach files?

EDIT: for now those who want to have a look at my files will have to ask for them by e-mail.. dont have webspace ready yet

[retepsnikrep]

Please post images of your schematics, you should be able to export your schematic to an image using the pcb123 software. If it exports to bmp files please convert them to jpeg so we can all view them. I think you can even post/upload images on here.

The resistor which feeds the voltage reference diode can be increased to 100k to reduce circuit current consumption.

[boelle]

well the pcb123 cant do much export... but i can print it to a pdf... but that dont help much since i cant attach anything to a post like this.. but hold on and i will arange some webspace

http://tina-og-bo.dk/slave.123
http://tina-og-bo.dk/Enter%20design%20title%20here.pdf

Edit: updated to include digi-key part numbers (not complete yet)

anyone that have time to cross check that i have choosen the right parts?

i might have choosen small tolerances that is a waste of money

[boelle]

the pcb123 file updated

d1 and r2 is missing... i need the digikey part number for both and package type for the PCB layout

still i would like someone to go over all the part numbers to see if i have choosen the best ones considering price/quality

/bo

[retepsnikrep]

Pulled my own Lithium pack out today after getting increasingly frequent Over & Under Voltage audible alarms from my BMS. Seems cell 30 is U/S and has developed a very high IR and is unable to accept any charge. Now waiting for a couple of spares from the supplier. After nearly 8,000 miles a failure is a bit annoying but not the end of the world, and a 2% failure rate if the rest are fine.

The system did it's job thought alerting me with increasing frequency that "Houston we have a problem!"

I was able to identify the faulty cell by watching the pack as regen/assist was applied. The over/under V leds would come on the faulty cell while the others remained off!

Had I completed my digital upgrade the dash screen would have told me which cell it was even earlier, must get on with that!! But I'm off on holiday to Shetland/Scotland soon for three weeks so need a quick fix for now!!

One pic showing Pack on bench and note cell 30 is first one lit which indicates the fault originated there and was forwarded round the pack to the audible warning.

http://www.solarvan.co.uk/insight/Cell30Failure.jpg

Bench testing of the cell shows it goes Over V as soon as any charge (>1A) is applied and is unable to hold a significant discharge load

Sorry Boelle just too busy at present to look at your stuff in depth.

[boelle]

no problem... i will go over it today and update files later

EDIT: Files updated... think i got it all except R2.. all footprints should be ok

what tolerance should be enough for resistors and the caps?

just to be sure but is http://www.solarvan.co.uk/bms/BMSProject041208.zip the latest stuff?

should there not be temp sensors for each cell?

[retepsnikrep]

I used 1% resistors as that's what I had, standard for caps it's not critical.

The schematics you are using should be latest, there may be slightly later software especially for the Master but you don't have that. Just check the thread.


Update

Swapped out my failing cell and now seems to be working OK again. May send it back to Hipower so they can have a look at it. Be interesting to see why it failed

I've been a bit luckier than Greg but also my cell failue could be completely different from the issue which caused his fire, who knows.

[boelle]

ok, i will go over it once more and update files

sunstone have agreed to have a look at it also to make sure footprints fits componets

but i think it's almost there, once complete i will have a go at the master (just for the fun of it)

but regarding temp sensors, do the master only support one ore one at each slave? or is this an upcomming feature?

[retepsnikrep]

The master can support upto about 4 I2c temp sensors at present, as each takes about a second to access.

The master takes temp readings every minute in the curent software.

You could have more but you will pay for it by slower cell voltage scanning etc. Plus you will have to modify the Master software to accomodate them.

I use two sensors at present one in each block of cells.

If you want one per cell that's a big ask and probably needs an independent system just for that!

I personally am not sure about individual cell temp readings, as unless the sensor is actually inside the cell you get the ambient or the cell connector temp not necessairly the internal cell temp which is what you need.

I suspect the Master will need a lot of work on software as it's designed for lithium cells and the data transmitted between the slaves and master is a single byte which covers a 0-2.55v range. I don't know what the working voltage range is for your cells?

[boelle]

maybe mod each cell... how far can you drill from the top before the cell is "open" ? then fit a sensor and fill with epoxy glue.... just a crazy thought....