Old BMS General Thread

[retepsnikrep]

Been discussing with my pcb man and looking at quotes for the actual pcb.

Looks like I'm going for a 32 slave board non surface mount about 9x9"

Why 32?

Well the Master can cope with 128 cells as is, so that's four boards.

Why non surface mount?

Well my pcb man says that would only save about 30% size wise, and make it very difficult to self assemble.

You only have to populate the boards for however many slaves you need so as I have 50 cells i will have one board with 32 (full complement) and one with 18. Boards will stack on top of each other.

The 32 cell board is very cheap even including tooling costs etc, each bare pcb is only about £35. Cheaper still if I order more later.

[boelle]

so there is not that big difference in whatever it's SMD or not?

i was thinking about ditching useing the sunstone software, it's very buggy, just deleting a schematic page makes it crash, placeing a wire on the schematic and the same thing happens...

would it be possible to get a copy of the files you send to pcbcart?

[retepsnikrep]

I'll post all the files later.

I suggest you invest in the picaxe VSM schematic and simulation package then you can use and modify my original design/s schematics.

It doesnt produce the actual pcb files but i have a very experienced chap who does that for me.

Peter

[boelle]

well i was just thinking: what works for Peter should work for me so why not just get the same PCB as him , hence the reason why I asked for the pcb files (for the digital slave)

what was your price for a complete digital slave module? just to compare the price

[retepsnikrep]

About £5.00 each when completed with components. Less than $8.00 each.

Remember i can reorder slave pcbs anytime.

I used the below software to do the schematics, I then sent the netlist and schematic to my pcb chap with 40 years of experience who lays it out for me.

http://www.picaxevsm.com/

[boelle]

well, it don't take rocket science to figure out that an reorder is much cheaper

the cost for each slave is 74 $ when ordering 16 from sunstone, that do not include the picaxe and import duties etc.

i assume that it would be no problem to size up the board you have to fit on top of a 200ah cell?

what do you use for current sensor?

[retepsnikrep]

Boelle

Send Me your full name and postal address & I shall send you a slave board and the parts to make it up free gratis. Won't be till i get back home though in about 10 days.

Have a good read of this entire thread, I think all your other answers are there. The slave pcb was made to fit 40-200A hipower cells but the holes can be file/slotted to fit others no problem.

I used an Allegro hall effect current sensor -100 to +100A giving 0-5v output (2.5v = 0A)

[GregsGarage]

$74 + VAT for one slave board? Keep in mind that you can get Cedric's cell protectors for around £15-£20, so any thing we do should be less than that.

The current sensor is an area that needs to be addressed. I had briefly looked at trying to find a suitable current sensor for 500 amps. The main criteria is that the output needs to range from 0 volts (-500 amps) to 5 volts (+500 amps), with the midpoint of 2.5 volts for 0 amps in order to work with the Master board/software. Peter's 100 amp sensor suits his needs, what we need is to find some possible sensors that are available to measure larger currents. It should be simple to adjust the software for different current ranges.

I like the 32 cell slave board idea Peter. Of course if you have several battery boxes you can just partially build both boards to suit. The cell count and board size seems a very good compromise.

[boelle]

Peter:

I cant take that offer, major reason is that i have no EV yet nor cells, my effort to make an SMD version was to see if it was cheaper to have it machine build

the bank has told me that it will last almost another year before i'm worthy enough to expand the loan so that i can get an saxo

in that time the design might have changed more than once

Greg:

yep 74 US $ pr board... not including the picaxe, also not including import duties etc. since it's made outside the EU

[retepsnikrep]

Boelle You don't need a cell just a 3-5v power supply to clip the board too, then you can at least fiddle around with one to see how it works. Upto you.

I checked the re-order cost for the small slave pcbs, inc delivery to me 100 boards are about $2.00 each. The Picaxe chip is about $2.00 in bulk and the other components are a couple of bucks. Certainly less than $10.00 per board/cell. I could build up about three an hour.

Greg

Allegro do a -150 to +150A version of the sensor I used.

Lem certainly do 0-400A (0-4v) output devices. Software can be altered as reqd to suit choosen sensor, might need some pre-conditioning to move signal to 0-5v input range for Master.

or make your own.

http://www.siliconchip.com.au/cms/A_30551/article.html

I'm hoping pcb man will finish 32 cell slave layout this week, will order 5
boards asap hopefully have them by time I get home.