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Re: Lithium Battery Monitor 48 cell

Posted: Mon Jun 11, 2012 7:28 pm
by GregsGarage
See if Maxim did a demo board for the chip. That may have the answer you need in the documentation/schematic for it.

Re: Lithium Battery Monitor 48 cell

Posted: Sat Jun 16, 2012 7:57 pm
by dillond666
I found a newer revision of the datasheet which had clearer information. :)

I have linked to my schematic. Most component values have yet to be filled in.
The functionality is barebones. The MCU listens to the heartbeat of the BMS and if it is absent the alarm output will be enabled.
Hi and Low voltage thresholds are set on the pin headers next to the Maxim chips.
The MCU will also switch the charger on and off. MCU knows charger is plugged in because it gets its power on pin 2 of the power connector
and powers an opto on the MCU pin.
http://dillond1.pwp.blueyonder.co.uk/MaximBMS.pdf

Comments?

Derek

Edit : spelling

Re: Lithium Battery Monitor 48 cell

Posted: Sat Jun 16, 2012 9:23 pm
by GregsGarage
The fuses connected to pin 13 will need to be rated at full pack voltage in the case of a open in the pack wiring. Or you can fuse at all the cell connections, right at the cells, which you should do anyway. On my Matiz, I can easily isolate all 4 of my battery packs using a combination of contactors, big red button and removable fuse on a anderson connector. With your system I would have to disconnect the bms from all the cells first before isolating any of my battery boxes. But if you have a single battery box then this is not much of a problem.

Looks good though.

Re: Lithium Battery Monitor 48 cell

Posted: Sun Jun 17, 2012 10:08 am
by dillond666
Spotted a few errors,

Error on startup/shutdown circuit on left hand MAX11080 chip.
Changed the alarm output to a switched relay, I think this will be less troublesome.
Put in a link trace between the MAX11080 chip connectors and reduced three of them from 13 to
12 pin, this should help eliminate wiring errors.

Thinking of a cell connector solution but can't find much other than D connectors :?

revised schematic: http://dillond1.pwp.blueyonder.co.uk/MaximBMS-V0.1.pdf

Derek

Re: Lithium Battery Monitor 48 cell

Posted: Sun Jun 17, 2012 10:50 pm
by GregsGarage
How about the Mini-fit connectors by Molex and others. Maybe reduce the number of cell connectors to just 2, a male and female so you can't mix them up.

Re: Lithium Battery Monitor 48 cell

Posted: Sun Aug 05, 2012 6:36 pm
by dillond666
Nearly there! Just a little more worrying, checking and double checking.
I feel the scope for cock ups on this board are immense.
My cells are on the boat from China though so I'd better get a move on :shock:

Re: Lithium Battery Monitor 48 cell

Posted: Mon Aug 06, 2012 6:24 pm
by retepsnikrep
That's impressive.

You don't seem to have a GND for cell1 or am i missing something?

Re: Lithium Battery Monitor 48 cell

Posted: Mon Aug 06, 2012 8:12 pm
by dillond666
Hopefully you're missing something :wink: The cell numbers represent the connection to the negative terminal of the cell hence 48 and 48+ at the other end.
I've added some ground planes on the bottom layer, one for each group of 12 cells and one for the MCU bit. Board is 160 x 160. I did get the text on the silkscreen back to front on the prog/run jumper though :oops: .Final checks then it'll be beyond my control :shock:

Re: Lithium Battery Monitor 48 cell

Posted: Mon Aug 06, 2012 9:33 pm
by GregsGarage
dillond666 wrote:The cell numbers represent the connection to the negative terminal of the cell hence 48 and 48+ at the other end.


Interesting numbering scheme, Peter and I have always done it the other way round, label cell 1 neg, cell 1 +, cell 2 +, etc. but there's nothing to say we are doing it right. :lol: Glad to see it coming along.

Re: Lithium Battery Monitor 48 cell

Posted: Tue Aug 07, 2012 9:32 pm
by dillond666
I've modified the silkscreen to start at GND and let the numbers represent the +ve cell terminals. I suppose it does make a little more sense :)
Sent the files off to Iteadstudio, cheaper than PCB Cart but still ended up 3 and a half times the headline price :x
Really hope I haven't messed this up or It'll be the most expensive beermats I've ever owned :D