A123 28S3P BMS Board

[peterperkins]

I have knocked up a BMS board for the A123 28S3P packs I bought recently from china.

My board is exactly same size shape and connector position as OEM BMS.
It fits into OEM BMS position on cell packs and plugs straight into battery blocks using same elusive and expensive JST A123 connector!

First slave on each board also monitors the two OEM NTC thermistors in the end of each pack.
Once I get the boards back from china, built and software written and tested i'll report back.

I may have some spares as I bought 25 boards and have 24 of the white A123 BMS connectors.
It's based on all my earlier BMS work on the BVS forum.

https://docs.google.com/spreadsheet/ccc?key=0AgpwHXS5JE6adHk0VkVEX1FjaTM4QzFRVmk2aXBaWnc
http://www.batteryvehiclesociety.org.uk/bvsorguk/forums/viewtopic.php?f=53&t=3379

 

[arkmundi]

Which A123 cells? Nice job.

 

[peterperkins]

The vict power OEM battery blocks. You must have seen that thread

 

[peterperkins]

Well after a few minor glitches and issues now got 4 boards built and two up and running on my bench test setup.

Need to tweak the voltage calculations and i'm also going to use Darell Taylors PBPRO oversampling routine to get 12 bit resolution with the 10 bit adc.

This is pretty much my old circuit but with a greatly reduced component count and using the 12F1822 chips's own internal voltage reference to calculate the cell voltage.

Note this test setup is also using the minimal 12F683 mini master.

The boards fit perfectly onto the A123 blocks and the cells connections just plug straight in

The lcd picture shows the number of cells (28) and pack Voltage on the first line.
On the second line we have the number and voltage of highest V and lowest V cell.

View attachment 2View attachment 1

 

[circuit]

I'm more curious how the original A123 BMS looks and works... Does it operate on canbus? How does it measure the voltages?

 

[flexy]

Nice work, Peter,

Could this design be adapted easily to 16S 0r 24S say?

 

[peterperkins]

I'm more curious how the original A123 BMS looks and works... Does it operate on canbus? How does it measure the voltages?

We have no idea how it works, that's why I built my own to fit in the same space and take advantage or the pre-wired plug and temp sensors etc.
It looks like a complicated bit of kit and you can find pics of the pc boards on this forum if you do some digging.

It would need a new pcb and sourcing of the connector so not that easy to change it for the other oem A123 packs.

 

[Martini]

Hello Gianni from Italy I am new in the forum some questions ,

I am working around my ultralight electric motorglider , I still waiting from China one pack of 28S3P A123prismatic battery

In order to reduce battery weight I would modifiy 28s3P to 24s3P its could be possible for you ?

Reagrding BMS did someones found information regarding: http://mit-evt.blogspot.it/search/label/Prismatic
they finally found the right way to comunicate with original A123 BMS or how I can solve the problem of BMS ?

Also wich type of battery charger you use for 28S3P pack .

Thanks in advance for any replay

 

[peterperkins]

That info from the MIT blog on them communicating with the A123 OEM BMS is interesting but is over two years old and no other updates?

I use hacked meanwell 48V 350w power supplies for my chargers.

 

[oatnet]

Very cool PP, I am interested. 8) I assume 2 boards per 28s3p pack like OEM?

-JD

 

[peterperkins]

Yes it's two boards per pack. One each end.

I have now made up 8 boards which is all I need at the moment for my 4 packs. Need to start getting my packs installed into some projects now.

 

[peterperkins]

Finally got four of my boards installed on two of my 28S3P A123 packs.

Need to do some work on my master board software which is basically a 12F683 pic, serial 16x2 lcd, chgarge control relay and a button. It communicates with the packs and displays the cell voltages, controls the charger etc etc etc.

http://www.youtube.com/watch?v=vwLwNX7nsb0
http://www.youtube.com/watch?v=tggbji0xw84
http://www.youtube.com/watch?v=s_hESEXRy5U
http://www.youtube.com/watch?v=CMn0vQYpjCo
http://www.youtube.com/watch?v=bQEk6EMlVr0

 

[peterperkins]

Finally got two of A123 packs installed in my HCH1 Civic Hybrid.

http://www.insightcentral.net/forums/other-honda-hybrids-discussion/24304-hch1-a123-60ah-pack.html

Still work to do on the BMS and the connecting wire.