16 Cell Multi Slave Board

Threads relating to the BMS system begun by Peter Perkins

Moderators: GregsGarage, retepsnikrep

lonestarrpm
Posts: 2
Joined: Tue Aug 23, 2011 9:51 pm

Re: 16 Cell Multi Slave Board

Postby lonestarrpm » Fri Aug 26, 2011 3:47 pm

Does anyone have a 16 cell slave board kit?

Or at least the boards printed up?

I know there is a 48 cell system built up for sale and I would like
to add 1-2 more boards

So I'm trying to find 1 or 2 boards either already made up or the board and possibly
components to make up myself.

Mike

User avatar
retepsnikrep
Posts: 1387
Joined: Sat May 26, 2007 4:50 pm
Location: North Yorkshire England
Contact:

Re: 16 Cell Multi Slave Board

Postby retepsnikrep » Fri Aug 26, 2011 3:58 pm

Where is there a 48 cell kit for sale? Why? Who?

I do have a couple of spare 16 cell boards built.

Peter
Regards Peter

Two MK1 Honda Insight's. One running 20ah A123 Lithium pack. One 8ah BetterBattery Nimh pack.
One HCH1 Civic Hybrid running 60ah A123 Lithium pack.

isaac_alaska1
Posts: 100
Joined: Sun Apr 03, 2011 7:41 pm

Re: 16 Cell Multi Slave Board

Postby isaac_alaska1 » Sun Sep 04, 2011 3:05 am

the batteries i'm building this system for are 5Ah turnigy lipo cells. each of 9 string is going to be tied together at the cell level, so each "cell" that the bms sees will be a 45 Ah cell. the bypass load transistor spec'd for the boards is good for up to 5 amps if used with a heat sink. assuming each one gets a heat sink, and the load resistors are all mounted off-board (i'm envisioning a load center consisting of a big heat sink/fan combo somewhere near the exterior of the battery box) does anyone know what the current limit of the board is? even at 2 amps with 48 cells in a string, it would only be about 400 watts of heat dissipated, which i think i could handle. i'm not sure if the traces in the board will handle 2 amps though. how bout 1 amp? this would be enough to balance the entire pack in 4.5 hours if they were off 10% from each other.

User avatar
retepsnikrep
Posts: 1387
Joined: Sat May 26, 2007 4:50 pm
Location: North Yorkshire England
Contact:

Re: 16 Cell Multi Slave Board

Postby retepsnikrep » Sun Sep 04, 2011 5:53 am

If you are talking about my 16 cell or 25 cell slave boards I would say each on board resistor should be limited to 500ma max. If you start pulling higher currents it may interfere with the pic due to the associated voltage drops in the rats nest wiring. The heat of course is another issue.

If you match the cells well for capacity etc and do an initial manual balance on the cells then 500ma will be more than enough for a short period of daily balancing at the end of a charge cycle. I've been using my BMS for nigh on three years now on a daily basis. My 40ah cells are still very well in balance and my 20ah cells balance within about 30 minutes at the end of a charge using 300ma balance current.

I note you are using LiPo cells. You may have to adjust the voltage levels in the various software modules and recompile it using pbpro for you batteries as they are not the same as Lifepo4 :shock:
Regards Peter

Two MK1 Honda Insight's. One running 20ah A123 Lithium pack. One 8ah BetterBattery Nimh pack.
One HCH1 Civic Hybrid running 60ah A123 Lithium pack.

isaac_alaska1
Posts: 100
Joined: Sun Apr 03, 2011 7:41 pm

Re: 16 Cell Multi Slave Board

Postby isaac_alaska1 » Sun Sep 04, 2011 6:44 am

okay, that's good to hear. i'll probably for a half amp, although i still want to try to move the load resistors off the board. when i used the minibms system, the heat from the load resistors would affect the resistance values of the rest of the board, and throw the voltage measurements WAY off. would be nice to move the heat off the board.
I'm going to have a ton of stuff to learn about programmming these, as all of the chips i will be using aren't programmed yet. (since i still need to acquire pics for the master and 3 slave boards.) i figured i would try to get the boards mostly built up before i started hounding everyone on what i need for programming. i'm guessing i will need to download the software from the site here, and get something that the chips fit into for programming them?

User avatar
retepsnikrep
Posts: 1387
Joined: Sat May 26, 2007 4:50 pm
Location: North Yorkshire England
Contact:

Re: 16 Cell Multi Slave Board

Postby retepsnikrep » Sun Sep 04, 2011 6:52 am

All the info you need is in these threads :wink:
Regards Peter

Two MK1 Honda Insight's. One running 20ah A123 Lithium pack. One 8ah BetterBattery Nimh pack.
One HCH1 Civic Hybrid running 60ah A123 Lithium pack.

GregsGarage
Posts: 870
Joined: Tue Apr 01, 2008 5:27 pm
Location: Galashiels, Scottish Borders
Contact:

Re: 16 Cell Multi Slave Board

Postby GregsGarage » Sun Sep 04, 2011 12:40 pm

isaac_alaska1 wrote:the batteries i'm building this system for are 5Ah turnigy lipo cells. each of 9 string is going to be tied together at the cell level, so each "cell" that the bms sees will be a 45 Ah cell.


How are you going to parallel the cells? There is a potential fire risk if you are planning to use the balancing leads on the packs for this as they tend to be quite small and a problem in one cell can see very large currents through the balancing wires. This could overheat the wires, potentially causing a fire.
Greg Fordyce

Daewoo Matiz
http://www.evalbum.com/4191

isaac_alaska1
Posts: 100
Joined: Sun Apr 03, 2011 7:41 pm

Re: 16 Cell Multi Slave Board

Postby isaac_alaska1 » Sun Sep 04, 2011 8:46 pm

i'm going to be building a bunch of fuse boards, each board will have a connection to attach the bms, 9 connections for the batteries, and 8 fuse banks. since the packs we're using are already configured in 6 cell units, each fuse bank will have 6 fuses. so these boards are gonna have 48 fuses each. and there will be 8 boards. LOTS of fuses, but i can't think of a better way to do it. any thoughts?

GregsGarage
Posts: 870
Joined: Tue Apr 01, 2008 5:27 pm
Location: Galashiels, Scottish Borders
Contact:

Re: 16 Cell Multi Slave Board

Postby GregsGarage » Mon Sep 05, 2011 8:19 pm

Have you had a look at http://endless-sphere.com/forums/index.php? Lots of people using RC cells to build packs. Look out for user Jeremy, he has experience with the pouch cells and is active here and on the ES forums.
Greg Fordyce

Daewoo Matiz
http://www.evalbum.com/4191

GregsGarage
Posts: 870
Joined: Tue Apr 01, 2008 5:27 pm
Location: Galashiels, Scottish Borders
Contact:

Re: 16 Cell Multi Slave Board

Postby GregsGarage » Mon Oct 24, 2011 3:44 pm

I noticed that cell 5 of my pack was getting ahead of the rest of the cells, so a bit of investigation using command 7 showed that the load wasn't switching on. Removing the board and examining solder connections didn't reveal any obvious dry solder joints. Turned out that it was a solder joint, but it would only go open after heating up a bit. Seems to be working now that I have gone over all the solder joints with the iron.
Greg Fordyce

Daewoo Matiz
http://www.evalbum.com/4191


Return to “BMS thread”

Who is online

Users browsing this forum: Majestic-12 [Bot] and 23 guests