4 to 24-cell Battery Management System (BMS)
I thought some of you would be interested in the 4 to 24-cell Battery Management System (BMS) that Gary Goodrum and Richard Fechter have been working on over on Endless-sphere.com so here's the latest. The new boards are in and they will be selling them on TPpacks.com and should be available for purchase Monday 3 November 2008. From my understanding they will be selling the bare board with the parts list and assembly instructions.
This BMS board is designed with channel flexibility, meaning you can build the board to have 4, 8, 12, 16, 20 or 24 charging and monitoring channels. Here is the board with 4 channels loaded;
- Click image to Enlarge.
Here is the board layout with all the channels;
- Click image to Enlarge.
During charging the BMS will monitor each cell in the pack and as the cell reaches full charge will decrease the current flow until it is off and the cell is fully charged. Each channel has a LED to show when the cell is charged. (see graphic above, orange LED) When all the LEDs are on the master LED will change from red to green and the BMS shuts off the charging current stopping the charge process. With the BMS monitoring the individual cells there is no need for a timer or you to shut off the charger when the charge is complete. To reset the BMS simply disconnect the power source and reconnect.
The BMS has a cut-off connection which is connected across the controllers brake switch to disable the controller when any cell drops below the minimum voltage. This will keep you from over discharging any one cell too far.
For more information on this BMS follow the link to Endless-sphere.com and read the post entitled "Even Newer 16-cell Battery Management System (BMS)"
Grandpa Chas S.
Here's a picture of the ver. 2.1 prototype. In the newest version of the boards, the junk with the red wires on the left has been incorporated into the board. As you can see, the control circuit is combined with the cell circuits for cells 1 to 4.
- Click image to enlarge.
Grandpa Chas S.
I ordered 2 boards and the parts required for them. They just came today!!! 
I am sorry I won't be home this weekend but I am taking a trip to look at a new milling machine to add to my shop so I can make some of my own parts. As soon as I can get the boards completed I'll let you all know how it goes.
Grandpa Chas S.
I have ordered two boards and parts as well, will take a couple of more days to get the parts though.
Have already put together one of Epeds design, works very well!
When the parts arrive I will be able to make comparisons...
Does anyone know the Mouser.com part number for the BD136 PMP Transistor (which replaced the KSA931YTA) that I should use for the BMS? I see six different part numbers for the ones that are in stock. I am ready to order the parts, however, I would like to make sure I get the correct part number for the BD136.
thanks.
4th+last try to post.Shorter version.Go to endless-sphere.com.You will fin this thread under batt tech.It's many pages,many of which I get lost.start there.Don't understand a part use search.e-s has huge archives.answers for anything you could imagine are in there.range from noob(me)to phd level ASK.I hold the record for dumb questions and it ain't stopped me yet.Goodrum +fecher are on there daily.If answers aren't basic enough just say so and someone will explainit simpler.People at V and E-S didn"t all wake up experts one day,they learned from others(and the gods of white smoke),they enjoy helping.A bms isused to keep the cells of batt as close to equal voltage as possible.If they get too far out of whack it shortens performance and life.A 3.7v cell max charge should be 4.2(this can vary) and the charger needs to slow,then stop charging each cell individually so the other cells can catch up and balance.The bms keeps charger from committing a murder/ suicide with your very expensive fickle lithium batts.Well thats a start.I'll get out of the way so someone who actually knows can step in.good luck,ask,welcome
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The BMS boards are going fast. I heard the first batch has sold out but you can still order for the next batch he has on order. They will just ship latter in the week.
Grandpa Chas S.