Thread: Low cost BMS
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Old 07-06-2011, 09:17 PM   #3 (permalink)
harlequin2
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Quote:
Originally Posted by Simy View Post
Does this have a safety to stop itself from draining the battery on a failure? Also, the master controller is programmable correct? I would like data logging if possible as well as balancing/charging/discharging functions. When I get off work I'll compare the two boards but this seems like it is more of what I wanted. =)


To me a BMS should control the on board charger or be strongly integrated into it, talk with the motor controller/inverter and alert the user to any 'off' conditions.
It should output pack voltage/amperage, and should alert if any single pack is higher or lower then the others and try to keep it in sync. If one pack is consistently being a PITA the system logs should show it so we can get rid of the one misbehaving battery.
Yes, in the event of comms failure, the shunt is turned off. Also, the the cell voltage drops too low, the shunt is turned off. The board only draws 1/2 mA so it isn't going to drain the cell appreciably, the self-discharge rate is higher than that.
Everything is controlled by the master and data logging could be added easily. I'm using a laptop as the master at present, but working on a PIC based unit that will do it.
My charger has inputs that allow it to be cut back to 1/2A or turned off entirely. The easiest way to provide those signals, and one that is more or less "universal" is to use digital outputs from the master ie ON/OFF.
When you say "pack" I presume you mean battery - which is the name for a collection of cells connected together I thought a pack was a collection of dogs......
The master can calculate the battery voltage by summing the cells and compare this with the direct input from the battery so it can see if there is a big difference and alert the user to possible link connection problems
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