I've started talking to a robotics guy I know from the local EV club about how we can use the balancer's warning to trigger some sort of pack disconnect. IMO this is pretty simple thing to do and can be done without cutting anything, and very minimal rewiring. I'm just not an electronics guru, so I need help to put it all together.
My current thought is to use a simple
VOX circuit (microphone activated switch) that is triggered by the buzzer on the balancers. The VOX circuit will feed a signal to a programmable micro controller (the
arduino is what I'm familiar with and its cheap). The micro controller will then control a relay to disconnect the pack from both the charger and dc to dc converter. This allows protection from both over and under voltage.
Once the pack is disconnected, we need to reconnet it somehow. But, with the arduino, we can do pretty much anything with it. We could wait an hour then reconnect the pack, hoping that the balancers have pulled the high cell back down and continue to top off the pack. As soon as the buzzers go off again, it would disconnect for another hour. Another alternative is that we could wait for a manual signal from the user to connect the pack again. This signal could be from another switch added up in the dash area, or even from turning the phev system of and back on (this would require tapping into the phev switch). At that point, the pack would be reconnected and ready to go.
The setup would cost less than $50.
The drawbacks of course are you are stuck with the balancer's set voltage points. Personally, I'd like to adjust them a little bit. However, this is a quick fix and I'm hoping Enginer eventually comes up with something on their own.
Thoughts?