Hi there - I need to combine together 3 lithium polymer battery packs. Each battery pack is a 4 cell (in series) pack, so the voltage of each pack could be as high as say around 18V, and I can't let it fall below
12V otherwise damage to the pack could occur. Once the battery pack is shut off I need drain on the pack to be brought to a minimum - I'd like it to be well under a milli-amp.Further, Each battery will be connecting to a separate (but identical) PCB. the PCBs will have 3 connections going between all of them - a power ground (the battery ground), ORed power high, and a low current switch connection (to turn off all batteries, regardless of voltage level).
I need to do the switching on the high side of the batteries, unfortunately. I need to protect the batteries from charging each other as that would (clearly) be less than good. So my first inclination is to have the positive side of my batter packs connected to the anode of a schottky, with the schottky's cathode connected to the source of a N-FET, and the drain connected to the ORed power supply. An unvervoltage protection circuit would be ORed with the switch line, and with some sort of charge pump that would drive the FET.
This would work. This is also a lot of parts - and I'm very space constrained.
I stated looking around and have found such a thing as an "N+1 and ORing Power Rail Controller". For example, the TI TPS2413:
This part won't work due to the 16.5V max bus voltage limitation, but otherwise, it looks like it handles... everything.
Does this sort of part sound like the right solution for me? Does anybody know of a similar part that can handle my bus voltage?
Thanks!
-Michael