My partners and I are considering building a small, external battery unit (EPU) to supply battery power to our soon-to-be-born SR22. The idea is to put together 2 12v small car batteries in series with an attached battery charger, contained in a vented, wheeleable container. This would be prewired so as to avoided any confusion about attaching cables to the EPU. Aircraft Spruce and Specialty has a plug for $35 which should fit a standard aircraft external connection (correct me if I’m wrong).
I know there are electrical guru’s out there and would appreciate any advice on such a system.
I understand that electrical consumption while “tinkering” with avionics etc., not to mention an EPU engine start, is high and that battery capacity is limited. We are basing at a new (can you believe it!) uncontrolled airport outside RDU that has limited capability to provide a jump if needed.