I have an android head unit that suffers (like most stereos) a power drop/fail on starting the car. While the unit is engineered to retain OS power for a few seconds,
- the dvd player has to restart, and
- (more importantly) the bluetooth restarts, momentarily dropping the connection with the ODB adaptor and resetting trip calculations in Torque
So I'm thinking of adding a smallish SLA battery (6Ah) for 3 purposes:
- Keep the stereo powered for engine starts
- Keep power to the head unit (it has an off mode that disables everything incl screen, but keeps android running)
- Enable running for shortish periods for "normal volume" music etc (1-30 min)
I'm not wanting a huge outlay or vehicle modification, so am considering:
- cutting the existing stereo power and making a power triangle:
- diode and 1A fuse from car battery to aux for charging (but not overcharging)
- diode and 5 or 10A fuse from aux batt to stereo to for power
- diode from car batt to stereo to stop the aux powering other circuits
- Earthing negative.
Will this work well? Will an SLA overcharge and gas off at car voltages? How much does a SLA demand at different charge/voltage levels? (Mainly my google foo is not helping, and gives me what a charger "should" do - interested in charging fuse size and battery longevity.)
Also, I'm having trouble finding 10A diodes - It seems I could use a bridge rectifier for my scenario as well - yes?
Note: I'll get my ammeter out and update with my expected current usage scenarios tomorrow