Adding 2nd 12v

when i used to do camper van conversions I'd do a second battery via an isolater, but in this instance I'd set it up with a switch so you use your second battery via an inverter and when that battery wears down you flip the switch so the inverter runs off the car's 12volt after you power the car up. That way you limit the use of your car's 12volt. Also if you can recharge you secondary battery via plugin charger at home you won't overwork your car's ability to recharge both 12 volf batteries, which would mean bad mpgs.

 

Fitting a second battery for your intended use would be a waste of time. The problem is that you want to run 600 watts for 6 hrs that is 600w x 6 = 3.6kw (3600w).

If you installed a second Optima rated at 36 amp/hr this would give you 432 watts (36 amps x 12v = 432 watts) or just under 45 mins of run time before needing to be recharged.

The only way round this just using the Prius is to use the Prius battery and leave the car in ready so that it is recharged constantly.

The current load for 600w at 12v is (600 divided by 12 =50 amps).

 

The figures quoted above are the absolute best you can expect from a new battery since the rate of discharge of a lead acid battery affects it's measured capacity.

The faster you discharge it the lower it's amp/hr capacity. I would expect no more than 25 amp/hr from the Optima at a discharge rate of 50 amps, there may well be a chart on their web site to give the actual figure.

The normal quoted amp/hr capacity discharge rate for most manufacturers is at a 20 hr rate. In the case of the Optima this would be a discharge of about 1.75 amps.

 

Exactly that. The Optima has a 35 amp/hr capacity at 20hr rate (1.75 amps) or 420 watts (35 amps x 12volts) and you wish to take out 600 watts a discharge rate of 50 amps.

 

To run the system just off 12 volt batteries you would need a battery or bank of batteries with at least 400 amp/hr capacity.