- March 2nd, 2017, 7:53 pm
My new Ecto build has two batteries (like the last one did) and the best cure I found for the double dead drawback is to have some form of disconnect between the two. I preferred a manual one so if I killed the secondary, the primary could still run the car (and also not overwork the alternator). Plus, it really is hard to determine run time (I've found) as there are other variables. Age on the batteries and whatnot.
So far as in amperage, there's a lot of variables there. What is wired to what in the roof rack? What lights are you using? Their draw? Mine is wired so everything stock about the car relies on the front, while everything from the radio to the lights works on the spare. My two lightbars are rotators with halogens, and pull about 30 amps combined. Not including sound.
I got the biggest dual-purpose I could. They're meant to charge/discharge but also give that strong oomph when starting. Basically with the two connected the starter spins the hell out of my engine.
Finally, mine also has a built in permanent charger. It's under one of the seats and I can plug her in (so if you're indoors or have a place to run an electric cord from, it's a good idea) now downside is it's an older charger I had, and I'm not sure how many amps it supplies, and it isn't telling me lol it's a digital one. I know the older analogue ones usually run 1-12 amps, with a 50 amp start, but that wouldn't work for my 30 amp draw, unless I wanted to sit on 50 amps all the time and I don't.
Oh, one more thing, you may want to invest in a better alternator to supply all that power. I'm planning to wait until my stock one dies, then I'll replace it with a bolt on that does 120 amps at idle (stock's top power output) and at 1200rpm (cruising speed) over 200 amps. When my spare's down in the 60% range, the stock alternator tends to whine when I connect the two, so I just drive her home and plug her in inside the garage.
Hope all this has helped.