Battery Selection

[Jimmycxc]

So basically, I have two red top Optima batteries in my car. One to power the car, and one to power the BTTF conversion items. They are run in parallel. Before the conversion, I had one regular lead/acid battery. Stupid me, did not realize that a normal battery tender would not maintain the charge of a gel battery. Long story short, with a failing alternator, essentially no battery tender and after 9 months, both my optima's are beyond repair and I need to replace them.

I don't have the receipts from when they were purchased so I don't think optima will replace them. If they won't, I'd like to go back to "regular" batteries and wondering if anyone sees any issues that may arise.

[David T]

I would set it up like they do in RV's, 1 bat for the motor and one for the BTTF stuff with an isolator so the alternator can charge both batteries but if you kill the BTTF bat you can still start the motor and drive the car. Or you can do it with switches, an isolator is more automatic. I would not have them in simple parallel.
David Teitelbaum

[Jimmycxc]

I do have a quick disconnect to separate the batteries when I am at a show so only the BTTF battery is draining when all the lights are on. When I bring it home, I'll put a battery tender on each battery. When the BTTF battery is fully charged, I'll connect them back together. But an isolator that does that automatically would be nice. I'll have to look into that. Thanks Dave. Do you see any issues with having two lead/acid batteries in the passenger compartment in terms of additional hydrogen fumes, as opposed to only one like normal DeLoreans?

[David T]

You do not want a battery loose in the passenger compartment. If you must put it in there get a battery box like they use on boats, fasten it down and vent it out of the passenger compartment. Manual switches are OK but it is too easy to make a mistake and drain both batteries. An isolator is the way to go. Some have a remote panel so you can override it and check battery levels. I would make up a plug where you just plug your charger in when you get home and it will charge both batteries. Again, look to the RV field, they have battery chargers that they use when they are plugged in and can be part of the isolator when on "shore power". Boats have similar, more expensive systems. They are also used on emergency vehicles (fire trucks, rescue vehicles and ambulances) when they are parked so everything is all charged up and always ready to go.
David Teitelbaum

[Jimmycxc]

Thanks Dave! Will check it out.