one battery to two

[jamesnmlaw]

My 1969 had battery-ectomy sometime in the past. The passenger side battery was removed and the wiring sealed well both at the battery and to the driver's side battery. I want to put in two batteries.

I'll have to put a terminal on the passenger side and reconnect to the driver's side battery. I'm looking at a couple of Miata batteries, Marathons, from Battery Mart ($79.95 each). These are 12 volts, sealed, leak & spill-proof, made in the USA.

My question: will adding in the 2nd battery cause any problems other than some extra bucks for the terminal and the battery? I'm concerned about overloading (overwhelming?) the alternator. I don't have a radio in the car, no GPS, no a/c, but I have some TTG fogs and hood-mounted Cibies for the Close Encounters of the Third Kind nighttime experience.

Plus, I need the juice sometimes to wake the 2.0 in the morning, if not driven in a week or so.

Please keep it simple as I don't understand why electricity doesn't run out of outlets and onto the floor (plugs?).

Thanks!

[dicklague]

I have 2 of the Miata batteries in my 1973 and they are a terrific choice. I bought my first from a Miata supply company. Was $130 or so. Bought my second some time later from just and auto parts store and looked the same and was much cheaper.

You will have no alternator problems. Remember you are hooking the batteries up in parallel. that means red + to black - on both batteries. This will give you twice the battery capacity but the same 12 volts.

2 batteries are there for weight an balance reasons, but it is nice to have a spare. If you have a battery go bad, just figure our which one it is and disconnect it and run on one and get a new one at your leisure.