Trickle chargers on dual battery cars (’72 Porsche 911)
filed in Misc Car Questions
Question: I have a ‘72 Porsche 911 that is under my care. It doesn’t get much use, >especially in the winter months, so I thought it would be a good thing to >attach a trickle charger (ala Battery Tender) to the battery. Thing is that >the car has two batteries. Is it possible to attach a single trickle charger >across the two batteries or must I accept the fact that I will need two trickle >chargers.
>Also, I would like to know why this car has two batteries. The only car I’ve >ever come across that has this unusual feature. I wouldn’t think that the >Porsche engine is that hard to crank over.
>And while I’m on the subject … it’s a real bear to get the car started. The >routine is to pump the accelerator several times, turn the ignition on, crank >for a few seconds until it almost catches, repeat 3 or 4 or more times until >the engines finally catches. Seems to be something to do with the choke, >problem is I can’t seem to locate a choke linkage. I can pick out the >accelerator linkages easy enough, but can’t seem to find the choke linkage. >Any pointers?
Answer: Are they two 12-volts in parallel, or two sixes in series? I wouldn’t know why Porche would do it either way, except for balance/packaging, etc.
If they’re in parallel (probable), you can hook up the trickle charger to one of the batteries, and it’ll “trickle” on over to the other one too (assuming they’re both in ok shape).
It might be a good idea, however, to disconnect each individual battery from the system and charge it for a week… like every spring. This way the weaker of the two batteries won’t get all the attention.
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