I'm thinking of adding an additional battery to my 99 Chevy Tahoe. I've been reading a lot about isolators and relays. I want to go the right direction but I would like not to spend a lot of cash on an isolator since a 200 amp relay is much cheaper, as far as I've seen doing research. I'm looking for any ideas as to what I should use and any other suggestions. Thanks.
The best way to add a second battery is to relay a pair of IDENTICAL batteries together so they connect in parallel when you move the ignition key to 'ACC' ... if they only connect when the car is running, or about to be running, some of the bugaboo problems with batteries draining off each other will be negated so you can get away with using different batteries.. but this isn't ideal. You really want to use identical batteries that are the same age.
If I were you, I'd go seriously out of my way to wire the batteries together with a relay.. you'll get a bit more voltage at the amps... using the isolator will cost ya a good volt or two.
Paralleled Yellow Tops are unstoppable.
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"I'm finished!" - Daniel Plainview