Re: Dual Battery re-visited Teamrush/CJDave &everybody
You are correct in the strictest theory, but the practice may be different...
If you have two new batteries, side by side, and the only time they are isolated are when the oil pressure is below 10 psi, then the logical thing to do is to swap the batteries around about every 6 months.
Proper battery isolators are temperamental, EXPENSIVE, and hard to tell when they have failed.
If you swap batteries about every 6 months, you will pull even enough on both to have them be reliable during their warranty lifetime.
This goes for any two like batteries manufactured about the same time.
All bets are off if you have a 'Mix-N-Match' setup in mind... Like a starting battery and a deep cycle....
Gell cells are a pain in the a$$, and the 'Six Pack' (looks like a six pack from the bottom) batteries are the worst.
The 'Jelly Roll' (layers of jelled electrolytes and flexible plates) rolled in a cylinder shape are the worst.
All jell cells have a problem with vapor discharge (they don't), and it can ruin the battery if the discharge is real bad.
You can buy gel cells that look like standard batteries for a lot less than the current crop of Jelly rolls.
(But since they look like any other batteries, a lot of guys won't want them. Not enough product recognition, but those guys pay $200 for disposable sunglasses too....)
Gell cells are not needed unless you plan to have the vehicle on it's roof on a regular basis... (I'm a better driver than that)
Find a liquid battery with good vapor and liquid recovery caps, and use it for $30 or $40 instead of $150 to $250.
With the 'Self Starter' wiring diagram we came up with on the other thread, anytime the engine is running, both batteries are used.
Anytime the engine is not running, (and alternator not charging) the batteries are isolated, and one is kept in reserve.
There are more complicated ways to wire it, but this seems the simplest....
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