wjb21ndtown

Does anyone use a battery isolator? And, if you're using a battery isolator do you still need two switches for a two battery set-up? Also, can someone explain to me why you need two switches?

I have an issue that is driving me nuts. When my battery 1 is completely dead it draws down power in battery 2, sometimes to the point where a very live battery 2 won't start my boat. I will have both switches on "2," and still frickin' nothing. I know it that one battery is draining the other because I will pull the negative off of the dead battery and the boat will sometimes start, even without any additional support to the live battery. It's not that big of a deal, because I keep a jump box on board. However, it's annoying as hell.

I was at the auto parts store the other day and I saw that they had a "battery isolator" which is supposed to counter act my issue. The wiring diagram on the back suggested using one battery switch and the "isolator." It's supposed to prevent current from crossing over somehow, when the batteries aren't on "all." I would love to get rid of one of those switches if I could, but I want to make sure I'm doing it the right way.


On a side note. I'm upgrading my alternator from a 55amp to a 65amp, should I also upgrade the positive wire that goes to the starter? I think it is a 10 gauge from the factory, but I could be wrong. Additionally, my old alternator had 4 wires on it, and the new one only has one. Any issues with that?

HaxbySpeed

Tuck your old wires out of the way and run a single 6-8 gauge wire from the new alternator directy to the starting battery. Put your start battery on the switch and run all other loads off the other battery. Use a good isolator, I like Yandina, to join the positives together and you're set. It's sometimes difficult on older boats that have had lots of additional wiring installed to completely isolate the two systems. If you turn the switch off and power everything up anything that isn't working will be hooked to the engine harness and if it's a heavy draw item it should be moved to the house battery. Hope that makes sense. Typing on an iPhone is tricky..

wjb21ndtown

I understand where you're coming from, but you're saying that I should run the alternator wire right to the start battery, instead of to the starter like it is from Merc?


I generally start my stbd. motor first, then the port motor. Should I run one alternator to one battery, and the other alternator to the other?


If I'm using an "isolator" do I still use two battery switches? The isolator that I was looking at only had one battery switch in the wiring diagram. (If anyone can explain the need for the two switches I'd love to hear it)


If I tuck the other two wires away, are there any other issues (like the volt meter not working)?

wjb21ndtown

This is driving me nuts. I hooked up the new 65amp, 1-wire alternator, and ran a new 8 gauge wire right to the battery. I left the wire long to be able to run it back to the starter if I'm later advised to do so. Everything worked out great. I check the power out put from the alternator at the end of the wire with it disconnected from everything and it reads 14 volts. However, the gauge on the dash still reads 10-11ish (definitely below 12).

Both batteries are new this year, and both batteries read over 12.5 volts. I'm at a loss... Gage is bad?