So, I thought I had this all sorted, but now I'm kind of questioning myself.

I'm wiring up dual batteries, and I'm wondering if the isolation solenoid is rated high enough. It's rated to 250 amps continuous, but when I'm winching, the winch could potentially take up to twice of that. In fact, I believe the winch solenoid is rated to 500 amps. If I'm winching and connect both batteries, will this burn the isolation solenoid out since it's only rated to 250 amps?

I was also going to add a 250 amp fuse between the isolation solenoid and the two battery leads, but I would think I would need to up that to 500 amp if I looking at needing the larger solenoid.

Background: I've done the 'Big 3' and upgraded to a 150 Amp alternator previously.





This solenoid is rated at 250 amps continuous. Should I match it to 500 amps?


Here's some pics of the setup so far (click to enlarge images):

Bye-bye radiator shround...


Sits nice...


Gotta chop the fuse box leg...


All tidy and neat...

After doing some more nosing around, I read through some other dual battery systems and it seems that the fuses and the worry of the solenoid not handling the load may have been a non-issue. Seems odd to not have fuses on there though. This is from the National Luna instructions, which is a different kit than the one I'm installing.

Scott,

It looks like you have a handle on things, but I'll chime in hear with the ever popular "opinion".

First let me compliment you on the install, it looks good. Although I'm not a fan of having that many positive feeds come right off the battery, I do like the terminals and how clean you left it.

So my personal experience is the 250A solenoid will do the job just fine. If it is rated that high for continuous duty, it will be at least 150% for surge. That said even double that will be ok for short duty. I've had a 100A solenoid on my rig for over 15 years, been through 4 or 5 batteries in each location. I have a forklift style connector on my front bumper connected to the auxiliary battery that I use for jump starting, and I've used it ALOT. No doubt I've had 2-300 amps at least 50 times go through that cranking a dead player, and propably 5-600 amps a handful of times when the stubborn dead vehicle should have been shot instead of revived.

So after all these years, and POS Optimas, Interstate, Exide, Diehard, and no name batteries. I still have the same "standard ignition" solenoid.

Now for fuses, no problem. Careful routing of those heavy cables is a must, it looks like you got that covered. I run the jumpers to the aux, you should run the winch that way, because I don't want that high amperage coming directly off my main battery. In the event of a dead short on the "jumped" vehicle, I figure the solenoid would implode before the thing killed my truck. That's not scientifically verified, just some Eye Ball logic!

This is one of the reasons for the second battery. I'm going to be moving over several of those feeds to the auxiliary (stereo, second fuse panel).

That's an opinion that I was looking for and for whom it's coming from that gives me a lot of comfort sticking with this setup. This is how they list it in the manual, so I'm confidant on the rating.



Sounds like the best way to run the winch is connected to the auxiliary then? I just want to confirm that I understand your explanation.

I appreciate the complement. I'm a bit of a novice, so it takes a lot longer to get everything the way I want it. I do like a clean engine bay and wiring though.

Here's how I left it last night before wiring the batteries to the solenoid. Getting rid of some of those leads will clean it up a bunch.