Pistol-McGee

Ive searched a while and ive found some threads on here, but im a bit confused (i get confused easily with electrical stuff, im more mechanical inclined)

I want to run quite a few lights on my jeep in the future, i figure total 6-8 offroad lights and possibly a inverter for laptops/computer inside jeep for GPS, drills, tools and maybe a winch depending on what kind i get.

What im confused on is how i would run it without them battling it out over charge. Ive seen some people use Ford starter solenoids and i have like 37000 of those sitting around from my dad/brothers early 70's ford they had

If someone has a wiring diagram i can probably do it myself but i havent found one around that i liked.

tl;dr: Can i use the 70's ford starter solenoids as a isolator or am i just reading things wrong? I need help making a wiring diagram/wiring up 2 batteries correctly for added accessories.

odgreen

does this help?

Pistol-McGee

^ That helps a lot Thank you

edit: Would i need a relay in there somwhere or is a switch fine?

odgreen

just a switch is fine the starter relay is just like a small relay where it take a small amount of amps to operate.

calvinator

As an alternative, check into a $15 Perko battery switch. Used commonly in the boating world. You can run 1 batt, 2 batt, both batteries, with the switch.

For my boat, I use 1 batt for the cruise TO, 2 batt for the return trip. This way the alternator gets a charge on both batteries.

Pistol-McGee

I thought about that as well, On our sailboat we had one but i didnt know if the sailboats 'both' was in series for the diesel starter

5-90

I know a lot of people (RVers, especially() use the Ford starter motor solenoids as battery isolators, but they're not designed for constant duty. When I was working parts, I had to explain this about once a week to someone (when they were wondering why they were buying their third solenoid that year...)

You can get a constant-duty solenoid to use, but that still requires some user input - and the charge drain won't be limited to the accessory battery unless you override the solenoid trigger lead OFF (doable. PM me your email addy for a wiring diagram in .pdf format - it's over the filesize limit to attach. 140K or so.)

However, if you want a "don't think" solution, get a solid-state isolator. This is essentially a high-current diode pack that allows alternator charge current into the battery, but won't allow discharge current to touch the starting cell (if you're wired up directly to the auxiliary battery, as you should be...) and you don't have to do anything about it.

Although, it's possible to wire up a solenoid as a bypass for the solid-state regulator and "self-jump" by flipping a switch, if your starting battery goes flat and your aux battery is still in good shape (I've set this up on heavy trucks before.) You can also "cut-in" your auxiliary battery if you note your alternator goes West on you - and get more runtime to get somewhere you can fix the thing.

Either way, you'd be better off with a dedicated deep cycle battery, instead of a "combination cell." You're probably not going to "self-jump" very often, and the construction and minor chemical changes in the pure deep cycle battery are more conductive to a full discharge/recharge cycle than the "combo" cell or the typical starting battery.

Although, if you can regulate the current going into the deep cycle for recovery from a full discharge, you'll get your battery to last even longer (a deep cycle is designed and built to be discharge fully at a relatively low rate, and will more fully recover if it is charged at a low rate as well. Say, 5Ah or less...)

If you use a switch to drive a solenoid, the solenoid itself typically takes 500mA-1A to engage the contacts. Solenoids are available in many ratings (I typically carry two ratings for constant-duty - 85A and 200A. This is the amount of current it will safely carry, all day every day, without a problem. Figure max charging current as max alternator output less 25-40A - more as the vehicle gets newer, and as engine management gets more complex.)

Could you use the Ford solenoid? Sure - for a while. But, I'd not consider it a permanent solution - it's usually cheaper to do something right the first time instead of doing it over and over again...

blasto9000

I agree with this. You can find them in auto parts stores where they keep the other battery-related items… usually called “battery isolator.” They are safe, reliable and heavy-duty.

There is one minor issue though, there is some voltage drop on the output side of an isolator… should be less than 1 volt. But it may cause a battery to appear that it’s not charging if the battery is weak (where the same battery would be fine if it was in single service). So your battery replacement interval may be somewhat shorter with an isolator.

If you want a “premium” battery isolator get one made for marine duty. I’ve seen them that go up to six batteries if you’re so inclined. ;-)