How to make a cheap isolated dual-battery setup for $50

[Jack Rabbit]

thanks

Thanks for the responses and advice.

I agree that the switch can be a bad idea especially if you rely on it to charge both batteries. A selector switch combined with an ACR (automatic charging relay) can overcome this somewhat. (see Blue Sea 7650) Although it doesn't really belong in an under $50 thread.

It allows you to keep only one battery on line but charge both when running. This in essence should save one battery for backup if needed and also allows the freedom to switch between batteries when necessary.

If I didn't already have an almost new starting battery, I would just get the 2 deep cycles and alternate them but I'm cheap like that. I will prob just try it with both kinds and keep them separated when needed or just switch to Deep Cycle (#2) when drifting.

Thanks again,

JR

 

[evldave]

I'm drunk. Just a friendly reminder you should not ignore Step 3 from the original post

 

[Livelarg]

Ok,
I have done this sweet little mod, but it is 9:20 in the AM, so I am stone sober. That may be why I'm having trouble.
It is all set up, but don't know how to test the system to make sure it is working correctly. I My thought was that once I gave power to the relay, I would be able to use a simple tester to see if power was going through the continuous relay. but when I do that, there is no power going through the relay.
So it is very possible I have no idea how this is supposed to work. So how do I test to make sure that the system works?

Thanks

 

[dwh]

Assuming you have the solenoid wired to the ignition...

The small terminal on the solenoid from the ignition should have no power when the ignition is off, and have power when the ignition is on. Put the tester between the small terminal and ground to test.

(If you have a solenoid with two terminals, then one should be from ignition, and the other to ground. If your solenoid only has one terminal, then that one should get power from the ignition and the case of the solenoid has to be grounded.)

With the ignition off, the large terminal on the cranking battery side should have the same voltage as the cranking battery, and the large terminal on the aux battery side should have the same voltage as the aux battery. Again, put the tester between the big lug and ground.

With the ignition on, there should be power at the small terminal where ignition is connected, and the voltages of both big terminals should be the same. Again, testing between the terminal and ground.

You can also disconnect both batteries from the big terminals on the solenoid, and test for continuity between the big terminals. If the ignition is off, there should be no continuity, and if the ignition is on, there should be continuity.

 

[dwh]

Oh...simple tester. I was thinking multi-meter.

Okay, well...disconnect the aux battery from the solenoid (or just unhook the + battery cable from the aux battery). Put the simple tester between the aux battery terminal and ground. With the ignition off, there should be no power on the aux battery terminal, with the ignition on, it should have power (from the cranking battery side through the solenoid to the aux battery side).

 

[Livelarg]

thanks againThanks for the great replies.
End up the big thing I needed was "If you have a solenoid with two terminals, then one should be from ignition, and the other to ground."
I thought they where the same. As soon as I connected one to a negative, heard the selenoid click on.

Thanks for all of this thread!View attachment 165933View attachment 165934View attachment 165935View attachment 165936View attachment 165937

I am leaving for a big trip, so wanted to whip this up. Hopefully, I will eventually do the high end set-up. But this will be nice for this trip.

 

[dwh]

Sometimes, being pedantic is not a bad thing.

Have fun!

EDIT: And none of those attachments work.

 

[Vicreo A Legarreta]

Well after reading the all treat I got to do my work on the ranger, first, my needs for a second battery is not to run a 12v cooler, the battery is going in the camper, only running some led light and a 12v fans, mostly at night, the solenoid is standard one used in ford ranger 60 amp (I think) or more, the cable I use is numer 8, still waiting for the cable I order to run from the front to the back, instead of conecting a wire from switch to solenoid I use a really so I can turn on and off the solenoid with a rocker switch , and if the turn the ignition off it will be off so no worries on that side, o and 60 amp in line fuse, well thanks for the great tip on the solenoid, I was gonna buy the costly system but I save some money :thumbup: some pics well is not done yet.

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[dwh]

the solenoid is standard one used in ford ranger 60 amp (I think) or more

Starter solenoids are not rated for "continuous duty". Be interesting to see how long it lasts...

 

[Vicreo A Legarreta]

You are right they're for short bursts at high amps whit high rate cable's like 0 or 1 than can deliver more amps, with a in line fuse 60 or less and the size of the cable like a 8 the demand is not to high, is like if is at float voltage draining the main battery to match the same voltage on the auxiliary battery, like if you forget to turn of the solenoid with the motor not running the battery's will balance the voltage in both at low amps, sorry if is confusing but is hard to putting from Spanish to English and correct me if I'm wrong :what:

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[dwh]

You are talking about the amp rating of the inside contacts (big terminals on outside).

Contacts are just "how much amps is okay", but it doesn't matter if they are contacting all day.


Contacts are not the problem. The problem is the electro-magnet (small terminals on outside) that is not designed for continuous use. The "coil" is what burns out because it gets too hot after a long time.

 

[Vicreo A Legarreta]

is the quality of the solenoid now I get it you are right and good point there, well I am going to test it and see how it works out, and I will report back, thanks dwh

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[ismael D]

I Like this idea start battery and home battery, charging form solor to home battery.
Please up date
Let us kmow
Keep up good work

 

[amockalypsenow]

Thanks for this man- great work!

 

[Livelarg]

Got my set up all set up. But the dang main battery fuse keeps clicking off. I got some ebay fuse block. Click off even when system isn't turned on ( I have switch inside). Will have to bite bullet and get a quality store bought fuse from oreilly auto for 33 bucks. Only 80 amp fuse I can find on the road.