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

[dwh]

About to leave to go camping off the grid for several days and realized that my battery is not charging when the engine is running. I have noticed that battery voltage has been lower than usual the last couple weeks but paid no attention as I have not been driving very far. Checked it out and found that voltage is staying the same when engine is off and running, it used to spike to 13.7v but just stays at 12.0v now. Any ideas what to check?

I have the same setup used here. My 12v ignition on runs to a piggyback in fuse block. Fuses are good. My 100a fuses appear to be good also. All bolts and fittings are tight. I have a multimeter and tried checking with it but honestly it has so many features that it confuses me.

Any help would be greatly appreciated!!!


EDIT: Jumped the isolater by putting the two hot wires together. No change in voltage read out with engine running or off. So it is safe to assume it is an issue between the isolator and house battery, correct?

Joe

If you bypassed the solenoid and wired the batteries directly together then the problem must be either the battery cables or the battery cable fuses.

You said something about 100a fuses being good. I'm guessing those are fuses at the batteries? Problem has to be there.

 

[RememberTheFallen]

If you bypassed the solenoid and wired the batteries directly together then the problem must be either the battery cables or the battery cable fuses.

You said something about 100a fuses being good. I'm guessing those are fuses at the batteries? Problem has to be there.

Ok, I will check there. I have one of the big fuses that was recommended right before the battery. I have never used them before but it doesn't look burnt or broken. I will go check that whole area again.

Thanks dwh!

 

[DiploStrat]

Free Advice

About to leave to go camping off the grid for several days and realized that my battery is not charging when the engine is running. I have noticed that battery voltage has been lower than usual the last couple weeks but paid no attention as I have not been driving very far. Checked it out and found that voltage is staying the same when engine is off and running, it used to spike to 13.7v but just stays at 12.0v now. Any ideas what to check?

I have the same setup used here. My 12v ignition on runs to a piggyback in fuse block. Fuses are good. My 100a fuses appear to be good also. All bolts and fittings are tight. I have a multimeter and tried checking with it but honestly it has so many features that it confuses me.

Any help would be greatly appreciated!!!


EDIT: Jumped the isolater by putting the two hot wires together. No change in voltage read out with engine running or off. So it is safe to assume it is an issue between the isolator and house battery, correct?

Joe

Don't go nowhere for the moment! Your problem may be greater than just your camper battery. You need to do a careful, step by step, check of your system. (And I may miss a few of the steps.

-- Note voltage of starter and camper batteries with engine off. Ideally, both should be in the neighborhood of 12.7v. (Nominal "full" charge.)

-- Start engine and note voltage of starter battery. Should quickly climb to something over 14v. This indicates that your alternator is working and producing voltage. (Won't tell you if it is producing current, but it is a basic starting point.)

If you are not getting 14v+ from your alternator, stop. You have a problem and your camper battery is irrelevant until you get it fixed.

If you ARE getting 14v, then:

-- Do you have 14v at the starter battery side of your isolator relay? If not, then the problem is between the relay and the starter battery.

-- Did the relay close and are you getting 14v at the camper side of the relay? If no, then the relay or its wiring is the problem.

-- If you have 14v at the relay, do you have 14v at the camper battery? If not, the problem is probably in the wiring between the relay and the camper battery.

Finally, is the camper battery properly grounded to the frame or back to the starter battery. Many problems in low voltage systems can be traced back to bad grounds.

This should get you started. Report your findings, ideally in a new thread, and you will probably get some good advice on how to proceed.

 

[RememberTheFallen]

Wow, thanks Diplostrat!

I will go back and check all of that shortly.

I bypassed the fuse right before my house battery and now showing 13.9v with engine running. Only issue is that fuse looks fine?

Sent from my iPhone using Tapatalk

 

[DiploStrat]

Small issue: Appears you have one of the Toyotas whose alternator is set to 13.9v. In the fullness of time, you may want to look into boosting that to closer to 14.4v (One of these might work: http://www.mechman.com/voltage-control-modules/) or using some form of battery to battery charger (CTEK, Sterling Power, etc.) as it is probable that your camper battery wants 14.4v for a full charge.

On the other hand, if you add a solar charger, and set that to the correct voltage, you will probably be fine as you are unlikely to ever drive long enough to "fully" charge your camper battery with the alternator.

 

[DiploStrat]

Wow, thanks Diplostrat!

I will go back and check all of that shortly.

I bypassed the fuse right before my house battery and now showing 13.9v with engine running. Only issue is that fuse looks fine?

Sent from my iPhone using Tapatalk

Looks dark at one end. Measure the resistance with your multimeter. Should show next to no resistance.

 

[dwh]

Set your multimeter to continuity (touch the probes together to make sure the meter is working, most will beep) then check across the fuse.

If no continuity, the fuse is blown.

 

[dwh]

And...

Damn...you blew a 200a fuse? Whatchoo been doin' boy?

 

[dwh]

And...

Nice ring.

 

[fiddypal]

Looks like a blown fuse to me! Black spot is pretty obvious, fuses will not always "pop" in the middle of the filament.

 

[carbon60]

Looks like a blown fuse to me! Black spot is pretty obvious, fuses will not always "pop" in the middle of the filament.

Damn...you blew a 200a fuse? Whatchoo been doin' boy?

Yeah, how did you blow a 200A fuse? :Wow1:

 

[RememberTheFallen]

Sorry to all that I didn't respond to as I was in a big hurry to get on the road and haven't had cell service. I need to check that fuse with the multimeter but the dark spot several of you have mentioned was a shadow. The whole fuse inside the window is shiny gold. That is why I was confused. Only thing I can think of was that I missed a loose bolt on that fuse before I changed it out. The system worked fine this weekend without any more issues.

 

[DiploStrat]

Great!

 

[ChadHahn]

I'm getting ready to order the parts to install a dual battery system and wonder if a Blue Sea 7622 ML-ACR Automatic Charging Relay could take the place of the solenoid?

Thanks,

Chad

 

[ChadHahn]

I thought it would work, but didn't want to order it and find out that I still needed a solenoid.

Thanks,

Chad