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

[mcskibadee1]

Gotta say that I did this last week and it is great. I bought this battery at 120 amp hour rating and spent another 50 on fuses, wiring, solenoid etc. I am looking at the low cost solar setup so the battery stays nice and fresh during the day running my edgestar fridge and other things. I have my compressor hooked up to the aux battery as well and while my two other friends had their cars running while filling their tires I was able to have mine off. It really is a cheap way to have peace of mind knowing your car will start and not be drained while running auxiliary items.

 

[doug720]

This same set up is done on boats too. You can make it automatic by using an oil pressure switch to activate the solitude also. When you start the motor, the OP switch allows charging. Both ways are easy, reliable and inexpensive.

 

[dlichterman]

This same set up is done on boats too. You can make it automatic by using an oil pressure switch to activate the solitude also. When you start the motor, the OP switch allows charging. Both ways are easy, reliable and inexpensive.

I used a timed relay in my system that lets me delay the joining for 10 minutes after I start the truck to make sure the starting battery is kept topped up. The part I found is "821TD10H-UNI" and can be found here: http://www.zoro.com/i/G1838392/?category=4853. The delay can be set to whatever you want. The way I did it I have a 3 way switch with 2 on positions that let me leave it in the automatic(time delay) setting, but also switch to the other on position and join the batteries immediately in case I need to self-jump.

 

[evldave]

Hey folks that are just now reading this thread, just a note I'm working on getting my pictures back up. Should be back online in the next few days. Sorry for the hassle

 

[FJRanger]

Hey folks that are just now reading this thread, just a note I'm working on getting my pictures back up. Should be back online in the next few days. Sorry for the hassle

No need for an apology, thanks for starting this great thread and working on the pictures!

 

[Gloftoe]

Hey folks that are just now reading this thread, just a note I'm working on getting my pictures back up. Should be back online in the next few days. Sorry for the hassle

Thank you, sir! I had private messeged you about them, and now I know you're on the case.

 

[MINO]

I've run into an issue with my starting battery (Diehard Platinum marine AGM) not getting a full charge and not sure why. I've been unable to start on a few occasions. I did not have any issues prior to the solenoid to the 2nd battery, although this could simply be coincidence. Hoping a guru can chime in.

My 2nd battery is connected via the Cole Hersee 24106 and 20ft of 4g cable to my slide camper. The battery is a larger 215AH AGM battery.
It also has 350ish watts of solar.

I usually let the starting battery get 10-20 minutes alone before I turn the solenoid on and for the most part the Tundra will start just fine.

On one 50 mile drive, my truck failed to start upon arriving the location. It wouldn't start with the solenoid connected (worth a shot) So I simply left the solenoid connected, let the solar charge for 15min, then I was able to start.

Just this weekend, while driving back from Big Sur we stopped in Santa Barbara for a bite. The batteries were connected for a good 250 miles and my truck failed to start. Again, I reconnected the solenoid, but now without sunlight, I assumed the batteries would equalize after a few minutes. A guess they did, and I was able to start the truck.

Open to ideas and recommendations.

Thanks.

 

[4RunAmok]

Would need to know more about changes you made to the main battery connections. Did you somehow remove the wire coming from the alternator? Fusible link blown?

The only alterations you should have made to the main battery was simply adding a cable from the battery post to the Cole Hersee 24106. Nothing more.

 

[MINO]

I made no changes to the factory cables. Simply added ground and + leads to the Cole and house battery.
Fusible link assembly is good.

 

[4RunAmok]

It's not unheard of for these AGM Die Hards to go bad. Remove the cable between the main battery and the solenoid, go to Sears, and have them test it. It should be under warranty.

 

[FJRanger]

It's not unheard of for these AGM Die Hards to go bad. Remove the cable between the main battery and the solenoid, go to Sears, and have them test it. It should be under warranty.

I've had one go bad. Sears tested the battery overnight and it wouldn't take a complete charge. They said it would get over 90% but wouldn't make it to 100% and asked what I wanted to do; like they had options

If they find anything wrong with it insist that it's replaced.

 

[dwh]

I've run into an issue with my starting battery (Diehard Platinum marine AGM) not getting a full charge and not sure why.

You're assuming it's not getting a full charge. It might be getting a full charge, but not holding it for long. That would be a dodgy battery.

Starting only draws the battery down like 1/5 of one amp*hour...almost nothing. Put a multi-meter on the battery and check its voltage with the engine running at high idle and the isolator solenoid off (batteries isolated). If the engine battery does nothing but start the truck, you should see it come up to over 14v in well under a minute.

Let it run 10 minutes, then shut it down and watch the voltage fall. It shouldn't fall below 12.8v, but if it's not getting a full charge, it might fall as low as 12.5v, or even 12.3v.

But at some point, it should stop falling and just sit there. If it keeps creeping down, then either the battery is bad and not holding a charge, or you've got some sort of phantom load drawing it down.

I've been unable to start on a few occasions. I did not have any issues prior to the solenoid to the 2nd battery, although this could simply be coincidence. Hoping a guru can chime in.

My 2nd battery is connected via the Cole Hersee 24106 and 20ft of 4g cable to my slide camper. The battery is a larger 215AH AGM battery.
It also has 350ish watts of solar.

I usually let the starting battery get 10-20 minutes alone before I turn the solenoid on and for the most part the Tundra will start just fine.

I've run dumb solenoids (split-charge relay) for decades. I don't time delay, they get tied as soon as I turn the key. I also run my aux battery fully dead all the time.

NEVER had a problem with it affecting the starting battery - unless the starting battery is already dodgy.

On one 50 mile drive, my truck failed to start upon arriving the location. It wouldn't start with the solenoid connected (worth a shot) So I simply left the solenoid connected, let the solar charge for 15min, then I was able to start.

I've done the same thing, but with a generator and battery charger instead of solar. Have done it a few times when I left the headlights on overnight, and a few times when the starting battery went bad.

It's nice to have a backup source of power.

 

[Gloftoe]

Hope I'm not being a bother, evldave. Any luck on the pictures? Thanks.

 

[evldave]

Pictures should be back...

 

[Gloftoe]

Pictures should be back...

Thanks very much!