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

[dlichterman]

If anyone here is on the fence about having a way to manually join the batteries I was able to test my system this weekend. I have a 2 way switch, one on position goes to a timer that waits 10 minutes before joining the batteries. The other on position immediately joins them. I left my aux lights on for a few hours this weekend and when I got back to my truck I had the dreaded relay click. I had enough juice to join the batteries and was able to self jump from my deep cycle. Just might want to keep this in mind for when something like this happens.

 

[4RunAmok]

Generally, the positive wire to the switch that combines the batteries comes from the aux battery. That's the one you hope has the power to jump your main battery so you can start your vehicle and let the alternator charge it all up again.

 

[jdinevens]

I'm wondering if you could add a pair of these:

led volt meter

one going to each battery perhaps on some sort of momentary switch so you can check it when needed. And then would it be as simple as hooking each two wire piece onto the pos/neg of each battery system and adding a momentary switch. does anyone know if they make a double in double out switch?

 

[wrcsixeight]

I'm wondering if you could add a pair of these:

led volt meter

one going to each battery perhaps on some sort of momentary switch so you can check it when needed. And then would it be as simple as hooking each two wire piece onto the pos/neg of each battery system and adding a momentary switch. does anyone know if they make a double in double out switch?

I have installed 2 LED voltmeters on my dash with the (+) voltage sense lines going directly to the battery terminals. I wish they were 2 decimal place voltmeters and red instead of green. They are too bright for night driving though, and one layer of 35% tint in front of them is not quite enough to dimm them sufficiently.

Very enlightening to see their differences when both are receiving alternator current and one is depleted.

I have them powered by the ignition and must turn the key to on to illuminate them. I might change that.

 

[jdinevens]

I have installed 2 LED voltmeters on my dash with the (+) voltage sense lines going directly to the battery terminals. I wish they were 2 decimal place voltmeters and red instead of green. They are too bright for night driving though, and one layer of 35% tint in front of them is not quite enough to dimm them sufficiently.

Very enlightening to see their differences when both are receiving alternator current and one is depleted.

I have them powered by the ignition and must turn the key to on to illuminate them. I might change that.

Awesome, yea there were a few different models on ebay, I think i might be able to fit two of these on the f650 dash kit stacked up......hmm

Here ya go

although I'm not quite sure how the 3 wire works based off their diagram.

 

[graynomad]

From the bottom of that page

Wiring:

Red: Positive +
Black: Negative -
White: Voltage measured

And the diagram shows the same, + can be any voltage from 4.5 -30V, they show a separate battery but I see no reason you can't just use either of your batteries as the power source for the display. If so then connect "Positive +" to "Voltage measured".

 

[jdinevens]

From the bottom of that page



And the diagram shows the same, + can be any voltage from 4.5 -30V, they show a separate battery but I see no reason you can't just use either of your batteries as the power source for the display. If so then connect "Positive +" to "Voltage measured".

Ahh I see, yea in the pictures they have toets voltage, I was like is this something new....

 

[landy89]

question about simple dual battery system

Would you mind giving me some electrical advice? i am having some trouble understanding what to do with my dual battery setup - i am worried that it is destroying my alternator. Here is the situation: I have two batteries, one for the motor and one for the fridge/fans/etc. I have the two batteries connected on the positive posts via a solenoid. The negative of the primary battery is attached to vehicle frame. The negative of the secondary battery goes to the fridge/fans/etc/ The negative posts are not connected. The alternator is connected to teh primary battery exactly like it would be in a single battery situation. The alternator is a 65Amp model. Could you please give me your opinion on this setup?

 

[graynomad]

The negative posts are not connected.

They should be, either directly or via the chassis (direct is best).

Is the second battery charging, I can't see how it is with no neg connection.

However I don't think you will be damaging the alternator.

 

[sfsmedic]

Ok I am semi electrical special (like helmet wearing special) so I need some assistance and maybe some splainging!!.

Growing up we had a boat we took everywhere for vacation, picture motorhome on the water. I remember it being just like this.

When we would motor or sail around it would be on both and when we would anchor we would put it on either battery 1 or battery 2 to run everything off of (i.e. lights, fridge, etc.) but we always just switched over to the other battery to start the engine. That way we knew we would always have a good battery. Basically my understanding was the engines could start off of either battery, the house stuff could run off of either battery. Am I correct in that assumption based off of my explanation?

Now jump over to trying to figure out a dual battery setup for my truck. Reading the OPs original excellent write up I understand it that this system seperates the battery so only one starts the truck and only one runs the house equipment. If this is an accurate understanding then would I need to tie the house battery into a fuse block and then wire all my accessories off that fuse block?

If the understanding of the OPs dual battery set up is correct, what are the advantages and disadvantages of that version versus what we had set up on my dads boat? It would seam that boat setup would be simpler in the long run as I am just adding a second battery to the bank but not having to do a second fuse block to start wiring all the accessories off of.

I am just trying to fully understand all of this as I have no real experience at all with doing this but in my situation it would be very foolish not to do something. My situation is I go on long truck camping trips for the purpose of hunting. Sometimes only 2-3 days sometimes 5-7 days. I am getting ready to buy a fridge for my truck, I have a winch already and would like to be able to charge other accessories such as my handheld gps and other tools i use for hunting. But always know I can start the truck because one battery is untouched from all of this.

Thanks in advance for all the help.

 

[IdaSHO]

I'm wondering if you could add a pair of these:

led volt meter

one going to each battery perhaps on some sort of momentary switch so you can check it when needed. And then would it be as simple as hooking each two wire piece onto the pos/neg of each battery system and adding a momentary switch. does anyone know if they make a double in double out switch?

Ive got a similar setup, using ubber cheapo ebay voltage gauges. Though mine are not the super bright LED. They are basic backlit LCD

Left gauge shows truck battery bank voltage when toggle switch is on.

Red lighted switch activates 200AMP continuous duty relay that charges the camper house battery bank

Right gauge shows camper battery bank when toggle switch is on.


Simple, effective, and CHEAP.

 

[jdinevens]

Ive got a similar setup, using ubber cheapo ebay voltage gauges. Though mine are not the super bright LED. They are basic backlit LCD

Left gauge shows truck battery bank voltage when toggle switch is on.

Red lighted switch activates 200AMP continuous duty relay that charges the camper house battery bank

Right gauge shows camper battery bank when toggle switch is on.


Simple, effective, and CHEAP.

Yea I'm hoping the two volt meters I ordered fit into one of th slots on this guy

Then i can wire in a DpSt switch in to view them.

 

[graynomad]

we always just switched over to the other battery to start the engine. That way we knew we would always have a good battery. Basically my understanding was the engines could start off of either battery, the house stuff could run off of either battery. Am I correct in that assumption based off of my explanation?

A simple switch like this works as you know, it's not ideal though because

a) It's manual and many people forget to change over, if you can live with that fair enough.
b) Crank batteries and house batteries should be different types because cranking and running a fridge are two totally different things that ideally should use different types of battery. Once again it works and it you can live with it fair enough.

I have done similar for years but used a deep cycle for the house and a relay powered by the ignition for the change over. It works well but the house battery never really gets fully charged because for some reason car charging systems don't seem to go up to the ~15V required and leave it there for an "absorption" phase.

I need to tie the house battery into a fuse block and then wire all my accessories off that fuse block?

Yep, that would be the way to go.

 

[IdahoXJ]

Truly a great article and timely for me. I have been wanting to do this. Thank you, thank you, thank you (in lieu of handing you another beer).

 

[sfsmedic]

A simple switch like this works as you know, it's not ideal though because

a) It's manual and many people forget to change over, if you can live with that fair enough.
b) Crank batteries and house batteries should be different types because cranking and running a fridge are two totally different things that ideally should use different types of battery. Once again it works and it you can live with it fair enough.

I have done similar for years but used a deep cycle for the house and a relay powered by the ignition for the change over. It works well but the house battery never really gets fully charged because for some reason car charging systems don't seem to go up to the ~15V required and leave it there for an "absorption" phase.


Yep, that would be the way to go.

Thanks. That helps and clears up a lot. Then would I be wiring the winch off the house or starting battery. Same with the LEDs that would be used while driving? Also looks like the original post is the way to go for me as you pointed out.


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