Dual Battery setup with different batteries

[AlexJet]

I'm planning on running Dual Batteries on my vehicle.
I have Painless Performance Dual Battery System which I'm going to use in my vehicle.
I know the ideal situation is to use 2 identical batteries, but due to space constrains I may need to run 2 different size batteries.
I'm looking into Odyssey 75/86-PC1230 and 34/78-PC1500. Both batteries are new.
Specs:
PC1230
- Cold Cranking Amps: 760
- Normal Cranking Amps: 870
- Reserve Capacity: 100min
- Nominal Capacity at 20hr: 55Ah
PC1500
- Cold Cranking Amps: 850
- Normal Cranking Amps: 1050
- Reserve Capacity: 135min
- Nominal Capacity at 20hr: 68Ah

Which battery should I run as Primary and what should be the secondary?

What is the best wiring approach to connect Dual Batteries? Painless recommends to connect everything to Primary and use Secondary as back-up. I have seen many people connecting all OEM wiring to Primary, Winch to Primary, Auxiliary wiring to Secondary.

 

[pugslyyy]

I'm planning on running Dual Batteries on my vehicle.
I have Painless Performance Dual Battery System which I'm going to use in my vehicle.
I know the ideal situation is to use 2 identical batteries, but due to space constrains I may need to run 2 different size batteries.
I'm looking into Odyssey 75/86-PC1230 and 34/78-PC1500. Both batteries are new.
Specs:
PC1230
- Cold Cranking Amps: 760
- Normal Cranking Amps: 870
- Reserve Capacity: 100min
- Nominal Capacity at 20hr: 55Ah
PC1500
- Cold Cranking Amps: 850
- Normal Cranking Amps: 1050
- Reserve Capacity: 135min
- Nominal Capacity at 20hr: 68Ah

Which battery should I run as Primary and what should be the secondary?

What is the best wiring approach to connect Dual Batteries? Painless recommends to connect everything to Primary and use Secondary as back-up. I have seen many people connecting all OEM wiring to Primary, Winch to Primary, Auxiliary wiring to Secondary.

While it may seem counterintuitive I would use the small as the primary and just have the OEM wiring to it (and maybe not the radio, extra lights if equipped, etc) - pretty much only what is absolutely necessary to drive the truck. Everything else (especially the winch and offroad lights) to the larger secondary.

 

[AlexJet]

While it may seem counterintuitive I would use the small as the primary and just have the OEM wiring to it (and maybe not the radio, extra lights if equipped, etc) - pretty much only what is absolutely necessary to drive the truck. Everything else (especially the winch and offroad lights) to the larger secondary.

I see your approach angle. I used the same methodology on wiring my 4Runner dual batteries, but they were the same type. I was told that I was wrong as if I need to winch myself then the winch will suck all the juice from Secondary and Alternator is connected to the Primary, so Secondary would be taking power not from the alternator, but from Primary which would be feeding by the engine itself. In fact I used winch once, so I don't have much experience on this side.

 

[pugslyyy]

I see your approach angle. I used the same methodology on wiring my 4Runner dual batteries, but they were the same type. I was told that I was wrong as if I need to winch myself then the winch will suck all the juice from Secondary and Alternator is connected to the Primary, so Secondary would be taking power not from the alternator, but from Primary which would be feeding by the engine itself. In fact I used winch once, so I don't have much experience on this side.

Ah okay I'm with you now - I was not familiar with Painless system and was thinking that there was a battery isolator in it and the primary would be the start/run battery and everything else would be on the secondary.

If there is no isolation I would be very very very wary of having unmatched batteries in parallel, enough can go wrong when they are same age / identical. At under $100 for a basic battery isolator is this something your project budget allows you to consider?

 

[1911]

I use two similar but different size batteries in mine; a Sears Diehard Platinum for the main and a larger Odyssey PC1500 for the second battery.

I have my winch and air compressor hooked up to the main battery and all other accessories hooked up to the second battery. That way, I can run my fridge and radios in camp and save my main battery for starting.

 

[AlexJet]

Ah okay I'm with you now - I was not familiar with Painless system and was thinking that there was a battery isolator in it and the primary would be the start/run battery and everything else would be on the secondary.

If there is no isolation I would be very very very wary of having unmatched batteries in parallel, enough can go wrong when they are same age / identical. At under $100 for a basic battery isolator is this something your project budget allows you to consider?

Painless system is a full system with insulator. They just refer to high draw accessories and that the Alternator is connected by default to the main battery, so the Secondary is always getting the power from alternator via Primary. Other then that system has full ability to switch the batteries on and off depend on your demand.

 

[AlexJet]

I use two similar but different size batteries in mine; a Sears Diehard Platinum for the main and a larger Odyssey PC1500 for the second battery.

I have my winch and air compressor hooked up to the main battery and all other accessories hooked up to the second battery. That way, I can run my fridge and radios in camp and save my main battery for starting.

What Dual Battery system do you run?

 

[pugslyyy]

Painless system is a full system with insulator. They just refer to high draw accessories and that the Alternator is connected by default to the main battery, so the Secondary is always getting the power from alternator via Primary. Other then that system has full ability to switch the batteries on and off depend on your demand.

Hmm, which Painless are you looking at? I'm probably looking at the wrong one because I'm just seeing solenoid/wires/switches.

 

[AlexJet]

Hmm, which Painless are you looking at? I'm probably looking at the wrong one because I'm just seeing solenoid/wires/switches.

40103
You can run both batteries completely independent, connected only when ignition is ON or full time connected all the time.

 

[pugslyyy]

40103
You can run both batteries completely independent, connected only when ignition is ON or full time connected all the time.

I think I would consider that a controller not an isolator (a fancy 1-2,1+2 switch). There's nothing to stop the batteries fighting with each other (again, if I am looking at it correctly) - which would be why having matched batteries becomes very important.

 

[AlexJet]

Should I buy an additional isolator?
What the difference between battery solenoid and isolator? I'm reading the Web, but getting confused as both seems doing the same.

 

[bfdiesel]

Should I buy an additional isolator?
What the difference between battery solenoid and isolator? I'm reading the Web, but getting confused as both seems doing the same.

The spelling

 

[pugslyyy]

Should I buy an additional isolator?
What the difference between battery solenoid and isolator? I'm reading the Web, but getting confused as both seems doing the same.

I would seriously consider a (diode) isolator - I think in the long run you'll be happiest with it. I'm biased because I've actually had batteries catch fire and melt on me while running down the highway before using the other method, and was made even more fun because it was in my Defender which meant I was sitting on them when it happened.

 

[pugslyyy]

Should I buy an additional isolator?
What the difference between battery solenoid and isolator? I'm reading the Web, but getting confused as both seems doing the same.

A solenoid could be considered a type of isolator, but I usually think diode-based when talking about isolators. (A solenoid doesn't restrict current flow to one direction like a diode will.)

The solenoid is great for preserving the charge of your starting battery - when the truck is off, the solenoid is off and the batteries aren't linked. The issue comes when the engine is running and the batteries are in parallel / charging. One battery can suck power from another, and they are sharing the same feed off of the alternator. So unless they are in the same condition / same capacity / same state of charge, they won't be in an ideal charging situation because they are being treated (by the alternator/regulator) as one big battery instead of the two (or more) separate batteries that they really are.

 

[Bretthn]

Subscribed. I am researching dual battery set ups as well. I have a rough sketch of a kit I am thinking about piecing together myself versus buying an off the shelf kit.