Dual battery questions

[Sixstrings93]

While I’m deployed, I’m planning out some needed add one to my rig. As the title says, I’m planning my auxiliary power set ups. Plan is to get an isolator set up for an auction battery I’m going to run separate from the crank battery. Main questions right now are, what is the best battery to run for this application? The main will only be used for crank and small accessories already attached. The Aux will run some lights and a small 40qt fridge, maybe a couple other accessories etc. I would like the option to have solar as alternate charging for the aux separate from the alternator. Lastly, does the crank and the aux need to be the same battery?

 

[Road]

Short answer: Yes, if only using a simple isolator, best scenario is to have the house and starting battery be the same type (flooded, AGM, or GEL etc), same size, and same age. That will be much easier for the battery's life in the long run.

Other arrangements are possible, of course, though you run the risk of one battery being regularly under or over-charged if, for example, you get a new AGM deep cycle and hook it up as your house batt, when your cranking batt is a flooded cell starting battery. You can do it, but you're hurting the life of the AGM. You'll find all kinds of guys saying "oh I've done that for years just a simple isolator with no issues" though the truth is they're hurting the house battery's life, if a diff type completely than the starting battery.

If they're the same charging profile (both flooded, for example) and of similar size and age, it's not as problematic.

If wanting to use a good deep-cycle AGM with whatever existing starting batt you have, best thing in the long run is to get a DC-to-DC charger like from REDARC, CTEK, or Victron for hooking up two different types of batteries, because they don't combine the two batteries into what the alternator thinks is one larger battery, but connects (not combines) and allows the stronger battery (usually the cranking battery while underway) to charge the other one. (usually the house battery).

Better DC-to-DC chargers have a built-in MPPT solar charge controller that makes it easy to hook up a solar panel at whatever point in the future you wish.

Here's more on batteries (using an AGM under the hood) with links to a post on dual battery systems and articles on battery charge settings and how to properly test an AGM:

Batteries?

So one of my next projects is my dual battery setup…and I’m looking for some feedback on brands, models, etc so I can make an educated purchase…. I have a 2021 Tacoma and plan on getting the Genesis dual battery mount/kit…

www.overlandbound.com

Can I connect dissimilar batteries in parallel:

Super Simple Dual Battery Project

Hey all, so a while back I decided I wanted a second battery in my truck, but I didn't need anything overly complicated, like solar charging, etc. My plan was to keep it simple, and easy. Battery isolator between the main battery and a second battery to keep both batteries charged, but not...

www.overlandbound.com

Tons of posts here on batteries, dual batt set-ups, stand-alone solar-batt set-ups (without using vehicle alternator), and more.

Hope you figure out the best way for you. Let me know if I can be of any further help.

.

 

[Clrussell]

Good info here

 

[Sixstrings93]

Short answer: Yes, if only using a simple isolator, best scenario is to have the house and starting battery be the same type (flooded, AGM, or GEL etc), same size, and same age. That will be much easier for the battery's life in the long run.

Other arrangements are possible, of course, though you run the risk of one battery being regularly under or over-charged if, for example, you get a new AGM deep cycle and hook it up as your house batt, when your cranking batt is a flooded cell starting battery. You can do it, but you're hurting the life of the AGM. You'll find all kinds of guys saying "oh I've done that for years just a simple isolator with no issues" though the truth is they're hurting the house battery's life, if a diff type completely than the starting battery.

If they're the same charging profile (both flooded, for example) and of similar size and age, it's not as problematic.

If wanting to use a good deep-cycle AGM with whatever existing starting batt you have, best thing in the long run is to get a DC-to-DC charger like from REDARC, CTEK, or Victron for hooking up two different types of batteries, because they don't combine the two batteries into what the alternator thinks is one larger battery, but connects (not combines) and allows the stronger battery (usually the cranking battery while underway) to charge the other one. (usually the house battery).

Better DC-to-DC chargers have a built-in MPPT solar charge controller that makes it easy to hook up a solar panel at whatever point in the future you wish.

Here's more on batteries (using an AGM under the hood) with links to a post on dual battery systems and articles on battery charge settings and how to properly test an AGM:

Batteries?

So one of my next projects is my dual battery setup…and I’m looking for some feedback on brands, models, etc so I can make an educated purchase…. I have a 2021 Tacoma and plan on getting the Genesis dual battery mount/kit…

www.overlandbound.com

Can I connect dissimilar batteries in parallel:

Super Simple Dual Battery Project

Hey all, so a while back I decided I wanted a second battery in my truck, but I didn't need anything overly complicated, like solar charging, etc. My plan was to keep it simple, and easy. Battery isolator between the main battery and a second battery to keep both batteries charged, but not...

www.overlandbound.com

Tons of posts here on batteries, dual batt set-ups, stand-alone solar-batt set-ups (without using vehicle alternator), and more.

Hope you figure out the best way for you. Let me know if I can be of any further help.

.

Great info! Much appreciated.

Ideally, I would like to run an Odyssy Deep Cycle for the house. I dont mind having to get a new crank battery and just make it the same as the house bat. So just making sure I dont buy unnecessary stuff. To run dual same same batteries with solar potential on aux bat., I need 2 same same batteries, an isolator, the DC/DC charger for even charge and solar hook up and i would be good to go?

 

[Road]

Great info! Much appreciated.

Ideally, I would like to run an Odyssy Deep Cycle for the house. I dont mind having to get a new crank battery and just make it the same as the house bat. So just making sure I dont buy unnecessary stuff. To run dual same same batteries with solar potential on aux bat., I need 2 same same batteries, an isolator, the DC/DC charger for even charge and solar hook up and i would be good to go?

.
Ethan - I'm glad the info was helpful.

If you're going to get a DC-to-DC charger, the batteries can be different in age, size, and/or type. Just a new deep cycle (Odyssey AGMs are great) and the DC-DC charger of choice. The better ones have an MPPT solar charge controller built in. You can keep the cranking battery you currently have and do not need a separate isolator in conjunction with the DC-DC charger.

That's what DC-DC chargers excel at; connecting (not combining) two different types of batteries without either one being over or under charged.

IF you want to add a battery to your current cranking battery with only a simple isolator (not a DC-DC charger), then the best scenario is to have them be the same size, type, and age.

Hope this helps further.

(edited for clarification)
.

 

[Sixstrings93]

Great info! Much appreciated.

Ideally, I would like to run an Odyssy Deep Cycle for the house. I dont mind having to get a new crank battery and just make it the same as the house bat. So just making sure I dont buy unnecessary stuff. To run dual same same batteries with solar potential on aux bat., I need 2 same same batteries, an isolator, the DC/DC charger for even charge and solar hook up and i would be good to go?

Also, I have learned that newer vehicles have smart alternators, so for future reference for people that see this thread, dont forget to double check what alternator you got

 

[Road]

Also, I have learned that newer vehicles have smart alternators, so for future reference for people that see this thread, dont forget to double check what alternator you got

.
Yep, that's a great point to remember for those new to considering dual battery systems.

Here's how REDARC explains it:

​

"Smart alternators vs fixed voltage alternators​

​

Fixed voltage alternators are becoming less common on new vehicles as reduced fuel consumption targets and more stringent environmental and emissions standards are adopted by manufacturers. A fixed voltage alternator has a high enough voltage to charge a secondary battery in the vehicle to a usable level for leisure or auxiliary use.​

​

The smart alternator system, also known as variable voltage alternators, allow the vehicle to control the output voltage and current from the alternator based on vehicle operating conditions. The idea behind this is to reduce electrical load and in turn mechanical load on the engine by the alternator. Unfortunately, this renders it unsuitable for charging a secondary battery system to a usable level.​

​

More on their page here, and why a DC-DC charger is better used with smart alternators:

The truth about alternators

With the constant evolution of technology in today’s modern vehicles and an increasing number of accessories and options available, setting up a dual battery system can feel more daunting than ever.

redarcelectronics.com

Also, I edited my post above to make more clear that you do NOT need a separate isolator or same battery type if adding a DC-DC charger into the mix. Just a good deep cycle and the DC-DC charger and keep the same cranking batt you have.
.

 

[Sixstrings93]

Also, I have learned that newer vehicles have smart alternators, so for future reference for people that see this thread, dont forget to double check what alternator you got

.
Yep, that's a great point to remember for those new to considering dual battery systems.

Here's how REDARC explains it:

​

"Smart alternators vs fixed voltage alternators​

​

Fixed voltage alternators are becoming less common on new vehicles as reduced fuel consumption targets and more stringent environmental and emissions standards are adopted by manufacturers. A fixed voltage alternator has a high enough voltage to charge a secondary battery in the vehicle to a usable level for leisure or auxiliary use.​

​

The smart alternator system, also known as variable voltage alternators, allow the vehicle to control the output voltage and current from the alternator based on vehicle operating conditions. The idea behind this is to reduce electrical load and in turn mechanical load on the engine by the alternator. Unfortunately, this renders it unsuitable for charging a secondary battery system to a usable level.​

​

More on their page here, and why a DC-DC charger is better used with smart alternators:

The truth about alternators

With the constant evolution of technology in today’s modern vehicles and an increasing number of accessories and options available, setting up a dual battery system can feel more daunting than ever.

redarcelectronics.com

.

.

I can’t speak for other vehicles, but on mine, a 2017 Jeep JK, it is t a “smart” alternator, but it also isn’t fixed voltage. It is a temperature adjusting alternator meaning it varies the voltage based on the temp in the engine bay. So I need a dc-dc charger. The best one I have found so far for my application is the Redarc dc-dc in your preferred amperage. According to the redarc site, this charger is also an isolator so I don’t need to buy both and is designed for an in-cab aux battery.

My plan now is to is to get the redarc dc-dc with the proper fuses (30amp since I’m getting the 25A charger) wire it permanent behind my front seats to provide easy access, and wire in a 12v connector hub for my fridge and run some camp lights to the Aux battery. When I can I will invest in a 300w solar to run while camped out.

I am still in Iraq for now, but when I get back, all the parts will be waiting for me so I will post pictures on this thread of the install for the people that come behind us on this thread!

 

[Road]

I can’t speak for other vehicles, but on mine, a 2017 Jeep JK, it is t a “smart” alternator, but it also isn’t fixed voltage. It is a temperature adjusting alternator meaning it varies the voltage based on the temp in the engine bay. So I need a dc-dc charger. The best one I have found so far for my application is the Redarc dc-dc in your preferred amperage. According to the redarc site, this charger is also an isolator so I don’t need to buy both and is designed for an in-cab aux battery.

My plan now is to is to get the redarc dc-dc with the proper fuses (30amp since I’m getting the 25A charger) wire it permanent behind my front seats to provide easy access, and wire in a 12v connector hub for my fridge and run some camp lights to the Aux battery. When I can I will invest in a 300w solar to run while camped out.

I am still in Iraq for now, but when I get back, all the parts will be waiting for me so I will post pictures on this thread of the install for the people that come behind us on this thread!

.
Yes, that's what I've been trying to explain. Having a good DC-DC charger eliminates the need for a separate isolator AND allows you to just get one new battery (deep cycle for the 'house' connections), and will allow future solar connections.

300w solar may be a bit of overkill, depending on what size deep cycle you get. For example, I have 100ah of Odyssey deep cycle in my trailer, powered by 120w of very efficient solar panel. It's plenty to power my 12v ARB fridge, water pump, LED trailer lights, occasional air compressor usage, occasional charging of my mobile devices and flashlight batteries, etc.

You also want to be sure whatever MPPT solar charge controller is in your DC-DC charger can handle the wattage of your future solar panel.

Good luck with it all; sounds like you're figuring out what you need.
.

 

[Sixstrings93]

I can’t speak for other vehicles, but on mine, a 2017 Jeep JK, it is t a “smart” alternator, but it also isn’t fixed voltage. It is a temperature adjusting alternator meaning it varies the voltage based on the temp in the engine bay. So I need a dc-dc charger. The best one I have found so far for my application is the Redarc dc-dc in your preferred amperage. According to the redarc site, this charger is also an isolator so I don’t need to buy both and is designed for an in-cab aux battery.

My plan now is to is to get the redarc dc-dc with the proper fuses (30amp since I’m getting the 25A charger) wire it permanent behind my front seats to provide easy access, and wire in a 12v connector hub for my fridge and run some camp lights to the Aux battery. When I can I will invest in a 300w solar to run while camped out.

I am still in Iraq for now, but when I get back, all the parts will be waiting for me so I will post pictures on this thread of the install for the people that come behind us on this thread!

.
Yes, that's what I've been trying to explain. Having a good DC-DC charger eliminates the need for a separate isolator AND allows you to just get one new battery (deep cycle for the 'house' connections), and will allow future solar connections.

300w solar may be a bit of overkill, depending on what size deep cycle you get. For example, I have 100ah of Odyssey deep cycle in my trailer, powered by 120w of very efficient solar panel. It's plenty to power my 12v ARB fridge, water pump, LED trailer lights, occasional air compressor usage, occasional charging of my mobile devices and flashlight batteries, etc.

You also want to be sure whatever MPPT solar charge controller is in your DC-DC charger can handle the wattage of your future solar panel.

Good luck with it all; sounds like you're figuring out what you need.
.

You’ve been a huge help!

 

[REDARC_Ryan]

.
Yes, that's what I've been trying to explain. Having a good DC-DC charger eliminates the need for a separate isolator AND allows you to just get one new battery (deep cycle for the 'house' connections), and will allow future solar connections.

300w solar may be a bit of overkill, depending on what size deep cycle you get. For example, I have 100ah of Odyssey deep cycle in my trailer, powered by 120w of very efficient solar panel. It's plenty to power my 12v ARB fridge, water pump, LED trailer lights, occasional air compressor usage, occasional charging of my mobile devices and flashlight batteries, etc.

You also want to be sure whatever MPPT solar charge controller is in your DC-DC charger can handle the wattage of your future solar panel.

Good luck with it all; sounds like you're figuring out what you need.
.

Great info! As for our BCDC Wattage isn't much concern its the Voltage. Our BCDC's are capped at 32VOC, so make sure your panels collectively do not exceed 32V or the BCDC will not accept your solar input.

 

[Sixstrings93]

.
Yes, that's what I've been trying to explain. Having a good DC-DC charger eliminates the need for a separate isolator AND allows you to just get one new battery (deep cycle for the 'house' connections), and will allow future solar connections.

300w solar may be a bit of overkill, depending on what size deep cycle you get. For example, I have 100ah of Odyssey deep cycle in my trailer, powered by 120w of very efficient solar panel. It's plenty to power my 12v ARB fridge, water pump, LED trailer lights, occasional air compressor usage, occasional charging of my mobile devices and flashlight batteries, etc.

You also want to be sure whatever MPPT solar charge controller is in your DC-DC charger can handle the wattage of your future solar panel.

Good luck with it all; sounds like you're figuring out what you need.
.

Great info! As for our BCDC Wattage isn't much concern its the Voltage. Our BCDC's are capped at 32VOC, so make sure your panels collectively do not exceed 32V or the BCDC will not accept your solar input.

Noted, 32 volts. The panels I am looking at right now are the goal zero panels so I’ll double check and shop around.

 

[REDARC_Ryan]

.
Yes, that's what I've been trying to explain. Having a good DC-DC charger eliminates the need for a separate isolator AND allows you to just get one new battery (deep cycle for the 'house' connections), and will allow future solar connections.

300w solar may be a bit of overkill, depending on what size deep cycle you get. For example, I have 100ah of Odyssey deep cycle in my trailer, powered by 120w of very efficient solar panel. It's plenty to power my 12v ARB fridge, water pump, LED trailer lights, occasional air compressor usage, occasional charging of my mobile devices and flashlight batteries, etc.

You also want to be sure whatever MPPT solar charge controller is in your DC-DC charger can handle the wattage of your future solar panel.

Good luck with it all; sounds like you're figuring out what you need.
.

Great info! As for our BCDC Wattage isn't much concern its the Voltage. Our BCDC's are capped at 32VOC, so make sure your panels collectively do not exceed 32V or the BCDC will not accept your solar input.

Noted, 32 volts. The panels I am looking at right now are the goal zero panels so I’ll double check and shop around.

Are you looking for fixed panels, or portable? And if Portable, looking for blanket or solid panel?

 

[Sixstrings93]

.
Yes, that's what I've been trying to explain. Having a good DC-DC charger eliminates the need for a separate isolator AND allows you to just get one new battery (deep cycle for the 'house' connections), and will allow future solar connections.

300w solar may be a bit of overkill, depending on what size deep cycle you get. For example, I have 100ah of Odyssey deep cycle in my trailer, powered by 120w of very efficient solar panel. It's plenty to power my 12v ARB fridge, water pump, LED trailer lights, occasional air compressor usage, occasional charging of my mobile devices and flashlight batteries, etc.

You also want to be sure whatever MPPT solar charge controller is in your DC-DC charger can handle the wattage of your future solar panel.

Good luck with it all; sounds like you're figuring out what you need.
.

Great info! As for our BCDC Wattage isn't much concern its the Voltage. Our BCDC's are capped at 32VOC, so make sure your panels collectively do not exceed 32V or the BCDC will not accept your solar input.

Noted, 32 volts. The panels I am looking at right now are the goal zero panels so I’ll double check and shop around.

Are you looking for fixed panels, or portable? And if Portable, looking for blanket or solid panel?

Definitely portable, and as far as blanket or solid, I can do either or

 

[REDARC_Ryan]

.
Yes, that's what I've been trying to explain. Having a good DC-DC charger eliminates the need for a separate isolator AND allows you to just get one new battery (deep cycle for the 'house' connections), and will allow future solar connections.

300w solar may be a bit of overkill, depending on what size deep cycle you get. For example, I have 100ah of Odyssey deep cycle in my trailer, powered by 120w of very efficient solar panel. It's plenty to power my 12v ARB fridge, water pump, LED trailer lights, occasional air compressor usage, occasional charging of my mobile devices and flashlight batteries, etc.

You also want to be sure whatever MPPT solar charge controller is in your DC-DC charger can handle the wattage of your future solar panel.

Good luck with it all; sounds like you're figuring out what you need.
.

Great info! As for our BCDC Wattage isn't much concern its the Voltage. Our BCDC's are capped at 32VOC, so make sure your panels collectively do not exceed 32V or the BCDC will not accept your solar input.

Noted, 32 volts. The panels I am looking at right now are the goal zero panels so I’ll double check and shop around.

Are you looking for fixed panels, or portable? And if Portable, looking for blanket or solid panel?

Definitely portable, and as far as blanket or solid, I can do either or

Keep an eye on our website over the next few months if you’re not in a rush

 

[Sixstrings93]

.
Yes, that's what I've been trying to explain. Having a good DC-DC charger eliminates the need for a separate isolator AND allows you to just get one new battery (deep cycle for the 'house' connections), and will allow future solar connections.

300w solar may be a bit of overkill, depending on what size deep cycle you get. For example, I have 100ah of Odyssey deep cycle in my trailer, powered by 120w of very efficient solar panel. It's plenty to power my 12v ARB fridge, water pump, LED trailer lights, occasional air compressor usage, occasional charging of my mobile devices and flashlight batteries, etc.

You also want to be sure whatever MPPT solar charge controller is in your DC-DC charger can handle the wattage of your future solar panel.

Good luck with it all; sounds like you're figuring out what you need.
.

Great info! As for our BCDC Wattage isn't much concern its the Voltage. Our BCDC's are capped at 32VOC, so make sure your panels collectively do not exceed 32V or the BCDC will not accept your solar input.

Noted, 32 volts. The panels I am looking at right now are the goal zero panels so I’ll double check and shop around.

Are you looking for fixed panels, or portable? And if Portable, looking for blanket or solid panel?

Definitely portable, and as far as blanket or solid, I can do either or

Keep an eye on our website over the next few months if you’re not in a rush

Haha no, no rush, I still have a few months left in the sandbox. I’ll keep an eye out on redarc!

 

[smlobx]

Hi folks. I just thought that I’d just give you my impressions of the Redarc 1240 BCDC controller.

In short it went very well. Now I have to say I am by no means an electrician in fact, I’m an electrical virgin…

Anyway, I had a couple of question about various steps and @REDARC_Ryan WAS ABLE TO GET ME THE ANSWERS QUICKLY. Tahnks!

Here are a few pictures of the install in my Jeep Gladiator with an Alu-Cab canopy in the back…

I HIGHLY RECOMMEND THEIR PRODUCTS AND SUPPORT1 THEIR PRODUCTS AND SUPPORT!

 

[REDARC_Ryan]

Hi folks. I just thought that I’d just give you my impressions of the Redarc 1240 BCDC controller.

In short it went very well. Now I have to say I am by no means an electrician in fact, I’m an electrical virgin…

Anyway, I had a couple of question about various steps and @REDARC_Ryan WAS ABLE TO GET ME THE ANSWERS QUICKLY. Tahnks!

Here are a few pictures of the install in my Jeep Gladiator with an Alu-Cab canopy in the back…

I HIGHLY RECOMMEND THEIR PRODUCTS AND SUPPORT1View attachment 203862View attachment 203863View attachment 203864View attachment 203865View attachment 203866View attachment 203867 THEIR PRODUCTS AND SUPPORT!

It looks great! Now go test it out