AGM Dual Battery System

[Tooolman]

I have a 2017 Tacoma Off Road and I'm interested in setting up a dual battery system that can expand to accept a solar charger at some point in the future. I have been researching many different dual battery setups and I'm wondering is anyone has real world experience with different systems, the benefits of each and the problems I might expect to encounter. I've heard good and bad things about Optima batteries and I'm also wondering what options are available for a solid reliable battery (or two).

 

[reaver]

What are you planning on running with it? I recently went through the process of figuring out power solutions myself.

After getting the agm battery (105Ah), isolator solenoid ($110 or so, including terminals and wires), fuse block, outlets, etc, I was looking at over $700, and it still wouldn't do everything I need, nor would it have solar capability.

As I'm sure you're aware, agm batteries have roughly half of their Amp hours that are usable. So, I was looking at $700 for what was a about 52 Ah.

What I opted to do, was pick up a 540Wh lithium power station for about 460. This gives me about 45 Ah of usable power, has a solar charger built in, and can run a fridge for about 30 hours on a full charge. I can also remove it from the truck, and use it to power both my wife and my cpap machines.

My plan is to combine this with an agm deep cycle starter battery that I can use to run things on the truck such as lights, and other things if need be.

For my needs, I think this is the best solution right now.

I bring this up to emphasize the point that, depending on what you want to do with your build, a dual battery system may not be right for you. They're great setups, but they do have their limitations, as does everything else.

Food for thought.

 

[Cpol]

 

[Kilo Sierra]

Are you planning on the dual battery in the engine compartment or in the cab?

If you're planning to use a DC-DC charger, they do make ones that are solar ready.

 

[Tooolman]

What are you planning on running with it? I recently went through the process of figuring out power solutions myself.

After getting the agm battery (105Ah), isolator solenoid ($110 or so, including terminals and wires), fuse block, outlets, etc, I was looking at over $700, and it still wouldn't do everything I need, nor would it have solar capability.

As I'm sure you're aware, agm batteries have roughly half of their Amp hours that are usable. So, I was looking at $700 for what was a about 52 Ah.

What I opted to do, was pick up a 540Wh lithium power station for about 460. This gives me about 45 Ah of usable power, has a solar charger built in, and can run a fridge for about 30 hours on a full charge. I can also remove it from the truck, and use it to power both my wife and my cpap machines.

My plan is to combine this with an agm deep cycle starter battery that I can use to run things on the truck such as lights, and other things if need be.

For my needs, I think this is the best solution right now.

I bring this up to emphasize the point that, depending on what you want to do with your build, a dual battery system may not be right for you. They're great setups, but they do have their limitations, as does everything else.

Food for thought.

My plan is to be able to run a camp refrigerator, water pump for sink water and lights as well as phone/ iPad/camera battery chargers. Solar would allow me to extend my run time on the aux battery without the need to start the truck. Mainly I want the insurance of never dropping my starter Battery so low that I couldn’t start the engine.

 

[Tooolman]

Are you planning on the dual battery in the engine compartment or in the cab?

If you're planning to use a DC-DC charger, they do make ones that are solar ready.

I believe that I would use a dc-dc charger that is solar ready. The second battery would ideally be in the engine compartment somewhere.

 

[Cpol]

 

[leeloo]

I was a cheap bastard and I tried what reaver posted, mine was 460 W. You can find them cheap, and they are cheap for a big reason. They are very slow to charge. When you leave from home, all is good. After you sit one day in one place, to charge them via a normal cigarrete plug thingie will take 8 h, that means you will have to drive 8 h. Even on a camp site with power connections they take 4-5 h. Most of them recommend that you don't charge and have consumers on them same time. They work, but most likely they will break fast. It is a good unit to have a as a back-up, it is light and mobile, most cand be used as a jumpstarter as well, so they are good to have in a pinch.
Than I got 105 AGM with a Voltage Sensing Relay, which is fairly cheap. The issue is your AGM will never be fully charged, a normal alternator wil not put out the 14.5V that an AGM will require to charge to 100% . Charging is relatavily slow, but much better than before. So you can still use it, but have in mind perhaps an even bigger battery. but that means more weight. If I wanted to stay 2 days on one spot, was impossible, had to start the engine and keep it running for 1 h at least.
So I bit the bullet and got a dc-dc. In 20 min the AGM is fully charged. I have a solar panel I can connect to it, but now since the battery is is charged much better, I will last 2 days anyway. I did some experiments with a 100w soalr panel, in ideal conditions will charge a bit over 1 amp so that covers whatever it is consumed by the fridge during the day and even charges the battery a bit, so in the evening has mor charge than in the morning even if I use it all day and charge phones on it, etc.
You can put an AGM in the engine compartment, but if you look at the spec sheet of any AGM it will half the life of it easy. Heat will kill even Optima or other manufaturers thay say that they are ok to use in the engine comparment. It will work but instead of lasting a good 7-8 years, will be done in 4 or less.

Redarc is expensive but there are other ones who work well if they are not in the engine comparment like Victron, CTEK, or other brands. A 20 amp is more than enough for 1 auxiliary battery.
So buy once, cry once.

 

[reaver]

I thought about the charge time for the lithium power station. I believe I can can get around it by using my inverter to charge it while driving.

I don't even have a fridge at the moment, so it's almost entirely going to be used to power CPAPs and charge camera batteries. Once I do get a fridge, I'll pick up some solar panels, and give that a shot. If it doesn't do what I need, or breaks, I'll bit the bullet and go dual battery, but I don't think I'll need to.

 

[Road]

A lot of dual charging systems with isolators and switches or DC-DC charging setups are expensive, overthought, and over-built for what most folks need for occasional adventures.

After spending as much time on the road camping and wandering off-grid as I do, living out of a vehicle on adventures lasting several months, I'm convinced a lot of gear folks buy (not just power systems) is because they think they have to have it to get by. And that it looks cool and everyone else is getting it, so you think you should too. I've done it myself more than I care to admit. I've sold or given most of it away. I still have a murder spork, brand new, I'm selling.

Battery systems for vehicle camping really do not need to be as complicated or as expensive as most setups seem to be trending towards.

You can also, and easily, put together a very efficient and long-lasting house battery set-up, with solar as primary input, that is independent of the starting battery.

I've been running two Odyssey 50ah AGM in my trailer for almost three years, completely independent of my starting batteries. I have a Duramax diesel, so two starting batts. Other than the trickle charge the trailer batteries get through the 7way trailer plug when driving, they are completely powered by solar. No isolator from the starting batteries, no DC-DC charger. I rarely ever run anything from the starting batteries unless driving down the road and charge my phone or use an iPod.

I do have a NOCO Genius Mini 2 smart charger ($99) hooked to the trailer batts if I ever want to plug into shore power. Not the NOCO jump starter deals, but a smart charger that stays in place 24/7. It's on the near wall in the image below, wired in full-time. I rarely use it, though like having it as back up.

My trailer batteries power my 12v ARB Fridge/Freezer, all the LED rock, work, and cargo lights on my trailer (second image below) the water pump, several USB ports for mobile devices, an air compressor, and through an inverter (now in the compartment next to the NOCO) charge my electric bike, camera batteries (I'm a photog so use a lot of rechargeables), all my flashlight and other rechargeable AA and AAA batts, and sometimes cordless power tool batteries. I also run my laptop regularly (even run a cord from trailer into the van to power it there) and occasionally an electric hair trimmer and other small tools.

While I'm not running all of that during The Big Pause, my trailer and batteries have not been hooked to shore power or the van for months and are still full every time I check them, just from the portable 120w folding panel I have strapped to the roof of the RTT. It's on the ground in the third image below.

I keep it strapped to the RTT roof when underway or parked for long anywhere. It pretty much lives up there, actually, unless I'm in camp, in which case I move it around during the day for maximum gain.

I agree with @leeloo, too, and am not a fan of the all-in-one type "power stations." They're mostly, from what I've seen, a dressed up battery with built-in inverter and usb outlets, marketed mainly to folks new to off-grid power as convenient and easy. I don't like them.



..

..


..

Power systems really do not need to be overly complex.

.

Roaddude - On the Road In North America - ROADDUDE

Roaddude - Traveling Photographer/Writer/Artist On the Road In North America. Gear, reviews, people, places, and culture.

roaddude.com

 

[RubiBluCru]

I know Renogy has an all in one MPPT/Solar charge controller.

 

[KonzaLander]

@Toolman - It sounds like your intended use and electrical demand is about the same as mine. If you like running wire and creating your own install, you will probably enjoy this type of build.

What I did is this: Replace starting battery with a parts store AGM. Install second house battery with a parts store AGM under the hood. I am currently running AGM's from Advance Auto. Both batteries are pretty inexpensive and you can get a discount by buying them online and picking up in the store. These batteries wont win any AH awards, but my house battery will run a fridge for 24 hours in the summer without a supplemental charge.

The batteries are connected together with a 500amp solenoid via cables I built. The solenoid is wired to a switch inside. The switch can trigger the solenoid with an accessory (key on) power source so it activates when I start the rig, or the solenoid can be triggered by a permanently on (direct to house battery) power source which is useful for a self jump start or for any other reason you want to connect the batteries. The best part? I know exactly what is happening to my batteries and when vs. being surprised due to a smart controller malfunction.

Here is a rough outline of how I approached installing the batteries. I'd guess I have roughly $4-500 in my installed system:
Basic Dual Battery Install in a '99 Land Cruiser

I recently added 100w of solar to my set up to supplement the house battery when I am parked for more than a day. The solar keeps the house battery topped off and the solar charge controller shuts off the solar charge when it sense the +14v from alternator when the vehicle is started. To keep the AGM's happy I added a diode to the alternator voltage sensing circuit so it now charges between 14.2-14.7v.

 

[RubiBluCru]

@Tooolman. I’m in the same boat. I can’t decide between a lithium or AGM for a second battery for my JKU. I would like to have solar charging. Currently the only thing that would be using is a fridge. Decisions...decisions.

 

[Tooolman]

@Toolman - It sounds like your intended use and electrical demand is about the same as mine. If you like running wire and creating your own install, you will probably enjoy this type of build.

What I did is this: Replace starting battery with a parts store AGM. Install second house battery with a parts store AGM under the hood. I am currently running AGM's from Advance Auto. Both batteries are pretty inexpensive and you can get a discount by buying them online and picking up in the store. These batteries wont win any AH awards, but my house battery will run a fridge for 24 hours in the summer without a supplemental charge.

The batteries are connected together with a 500amp solenoid via cables I built. The solenoid is wired to a switch inside. This switch triggers the solenoid with an accessory (key on) power source so the solenoid activates when I start the rig, or a permanently on (direct to house battery) power source which is useful for a self jump start or for any other reason you want to connect the batteries. The best part? I know exactly what is happening to my batteries and when vs. being surprised due to a smart controller malfunction.

Here is a rough outline of how I approached installing the batteries. I'd guess I have roughly $4-500 in my installed system:
Basic Dual Battery Install in a '99 Land Cruiser

I recently added 100w of solar to my set up to supplement the house battery when I am parked for more than a day. The solar keeps the house battery topped off and the solar charge controller shuts off the solar charge when it sense the +14v from alternator when the vehicle is started. To keep the AGM's happy I added a diode to the alternator voltage sensing circuit so it now charges between 14.2-14.7v.

That's a really clean installation. I like the simplicity which would also seem to equate to reliability. What's the purpose of the voltmeter interrupt switch? Did you create a material list (brands, where purchased, etc.) Does you house battery only charge from the alternator? Do you get enough voltage from your Land Cruiser alternator to full charge the AGM batteries? I've heard that a standard alternator does not put out enough voltage to fully charge AGM batteries. Have you had and heat issues with your AGM's running under the hood?

 

[1Louder]

Had dual battery, removed dual battery. I have no need for the complexity and cost of all of that. 1 X2 Group 31 battery, 1 - 100 watt solar panel on the roof, 1 "Jumpbox" in case I kill my only battery. I never have by the way.

My 2 cents.

 

[KonzaLander]

My theory is that with a simple set up I could easily field repair or field bypass any part of the system without an issue. I know most of the aftermarket options are well built and I researched them heavily before starting my own build. There are instances right here on OB where somebody installed a kit (or had it installed) and ended up with dead battery(ies) in the field.

What's the purpose of the voltmeter interrupt switch?

It turns the voltmeters off.

Did you create a material list (brands, where purchased, etc.)

I did not, but most of the supplies came from Amazon so I could round up some details.

Does you house battery only charge from the alternator? Do you get enough voltage from your Land Cruiser alternator to full charge the AGM batteries? I've heard that a standard alternator does not put out enough voltage to fully charge AGM batteries.

I have AGM's for starting and house. They both charge from the alternator. I installed a diode on the alternator voltage sensing circuit. This tricks the alternator into charging at a higher voltage, about a 0.5 volt increase. I now see between 14.2 and 14.7 volts charging voltage from the alternator.




The house battery is also charged with a solar charge controller set to charge an AGM profile.

Have you had and heat issues with your AGM's running under the hood?

No issues with heat. I've run an AGM under the hood of my hot blooded Jeep for a decade. The first was a Diehard Platinum that died at 6 years, but that was my fault (left aux light on for a week). The current AGM in the Jeep is a 4 year old batteries plus AGM (not the X2).

I have no reason to believe an AGM will suffer under the hood of my Land Cruiser.

 

[Tooolman]

Had dual battery, removed dual battery. I have no need for the complexity and cost of all of that. 1 X2 Group 31 battery, 1 - 100 watt solar panel on the roof, 1 "Jumpbox" in case I kill my only battery. I never have by the way.

My 2 cents.

Thanks, there is definitely some wisdom behind not installing what is not required. I do have a jump box that I carry as much to help others as to back my rig up.

 

[Tooolman]

Thanks, there is definitely some wisdom behind not installing what is not required. I do have a jump box that I carry as much to help others as to back my rig up.

BTW are you running an AGM or standard lead/acid battery?

 

[1Louder]

BTW are you running an AGM or standard lead/acid battery?

AGM , X2Power Premium AGM BCI Group 27F Car and Truck Battery - SLI27FAGMDP at Batteries Plus Bulbs similar to a group 31.

 

[leeloo]

What ever solution you will use, use appropiate size wires and fuses. If you think a dual battery setup is expensive, a fire is even more expensive..