Dual battery charging idea? (1 Viewer)

ChaserFJ60

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1984 FJ60 2FE

Due to parts availability and my circumstances, I currently have two AGM battery's and two alternators. An fj60 and an fj62 alternator based off this FJ60 Dual Alternator - https://forum.ih8mud.com/threads/fj60-dual-alternator.94294/

Things is, I don't want or need two alternators, its more equipment to maintain and if something breaks its more $$, belts are hard to find in the right size, and there's more specialty hardware involved that I don't have access to. But I really like having two batteries and I really don't want to spend the $$$ for a DC to DC charger. The price seems a bit steep for what it does, or maybe im just naive to the battery charging world and still have much to learn.
I DIGRESS.

So given that AGM battery's are picky and want to be charged individually, I was thinking I could just program an Arduino that detects which battery is at a lower voltage, then fires a relay to send 100% alternator charge to the lowest charging battery until that battery is at a 100% charge. After the initial battery is charged it will test to check which battery is at the lowest voltage and repeat the process. The only difference I can think of here is the frequency of charge time from the alternator is decreased. I will add that a charging priority would be given to the starting battery.

For example. We will refer to our starting battery as A and our auxiliary battery as B and a full battery is 12.7V. Say A is at 12.5V and B is at 12.6V; Because A is lower, A will get full alternator charging until it reaches 12.7V. Now say A is at 12.1V and B is at 11.9V; Battery A will get charging priority because it is our starting battery and its more important that battery A stays charged than B. A minimum Emergency threshold will be put in that overrides B's charging IF and ONLY IF A goes under say 50% charge capacity. As long as A is above 50% capacity then the Arduino will alternate which battery gets charging priority based off of which batter has a lower voltage. IF both battery's are at a FULL charge then charging will default to A and charge as if it were in a single battery configuration - until B drops say 20% below A (To avoid a rapid back and forth transfer of charge).
This is just a rough draft of how my charging algorithm would work. I know I can do it, I don't know if it's a healthy solution for the battery's and will promote longevity.

If you know anything about charging systems or battery's please leave some input! Thanks for reading.
 
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Why not install a 200 watt solar panel on the roof and keep that second battery separate from the ignition system. Run your lights and accessories off the solar charged battery. If you’re in a bind you can swap or jump batteries.
My sister runs a set up like this in her camping suburban and I am acquiring the materials to install a set up like this in my 60.
I’m going to run a fridge 24/7 and don’t want to draw off my truck battery. It’s probably overkill but I would like to have power for air compressor, winch, and light bars etc...
 

ChaserFJ60

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Why not install a 200 watt solar panel on the roof and keep that second battery separate from the ignition system. Run your lights and accessories off the solar charged battery. If you’re in a bind you can swap or jump batteries.
My sister runs a set up like this in her camping suburban and I am acquiring the materials to install a set up like this in my 60.
I’m going to run a fridge 24/7 and don’t want to draw off my truck battery. It’s probably overkill but I would like to have power for air compressor, winch, and light bars etc...
Even though regular adventures are the goal, I'm a full time college student and never have time to go out and this FJ60 is my daily driver so I want to keep it as streamlined as I can.
Right now im going through a De-modification phase where i'm undoing all the crap mods I installed when I was in high school. Im debating getting rid of the 2nd battery all together and having my ARB compressor, winch, lights, radio come from the starting battery instead. Getting rid of the 2nd battery would be a great excuse to clean up my terrible high-school days wiring job. Im stuck on what I should do.

I just don't see any value in paying $200 for a battery switch. Im still exploring options on how to do mysetup. This is only plan B
 

rhah

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Even though regular adventures are the goal, I'm a full time college student and never have time to go out and this FJ60 is my daily driver so I want to keep it as streamlined as I can.
Right now im going through a De-modification phase where i'm undoing all the crap mods I installed when I was in high school. Im debating getting rid of the 2nd battery all together and having my ARB compressor, winch, lights, radio come from the starting battery instead. Getting rid of the 2nd battery would be a great excuse to clean up my terrible high-school days wiring job. Im stuck on what I should do.

I just don't see any value in paying $200 for a battery switch. Im still exploring options on how to do mysetup. This is only plan B
You have an ultimate dual alt setup

many people pay loads of money for a setup like that for a 2f

clean your wiring up and keep your dual alts it’s a huge benifit for a not a lot of headache, not like you added a new belt and now have to maintain it or its a lot of work to install, all the hard stuff is done.

if not, do the solar. Stock fj60 Alts I have found are good for the truck and charging your cell phone anything more and the whole system strains and struggles.
 
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Even though regular adventures are the goal, I'm a full time college student and never have time to go out and this FJ60 is my daily driver so I want to keep it as streamlined as I can.
Right now im going through a De-modification phase where i'm undoing all the crap mods I installed when I was in high school. Im debating getting rid of the 2nd battery all together and having my ARB compressor, winch, lights, radio come from the starting battery instead. Getting rid of the 2nd battery would be a great excuse to clean up my terrible high-school days wiring job. Im stuck on what I should do.

I just don't see any value in paying $200 for a battery switch. Im still exploring options on how to do mysetup. This is only plan B
Having a second battery is prime and worth the money, effort, and relestate in my opinion. Being that you’re in college I understand the squeeze. However, if you have two good AGM batteries I would most certainly use them.

My sister is a seasoned camper/overlander and so is her boyfriend. They thought they had prepared for everything when they left a door ajar overnight and drained the battery in the truck. Their friend had just installed the second battery/solar panel/inverter system for them and they were able to jump the dead battery with the charged one 30 miles from the nearest rangers station. And that was after using an electric blanket all night off that battery. So it was a life saver when they needed it.

I spend almost all of my time in my truck so I need the reliability of a second battery. I like the idea of a second alternator but I’m not desmogged yet and I don’t want to have to rely on the gas engine to recharge my electrical system. A 200 watt panel from Newpowa is about $175-200 and a good MPPT charger is around $100.

Hell, you could get a charge manager set up to omit the alternators all together and charge the whole system on solar.
 

g-man

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It's important to know what you are powering with your second battery. If for instance you have your winch on it, that could draw it down quickly ...then you want it connected to an alternator. But lets say its a deep cycle and you power an inverter and do some camping inside your vehicle and you just want your primary battery and alt to charge it, then a 12V to 12V dc trickle charger can be used to keep it topped off. They are around $30 or less and have an automatic float mode to prevent overcharging.
 
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It's important to know what you are powering with your second battery. If for instance you have your winch on it, that could draw it down quickly ...then you want it connected to an alternator. But lets say its a deep cycle and you power an inverter and do some camping inside your vehicle and you just want your primary battery and alt to charge it, then a 12V to 12V dc trickle charger can be used to keep it topped off. They are around $30 or less and have an automatic float mode to prevent overcharging.
That’s actually a really great idea. I’m going to seriously consider that one...
 

rhah

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ottawa, kansas
It's important to know what you are powering with your second battery. If for instance you have your winch on it, that could draw it down quickly ...then you want it connected to an alternator. But lets say its a deep cycle and you power an inverter and do some camping inside your vehicle and you just want your primary battery and alt to charge it, then a 12V to 12V dc trickle charger can be used to keep it topped off. They are around $30 or less and have an automatic float mode to prevent overcharging.
Wow 🤯

with @cps432 on that one
 

ChaserFJ60

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I dont know why, I just dont want the two alternators. I feel it over-complicates what should be simple setup. Maybe I'll put it back in if my current setup gets overworked.
I spent all day cleaning out my rats nest wireing and Im loving the way its going together without all the unnecessary relays. I might do @g-man idea
 

OSS

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I used one of these for 28 years. Never a problem even when mixing AGM and flooded lead acid

iu.jpeg
 

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