Deep cycle agm battery replacement?

phantasticphil

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Oct 27, 2024
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Portland Oregon
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2012 FJ Cruiser, 2024 Land Cruiser
I'm wondering if anyone's considered or have upgraded/replaced the 12v battery with an agm deep cycle like the x2 power battery?

I'd like to have the ability to have power with the car off and not have to worry about charging an external power station for a fridge etc.
 
I installed an Optima DH6.
Nice! How are you managing the voltage requirements of that battery to get it full? I run a 100ah x2 power battery in my FJ and had to do a fuse mod to get the alternator to voltage that these like to see. I feel like that plus a jumper (similar to the setup I have now, single battery for starting and accessories) would enable me to solve the problem.
 
Nice! How are you managing the voltage requirements of that battery to get it full? I run a 100ah x2 power battery in my FJ and had to do a fuse mod to get the alternator to voltage that these like to see. I feel like that plus a jumper (similar to the setup I have now, single battery for starting and accessories) would enable me to solve the problem.
Mine is a direct replacement, not an additional battery. As far as the alternator, the LC doesn't have one. The LC uses a DC to DC inverter from the traction battery (hybrid) to charge the 12v battery. There is a constant draw on the on the 12v system somewhere and, in my case, the old battery would go flat if I didn't drive it at least once or twice a month. When I get caught up on my mods, I plan on doing some snooping and figure out which circuits are responsible and if a simple shut off switch could be used, or if a battery disconnect switch is in order.
 
Im wondering if my dash cam is a draw... its always on. The OEM dash cam that came with my LC
 
Mine is a direct replacement, not an additional battery. As far as the alternator, the LC doesn't have one. The LC uses a DC to DC inverter from the traction battery (hybrid) to charge the 12v battery. There is a constant draw on the on the 12v system somewhere and, in my case, the old battery would go flat if I didn't drive it at least once or twice a month. When I get caught up on my mods, I plan on doing some snooping and figure out which circuits are responsible and if a simple shut off switch could be used, or if a battery disconnect switch is in order.
Yep understood that it's a direct replacement, that would be my plan as well. The float for that battery will need 13.2 to 13.8 volts, the charge will need 13.8 to 15 volts. That is higher than the battery you replaced. The "full" voltage once nothing is on it should be around 13 volts, not 12.6.

I would assume the LC charger for that battery is targeting a range that is full at 12.6, which will require lower charge voltage than the AGM battery will. If you go test the voltage without anything connected (assuming there's passive draw and/or trickle), I'd be curious to know what the current voltage is. My guess is that it will be around 12.6, which I think is roughly 70 - 80% of that batteries capacity (don't quote me on this).
 
Yep understood that it's a direct replacement, that would be my plan as well. The float for that battery will need 13.2 to 13.8 volts, the charge will need 13.8 to 15 volts. That is higher than the battery you replaced. The "full" voltage once nothing is on it should be around 13 volts, not 12.6.

I would assume the LC charger for that battery is targeting a range that is full at 12.6, which will require lower charge voltage than the AGM battery will. If you go test the voltage without anything connected (assuming there's passive draw and/or trickle), I'd be curious to know what the current voltage is. My guess is that it will be around 12.6, which I think is roughly 70 - 80% of that batteries capacity (don't quote me on this).
Once it comes off the trickle charger (C-Tek) it's around 12.8 -13.1, which I think is normal............ sitting for a week it'll drop to 12.1 another week of sitting down to 11.9 etc.... all the way to "not enough to start it". If I don't plan on driving it for more than a week, I plug the trickle charger in.
 
Once it comes off the trickle charger (C-Tek) it's around 12.8 -13.1, which I think is normal............ sitting for a week it'll drop to 12.1 another week of sitting down to 11.9 etc.... all the way to "not enough to start it". If I don't plan on driving it for more than a week, I plug the trickle charger in.
Ahh I see, how are you running the trickle charger? Plug in at home or something with the inverter? I could see a trickle charger being used while running and the inverter is on up meet the voltage requirements of the battery, but then again it's pretty much the same thing as just charging an external power station ๐Ÿ˜ญ.

And ya wow, that's a big drop in voltage!

Looking forward to a hack that allows us to leave the inverter on all the time..
 
Ahh I see, how are you running the trickle charger? Plug in at home or something with the inverter? I could see a trickle charger being used while running and the inverter is on up meet the voltage requirements of the battery, but then again it's pretty much the same thing as just charging an external power station ๐Ÿ˜ญ.

And ya wow, that's a big drop in voltage!

Looking forward to a hack that allows us to leave the inverter on all the time..
Plug in the wall for me. I did purchase a capacitor jump box that's dedicated solely to the LC. On the several occasions the 12v battery went flat the jump box was enough to get the 12v system online and allow the traction battery to start the engine.
 
My battery went flat again yesterday. I got all kinds of error messages that went away after a day. I'm looking for a direct replacement. All I was doing was opening the moon roof a couple of times working on the roof rack and I left the vehicle on for about an hour. I'm worried I can't even listen to the radio without the engine on - I don't go anywhere without my booster and don't trust factory battery (at least the one I have) - I'll try the Optima you are recommending! Thanks :)
 
Plug in the wall for me. I did purchase a capacitor jump box that's dedicated solely to the LC. On the several occasions the 12v battery went flat the jump box was enough to get the 12v system online and allow the traction battery to start the engine.
Are you attaching the trickle charger to the battery directly in the rear compartment or are you using the jump start connection under the hood?
 
Both..... LOL I installed pig tails at the battery and under the hood. Initially it was for 12v convivence while working under the hood and appliance port for the rear. I have since moved to an EcoFlow Delta 2 max and now they are for trickle charging and 12v accessories like my electric scissor jack.
 
Both..... LOL I installed pig tails at the battery and under the hood. Initially it was for 12v convivence while working under the hood and appliance port for the rear. I have since moved to an EcoFlow Delta 2 max and now they are for trickle charging and 12v accessories like my electric scissor jack.
So you can use the jump connector in the right fuse box under the hood to trickle charger the battery without jacking up anything. I only drive mine every few weeks at this point. Raising the hood is easier than getting to the battery for me. Its also way closer to the outlet and I dont need an extension chord.
 
So you can use the jump connector in the right fuse box under the hood to trickle charger the battery without jacking up anything. I only drive mine every few weeks at this point. Raising the hood is easier than getting to the battery for me. Its also way closer to the outlet and I dont need an extension chord.
I've had success doing it with my under hood pig tail.
 
I've had success doing it with my under hood pig tail.
One more and I will leave you be. You pigtailed the red/positive off the jump start terminal I assume. Where did you connect the negative wire from the charger. Just ground it to a metal part of the car?
 
One more and I will leave you be. You pigtailed the red/positive off the jump start terminal I assume. Where did you connect the negative wire from the charger. Just ground it to a metal part of the car?
There are several OEM grounding points all over the engine bay (along the fenders) I used one somewhere around the air box.
 
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