Adding an Auxiliary Battery

[Groffer]

I've been looking into adding an auxiliary for secondary features such as lights and a DC-AC converter for the back of the pickup so I won't have to leave the truck idling while running these accessories.

I picked out a 100 Ah Lithium Iron Phosphate Deep Cycle Battery (LiFePO4) with a 12V 20A battery charger (I'm not concerned about charging it quickly).

I know how the wiring and everything should go, I plan on putting it into the bed for now and eventually moving it to the engine bay once I put the ram airflow air intake on it so I have room in there.

My biggest concern is a fire hazard at this point. I plan on having my breakers and everything on it - should I have anything to worry about? Would it get too hot in the bed of the truck with the Tonneau on it? I'm from NY

Here are the main components:

20A Charger

100Ah Battery

 

[hogger]

Would it get too hot in the bed of the truck with the Tonneau on it?

IMHO probably. I have 2 x 100Ah LiFePO4 batteries, and I unload them after each road trip. I have a fiberglass topper on my bed, and during the days right now, the outside air temps hit the mid 70's, but inside the sealed up topper + bed, it's hitting close to 120F. Most of the these batteries have a max temp spec in the 120-150F range. During road trips, the batteries are buried under a lot of other junk, which seems to help them stay relatively cooler. I also tend to be driving during the day on road trips, so I suspect that helps cool the back a bit as well, even without open windows. I would definitely keep Li* out of the engine bay. The couple times this winter (SoCal) that I polled the IBS temp after driving around short distances, I got back about 125F.

 

[Groffer]

IMHO probably. I have 2 x 100Ah LiFePO4 batteries, and I unload them after each road trip. I have a fiberglass topper on my bed, and during the days right now, the outside air temps hit the mid 70's, but inside the sealed up topper + bed, it's hitting close to 120F. Most of the these batteries have a max temp spec in the 120-150F range. During road trips, the batteries are buried under a lot of other junk, which seems to help them stay relatively cooler. I also tend to be driving during the day on road trips, so I suspect that helps cool the back a bit as well, even without open windows. I would definitely keep Li* out of the engine bay. The couple times this winter (SoCal) that I polled the IBS temp after driving around short distances, I got back about 125F.

That's a good point, overheating would definitely be a concern. I was thinking about it a little more and I have two options; keep in mind I'm only ever going to be pulling 10A at the MOST, but usually 5A for now.

1) Wire in a quick disconnect so I can just pull the battery out the back of the truck and put it on a trickle charger overnight, don't need a DC-DC charger

2) Ditch the whole aux battery idea and wire in a low-voltage disconnect switch coming off of the main battery so the lights don't drain it. This option also saves me $450+ that I could use to get a nice jump starter pack instead

 

[hogger]

That's a good point, overheating would definitely be a concern. I was thinking about it a little more and I have two options; keep in mind I'm only ever going to be pulling 10A at the MOST, but usually 5A for now.

1) Wire in a quick disconnect so I can just pull the battery out the back of the truck and put it on a trickle charger overnight, don't need a DC-DC charger

2) Ditch the whole aux battery idea and wire in a low-voltage disconnect switch coming off of the main battery so the lights don't drain it. This option also saves me $450+ that I could use to get a nice jump starter pack instead

I've designed my system to be able to power a 2000w inverter at full power. I also set it up to "trickle" backfeed the truck at up to 18A, (still adjusting due to lack of diligence calculating the loss on the back feed circuit, only getting about 10A). The batteries each have 2x AS150u, which claim 70 continuous current handling. So pretty quick to disconnect. I spend more time dealing with the tie down for the battery box! For lower currents (<30A), XT-60s aren't bad, and I like that there's cheap little protection caps you can buy off the shelf to cover the contacts when not in use. Wish someone made them for the AS150u's

The truck is an absolute battery hog when it's "off", I'd recommend running the aux battery. My aux battery ends up supporting the truck over night on road trips. Basically every time I open the door to get something around camp, it fires up the infotainment system, and leaves that running for a while (but insists on killing the interior lights after a couple minutes so they are effectively useless!). When the infotainment system spools up, the truck is drawing about 6-8A off my aux bank. That's in addition to whatever it's pulling from it's own starter battery. I think with a clamp meter, I estimated somewhere near 11A draw by the infotainment system. Do that a few times and it quickly runs the battery down. Then there's the night I forgot to hide the FOB from it in the Faraday bag. Barely had enough left in the starter batterry to start in the morning! Carrying a jump starter is essential. Get a good one. That V8 takes a lot to turn over. Again due to the heat issue, I stick to SLA. I haven't measured what the interior of the truck gets up to, but years ago when I left a high/low thermometer on the back seat of my Camry, it registered out of range (>150F) on a warm SoCal day.

I'd like to eventually figure out how to mount my aux batteries in some of the space under the truck, but I haven't had time to work out a mounting solution down there. Should keep them cooler, and free up some space in the bed. I'm not a fan of sleeping right next to those little bombs.

Another thought I had just now given that you are in NY. LiFePO4 is not supposed to be charged below freezing. I notice the AMZN listing does not mention low temp protection built in for that battery, but even if it did, Will Prowse of the DIYSolar forum has demonstrated that some "economy" batteries that do claim it don't actually work correctly.

 

[boogielander]

In-depth View of Electrical System for Overlanding and Offroading

This technical post was first posted to Jolly Rogue Co's Blog here on 3/30/2024. You can find all of my instructional and technical postings here Introduction Electrical systems are critical to a successful modern overlanding trip. Everything that we rely on for a good overlanding experience...

5thgenrams.com

so this is my setup. i dont think you have much to worry about. at 20A it shouldn't give you any problems (i'm running my Renogy DC-DC at 50A max lol) provided that you use proper gauged wires.

but out of curiosity, can you throw in one of those bluetooth thermometer under the bed cover and see how hot it goes?

 

[hogger]

but out of curiosity, can you throw in one of those bluetooth thermometer under the bed cover and see how hot it goes?

No BT, but I have some other temperature monitoring capabilities, and of course I can read the IBS temp. That being said, it's going to have to wait a couple weeks. Truck is currently out of service AGAIN(!!!) for a recurring check engine light, and it just got pushed back (dealer) another week to get it looked at.

 

[boogielander]

No BT, but I have some other temperature monitoring capabilities, and of course I can read the IBS temp. That being said, it's going to have to wait a couple weeks. Truck is currently out of service AGAIN(!!!) for a recurring check engine light, and it just got pushed back (dealer) another week to get it looked at.

damn that's rough!

im just curious how hot it gets in there with the cover.
WIth the GFC, since the camper is not 100% sealed temperature is not really a concern for me. i mean, if anything, since the truck sits at home most of the days, I can just leave one panel open lol
or i can always install the vent to keep the airflow going.

possibilities are endless with GFC lol

 

[RHCan]

Added 2nd battery under hood

 

[boogielander]

Added 2nd battery under hood

drooling over that mopar CAI

 

[jimothy]

Caveats about lithium under the hood aside, here’s my current alternative to an aux battery: a LiFePO4 starter/deep cycle battery.

I am concerned about temperatures. I’ve got a quartet of Govee Bluetooth thermometers: under the hood next to the battery; another with a corded temperature probe taped to the side of the battery, under the heat blanket; one in the cab, and one in the bed. Each keep a history of temps, so I can see the high/low temps.

What I’ve done since the last time I wrote about this project (aside from adding the wired thermometer probe) is wired up my solar charge controller. That’s right, I can now charge my starter battery from the sun!

In the picture below, I’ve got a portable 400W solar panel, but I’ve also got 350W panels on my rooftop tent (not in my rack at the moment). That would allow me to charge the battery via solar when I drive. But isn’t that the job of the alternator (or DC-DC charger in the case of an eTorque like mine)?

Yes, but the Ram doesn’t know how to charge the LiFePO fully; I’m still tweaking settings in JScan, but according to the battery’s Bluetooth BMS, the Ram stops charging it around 75-80%.

It’s too earlier to say what temperatures will do to the battery’s health over time. I feel it’s more likely I will have burned a pile of cash with this experiment that burn my truck in a ball of fire, but hopefully neither.

There’s a guy who has been running this same battery in his Tacoma for two years running, and neither he nor his battery have died so far, so I’m hopeful.







Plus, a bonus pic of my lovely assistant, Addie, who wanted to be part of my wiring effort.

 

[RAM Patriot]

If you have a lead acid battery or AGM as your starter battery I would purchase an auxiliary battery that is the same type of battery and cranking amperage to help with the charging profile.

Lithium battery manufacturers recommend specialized lithium battery chargers for optimal performance.

When I setup my auxiliary battery I used the REDARC Smart Start SBI12, which is a 100A 12V battery isolator which protects the start battery from excessive discharge, while allowing the auxiliary battery to supply charge to non-essential loads.

 

[boogielander]

If you have a lead acid battery or AGM as your starter battery I would purchase an auxiliary battery that is the same type of battery and cranking amperage to help with the charging profile.

Lithium battery manufacturers recommend specialized lithium battery chargers for optimal performance.

When I setup my auxiliary battery I used the REDARC Smart Start SBI12, which is a 100A 12V battery isolator which protects the start battery from excessive discharge, while allowing the auxiliary battery to supply charge to non-essential loads.

View attachment 181904

View attachment 181901
View attachment 181903

redarc is good but just so bank lol
but i have to admit, they are the best option out there.

 

[boogielander]

View attachment 181863 Caveats about lithium under the hood aside, here’s my current alternative to an aux battery: a LiFePO4 starter/deep cycle battery.

I am concerned about temperatures. I’ve got a quartet of Govee Bluetooth thermometers: under the hood next to the battery; another with a corded temperature probe taped to the side of the battery, under the heat blanket; one in the cab, and one in the bed. Each keep a history of temps, so I can see the high/low temps.

What I’ve done since the last time I wrote about this project (aside from adding the wired thermometer probe) is wired up my solar charge controller. That’s right, I can now charge my starter battery from the sun!

In the picture below, I’ve got a portable 400W solar panel, but I’ve also got 350W panels on my rooftop tent (not in my rack at the moment). That would allow me to charge the battery via solar when I drive. But isn’t that the job of the alternator (or DC-DC charger in the case of an eTorque like mine)?

Yes, but the Ram doesn’t know how to charge the LiFePO fully; I’m still tweaking settings in JScan, but according to the battery’s Bluetooth BMS, the Ram stops charging it around 75-80%.

It’s too earlier to say what temperatures will do to the battery’s health over time. I feel it’s more likely I will have burned a pile of cash with this experiment that burn my truck in a ball of fire, but hopefully neither.

There’s a guy who has been running this same battery in his Tacoma for two years running, and neither he nor his battery have died so far, so I’m hopeful.

View attachment 181858
View attachment 181859
View attachment 181860 View attachment 181861 View attachment 181862
View attachment 181866


Plus, a bonus pic of my lovely assistant, Addie, who wanted to be part of my wiring effort.

Addie is cute!
that aside, I ran my LiFEPO4 as starting battery in the 4Runner and that went though trips in the desert and it was fine. i think for batteries designed to be starting battery it shouldn't be a problem with heat, but that's just what I think.

also, if you could push the truck to push over 14v that should keep the LiFEPO4 happy.

 

[RAM Patriot]

redarc is good but just so bank lol
but i have to admit, they are the best option out there.

They are a little more than some of the China alternatives, but they are the best in the industry and stand behind there products.

Another reason I went with REDARC isolator, when the start battery and the auxiliary battery are linked a red led is visible on the isolator.

 

[c3k]

Second battery guys...where did you source the passenger-side battery tray?

 

[jimothy]

also, if you could push the truck to push over 14v that should keep the LiFEPO4 happy.

Unfortunately, I haven’t been able to get it to charge anywhere near that with JScan yet. I feel like I must have done something wrong, because it sits around 13.2V, sometimes lower, which is quite low for LFP. When it’s charging, it peaks around 13.6, sometimes 13.7 volts, as reported by the battery’s BMS and the truck’s IBS (via JScan).

 

[RAM Patriot]

Second battery guys...where did you source the passenger-side battery tray?

Had to retro fit a battery tray from a 2500.

Installed Dual Battery with Redarc Isolator

After installing Mopar’s “Ram Airflow” Cold-Air Intake System; I now have the room to install a second battery to run accessories without draining the starter battery. Does anyone know if the Battery Tray from the 2500's Passenger Side (Right) Battery Tray - Mopar (68350658AC) have the same...

5thgenrams.com

 

[boogielander]

They are a little more than some of the China alternatives, but they are the best in the industry and stand behind there products.

Another reason I went with REDARC isolator, when the start battery and the auxiliary battery are linked a red led is visible on the isolator.

yeap i like how they have the entire ecosystem and is trusted by expedition teams.

 

[ayoslickxd]

i made. a battery box basically pelican case with lifepo4 and inverter and. have wires for disconnect to my redarc 50amp charger. … i put fans in the box to circulate air ….