Has anyone tried running a lithium battery under the hood in their 2025+?

[Largefarrva]

Just wondering if anyone has changed out their agm (main and aux…or just main) battery under the hood in their 2025 or 2026 with a lithium battery.

 

[boogielander]

thought about doing that on a 2022 e-torque but ultimate didn't. had to pass up on the sponsorship opportunity due to voltage with e-torque.

what is your running voltage on the 25/ 26? if it's over 14v constant then you'll be fine with a LiFEPO4. if not then it is not recommended because LiFEPO4 is best charged at 14.4v

 

[Largefarrva]

thought about doing that on a 2022 e-torque but ultimate didn't. had to pass up on the sponsorship opportunity due to voltage with e-torque.

what is your running voltage on the 25/ 26? if it's over 14v constant then you'll be fine with a LiFEPO4. if not then it is not recommended because LiFEPO4 is best charged at 14.4v

So far it’s usually in the 13’s. The only time it would be 14-14.5v is after starting the truck and the charging system senses that the agm needs to be boosted due to the high discharge from starting.

A few weeks ago I had a Titan8 LTO lithium battery installed for my stereo system. So now my charging voltage tends to be in the low 13’s because the lithium battery is keeping the agm pretty much topped off all the time. If the truck sits for a day or two it’ll charge at 14-14.2v for a while but then it drifts back down to the low 13’s.

So I am going to replace the Titan8 with a battery bank I built myself made out of 20Ah LTO cells because the Titan8 is unreliable (very cheaply made).

So I was considering replacing the agm batteries under the hood since they are so much better than agm and with all these issues being reported with trucks draining down over night.

My concern is how the charging system will work with either LTO or lifepo4 lithium. So I was wondering if anyone has made the switch.

 

[boogielander]

i see. i ran LiFEPO4 on my 5th gen 4Runner before for about half a year or so and didn't get any problem, but then that was one with less CANBUS than our trucks and less computer intensive rig.

 

[LouNY]

I have a Lithium battery in my side x side. It works great in the summer, late spring and early fall. It pure dee sucks in the winter time. I have to use my boost pak when it's cold out. The cold Lithium will not crank it over. When it's very cool if I turn the lights on for a minute or two then try the starter it may crank over if not after a couple of tries warm up the battery it will work.

 

[boogielander]

I have a Lithium battery in my side x side. It works great in the summer, late spring and early fall. It pure dee sucks in the winter time. I have to use my boost pak when it's cold out. The cold Lithium will not crank it over. When it's very cool if I turn the lights on for a minute or two then try the starter it may crank over if not after a couple of tries warm up the battery it will work.

they need blankets, or see if they have self-heating ones.
If i move to somewhere that is really cold then I'll have to swap the LiFEPO4 in the bed (that powers my camper lights, run my laptop and diesel heater) to a self-heating unit.

 

[gofish]

Oh boy, what a first post, but here we go. I can chime in here. Hopefully others can chime in with their thoughts as well. I got a '26 1500 3.0L HO that I'm learning all sorts of things about right now, most of all the 12v and charging systems. (foreboding)

I dove in with both feet. May have bitten off more than I cared to chew, honestly. I figured I'd go ahead and replace not only the Aux battery with a LiFePO4, but also the Main battery too. 186Ah between the Main and Aux with half the weight to boot seemed like a good amount of juice for the squeeze, and I'm usually pretty savvy with stuff like this. I've worked on various cars over the years, and I wasn't too intimidated going into it.

I got an Alldata DIY subscription for the '25 1500 since the '26 isn't available yet. The material differences between the '25 and '26 are likely few and far between (someone correct me if I'm wrong here). I read a good amount about the charging and 12v systems before pulling the trigger and buying the batteries and necessary hardware. Namely, the about the two IBS sensors, as well as the alternator:

"The IBS monitors the battery voltage as well as current flow into and out of the battery. The IBS has a built-in thermistor that calculates the battery temperature. The microprocessor uses this data to calculate battery State of Charge (SOC), battery internal resistance, charge received, electrical demand, and time in service. This information is reported through the LIN Bus circuit to the Body Control Module (BCM). The BCM broadcasts the information to the Powertrain Control Module (PCM) over the CAN Bus."

"Most current vehicles utilize the Smart Charging control strategy. This strategy helps to improve vehicle performance, reduce CO2 emissions and increase fuel efficiency. The control strategy takes into account battery state of charge and electrical loads on the battery, as well as engine load. Vehicles that utilize the Smart Charging control strategy are equipped with an Intelligent Battery Sensor (IBS). The IBS is an important component of the Smart Charging control strategy.

• Idle and acceleration: Charging is typically suspended during idle and acceleration conditions. Due to this strategy it can be common for the alternator output to be equal to, or close to typical battery voltage at idle and during engine acceleration.
• Steady state speeds: During steady state speeds the charge rate is typically low, just enough to maintain battery voltage.
• Deceleration (regenerative braking): The charge rate is typically very high during deceleration.

The Smart Charging strategy can be used with any combination of the following vehicle configurations:

• Single Battery System
• Dual Battery System
• Electronic Voltage Regulation (EVR) Charging systems which use a standard alternator directly controlled by the PCM
• Charging systems using a smart alternator communicating with the PCM via LIN Bus

On vehicles equipped with a smart alternator, the PCM sends the voltage set point and ramp time commands to the alternator via a LIN bus communication circuit. The alternator controls the charging rate based on these commands."

I don't know what constitutes a "smart alternator", and I'm not sure if my truck has one. There's nothing on Alldata that I can find to help determine either way. But regardless, there is an IBS sensor located at the negative terminal of each battery, and since they supposedly have the ability to determine internal resistance, I figured that's the key right there. The two IBS's will each see that they're effectively connected to a LiFePO4 battery given that LiFePO4 batteries typically have about a 2-4x lower internal resistance than AGM batteries, and the resting voltage at 100% SOC is considerably higher. In turn, the IBS and alternator communication with the PCM should supposedly use this information to set the regulated voltage accordingly.

"Supposedly" being the key operator here... I'm now knee-deep into this, and I've run into a couple significant problems so far. First, the alternator clearly doesn't control the voltage in accordance with the battery's internal resistance and chemistry. The PCM/alternator lets the system voltage climb to over 16.2v at very mild acceleration RPM's, and around 15.2-15.5v at idle/cruising. It's not the batteries I'm worried about. The BMS's provide sufficient protection for the batteries should the thermals climb too far. It's the truck itself at that point which runs the risk of overvolting and doing god knows what to various electronics. I had all kinds of warning lights going off, notifications of systems getting disabled due to the voltage, which thankfully would reenable themselves each time the voltage dropped back down to less than 16v. At one point, I ended up with a blank IP cluster display with a red light of death in the lower right, and a no-start condition to top it all off. Thankfully I take tools everywhere I go. Disconnecting/reconnecting the main battery and leaving the IBS disconnected was enough to get it to start again. Beelined it home after that, got a 60A DC-DC LiFePO4 charger, and installed that.

The problem I have right now is still voltage regulation. I need to control the system voltage, and the only way I know that to be possible with the LiFePO4 charger is to install it in between the alternator and the rest of the 12v system. So I found the positive alternator cable and wired the charger input to that, and then wired the output to the 300A shunt terminal on the engine bay fuse box/PDC that the alternator + normally connects to. Truck started up just fine with that arrangement, but within about 10 seconds, the system voltage plummeted to under 10v, engine quit and everything died. I'm not sure if this is because the alternator refused to accommodate the load being pulled by the LiFePO4 charger at idle RPM's, or if the current needs by the vehicle far exceeded 60A, thus draining the potential and pulling the voltage down. It appears the over-discharge protection tripped the 36Ah Aux battery to effectively 0 volts, and after disconnecting/reconnecting it was at about 10.5v, so roughly 95% depth of discharge. Whatever the case though, this was a dumb idea. Best case scenario, I was knee-capping a 240A alternator to 60A. Worst-case, the truck turns into a dead stick within 10 seconds of starting.

So now, I'm looking at either a LiFePO4 alternator regulator like this, or literally adding (x) feet of 2/4AWG to the alternator cable to drop the voltage the old fashioned way. Neither prospect excites me. I'm open to suggestions primarily, or criticisms sparingly. I'm already giving myself enough **** right now, frankly. Having a new truck that's not drivable is gut-punchy enough as it is.

So yeah, I've dabbled in this. Care to join in the fun?

Edit: I don't suppose there's anything in AlfaOBD I can change to modify alternator/charging/battery type/voltage set point parameters? Wishful thinking, probably.
Edit 2: Yep, wishful thinking.

 

[boogielander]

Oh boy, what a first post, but here we go. I can chime in here. Hopefully others can chime in with their thoughts as well. I got a '26 1500 3.0L HO that I'm learning all sorts of things about right now, most of all the 12v and charging systems. (foreboding)

I dove in with both feet. May have bitten off more than I cared to chew, honestly. I figured I'd go ahead and replace not only the Aux battery with a LiFePO4, but also the Main battery too. 186Ah between the Main and Aux with half the weight to boot seemed like a good amount of juice for the squeeze, and I'm usually pretty savvy with stuff like this. I've worked on various cars over the years, and I wasn't too intimidated going into it.

I got an Alldata DIY subscription for the '25 1500 since the '26 isn't available yet. The material differences between the '25 and '26 are likely few and far between (someone correct me if I'm wrong here). I read a good amount about the charging and 12v systems before pulling the trigger and buying the batteries and necessary hardware. Namely, the about the two IBS sensors, as well as the alternator:





I don't know what constitutes a "smart alternator", and I'm not sure if my truck has one. There's nothing on Alldata that I can find to help determine either way. But regardless, there is an IBS sensor located at the negative terminal of each battery, and since they supposedly have the ability to determine internal resistance, I figured that's the key right there. The two IBS's will each see that they're effectively connected to a LiFePO4 battery given that the internal resistance of LiFePO4 batteries are typically have about a 2-4x lower internal resistance than AGM batteries, and the resting voltage at 100% SOC is considerably higher. In turn, the IBS and alternator communication with the PCM should supposedly use this information to set the regulated voltage accordingly.

"Supposedly" being the key operator here... I'm now knee deep into this, and I've run into a couple significant problems so far. First, the alternator clearly doesn't control the voltage in accordance with the battery's internal resistance and chemistry. The PCM/alternator lets the system voltage climb to over 16.2v at very mild acceleration RPM's, and around 15.2-15.5v at idle/cruising. It's not the batteries I'm worried about. The BMS's provide sufficient protection for the batteries should the thermals climb too far. It's the truck itself at that point which runs the risk of overvolting and doing god knows what to various electronics. I had all kinds of warning lights going off, notifications of systems getting disabled due to the voltage, which thankfully would reenable themselves each time the voltage dropped back down to less than 16v. At one point, I ended up with a blank IP cluster display with a red light of death in the lower right, and a no-start condition to top it all off. Thankfully I take tools everywhere I go. Disconnecting/reconnecting the main battery and leaving the IBS disconnected was enough to get it to start again. Beelined it home after that, got a 60A DC-DC LiFePO4 charger, and installed that.

The problem I have right now is voltage regulation. I need to control the system voltage, and the only way I know that to be possible with the LiFePO4 charger is to install it in between the alternator and the rest of the 12v system. So I found the positive alternator cable and wired the charger input to that, and then wired the output to the 300A shunt terminal on the engine bay fuse box/PDC that the alternator normally connects to. Truck started up just fine with that arrangement, but within about 10 seconds, the system voltage plummeted to under 10v, engine quit and everything died. I'm not sure if this is because the alternator refused to accommodate the load being pulled by the LiFePO4 charger at idle RPM's, or if the current needs by the vehicle far exceeded 60A, thus draining the potential and pulling the voltage down. It appears the over-discharge protection tripped the 36Ah Aux battery to effectively 0 volts, and after disconnecting/reconnecting it was at about 10.5v, so roughly 95% depth of discharge. Whatever the case though, this was a dumb idea. Best case scenario, I was knee-capping a 240A alternator to 60A. Worst-case, the truck turns into a dead stick within 10 seconds of starting.

So now, I'm looking at either a LiFePO4 alternator regulator like this, or literally adding (x) feet of 2/4AWG to the alternator cable to drop the voltage the old fashioned way. Neither prospect excites me. I'm open to suggestions primarily, or criticisms sparingly. I'm already giving myself enough **** right now, frankly. Having a new truck that's not drivable is gut-punchy enough as it is.

So yeah, I've dabbled in this. Care to join in the fun?

Edit: I don't suppose there's anything in AlfaOBD I can change to modify alternator/charging/battery type/voltage set point parameters? Wishful thinking, probably.

Where did you find the PCM/ alternator lets the ssytem voltage climb to over 16.2v? it should not be that high at all.

 

[gofish]

Where did you find the PCM/ alternator lets the ssytem voltage climb to over 16.2v? it should not be that high at all.

That is a first-hand observation, my friend. In the cab, rolling down the road. In excess of 16.2v, I saw it with my own eyes. Enough for the ECU/PCM/BCM to disable various systems like active lane management, Electronic Stability Control, etc. Enough to put the starter into a protection mode that refused to let me start the truck before a 4-minute timer counted down to zero.

 

[boogielander]

That is a first-hand observation, my friend. In the cab, rolling down the road. In excess of 16.2v, I saw it with my own eyes. Enough for the ECU/PCM/BCM to disable various systems like active lane management, Electronic Stability Control, etc. Enough to put the starter into a protection mode that refused to let me start the truck before a 4-minute timer counted down to zero.

i meant it showed on the dash 16.2v?
I assume this was with stock battery?

 

[gofish]

i meant it showed on the dash 16.2v?
I assume this was with stock battery?

Yes, 16.2v on the dash, which was as high as the number got, but I could tell it was going higher than that because it would start disabling various systems at 16.2v when acceleration was increased further.

No, like I said, both batteries were swapped with LiFePO4's. 150Ah on the main, and 36Ah on the Aux. There is no lead-acid under the hood.

 

[boogielander]

Yes, 16.2v on the dash, which was as high as the number got, but I could tell it was going higher than that because it would start disabling various systems at 16.2v when acceleration was increased further.

No, like I said, both batteries were swapped with LiFePO4's. 150Ah on the main, and 36Ah on the Aux. There is no lead-acid under the hood.

well my guess is the BMS in the truck not recognizing LiFEPO4 and therefore pushing more current to it due to less resistance or whatever the chemistry things are, and that probably fried something.

before you do anything else, have you tried putting the OE batteries back?

 

[jimothy]

Edit: I don't suppose there's anything in AlfaOBD I can change to modify alternator/charging/battery type/voltage set point parameters? Wishful thinking, probably.

Does AlfaOBD work on 2025+ Rams yet? I thought it was only for 2024 and earlier.

 

[jimothy]

Incidentally, I’ve been running a LiFePO4 starter battery on my 2021 ETorque for a few years now. It works, though it’s state of charge is held pretty low, mostly because the way ETorque works so not completely relevant to the Hurricanes.

Some things that are relevant, though:

The battery is self heating, allowing it to charge below freezing. Here in Atlanta, we don’t get a lot of sub-freezing weather, but we do get some, so it’s good to have.

The battery will shut off charging above a certain temperature (150-ish). I’ve had this happen several times, mostly in stop and go traffic in the summer, but also in my late September trip to the Rockies. Lots of slow moving, high altitude travel on rutted and rocky forest service roads, and a good amount of time in 4Lo, so under the hood temps climbed.

With the ETorque , the 48V battery, generator, and DC-DC converter kept the 12V system humming even though the LFP battery would not accept a charge (it would continue to discharge). I assume you’d be okay in a Hurricane, as well, with the alternator providing needed current when the battery blocks charging, but it’s something to be cautious about about.

(My setup also allows me to charge the starter battery from solar as well as my camping auxiliary battery, so if the starter battery got too low to start the truck, I wouldn’t be stranded. But I might have to wait hours for the battery to cool down. So bring a jump starter pack just in case).

Running a LFP starter battery was an interesting experiment for me. It works, and to be honest, I’d probably do it again, especially now that there are more dual purpose LFP batteries on the market at reasonable prices. But I wouldn’t necessarily recommend it, mostly because it didn’t really do what I wanted it to do: remove the need for an aux battery, because the SOC while driving is going to be well below 80%.

 

[gofish]

well my guess is the BMS in the truck not recognizing LiFEPO4 and therefore pushing more current to it due to less resistance or whatever the chemistry things are, and that probably fried something.

before you do anything else, have you tried putting the OE batteries back?

Yeah, hooked everything up back to stock and it's fine. Voltage normal, no codes except the historical ones stored from before. C2101, P0563, and P2AF5.

Suffice it to say, "smart" is not a qualifier I'd use to describe this charging system. It will absolutely choke on a full LiFePO4 swap. Recoverably, but still... Thing choked hard.

 

[gofish]

Does AlfaOBD work on 2025+ Rams yet? I thought it was only for 2024 and earlier.

Probably not. Wishful thinking for sure.

 

[HSKR R/T]

Oh boy, what a first post, but here we go. I can chime in here. Hopefully others can chime in with their thoughts as well. I got a '26 1500 3.0L HO that I'm learning all sorts of things about right now, most of all the 12v and charging systems. (foreboding)

I dove in with both feet. May have bitten off more than I cared to chew, honestly. I figured I'd go ahead and replace not only the Aux battery with a LiFePO4, but also the Main battery too. 186Ah between the Main and Aux with half the weight to boot seemed like a good amount of juice for the squeeze, and I'm usually pretty savvy with stuff like this. I've worked on various cars over the years, and I wasn't too intimidated going into it.

I got an Alldata DIY subscription for the '25 1500 since the '26 isn't available yet. The material differences between the '25 and '26 are likely few and far between (someone correct me if I'm wrong here). I read a good amount about the charging and 12v systems before pulling the trigger and buying the batteries and necessary hardware. Namely, the about the two IBS sensors, as well as the alternator:





I don't know what constitutes a "smart alternator", and I'm not sure if my truck has one. There's nothing on Alldata that I can find to help determine either way. But regardless, there is an IBS sensor located at the negative terminal of each battery, and since they supposedly have the ability to determine internal resistance, I figured that's the key right there. The two IBS's will each see that they're effectively connected to a LiFePO4 battery given that LiFePO4 batteries typically have about a 2-4x lower internal resistance than AGM batteries, and the resting voltage at 100% SOC is considerably higher. In turn, the IBS and alternator communication with the PCM should supposedly use this information to set the regulated voltage accordingly.

"Supposedly" being the key operator here... I'm now knee-deep into this, and I've run into a couple significant problems so far. First, the alternator clearly doesn't control the voltage in accordance with the battery's internal resistance and chemistry. The PCM/alternator lets the system voltage climb to over 16.2v at very mild acceleration RPM's, and around 15.2-15.5v at idle/cruising. It's not the batteries I'm worried about. The BMS's provide sufficient protection for the batteries should the thermals climb too far. It's the truck itself at that point which runs the risk of overvolting and doing god knows what to various electronics. I had all kinds of warning lights going off, notifications of systems getting disabled due to the voltage, which thankfully would reenable themselves each time the voltage dropped back down to less than 16v. At one point, I ended up with a blank IP cluster display with a red light of death in the lower right, and a no-start condition to top it all off. Thankfully I take tools everywhere I go. Disconnecting/reconnecting the main battery and leaving the IBS disconnected was enough to get it to start again. Beelined it home after that, got a 60A DC-DC LiFePO4 charger, and installed that.

The problem I have right now is still voltage regulation. I need to control the system voltage, and the only way I know that to be possible with the LiFePO4 charger is to install it in between the alternator and the rest of the 12v system. So I found the positive alternator cable and wired the charger input to that, and then wired the output to the 300A shunt terminal on the engine bay fuse box/PDC that the alternator + normally connects to. Truck started up just fine with that arrangement, but within about 10 seconds, the system voltage plummeted to under 10v, engine quit and everything died. I'm not sure if this is because the alternator refused to accommodate the load being pulled by the LiFePO4 charger at idle RPM's, or if the current needs by the vehicle far exceeded 60A, thus draining the potential and pulling the voltage down. It appears the over-discharge protection tripped the 36Ah Aux battery to effectively 0 volts, and after disconnecting/reconnecting it was at about 10.5v, so roughly 95% depth of discharge. Whatever the case though, this was a dumb idea. Best case scenario, I was knee-capping a 240A alternator to 60A. Worst-case, the truck turns into a dead stick within 10 seconds of starting.

So now, I'm looking at either a LiFePO4 alternator regulator like this, or literally adding (x) feet of 2/4AWG to the alternator cable to drop the voltage the old fashioned way. Neither prospect excites me. I'm open to suggestions primarily, or criticisms sparingly. I'm already giving myself enough **** right now, frankly. Having a new truck that's not drivable is gut-punchy enough as it is.

So yeah, I've dabbled in this. Care to join in the fun?

Edit: I don't suppose there's anything in AlfaOBD I can change to modify alternator/charging/battery type/voltage set point parameters? Wishful thinking, probably.
Edit 2: Yep, wishful thinking.

60 amps is definitely not enough to run modern vehicles with all the electronics in them. Which is why alternator output are so much higher in modern vehicles than the old school 40 amp alternators used in the old school cars with points ignitions and lights being the only draw.