Swapping Lead Acid for Lithium: Do Tow Vehicle Charging Systems Need Upgrades?

[DWGERLI]

Swapping out my acid battery on our travel trailer for a lithium battery. Do you need to make any changes to the tow vehicle charging system?

 

[Riverbug]

Nope. The gauge of wire in the stock harness does not allow enough current to pass through to cause a concern. If you upgraded to a larger cable for some reason without other additions, then you could have a problem. But with OEM setup, no problem.

 

[DWGERLI]

The truck is still all OEM with original alternator and trailer light cord that would charge the battery while traveling. So, i should be good to just swap the old acid battery for the lithium one. Concern was over charging issue. See lots of post and DC to DC units.
Thank you for any advise.

 

[Riverbug]

You could just swap in an LFP (LiFePO4) battery and call it a day. A DC-DC charger would allow you to increase the charge rate to the battery while under tow. But it requires larger cables and extra work to do that. I would start with swapping the battery and then see what you really need. You may find you do not need to charge while under tow. It all depends on your usage habits, size of your LFP battery bank, solar, how much you are camping off-grid, etc. Typically, you get more bang for your buck if you go with one larger battery than several smaller ones (i.e., one 200+AH vs two 100AH). Hope that helps!

 

[DWGERLI]

Great, that sounds like a plan. Again, thank you for the advise. Safe travels and good health.

 

[Wichita Dave]

I bought a 100AH LiFePO4 battery because I have a 12v refrigerator.
I never did the dc-dc charger and have had no issues (but I have 165w of solar).

Later I bought a 2000W Renogy inverter. It won't run my microwave because the on-board battery management system clamps the current draw at a level insufficient for the inverter to produce the power required for the microwave.

A bigger battery is better for that reason.

 

[DWGERLI]

Thank you for your advice. I am going to change out to the lithium battery and see what happens. Also have the same 12 volt frig with 185 amp solar.

 

[Xlsmle]

Simple answer is no. Went from lead acid to lithium years ago and no problems with tow vehicle original charging system.

 

[DWGERLI]

Great, thank you.

 

[jasonPlegrand]

Hey, just want to ask a question regarding swapping lead acid to Lithium, I have 2 lead acid now in my 2021 Solitude with a res fridge, don’t do any off grid to speak of, is one lithuim group 24 better than 2 lead acid? or should I get a group 31?? don’t know much about electricity other than it can kill you! I’m a union carpenter.

 

[Riverbug]

Hey, just want to ask a question regarding swapping lead acid to Lithium, I have 2 lead acid now in my 2021 Solitude with a res fridge, don’t do any off grid to speak of, is one lithuim group 24 better than 2 lead acid? or should I get a group 31?? don’t know much about electricity other than it can kill you! I’m a union carpenter.

It depends on your perspective. Some people are still die-hard lead acid - mainly due to costs. But costs aren't so much of point these days as LFP batteries have become pretty competitive. You can still buy expensive versions of them, but now there are economical and reliable brands out there too.

So, based on voltage curve, weight savings, ability to draw down without causing undue damage, and battery life, there are reasons to prefer LFP over lead-acid. My choice hands-down is LFP. Make sure you get one that has high and low voltage cutoff, high and low temp cutoff, etc. Bluetooth is nice but not required. More conservative installers will incorporate a MRBF terminal fuse for extra protection.

Hope that helps!

 

[Wichita Dave]

Look at a state of charge graph for a LFP battery. You will still have 12 volts down to about 15% capacity. At 15% capacity your lead acid batteries are ruined!

Also, you can bulk charge LFP to 100% capacity. With lead acid, the charge rate drops for the last 20% IE it takes much longer to charge a lead acid battery.

 

[coastn]

Been considering doing the same swap to Lithium. Not concerned about charging from TV but a while back heard rumors that it caused problems to the truck's alternator. I try to tow 4-5 hours max a day. My new '26 RAM came with dual alternators. Am I good to go with just dropping the Lithium in?

 

[JKellerJr]

Been considering doing the same swap to Lithium. Not concerned about charging from TV but a while back heard rumors that it caused problems to the truck's alternator. I try to tow 4-5 hours max a day. My new '26 RAM came with dual alternators. Am I good to go with just dropping the Lithium in?

Yes, you can drop in lithium without issue. As long as your not changing the stock charging system on your truck you will not hurt the alternator.

That rumor started with a video showing and alternator hooked up directly to a lithium battery and the alternator burning up. Lithium's can take a much faster charge than lead acid and if the alternator is connected directly to lithium that is low on charge, the alternator will run at full output for an extended period of time. They are not designed to do that. Running through the stock system, the output through the 7 pin is restricted ,it will not hurt the trucks alternator.

 

[coastn]

Yes, you can drop in lithium without issue. As long as your not changing the stock charging system on your truck you will not hurt the alternator.

That rumor started with a video showing and alternator hooked up directly to a lithium battery and the alternator burning up. Lithium's can take a much faster charge than lead acid and if the alternator is connected directly to lithium that is low on charge, the alternator will run at full output for an extended period of time. They are not designed to do that. Running through the stock system, the output through the 7 pin is restricted ,it will not hurt the trucks alternator.

That's a relief..thank you!

 

[jkwilson]

One big risk when a lithium as the only battery in the system is the behavior when the BMS sees a voltage or current higher than it likes. It removes the battery from the circuit. An alternator running without a battery can have problems, as can the systems being powered since the battery is part of the regulation and filtering system. The vehicle may stall or the charging system may be damaged.

But that’s not the case with a trailer battery added to the existing system.

 

[k.darwin]

I had problems. Same problem with two different trucks, 2017 Colorado and 2023 Ram, both diesel. Using two different trailers, but the same BattleBorn battery.

After swapping to lithium, the tow vehicle would drain (not charge) the TT battery. The lower voltage in the truck allowed current to flow from the higher voltage of the lithium TT battery. The smart charging system in the truck never turned the alternator on because the voltage never sagged. The battery drain even continued while the truck was stopped and shut off because the 12v line in the 7 pin is not switched.

The 8 hour drive to a campground drained the TT lithium battery by about 30%.

Of course had I not been monitoring it with a Victron shunt I'd have never noticed.

My solution is to pull the truck fuse for the 12v 7 pin line. This stops the drain but does not allow the truck to charge the TT battery. For that I'd need solar on the coach or a DC-DC converter between the truck and trailer.

 

[Jerry Davis]

That's a relief..thank you!

WE have a 2024 GD 303 and the stock battery they had in it was cheap. It could hardly supply enough power for the slides ( I do know to have shore power on when available to operate slides). We have a 2024 chev 2500 diesel. I changed out to a lithium battery and no problems. Just up the charge controller for lithium to increase voltage for lithium batteries. We do have solar, in hind site. I wish I had gone to the 230 amp lithium instead of the 100 amp. The prices have been coming down on the lithium. Now if I use just battery for slides, they have no problems

 

[JKellerJr]

I had problems. Same problem with two different trucks, 2017 Colorado and 2023 Ram, both diesel. Using two different trailers, but the same BattleBorn battery.

After swapping to lithium, the tow vehicle would drain (not charge) the TT battery. The lower voltage in the truck allowed current to flow from the higher voltage of the lithium TT battery. The smart charging system in the truck never turned the alternator on because the voltage never sagged. The battery drain even continued while the truck was stopped and shut off because the 12v line in the 7 pin is not switched.

The 8 hour drive to a campground drained the TT lithium battery by about 30%.

Of course had I not been monitoring it with a Victron shunt I'd have never noticed.

My solution is to pull the truck fuse for the 12v 7 pin line. This stops the drain but does not allow the truck to charge the TT battery. For that I'd need solar on the coach or a DC-DC converter between the truck and trailer.

That's a new one for me. There's always that unexpected scenario out there. The theory behind it is sound. Its surprising that there isn't enough voltage drop from the trailer all the way to the front to the truck to prevent that but here we are! I haven't had that issue on my GM's and my buddy has a Ram that hasn't had the issue

An easy/cheap way to prevent that would be to use one of these:

Amazon.com

 

[k.darwin]

Honestly, I had not been checking current flow during our drive using the Victron smart shunt I would have never known. The power converter would charge up the battery once I got to camp and I'd have been totally unaware.

I suspect a lot of folks who say "no problem" are simply unaware. And I guess in the end, there really is not problem.