RV Upgrades – Switching to Lithium 20

When we purchased our RV in Nov. 2012, one of the first things I did was replace the old batteries that were in the RV. They were corroded and tired, reaching the end of their useful life.
I considered sealed batteries, but at about twice the cost of flooded cells, they didn’t seem worth the investment at the time.  A few weeks later, I discovered how difficult it was to check the water levels in my new batteries and added a watering system which added 25% to the cost. I had pretty much regretted not spending the extra money for the good stuff and swore not to make the same mistake again.

Those batteries had been with us for nearly four years, through two years of part-time RV travels and another two years of fulltime RV living, including a summer in Alaska with lots of dry camping and just two weeks in campgrounds with power in the first five months of 2016.

At the end of 2015 we began to notice that the batteries were not standing up well to heavy loads, like the microwave or the toaster oven. Their capacity didn’t seem to be too reduced, but the state of charge ( SoC ) that we were able to run kitchen appliances seemed to get lower as time went on.
By the summer of 2016 we found that not only were the batteries sagging under heavy loads ( by now we were running the generator almost any time we needed them below 90% SoC ) but that voltage at 60% SoC was lower than it should have been, which meant we weren’t really at the state of charge our meter was telling us we were, which meant the batteries had significantly lost capacity. It was time for new batteries.

I had been following the adventures of fellow travelers that were some of the early adopters of Lithium batteries ( Technomadia ) and some of folks who had purchased as the technology matured somewhat ( Jason and Nikki Wynn, as well as Josh and Marie of Ardent Camper ) but was pretty sure, after looking at pricing, that the batteries and the systems that were required to charge them were out of our reach. 400Ah of batteries ( the minimum I determined we could live with happily ) would be $4000, plus I might have to change my inverter/charger to a newer, more programmable unit, which would cost another $2000. That’s a budget breaker for us and I figured I’d have to break my promise to myself.

So I decided that this time, we’d buy AGM batteries, most likely Lifelines, since they had worked well and lasted a long time for my brother and sister-in-law ( http://where-rv-now.com/Notes/Amp/ ). They had owned their Lifeline brand AGM batteries for the last 12 years, admittedly not all of them on the road, but they’re still working, which is a pretty good testimonial.

I was at the point of pricing new Lifeline’s  for $1200 when I had a chance conversation with Jason Wynn who told me that he had several RELiON 200Ah Lithium Ion batteries that were removed from their sailboat in the upgrade to newer, larger batteries of the same brand. The batteries had experienced just two seasons of sailing ( less than 400 cycles of their expected 5000 cycle lifespan ) but they would sell them for half of retail, just $2400 for two of the batteries.

As interesting as that was, as I called RELiON and spoke to the very helpful Charlie Messina in their customer support department, I began to realize that all of the charging devices that our RV had: alternator, solar controller and inverter/charger, could all be configured to meet the RELiON charge parameters. This meant that I wouldn’t have to change anything but my batteries. This is the document I got from RELiON describing what I needed to do to charge the RELiON batteries – Relion Lithium Battery Charging Info and Troubleshooting 2-2016 (1)

Quality AGM batteries for my RV ( four 6V Golf Cart batteries ) are roughly $1200 for 440Ah of batteries. At full retail, 400Ah of RELiON batteries are $4800, or four times as much. Other Lithium batteries can be had for a somewhat less. Starlight solar sells the Elite Power Solutions battery systems with BMS for DIY installation for about $3500.

The prices of the different options looked like this:

Option 1. Replace the existing flooded batteries with new, quality flooded lead-acid batteries – $600 for four Trojan T-105RE’s (450Ah/225 Ah usable at 50% SoC ). Inexpensive, need maintenance ( watering), prone to corrosion. This is the long-time standard for RV batteries, flooded lead acid batteries are a model of stable technology if there ever was one. They’ve been around since the 1850’s and have not changed a lot.

Option 2. Upgrade to AGM ( sealed lead acid ) batteries of the same size – $1300 for four Lifeline GPL-4CT’s ( 440Ah/ 220Ah usable at 50% SoC ). Cleaner, no maintenance, better high-current performance. The new standard for batteries for RV’s. For most folks, these are worth the extra money.

Option 3. Upgrade to some variety of Lithium batteries – $2400 ( used ) to $4800 for 400Ah/320Ah usable at 20% SoC of batteries and management system. No maintenance, but might require some hardware changes to meet charging requirements. Quite possibly the future of energy storage in RV’s.

So, are they worth it? To answer the question, we need to quickly look at the advantages and disadvantages of each type of battery. I’m not going to consider flooded batteries here, that’s what came out of the RV and I’ve already decided that AGM’s would be worth the extra money.

First, AGM’s.

  • AGM batteries are pretty happy working from most 12v charging systems in RV’s, so compatibility isn’t an issue.
  • Generally, most folks suggest not taking lead-acid batteries below 50% SoC. However, many AGM battery manufacturers rate the lifespans at 20% SoC. According to their documentation, about 1000 cycles when discharged to 50%, 600 cycles or so when discharged to 80%.
  • AGM batteries lose capacity when cold, but they can continue to be charged and used fairly normally. Ideally, they need charging systems to have a temperature sensor and adjust charging voltages to fully charge in colder temperatures.
  • AGM’s handle high current discharges better than flooded batteries, but not as well as lithium.
  • Long history of safe operation. Millions in service.
  • Weight of four batteries – 265lb
  • Lead Acid batteries charge at slower rates than lithium. Above 75% SoC, they’ll begin to slow down, and the last 15% or so technically needs several hours to do, regardless of how large your charger is.
  • Lead Acid batteries do best if they’re fully recharged every time they’re discharged. Partial recharges reduce lifespan.
  • Lead Acid batteries lose more voltage as they discharge, making it hard to run high draw items when SoC is low.

Next, Lithiums.

  • Some RV charge systems will work fine with Lithium, some will not. It depends on the adjustability of your systems and the capacity of the Battery Management System ( BMS ) to deal with incoming voltage. I’m able to configure my chargers to work fine with the RELiON battery charging specifications, but they might not be a good fit with some other batteries and battery management systems. Generally speaking, though, if your charger will work for AGM’s, they’ll work for RELiON batteries.
  • Lithium batteries need more supporting hardware for safety and monitoring. Contactors to disconnect the batteries if the voltage goes too high or low, a BMS to monitor individual cell charge states and temperature.
  • Lithium RV batteries get a bad rap for safety from phone batteries, but most of the issues ( heat, overcharging ) are addressed by the BMS. The Lithium batteries used in RV’s are a different chemistry than those typically used in phones. RV batteries are typically LiFePO4 while phones use LiCoO2, which are more compact and have a greater energy density, but less thermal and chemical stability.
  • Warm conditions can reduce the lifespan of Lithium, while cold reduces capacity less than AGM, most lithium batteries should not be charged if they’re below freezing ( less than 32F/0C ), though they can be used. RELiON suggests that below freezing, charge rates be reduced for the first half hour, after which the batteries should be warmed internally, and after that charge rates can be upped to normal.  More on this in a bit.
  • Expected lifespan of the RELiON batteries we bought are predicted by the manufacturer to be 4k cycles to 20% SoC, 6k cycles to 50% Soc. These lifespans may be somewhat extended by moderate or low charge/discharge rates ( our use in the RV would fall into this category ) and our typical usage would rarely take them down below 50%, based on the previous 2 years with our old batteries.  Essentially, the predicted lifespan could be 4-10 times as long as AGMs.
  • Lithiums are routinely run down to 20% SoC, while most folks only take AGM’s down to 50%, giving a slightly smaller Lithium battery bank more usable capacity – 320Ah vs. 220Ah, an increase of 45%.
  • Weight of two batteries- 144lb – This is roughly 120lb less than AGM, which is not insignificant on our heavily loaded RV.
  • Size of two batteries is significantly larger than AGM. Each battery is 8D size, 20″L x 10.5″W x 9″H, so they’re not going to fit where the old batteries were, they’re going to need a new location, which means at least a little rewiring. I’ll be building a box to hold them to both insulate against warmth and cold, and to allow us to put items on top of the batteries without shorting anything out.
  • Lithium batteries charge at full rates to nearly 99% SoC. Our charger can put out 75A, so that full charge current goes into the batteries until they’re nearly full, so a full recharge on a generator ( or even on solar ) could take hours less time.
  • Lithium batteries do not need to be fully recharged each time, so a partial charge is fine. In fact, it may be that partial charges extend the battery lifespan.
  • Lithium batteries are more efficient, wasting less energy to charge or discharge. It’s a small difference, but potentially 10%.
  • Lithium batteries drop voltage less when powering heavy loads and as they discharge, allowing us to run the microwave or toaster oven even when the batteries are at a low SoC.

So, AGMS are cheaper, but they don’t last as long, are heavier, slower to recharge and less efficient, better in cold. Lithiums are lighter, longer lasting, faster to recharge and more efficient, but cold is something to be careful of or mitigated. Essentially, we’d get at least 4X longer lifespan, 100 lb less weight and 45% more usable energy. For us, that was worth the extra money.

So, about the cold limitations of LiFePO4 batteries. It’s a little confusing. Some manufacturers ( RELiON included ) quote operating temperatures that go significantly colder than freezing ( RELiON claims -4 to 158F ) but a read of their charging specs seem to indicate that’s for discharge ONLY, which seems contradictory to me.
Apparently charging Lithium batteries in the cold is such an issue, that some other installations ( AMSolar’s Signature Series ) even include a cold temperature disconnect.

In the last two years on the road, we’ve spent several weeks in sub-freezing winter temperatures. Most of those nights have been spent in campgrounds with power where we don’t need to charge the batteries, but more than a few have been dry camping where we depend on power from the batteries to run the RV, including the ever important furnace. So disconnecting the batteries wasn’t really going to work for us.

Because they don’t need venting like lead-acid batteries, many folks modify their RV’s to keep the batteries inside the RV, where they are kept at moderate temperatures. We didn’t have room for that, so they were going to have to live out in an unheated compartment. However, the batteries would not fit in the original battery compartment where I had four 6V batteries. Instead, I was going to put them in the storage compartment next to the existing ( cold, vented, steel-floored ) battery compartment, which would be a little warmer than the surrounding air and had enough space for me to build an insulated box. I also decided to add a 12v electric RV tank heater to try to keep them above freezing, even if the compartment containing the battery box got below freezing. I also planned on installing a thermometer with a remote sensor in the battery box, so we’d know how they were doing and, if too cold, could limit charging rates.

Finally, I looked at the existing wiring inside the current battery compartment and planned out what components I’d need to move, and which wires I’d need to extend to the new battery location. It would require making a few cables, but since the compartments were right next to each other, it seemed pretty manageable. I had the tools and shortly after the batteries arrived, we’d be stopped for a few weeks in Virginia, where I’d have a garage and a workbench to use.  Here is the old battery compartment, next to the new compartment we’d be using.

We took the leap and ordered the batteries. At the time, we were staying with Jeanette’s brother and sister-in-law, so we had them shipped to their house. It took a little longer than we planned ( hurricane Matthew interfered with shipping…) but they arrived in good condition, crated and protected.

Per instructions, they were shipped at about 40% SoC, so the first thing I did was balance them out so they were at the same voltages by putting a light bulb on the one with a slightly higher voltage and a charger on the one with a slightly lower voltage.

Then, I started building my battery box from 5/8 plywood with styrofoam for insulation.

It took me a few days of part-time work to make the box. I’m not much of a carpenter, nor even a planner.  Meanwhile, I got 2/0 cable and ends from a welding supply store and made up the cables I’d need to migrate the battery connections one compartment over. An Amazon order supplied the thermometer with a remote sensor that would monitor the internal temperature and the tank heater.

Below is the tank heater.  Unfortunately, I didn’t take any photos while I was installing it, but in part because I was hesitant to put the flexible heating pad under the batteries, partly because it arrived after the box was almost finished, it’s on top of the batteries and under the insulation. This is less than ideal ( heat goes up ), but it works well enough for now. I’ve got some ideas about how to improve this and may try to make some adjustments when we’re parked somewhere with tools and a workbench.


When the box was completed, I pulled the old batteries out of the compartment and brought them to O’Reilly auto parts, who gave me a $10 store credit for each of them, with which I bought oil and filter for a change for Lana ( our Jeep ).  The watering system off the old batteries was quickly sold to a FB friend on one of the solar RV groups.

The positive and negative battery wires, along with the battery disconnect and 300A catastrophic safety fuse were moved to the new compartment, along with an extension of one of the charge wires.

1/4-20 all thread steel rod went through the floor of the compartment, backed by steel bars top and bottom to keep the box from shifting around. Then the batteries, insulation, heater wiring and temperature sensor went in and I closed up the battery box.


I double checked my wiring, checked it all one more time, then I flicked the switch and everything began to work fine. Woo-Hoo!!!

The batteries charged hard for a few hours ( to nearly 99% ) then quickly tapered off and were full. It would be a few weeks before we really got to test them, but in testing them with the microwave they held up well with very little voltage sag.


A few weeks later we got to give the batteries a much harder workout. Over Christmas, we used them quite a bit while dry camping, cooking much of our Christmas dinner in the microwave and toaster oven while it was cloudy. We drained them down to 25% SoC over another busy day and even at that point, voltage was good and the batteries held up well. They charged back up from 25% to 100% in about five hours.

The insulated box works as designed, moderating both hot and cold temperatures. Even when the compartment warms up from engine heat and the exhaust passing nearby, the batteries stay pretty cool. At night, their temperature is warmer. The coldest we’ve been since we installed the batteries was a night with a low of 14F and the batteries stayed above freezing with the heater on.

So, was it worth it? Yes. The improved capacity ( +45% ), reduced weight ( 100+ lb ), potentially 4x the lifespan and better overall performance were worth the money and effort to install the batteries, even at roughly double the cost of AGM batteries.

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20 thoughts on “RV Upgrades – Switching to Lithium

  • Robert Fruth

    Great write up. I tried to reach out to the Wynns about the “other” two batteries they had left, but I imagine they already sold them as they are on their new boat enjoying the warm water. Hope they last as long as expected for you. Best of luck.

    Robert Fruth

    • Eric Post author

      Thanks for the feedback, we’ll update the post after we’ve lived with the batteries a year or so. I may be able to reach the Wynns. PM me on FB.


  • Joe the computer guy

    Nice recap. I am doing an install next week with GBS lithium (Starlight Solar) and a 960w solar install too. 600AH battery bank.
    I will not be documenting it as well as you did though. Thanks for sharing

  • George

    Thanks for the write up! Excellent job! If you look at Photo #6, test fitting, Is that the tank heaters on top of the batteries? That is an excellent idea. I have been thinking a lot about the cold charging problem with Li-Ion and this seems like a very practical solution.

    • Eric Post author

      Unfortunately, the delivery of the tank heater was delayed until after I had finished the assembly of rest of the battery box, so it’s not in any of those photos. In fact, I was unsure it would make it in before we left VA. Once it arrived, I opened the battery box back up and installed it, just before the 14F weather showed up as well.

      I’ve updated the blog post to reflect this and added a product photo. Thanks for reading and commenting.

  • Claude

    This is great input for a wannabe fulltimer soon who will go lithium. I even inquire with the Wynns for those ReLion batts…but since I live in Canada…the freight was just insane.

    Since we are in Canada, low temps are common and I’m just wandering about the foam insulating and the heat pad temp? Usually foam gets deformed and could also catch fire while heated depending on the foam type. Maybe the heat pad doesn’t get really hot???

    • Eric Post author

      The heating pad has an internal thermostat. On at 45F, off at 65F, so it does not get very warm. It’s designed to be stuck on a plastic tank.

  • Claude


    Ok for the info. I knew those heat pads were for water RV tanks but was just wondering if they were generating too high of temp for your foam…that all.

    I have a class A and will retire in 3 years and will fulltime. Guys like you help a lot because I have 3 years to think of my set-up. Probably will have heat pads on all water tanks and now on my futur Li batts too. just susbscribed to your site.

    • Eric Post author

      When you’re shopping for an RV,also look for enclosed and heated tanks, valves and water lines. Electric heating is nice if you’re on shore power, but if you’re planning on dry camping in colder areas, a duct from the furnace into the wet bay is better since it requires a lot less power.
      Well insulated walls and double pane windows keep the RV comfortable in both warm and cold places.

  • Claude


    We already have a class A (Triple E Commander 32´)but we aren’t retired yet (3 years). We will install as much solar panels as the roof can take and ajust the battery bank accordingly along with the inverter. But they will be Lithium. Prices are going down so I’ll wait. As for winter pack, we will had heat pads to all plastic tanks and heat the wet bay.

  • chris p hemstead

    I’m confused about charging.

    The literature on charging I’ve read indicates that Li’s charge at a single voltage, yet another paper says you should charge until they reach a certain voltage, say 14.6v.

    What is correct? If it’s a single voltage, how would any controller know when to stop?

    • Eric Post author

      Because they’re different than lead-acid batteries, they can work well with a constant voltage charger, because they don’t need a large voltage differential to fully charge. However, the “constant voltage” is relative. Check out the charge voltage profile on the constant current charge graph in page two of the spec sheet for my batteries. – RB200 spec sheet

      Like all batteries that I’m aware of, the charge voltage changes as the charge state of the battery does, and that voltage varies depending on the ability of the charger to deliver enough power. Even on a constant-voltage charger, the “constant” voltage is drawn down by the load of the battery, then rises as battery voltage rises and charge current drops.
      On a lead acid battery, the voltage difference between charged and discharged is greater ( about 1v on a 12v battery ) than a Lithium battery ( about .5v on mine – see spec sheet above ), but the principal is roughly the same.

      So, most modern chargers have three stages. Bulk, absorb and float. Bulk typically has lower voltages, but these voltages are higher than the nominal voltage on a Li ( or lead-acid ) battery, so the power flows into the battery. With a Li battery, the voltage doesn’t really climb that much while the battery is still <98% SoC ( state of charge ). In a lead-acid battery, the voltage comes up much earlier, about 80% SoC. When the voltage climbs, the charger switches to Absorb mode, where the voltage climbs to 14.6V and current drops. Because a Li battery is already pretty close to fully charged, absorb mode on Li typically doesn't last very long.

      When the charger gets to 14.6v, it's time to stop charging ( mostly ) and go into float mode, where battery voltage typically drops to 13.6V, just enough to balance out the voltage in the battery.

      With RELiON batteries, these voltage values are close enough to lead-acid AGM battery values that a good quality charger on the AGM setting works well.

  • Christophe

    Nice upgrade, Eric!
    I’m planning mine as well: I got some Lithionics batteries and like you I’m thinking of the storage area next to the current battery bank. I have a Winnebago View 2017.
    Have you been in subfreezing temps yet? Like mid 20s. I wonder what the temperature inside the battery box is w/o the heating pad on at dawn. LFPs warm up a bit under load and if they’re well insulated, I wonder how all that works.
    Same for warm temps, right? You don’t want them to be anywhere near 130F so insulation should keep them cooler but again, till what point?