Saturday, March 18, 2023


RVelectricity™ – Should you upgrade to lithium batteries immediately?

Dear Mike,
I’ll be picking up a new Forest River Berkshire 45CA (45 foot diesel) from the dealer in a month or so. I am having him put 525 watts of solar on it. It’s prewired for 550.

According to the Forest River owner’s guide online, it has the following:

  1. Jaboni solar controller 30A mppt-rvc
  2. Magnum 2800 watt inverter model ms
  3. Jaboni 175 watt solar panels
  4. Six 6-volt deep cycle house batteries
  5. Two (2) 1900 CCA at 0 degree Fahrenheit, maintenance-free chassis batteries, I assume

My question is, can and should I have them put in lithium batteries right away so I don’t have to mess with it later when the stock ones go bad? I’m not sure what all can be run off the battery bank so I’m not even sure what the right questions are to ask the dealer.

Do you have any stock questions that you would always ask? Do you have any advice, because I’ll need to let them know in time to order and install, if it makes sense.

Thanks. —Terry

The following is from Google

Dear Terry,
An interesting question. If there was only a single FLA (flooded lead-acid) battery already installed in your new RV, the answer would be simple: Replace it with one or more lithium batteries. However, you have quite a bit of storage available already, so maybe the answer isn’t quite so obvious.

What are we working with?

So, just how much battery storage will you have with the already-installed FLA batteries? And what would you have to gain by doing a preemptive swap for lithium technology?

From your pictures I can see that these are Centennial Deep Cycle FLA batteries rated for 220 amp-hrs of storage. Of course, these are 6-volts each, so they have to be installed in Series/Parallel/Parallel mode.

Now, battery amp-hr capacity isn’t as simple as adding up all the amp-hrs in a series/parallel system. You have to consider that three pairs of 6-volt batteries need to stacked in series to create a 12-volt battery stack, then those 3 battery stacks need to be wired in parallel to create a battery bank.

How does it all add up?

From my diagram you can see that each series-stack of 6-volt batteries can provide 220 amp-hrs of power (instead of 440 amp-hrs, as one might guess). When batteries are wired in series, you add the voltage (6+6=12 volts) but the amp-hr capacity only equals a single battery rating (in this case, 220 amp-hrs). When batteries are wired in parallel, the voltage stays the same (12 volts) but the amp-hr capacity adds together.

So, for your six 6-volt batteries in series/parallel, that works out to 220 + 220 + 220 = 660 amp-hrs at 12 volts DC. That’s a large amount of capacity by any standard, but it’s not the entire story.

Don’t bring me down (Thanks, ELO)

For best lifespan, you don’t want to discharge a FLA battery to below 50% of its SoC (State of Charge), so you really can’t use the entire 660 amp-hrs of capacity. It’s more like 330 amp-hrs of usable storage capacity before damaging the batteries. So, six of the 220 amp-hr FLA batteries are essentially a 330 amp-hr battery bank. But lithium batteries can be discharged down to 0% SoC without damage. See below….

Going for Zero (or Zed)

If you were to change out to lithium batteries, as mentioned, they can be discharged down to 0% SoC without damage. So a single 100 amp-hr lithium battery can provide an actual 100 amp-hrs of storage, two of them would be 200 amp-hrs of storage, three would be 300 amp-hrs of storage, etc.

In a nutshell, if we replaced all six of your existing FLA batteries with three 100 amp-hr lithium batteries, then it would be about an even wash of 300 amp-hrs vs 330 amp-hrs of storage. But if you replaced your six existing FLA batteries with six 100 amp-hr or three 200 amp-hr lithium batteries, you would essentially double your battery bank storage from 330 amp-hrs to 600 amp-hrs.

The following is from Google

More swapping…

Or, if you swapped in a pair of the Mastervolt 400 amp-hr lithium batteries (like the one I have in my Geo Pro prototype trailer), that would give you 800 amp-hrs of lithium battery storage compared to the 330 amp-hrs of FLA storage capacity. Now that would be some serious amp-hrs of capacity, but it certainly would lighten your wallet a bit.

So do you need to do this swap up front?

If I were you, I would stick with the existing 660 amp-hrs of deep-cycle FLA batteries for now, and add more solar panels and a separate solar charge controller if you want to boondock for longer periods of time. You might even consider adding portable solar panels that could be deployed out in the sun, while your RV stays in the shade.

But when those FLA batteries give up the ghost in a few years (sooner if you don’t maintain proper water levels and maintenance charging), then go ahead and swap in lithium batteries. By that time there should be at least a 30% drop in the price of lithium batteries, so the deal will be even better.

Let’s play safe out there….

Mike Sokol is an electrical and professional sound expert with 50+ years in the industry. His excellent book RV Electrical Safety is available at For more info on Mike’s qualifications as an electrical expert, click here.

For information on how to support RVelectricity and No~Shock~Zone articles, seminars and videos, please click the I Like Mike Campaign.




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2 months ago

Stackable Integrated Battery’s most popular products in Europe in 2023

Richard Chabrajez
1 year ago

Hi Mike,
Have you written any articles detailing a complete conversion from deep cycle to Lithium (ie- chargers, inverters and other peripheral equipment required for the conversion)? I’ve viewed the “packages” offered on the Battleborn site but it would be nice to have your expert opinion .

1 year ago

Part of this discussion should be changing of charging circuits and how much use will be in the cold. Some lithium batteries have a warming circuit. Battery technology is rapidly changing, should be better/cheaper in the future.

Mike Sokol
1 year ago
Reply to  TomS

This isn’t a discussion about what it takes to switch to Lithium batteries. It’s about why the OP should keep his Lead-Acid batteries for now.

Ray Cordero
1 year ago

I replaced my 2 FLA batteries 4 years ago with four 6V AGM batteries (220 usable ahrs). I think my inexperience with correctly charging the AGM batteries lead to their early demise. I searched for an equivalent replacement and found that one 300ah Ampere Time LifePO4 battery would cost the same as my four AGM batteries. So I bit the bullet and upgraded. This battery does not have a low temp cut off so I do heat up the storage bin it’s located in to make sure it never falls even close to 32 degrees.

David Telenko
1 year ago

WOW, Mike mentioned that those Mastervolt 400 amp-hr would lighten your wallet a bit!! More like your bank account @ $9,949.00 ea. plus shipping! At a WAG, I’m thinking 6 of those puppies + all the extra stuff to support those batteries, you looking at $75,000.00, Hmmm I’ll keep my 4, 390 amp-hr AGM batteries for a bit longer!

Mastervolt 12V 400Ah MLI Ultra Lithium Battery, 5500Wh

Mike Sokol
1 year ago
Reply to  David Telenko

You only need 1 of those batteries, not 6… 😁

1 year ago

Too few writers mention that the content of lithium batteries (molybdenum sulfide lithium) is so unstable that the batteries must be assembled under mineral oil. Any contact with air and they burn so profusely that they nearly explode. Fire departments will not even attempt to extinguish a Tesla fire. They just sit back and let it burn. If the battery case is compromised (think accident or manufacturing error) I don’t want to be anywhere near your rig. Also, Elon still hasn’t figured out how to recycle or dispose of these things safely yet.
I don’t mean to sound like an alarmist, I just think this is a factor most don’t consider because the industry doesn’t want to broach the subject. Thank you.

Jeff Craig
1 year ago
Reply to  Paul

Recycling happens all the time. The issue is ‘scaling up’ and making it more economical. But, as with ALL technology, the market will find a way to make it more profitable. There are many places that you can get these batteries recycled, just like TV’s and other electronics.

Mike Sokol
1 year ago
Reply to  Paul

That’s not how Lithium Iron Phosphate batteries in RVs work. Those are completely stable. You’re referring to lithium-cobalt oxide (LiCoO2) batteries used in cell phones and other mobile electronics. That’s the type of Lithium battery that can go into avalanche failure and go up in smoke.

Gregory Illes
1 year ago

One thing that doesn’t get enough attention: when running lithiums (LFP’s), the bottom 10% falls like a rock, and is difficult to use without tripping the BMS. The top 10% is not easy to achieve, because charge rates fall off quickly and the “rapid charge” feature of LFP is more equal to LA batts at the top end. Moreover, LFP life is reduced by time spent at full charge.

What this all means is that, practically speaking, I routinely use about 80% of my LFP capacity rather than 100%. About 8 years of experience with this now. If you read the dirty details on spec sheets, they will often say “Usable SOC range, 10% – 90%”, which confirms my experiences.

1 year ago


I’ve heard that the FLA 50% rule is true but misleading. In that, the total lifetime amp-hrs is similar between discharging to 50% vs discharging to 20%. (If you sip your beer, it will last longer but it’s still 12oz.)

Do you have any comments or hard data? If true, I’d lean towards the 20% option.

Mike Sokol
1 year ago
Reply to  Irv

Sounds like a good topic for an article. I have tons of graphs from the major FLA manufacturers that I can reference. Plus how about an Ask-the-Expert webcast? I’ll ask around…

Ray Cordero
1 year ago
Reply to  Mike Sokol

Mortons on the Move did a great YouTube video on this in case you’re interested.
Don’t Waste Your Money On Batteries – The Shocking Truth I Discovered When Testing RV Batteries – YouTube

Jeff Craig
1 year ago
Reply to  Ray Cordero

Second this recommendation! When I get solar installed, I’m following their recommendations on Battle Born batteries, and have an extra mount installed for two more batts.

1 year ago

When I purchased my new motorhome, the head of service at the dealership — an exceptionally honest young man — told me that, if it were him, he would live with the unit and its 330AH of AGM power for a while, since I might find it adequate for my needs. Sure enough, he was right. I can even run my air conditioner for over an hour on my battery and still have 70% full battery capacity. (I have a three way fridge and gas stovetop. Both make a big difference in terms of battery needs.) With all the buzz about lithium on every website, it’s really easy to get caught up in the “more more more” craze, but at least when I finally do upgrade to lithium — and I will — I’ll know exactly what I need and I won’t be tempted to over purchase. (Actually, I will be tempted to over purchase, but I’m going to try to be reasonable. If nothing else, it’s better for the planet to only install what I actually need.)

Mike Ward
1 year ago
Reply to  Tsippi

If those batteries are charging from your engine alternator, additional items may be needed to avoid damaging the alternator. Additional items may include a battery isolator designed for lithium batteries or a DC-to-DC charger.

Mike Ward
1 year ago
Reply to  Mike Ward

oops, didn’t mean that as reply to @Tsippi 🙂

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