Why would you want a lithium battery pack?

24

By Greg Illes

Lithium batteries have truly extraordinary advantages for certain types of RV life — but they have their “dark side” as well. You need to be very well informed to make the “lithium decision.”

First off, NO, they won’t catch fire

 

There are literally dozens of lithium battery chemistries extant, and the one used in vehicles is lithium-iron-phosphate. Those chemical symbols are Li, Fe, and P, so the batteries are called LFP batteries (or occasionally LiFePo). The iron-phosphate chemistry does NOT have the “runaway” thermal characteristics of other technologies, and LFP batteries simply cannot self-incinerate.

Now that the main hurdle is behind us, let’s look at all the pros and cons. There are quite a few.

LFP Batteries are “nearly perfect” in operation

By this, I mean to say that LFPs are incredibly efficient and flexible compared to lead-acid (LA) batteries.

  • Charge very quickly — Can easily charge at 100% of rated capacity (LA limited to 10-20%). This means that a full charge can be reached from a full discharge in typically only a few hours, whereas LA batteries can take a full day or more to fully charge.
  • Discharge huge currents with no penalty — Can discharge at 300% of rated capacity with no reduction in lifespan or capacity. LA batteries will take at least a 50% hit in capacity and life if routinely discharged at more than 10% capacity.
  • Can be discharged to 95% with no penalty — LA batteries will lose 50% of life or more if discharged to more than 50%.
  • No problem being left at partially charged levels — LA batteries will lose 50% of life if kept at partial charge states. LFP batteries actually like being partially charged, and it can even increase their life.
  • About 1/4 the weight and 1/2 the size of an equivalent LA pack — In addition to smaller/lighter, LFP also can be mounted in any position/orientation; as an added bonus, they require no ventilation.
  • Slightly higher output voltage — at 13.3V nominal instead of LA’s 12.6V, lights burn brighter and motors turn faster. Everything works just a little bit better.

Here’s a typical real-life example of how this works out: My microwave oven draws about 120A out of my power inverter. This causes about a 0.8V drop on the supply lines, which brings the inverter voltage down to 11.8 when running on LA. The inverter sees the battery as “discharged” and kicks off to save the battery. But on LFP operation, the voltage goes from 13.3 to 12.5, and the inverter is happy as can be.

Furthermore, the 120A draw, which would impair LA capacity and lifespan, is “no problemo” for the LFPs. And when I’m done microwaving, the LFPs suck up everything that my solar panels or engine alternator want to provide — there’s no “float charge” charging resistance on LFPs like there is on LAs, and they charge back up again at warp speed.

Microwave, hair dryer, vacuum cleaner, electric power tools, you name it — they’re all welcome in my coach.

LFP Batteries are very touchy to manage

LA batteries will take certain types of abuses that are simply fatal to LFPs. LFPs require much more precise management.

  • VERY sensitive to over-charging or under-charging — If an LFP is discharged below about 10.6V, or charged above 14.6V, IT WILL DIE. That’s an unrecoverable, expensive proposition. And dead is dead, no CPR, as in throw it away.
  • MUST HAVE battery-management system (BMS) to protect from over/under charge — It’s possible to manually manage charging and discharging, but sooner or later a mistake will be made, with expensive results. The ONLY way to manage LFPs is with an automatic electronic BMS. These can be done inexpensively, but they have to be reliable in the extreme; and they are a possible point of failure.
  • Significant up-front cost — LFP systems can range from $1000-$5000 or more, depending on capacity, sophistication of the BMS, and installation costs. A much longer lifespan helps to offset the per-year cost, but it’s still a big chunk of change all at once.
  • Not fully compatible with existing engine alternators, solar chargers, and shore-power converters — An alternator typically puts out 14.8-15.5V at no-load, and it will trip a BMS. This must be managed, but there are multiple choices how to do so. Chargers and converters have a different issue, in that they will tend to “see” LFPs at 13.6 as fully charged when they still have much capacity remaining. Again, there are multiple choices to manage this — all of which add to the system expense.
  • Narrower operating temperature range — LFPs are typically rated at -20 F to +140 F, while LAs will see -40 F to +160 F ratings. Not that big a deal for most of us. BUT there’s a larger concern: LFPs also should not be charged below 32 F, and this can require battery heaters if they are operated near freezing temperatures; installing them in a heated area is also an option.
  • More complicated to get service and replacement parts — It’s easy to get another 12V LA battery at any auto parts store. (Maybe not exactly the one you wanted, which can be a problem when running batteries in parallel, but that’s a longer discussion.) But LFPs are going to be special order anywhere you roam, and it could take many days to get a replacement. This requires a “fall back” strategy to keep the coach operational in the case of an LFP system failure.

When I installed my LFP system I built a semi-custom BMS and attached it to the access cover (the little tab at the back in the photo). Now, in the space where 2-3 golf cart batteries used to live (about 110AH usable), I luxuriate in 360AH of King-Kong style capacity.

SolarBasics-LFPbatts - CopyIf this all sounds complicated and difficult, well, yes, it is and can be. Although there are some “drop-in” LFP batteries with built-in BMS modules, these tend to not have the extreme discharge currents of a custom system, nor are they rated to operate in parallel. They are also considerably more expensive and not as space-efficient. But for the lower-current/capacity user, they just might be the ticket.

A full custom conversion is not for the faint-of-heart, and being technically savvy and handy is very much an advantage (although there are some LFP systems being delivered as built-in options in high-end expedition vehicles). I would have to say that by far the biggest LFP advantage goes to the boondocker and remote camper. Folks who stay hooked up most of the time, or don’t mind running the generator a lot (gag), really won’t see a benefit.

But I can tell you unequivocally, I’ve had these batteries in my coach for three years now, and I’ll never go back to LA batteries. For one thing, in my small class-A, I could never fit 360AH (usable) of capacity using LA technology. And between my solar panels and engine alternator, my LFP batteries charge so quickly that I never have to use a generator; in fact, I don’t even carry one any more. For us, the LFP advantages far outweigh the disadvantages, and we have gotten very accustomed to running with this incredibly flexible, wonderfully quiet power source.

Greg Illes is a retired systems engineer who loves thinking up RV upgrades and modifications. When he’s not working on his motorhome, he’s traveling in it. 

##RVT822 ##RVDT1388

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Bill Fisher
2 months ago

I replaced our 6 volt lead acid batteries with lithium and would not go back to LAs. The many advantages of lithium batteries mentioned in the article far outweigh the upfront cost issue to me. I use 600 watts of solar to keep them charged.

Suru
2 months ago

Thank you for a very informative and easy to understand article.

andy
2 months ago

Greg, this article was written in late 2017. Any updates since then?

Gregory Illes
2 months ago
Reply to  andy

Andy, it’s been a wild ride. Absolutely perfect installation for almost 3 years, but then I had the RV in maintenance/storage for six months. I thought it was managed properly, but it got unplugged for over 4 months. The BMS I installed was home-grown, and allowed a small parasitic current to stay alive, plus a battery monitor. It was just enough to kill the entire pack ($Ouch). To add insult to injury, a portion of the BMS died, and I could not get replacement parts.

After that expensive misadventure (I replaced the pack), I decided on a more manual BMS design, one which would draw zero current when the pack was shut off. I also separated the cell-balancing circuit, and I use that manually as well.

I still wouldn’t trade the LFP for lead batteries, at almost any cost, but it’s certainly not trouble-free (any more than any other battery I guess).

Admin
RV Staff (@rvstaff)
2 months ago
Reply to  Gregory Illes

Thanks for the update, Greg! Stay cool, and stay healthy. 😀 —Diane at RVtravel.com

Judy S
2 months ago
Reply to  Gregory Illes

Wow, Greg, thanks for that update. I feel the same way about my custom LFP bank and I learned some more from you.

Harry
2 months ago

If you don’t carry a gen anymore how do You run your AC when boondocking? Maybe one hour on the 360 amps of batteries.
What is lightning speed to recharge?
Drop in LFP with BMS are the same size, not half size of LA, that I have seen. I would also say they are 1/3 to 1/2 the weight of LFP, not 1/4.
I would not limit the the “system cost” up to $5000, I know people that have paid 3 -4 times that amount!
I have 200AH from Battle Born, total investment $1700, just dropped in. Not worried about freezing. 400 watts of solar helps charge.

Gregory Illes
2 months ago
Reply to  Harry

Harry, for a long time I ran without an A/C. Recently, I added a Polar Cub, which draws about 90A out of the batteries (now 400AH). That’s about 2 hours, and I count on solar to re-charge it. Otherwise, gotta boondock where it’s not so hot (my preference anyway).

Truthfully, I’d hate to use the A/C, it’s only for emergencies and not routine travel. I’m still thinking about carrying my Yamaha EF2000 to run it. Ugh.

Judy
2 months ago
Reply to  Harry

Good question, Harry. I get asked that a lot because my class B has only solar (no gen, no propane). I have a 12v AC from Crusin Comfort that can run for about 7 hours before draining the LFP batteries so much that the BMS would shut them down (if I’m not out in full sun or running the engine).

Those AC units are expensive though, in the $4k range. For reference, I run it off about 400 watts of solar and 420ah in four LFP batteries.

Like Greg, I run mine only when absolutely needed and I tend to boondock in good climates. There’s nothing like shore power for unlimited AC. Running 12v AC requires some mindful power management. If I preferred campgrounds with hookups, my setup would be overkill.

Irv
2 months ago

Well done article. (I wish this website let us vote for articles.)

Bill T
2 months ago

Hi Greg. I wanted to let your readers know that switching to lithium from LA, I believe, would solely depend on your usage needs. My wife and I have RV’ed for more than a decade with a single 12 volt group 27 LA battery. I added 160 watts of portable solar which works great for keeping the battery charged to meet our daily and nightly power needs. On bad weather days, or when I need 120 volts, I run the generator to keep things topped up. I have read so many articles and have seen dozens of videos on lithium battery systems but IMO they are not the end all be all for RV’ing ,that the industry and it’s ambassadors often proclaim. You can have a great time camping off grid with the original equipment your RV came with, if you understand power conservation and don’t need all the Netflix or other “sticks and bricks” amenities while camping.

Gregory Illes
2 months ago
Reply to  Bill T

Bill, it’s absolutely true that EVERYBODY has different needs and wants. Me in particular, I wanted to NEVER run a generator if at all possible. Eventually, I stopped carrying one. I also wanted to run the microwave, pretty much impossible with my 2 golf cart batteries (voltage sag). Then, after I discovered that my LFP charged so much faster than my lead batteries (able to use all of my 400W of solar), I was hooked for good. YMMV as they say, keep on truckin’.

Robert Pulliam
2 years ago

I must’ve missed something in the article on batteries, if your microwave draws 120 amps, how big is the RV it’s in? Do you have 3 50A electrical cords and campground plugs to power your RV?

DAVE TELENKO
2 years ago

Hi Greg, thanks for the great article on LFP batteries. I have a 2017 Forest River that had 4@6VDC batteries. Well these batteries ,2 of them leaked at the seams that caused corrosion all over the place. Of course F/R doesn’t cover corrosion, even thought the dealer did a test & said those 2 needed to be replaced. The worst of it is that the compartment was loaded with 4 relays, 2 solenoids & other electronic gismos. So I went out & bought 4 L16 AGM batteries. My reason for buying the AGM’s was they emitted very little gasses that would corrode & eventually destroy some of the electronics in that compartment. Just another reason to use AGM batteries.

Wolfe
2 years ago

Diane: 1/20C is 5A for 20 hours. Please fix typo. Thanks.

Admin
RV Staff (@rvstaff)
2 years ago
Reply to  Wolfe

You’re welcome, Wolfe. Your own on-call (human) spellchecker. 😉 😀 —Diane at RVtravel.com

Wolfe
2 years ago

Excellent write up, but there are a few technical issues that may confuse readers. I’ve done a LOT of work with lead and lithium battery packs, soooo…

1) LiFeSO4 batteries absolutely CAN catch fire if shorted or charged to too high voltages, and the substrate is flammable if that occurs. What they won’t “generally” do is catch fire “spontaneously” like LiPo batteries (which can internally short more readily if damaged). So, not totally safe, just better than some other LiPO chemistries.

2) Speaking for engineering precision, “rate of charge” and “state of charge” (vs capacity) units got mixed above. LiPOSO4 can be charged at multiple “C” (eg a 100AH LiFe battery can be charged at “1 C” by 100A for a little more than an hour, unlike a LA battery that shouldn’t really be charged faster than 1/20th C is 5A for 10 hours). And yes, LiFe/LiPO can be discharged at whopping many-C rates LiPO especially is often happy at 30C (discharging your battery in *2* minutes without damage).

3) Lithium batteries DO have a charge penalty, but as mentioned, it’s actually at the high-end. When not in use, it’s best to reduce your battery charge to 50% for “storage” and recharge right before usage. Holding a full charge will shorten the capacity of LiPO noticeably, and LiFE more modestly.

4) Plug-and-play lithium systems are still at a price premium, and DIY should only be attempted if you know what you’re doing (since a 10KWh “bomb” is kinda dangerous if you don’t). That said, more electrically familiar readers CAN assemble a “King Kong” power system under $1000. Discretely isolating the battery/load vs alternator/converter through a decent wattage CV/CA (constant voltage/constant amperage) charge controller is all it really takes. But again, don’t attempt if you don’t know what the last sentence said. 🙂

Play safe out there, or at least video the explosion…

Will Swarts
2 years ago

The #1 disadvantage you did not mention is the cost. They are 5-10 more expensive than a LA battery.

Greg Illes
2 years ago
Reply to  Will Swarts

Will, you’re right about the cost (actually I DID mention the cost briefly in the third bullet in the disadvantages list). I only commented that the batteries last a lot longer to make up for it, but it’s still a big hurdle up front.

In fact, I believe this up-front ticket is so huge that it’s likely to prevent most folks from thinking seriously about the other trade-offs. Hopefully, the advent of electric vehicles will help to drive down the LFP costs over time.

Joseph Kleinsmith
2 years ago

Interesting comparison of lithium vs liquid acid batteries.
BUT how does lithium compare to AGM (Glass May) batteries including size, weight, cost, life span, durability, etc.
I have 4 AGM 6volt batteries that operate off of 4 – 100 watt solar panels.