By Mike Sokol
Welcome to my J.A.M. (Just Ask Mike) Session, a weekly column where I answer your basic electrical questions. If you’re a newbie who’s never plugged in a shore power cord (or ask – what’s a shore power cord?), or wonder why your daughter’s hair dryer keeps tripping the circuit breaker, this column is for you. Send your questions to Mike Sokol at mike (at) noshockzone.org with the subject line – JAM.
We really would like some more capacity for my RV while boondocking, especially to run my CPAP machine and residential refrigerator. But we keep getting conflicting reports about if we can simply swap in a Lithium battery to replace my current lead-acid batteries, or do we need to change out the charger/inverter as well. A local RV shop says you just stick in a Lithium battery and it will work just fine, but will that work? Do I really need to replace my perfectly good converter at the same time? That’s a lot more cost than we bargained for. —Connie and Jim
Dear Connie and Jim,
Lithium (actually Lithium Iron Phosphate) batteries are great, not only due to the reduced weight and increased number of charge/discharge cycles. But you get a lot more percentage of power out of this technology compared to lead-acid, allowing you to discharge them down to 20% or even 0% of their rated capacity without harming their life.
So while a 100-Ah lead-acid battery should only be discharged down to 50% of its rated capacity to keep from shortening its life (that would be around 600 watt-hours of power from a 100-Ah battery), a 100-Ah Lithium battery can provide 960 watt-hours (discharging to 20% of capacity) to 1,200 watt-hours (discharging to 0% is allowable with some Lithium Batteries) of power from the same size battery. Pretty incredible, but at a higher initial cost. When comparing costs of the lead-acid batteries to lithium iron phosphate batteries, the cost per kilowatt hour for a lithium iron phosphate battery over its lifetime is lower when compared to lead-acid chemistries even when the cost of potential chargers or other components are included. The lower long term ownership costs and increased power of having a lithium iron phosphate battery is one reason why many RVers are switching to lithium iron batteries.
And that cost is what?
Well, Lithium batteries are pretty picky about two important things: (1) They don’t behave well if you try to charge them at a low temperature; and (2) They don’t charge well from a standard converter/charger that’s only rated for flooded cell or AGM lead batteries. The first part is easy since many Lithium batteries have built in heaters or a heating blanket wrap that warms them up before they’ll accept a charge. But the second part is a bit more tricky (read – expensive), since most converter/inverter chargers that were installed in your RV beyond the last 5 years do not have a lithium battery charging setting.
Is that bad?
While you may not notice it at first, charging a Lithium Battery from a converter set for Lead or AGM batteries will ruin the battery prematurely. So instead of the 2,000 charging cycles and 10-year service life of that expensive battery, you can lose half (or more) of its life because one can actually damage the battery by using the wrong charger. And that means you could be replacing it again in a few short years, rather than getting the full service life you paid for. Doing so is just throwing your money away, and nobody likes to do that. The known exception to this is Progressive Dynamics, Inc.’s (PDI) converter charger. Their lead acid converter chargers will not damage lithium-iron phosphate batteries.
According to Progressive Dynamics (a long established manufacturer of converter charges for RVs and boats), charging times can also be affected. When a lead acid charger is connected to a lithium iron phosphate battery it will take 6 to 8 hours to charge only to 79%, while a lithium-iron compatible Progressive Dynamics converter charger connected to a lithium-iron battery will charge to 100% in 90 minutes. And fast charging times is a huge advantage for getting lithium-iron batteries that ought not to be missed.
What to do?
Well, first you need to identify the brand and model of your converter, inverter or charger that’s actually charging your existing RV house batteries. Then you need to see if they have a setting for Lithium batteries. Don’t take the word of an RV shop that’s trying to sell you an expensive Lithium upgrade. No, you need to confirm this yourself with the charger manufacturer.
If you don’t have a converter with a Lithium setting, then factor in the cost of a new converter, which should not cost more than $200 to $500. But if your converter DOES have a Lithium battery setting, then you’re in business and your RV shop can adjust the settings and literally drop in a new Lithium battery replacement. But don’t just take their word for it: Caveat Emptor (Buyer Beware).
For more information
Here’s the Lithium battery company I’ve been working with on my swing-compressor refrigerator project. For more information on their Lithium Ion-Ready™ batteries, go HERE. Or send an email to email@example.com. [Note: Briter Products’ Lithium Ion-Ready™ batteries are Lithium Iron Phosphate (LiFePO4) Deep-Cycle 12V 100Ah batteries.]
I’ll write more soon on the differences between Lithium ion versus Lithium iron batteries, including their intended uses. Plus I’m gathering information on the various Lithium Battery manufacturers and will attempt to do an analyses of the pros and cons of each brand in the spring, but there’s a lot of information to wade through.
OK, everyone. Remember that electricity is a useful and powerful force, so we all need to pay attention to safety precautions while using it.
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 Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.
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