SYSTEM UPDATE! RV Lithium/AGM Battery & Electrical System Upgrade

Hi Jonathan! Thanks so much for the kind words... we always love to hear that we've been helpful! And sorry to hear you're having trouble with your lithium charging from the engine. We don't have a specific answer for you, but have a thought: it sounds like it's probably an issue with the voltage regulator on the alternator. Since we assume that your RV originally came with flooded lead-acid batteries, your alternator was probably matched to them... and relies on specific voltages and resistance to know when to supply power to charge them. Since Lithium batteries are a different beast, we'd guess that you're running into an incompatibility issue.

For example, the eGEN system from Xantrex, when installed at the factory as a generator replacement in a Class B/C RV, usually has a very high-amperage, lithium-compatible alternator installed. As we understand it, the "lithium-compatible" part has to do with the voltage regulating circuits... that are programmed to the proper voltages for lithium charging. So our guess is that one of two things is happening:

Your alternator's voltage-regulating circuit is seeing the higher voltage from the lithium batteries (either initially OR after a few minutes of charging... where the lithium's voltage rises quickly) and is thinking the batteries are full, so it disconnects Your alternator's output is too high... causing the BMS in the Battle Borns to shut down charging input.

The headlights situation also sounds like a voltage-difference issue. Since lithium batteries rest at about 13.3 (± a couple of tenths of a volt, based on manufacturer), it's likely that the alternator isn't kicking in because it is "seeing" the higher voltage... and thus the lithium batteries are providing charge to replenish the starting battery (which is at a lower resting voltage), draining them while you're driving. Sounds like you may need to install a large diode system between the Battle Borns and the rest of the system, which at least would keep power from draining from them back to the engine loads.

There were similar issues early on with a lot of Airstream owners who installed lithium batteries. Even though the battery manufacturers claimed that their BMS would handle charging by just about any charger... the reality was often different. They'd take their RV out for the weekend, using power. When they returned and plugged them in to charge up, the charger would kick on... making them think the batteries would be re-charged fully for their next trip out. But since the lithium batteries have different voltage and charging behavior, the RV's charger would kick off after about 10-15 minutes, thinking the batteries were already full. When the owners would take them out the following week... the batteries were not at 100%! They ended up having to replace their converter/charger in order to get one that worked better with lithium. This is why we're always skeptical of claims that lithium batteries are "drop-in replacements" for lead-acid. They may be SIZED the same, but the differences in voltage profile and charging characteristics can cause niggling issues that make them misbehave.

We'd suggest that you contact Battle Born to see what input they may have for you. It's possible that you could install a voltage regulator (which might have its own diode to prevent unwanted discharge) inline between the engine's alternator and your Lithium batteries... one that would handle the differences and ensure the battery get charged. Barring that, you may need rewire things to disconnect your house batteries from the engine's existing alternator... and add a second, lithium-compatible alternator that would be dedicated to charging your house batteries while you're driving.

Sorry we don't have a more-definitive answer. But let us know how you make out... or if you have more questions! We'll do our best to clear things up (and not muddy them more)! LOL!

Hi Don! We’ve been seeing more and more info about the Volta power system recently, most likely because of their involvement with Winnebago. It’s definitely an interesting looking system, and there are some advantages to operating at higher voltage, but we definitely liked the (relative) simplicity of installing a 12 V battery into our existing 12V system as an aftermarket install.

We’re not 100% plugged into what Xantrex’s plans are long-term, but we do know that they currently offer a 400Ah version of the same battery we have, that’s being installed in Class B units like the Coachmen. It’s basically a similar form factor to ours, just a little bit smaller... so we’re not sure if it would fit in your battery tray, since you have just a single row of batteries instead of a grouping of two pairs side-by-side.

More details about the The batteries, etc., should be coming out sometime this year. Again, we don’t know the schedule, but we do know that it was Xantrexks intention to start having authorized installers certified in 2019. So once that happens, the information should start becoming more public.

Sorry we couldn’t be of more help, but we hope this provided some more information for you.

Thanks Paul! This isn't available for aftermarket purchase yet, so we don't know the pricing. We will of course keep everyone posted as we know more.

Hi Don. The new units (like the one you have) work differently than our older one (which doesn’t have the same surge protection and circuit-testing capabilities). Technically, with our unit, you’re supposed to plug it into the pedestal and check that the center of three lights is lit... if not, don’t plug the RV into the Autoformer. Since we also have a SurgeGuard unit, downstream from our Hughes, that does some of the same circuit testing, we actually rely on THAT unit for determining the viability of the connection. With the newer Autoformer units, we’d suggest following their instructions to ensure you’re benefitting from all of the circuit testing they are doing on the pedestal power... BEFORE connecting your RV. Makes for a bit more complicated of a connection process, but it will help ensure you don’t expose your RV to bad power.

Hi Matt! Sorry to hear your inverter died on you, but we think you'll be happy replacing it with the same Freedom SW 3012 we're using. We've been loving ours... it just works! Unfortunately, we still have no idea on the pricing or availability schedule for the Freedom e-GEN battery. It's currently only available as an OEM/factory-installed option from a couple of manufacturers (mostly Class B), but we know they're working to get it installed in Class A's, too. Just don't know when... they're doing their due diligence and being very thorough to be sure everything is working as expected. As soon as we hear anything more, we'll be sure to post an update about it.

As far as recommendations for other lithium systems, we don't really have much to share. There are one or two systems like the Freedom e-GEN that are currently being tested by various RV manufacturers (for instance, Winnebago is working with Volta), but as far as we know, they aren't available for aftermarket install, either. Aside from those, there are a whole slew of "drop-in" replacement batteries available now (and it seems like there are more available every day), but we don't have any experience with them to be able to recommend one over another.

While it may not turn out to be an issue in the long run, one concern we have with them is that there currently aren't any that have been tested against the UL1973 standard (for "Stationary, Vehicle Auxiliary Power, and Light Electric Rail (LER) Applications"), which is the standard that applies to RV household batteries. A key component of that standard is a test of their ability to be daisy-chained together (like in typical RV applications with series, parallel, and series-parallel configurations). Since these drop-in replacements are often just re-packaged versions of standard consumer-level lithium cells (with some additional circuitry added in and wrapped in a standard-sized battery case), we worry that they could be a hazard.