RV Lithium/AGM Battery & Electrical System Upgrade – Part 1 – Project Intro

Hi Don! Sorry for the delayed reply... we were in Fredericksburg, TX for the premiere of "The RVers" and have been a bit disconnected. We haven't seen that unit from AM Solar, but it's definitely an intriguing option. Especially for a retrofit situation in conjunction with a hybrid inverter! Thanks for sharing it... it's always good to be aware of options like this!

Hi Joe. That lithium battery manufacturer wasn't lying... you definitely want to be careful with "dumb" alternators charging lithium batteries... for two reasons, actually. First is that the alternator isn't designed to cut charging to the lithium when the battery reaches full, and lithium batteries HATE being overcharged. It puts them into their danger zone, where they begin to overheat and can result in fire. That's way every battery offered for these kinds of applications has a BMS (Battery Management System) either built into the battery or external to the battery. It monitors the battery state and ensures that the battery is kept safe. The problem is, at the overcharging end of the spectrum, the BMS would have to shut the battery down completely to prevent the alternator's charge from doing damage... which would mean you'd lose juice to everything that the lithium battery powers. Not good... PLUS, you're then ONLY relying on the BMS to protect the battery. And what happens if the BMS doesn't work right? You could be in trouble.

The second issue is the fact that lithium batteries don't recharge the same way typical lead-acid batteries do. Lead-acid batteries have increasing resistance to charging as they get closer to full, so they push back against the alternator's output... but lithium doesn't. It's resistance curve is both steady... and low. So the alternator doesn't get any kind of feedback that the battery is nearly charged... so it just keeps pumping out 100% of its output, all the time. So it's possible that you could cause a premature failure of your alternator.

All that said... our system IS setup to allow the alternator to charge the lithium battery while we're underway. Xantrex integrated a custom charge controller with the solenoid that was previously used by our BiRD (Bi-directional Relay Delay System). The BiRD allows the house batteries to charge off the alternator when we're driving... or the chassis batteries to charge off the inverter/charger when we're on shore power. The custom charge controller they installed uses charging voltages that are more appropriate for a lithium battery... and it disconnects the solenoid that joins the two battery banks together when the lithium battery is nearing full. That way, the lithium battery gets isolated from the alternator to protect it... and the alternator then only "sees" the chassis batteries, which are still lead-acid (AGMs).

Not sure what system your Itasca is using... but I'd bet it's something similar to our BiRD from Intellitec. You may want to post questions about it on the Winnebago forum over on iRV2.com (it's free) to see if anyone can point you to more detail about it. But we'd bet that there's another circuit/relay involved... that receives a triggering signal from either the ignition switch OR the battery boost switch, sending the "close" signal to the larger solenoid that connects to two battery banks. So you may be able to install an interrupt switch somewhere in that circuit to prevent the big solenoid from closing.

Hope this all helps... fire back with any questions you still have (or that we just created, LOL!)!

Hi Jeff. Those are old MCD wheel covers that have long since been discontinued. We hopefully have a lead on a new type of wheel cover that we’re expecting to come out later this year. As ours are getting very old, we’re eager to find out more, and will of course keep everyone posted when we do.

Thanks, Craig! And that's a good question. We'll see if we can ask one of our Xantrex contacts about that... although since they're just now getting Lithium batteries to market (along with the rest of the RV industry), our bet is that they'll be waiting quite a while before making any switch! ?

Hey Smitty! Sorry to hear you had that experience with your Magnum MS2812 and your Lifeline batteries! If you don't mind sharing, what exactly was the issue that caused them to fail prematurely like that?

But we TOTALLY get why you'd stick with Lifelines a second time if they gave you a deal good enough not to pass up! Lithium is still early-adopter-priced... so waiting a couple of years will just mean that more kinks are worked out and prices will come down.

As far as our plans on depth of discharge percentage (DOD%)... we're targeting an 80% DOD max. Technically, this battery has 90% useable. But, of course, doing so comes at the cost of lifecycles. At 80% DOD, we should be somewhere in the 3,000 cycles range... which is PLENTY of life for us. Using less will increase it... but using more would decrease it, and we want to avoid that if we can. So this 600Ah battery has a THEORETICAL max of 540Ah of useable power... but we'll be targeting 480Ah as our practical limit. Not a bad increase, since the 4 x Lifeline GPL-4CT AGMs it's replacing only had 220Ah (at 50% DOD). And it weighs 100lbs less! NICE!

We don't want to share too much here, as we don't want to give it all away before we get the videos launched... plus, we've only got a week of use under our belts... but so far, so good. It's been overcast and raining about 90% of the time, so we haven't seen any solar benefit on this trip. But we're loving the lifestyle improvements the lithium is already providing. We're very happy!

Hopefully the sun will come out again while we're dry camping, so we can get a feel for how well it keeps up with demand. We know that 375W isn't going to be enough... but it will be interesting to see how the lithium soaks up those solar electrons, and whether or not we see a difference in the amount of charging we get in a day.

Thanks for hanging with us... and enjoy a nice glass of scotch! ?