At first I really intended to keep the crummy flooded lead acid batteries that came with my coach.
They need to have water added every month, only have about 110 Amp-Hours (for 2, because you can only discharge them 50% if that before damaging).
They weigh 60-70 pounds each.
In spite of all that, they work fine and should last a few years. Even when we are dry camping (so called boondocking) we only use about half that each day. And every day we go somewhere so the alternator charges them, and even if we didn’t the sun quickly recharges them also.
However, we really really really want a compressor refrigerator, that will use about 50 amp hours a day all by itself, so that wouldn’t leave much to dry camp with.
This upgrade solves that. We will have almost double the usable amp-hours, albeit at an exorbitant price.
So the first, step is, I had to tweak the stock Magnum inverter charger with a better remote that allows you to tweak for Lithium. See Magnum Remote ME-RC50.
It also helps to have battery monitoring. No sense in having fancy Lithium batteries and have no clue what the state of charge is. So I had already installed the Victron BMV-712.
After that, this is a pretty easy task. You just rip out the old batteries and drop in the new. A few caveats: the new batteries are wired in parallel instead of series so you need 2 new cables.
I went for the giant 2/0 cables which are a bit overkill but with copper too big is always good. The other advantage is these are very flexible, so easy to use. Sadly Amazon doesn’t have the right size in the ones I prefer but you can order them here: 21″ X 5/16″ 2/0 battery cables. You need one red and one black, and be sure to specify 21″ and 5/16″ end on both sides.
Some safety notes. I switched off the battery and unplugged the coach. I still treated every wire as hot. The safe way to remove battery cables, which I often see mechanics get wrong is, remove the negative first. That way, if you accidentally contact metal somewhere, no shower of sparks. Likewise, as you wire these back up, always start with positive.
Note that there is a right way and a wrong way to wire batteries in parallel. You can just wire both batteries directly to a distribution bus bar, which I didn’t do.
Or you can wire the coach negative to one battery and the coach positive to the other battery, which I did, and then join the negatives and positives on both.
What you should not do is wire the coach negative and positive to one battery and then parallel wire the second battery. This will sorta work, but the second battery will have a slightly higher cable run and a tiny voltage drop to it, so the pair won’t work as well together. So if you look carefully at the final installation photo each battery has one post with only one connection, which are the new 21″ cables.
Next there are a couple bolt heads sticking up on the floor on the sides of the battery compartment. At first I was going to cut a 3/8″ piece of plywood, but I ended up using 2 rolls of a 3/8″ rubber material I have used before. The rubber cuts (fairly) easily with a knife and gives these babies a soft ride.
Finally the batteries showed up! They came superbly shipped in separate boxes with deep layers of styrofoam protection.
The final result is below. A couple additional notes:
Note that in my excitement to fire these up, I forgot to take a picture of the wiring, but here is a crude diagram:
Be sure to torque the bolts down to 10 foot pounds or so. Loose battery terminals can cause very bad things.
I had to remove all of the battery stops screwed into the floor of the compartment except for the rear one. The new batteries are much wider. In fact they barely fit lengthwise.
I used some left over rubber to put some small strips on the left and and right and in between the batteries so they don’t bounce around.
The battery door also has some metal hold down bars that if left on would touch the battery terminals. A lot of people just remove these. I ran out of daylight today, but I plan to reinstall them moved slightly over to clear the terminals. While I doubt I will drive off a 3 foot curb and bounce the batteries, battery hold downs are installed for a reason presumably.
So how did they work?
Well, for starters, I reset the charger profile in my new Magnum remote to CC/CV which is available on later revisions using these settings:
- Max Amps – 100 – default
- Charge Volts – 14.4
- End Charge – 60 minutes – default
- Recharge – 13.3 Volt (which is 90% of a fully charged battery)
- Max charge – 12 hours (default)
These were gleaned from a couple contradictory articles written by Battleborn. I plan to call them and see if any tweaks are appropriate, together with my actual experience after using them. If you have an older controller that does not support CC/CV, you may be able to still use them with settings recommended by Battleborn, but I didn’t have to do that.
The solar controller has no such settings, so I just changed to AGM as recommended.
As soon as I powered up everything and put in these settings, the magnum charger quickly started pumping 50-60 amps in, even though the batteries were shipped 90% charged, and topped them off in short order.
Batteries seem to work great as expected. I’ll be doing a few tests, namely, seeing how they stay charged on shore power, as well as testing how they charge with solar and alternator.
So I’ll update with results soon!
First Update 09.11.2019 The RV is in storage; I’m too busy to travel for a bit.
I stopped by to clean up the install, including lowering the battery hold downs slightly and centering them over the new batteries.
That completes the installation. While I was there I checked and the batteries were still about 98% charged on shore power, which is good.
I have some significant “vampire” loads. Among these are the propane solenoid (I plan to address that), the battery monitor, and my Internet router. So if the charging wasn’t working by now I would see some depletion, so all is well so far.
I still need to test the alternator and solar charging, but I’m pretty confident that will be fine. Some have reported the alternator will fail to charge the Lithium batteries past 80% or so because of the way the relay works. Even if that were true I doubt I would bother to address that as the 400 watts of roof solar would fill in the rest quite quickly.