Until now, we have maintained the charge on our RV chassis batteries with electricity from our inverter. Here is a solution for solar charging RV chassis batteries without using our inverter. Someday (soon), our new DC-to-DC converter will be the only charge source for my RV chassis battery because I won’t be driving the RV.
Putting our RV in storage
Honestly, one year ago, I would have said this problem doesn’t apply to me. The reason is that we run our inverter 24 hours a day. Why would I turn it off? I live in the RV. Then we started thinking about a vacation and putting our RV in storage. We have never put our RV in storage. Later, I will discuss our upcoming vacation, but for context, when we put the RV in storage, I want the chassis battery charged when I return.
Charging chassis batteries
Until now, we have had two methods of keeping our chassis battery charged. The first method is a BatteryMINDer hooked up to an outlet inside our RV, which takes power from the Alternating Current electrical system created by our inverter.
Lead sulfate
We also use a Pulse Tech Solar Pulse 12-watt solar panel on our RV to keep the chassis batteries desulfated. Here is a photo of the box, followed by a photo of the Solar Pulse installed on our RV roof.
Lead sulfate is a crystal created during a lead-acid battery’s discharge and is the number one reason chassis batteries fail. If you have ever seen a white powder on your car battery, this is lead sulfate. It is a sign that your car battery is failing. When lead sulfate covers the lead plates inside your chassis batteries, they will no longer start your RV. The Solar Pulse helps keep the lead sulfate from causing premature death to the battery.
Ample Solar
We have enough solar panels, even during a cloudy day, to keep our RV running indefinitely, especially in storage. This goes double when we empty our refrigerator and turn off our inverter.
Why do I want to turn off the inverter?
I would love to turn everything off when I put the RV in storage, but that isn’t practical. We haven’t ever put our RV in storage, so it is new territory for us that I am preparing for. I don’t anticipate any problems, but having the inverter off and disconnected from the battery is a precaution I would take if I weren’t a full-time RVer and frequently put my RV in storage.
The inverter’s primary purpose is to power our refrigerator and televisions. We won’t need the televisions, and the refrigerator will be empty and open when we put it in storage. There isn’t any reason to leave my inverter on when I put the RV in storage. It probably wouldn’t fail while the RV is in storage, but if I turn it off, it won’t fail. It will be ready to work when I return if I remember to turn it on.
How do we transfer DC electricity to various locations in our RV?
This isn’t the first time we have used DC-to-DC converters to move electricity from one source to a different location. The DC-to-DC converter was the essential component that allowed us to combine AGM lead-acid and lithium batteries and keep both battery banks happy. Here is a link to our battery setup using both kinds of batteries. Hybrid Mongrel Battery
Later, we removed our AGM batteries to save four hundred pounds of weight and went to one lithium battery to power the DC portion of our RV. The single battery in the following photo powers the DC system and is a backup for situations where we exhaust our main lithium battery bank. Here is a link to the story about replacing four AGM batteries with one lithium battery. One lithium battery
Why must I charge my chassis batteries when I store the RV?
This is because my chassis batteries leak. No, not acid, but rather, they lose a little of their charge every day if I don’t constantly charge them. They lose some of their charge because they are lead-acid batteries. All lead-acid batteries, unless constantly charged, will lose their charge even if disconnected. They also lose a little charge due to loads I can’t turn off. These are called parasitic loads; even though they are tiny, they add up. They are in our RV and our car. A small load, over time, will result in a dead battery.
Options for charging my chassis batteries without my inverter.
The first option I thought about was to add a small solar panel to the roof that is big enough to charge my chassis battery while the RV is in storage. That way, I could turn off my house batteries and main solar array when I put the RV in storage. If a small solar panel were directly connected to my chassis batteries, it would do the job nicely.
It is critical to recharge or maintain the charge on my lead-acid batteries daily. Even better than recharging daily (for battery health) is to charge them constantly 24 hours a day and never let the charge deplete. Every recharge will deposit a small amount of lead sulfate on the battery, and rather than remove it, the very best method is to keep it charged rather than recharge it.
I already described how I want the inverter off when storing the RV. Yet I have a large solar array and house battery bank that won’t be doing (anything) much work. Thus, to keep my chassis batteries fully charged, I installed another DC-to-DC converter between my Lion Energy battery and chassis batteries that will still work with my inverter turned off.
Does it work?
The following photo is my 2008 vintage solar controller, which I wasn’t using except as a cover for a hole cut in our wall. Even though it isn’t connected to any solar panels, it does a great job as a volt meter for my chassis batteries.
Final thoughts
I did this conversion to prepare to put the RV in storage, and it works so well that I wish I had done it four years ago, even though I lived full-time in our RV. The arrangement has merit in keeping the chassis batteries fully charged and is a much better solution than my previous BatteryMINDer charger. Since the BatteryMINDer is a maximum of one amp, it barely kept up with my chassis batteries’ power needs.
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This is a great way to keep your chassis battery healthy without the RV being plugged into an outside electricity source.
Why not get another small solar panel to keep the battery fully charged?
I already have plenty of solar panels. However, I do plan on a small solar panel to keep my car battery charged when I am gone. Ideally I will put it behind the windshield, inside the car, and charge the car battery that way. Unlike my RV, maybe I will have access to 110-volt power near the car so I can plug in a battery tender to keep the car battery fully charged.
I have the new 50 amp DC to DC that I use to charge my house batteries as I drive. Works really nice. I’m using the alternator to charge on those rainy or cloudy days I just don’t get enough solar. I can’t see how you are connecting this. Does yours charge both ways or are you just running it the other way so you don’t charge the house batteries from the engine?
While it is connected, the engine alternator only gives the Lion Energy house battery a negligible charge. This battery is almost always full because it is constantly charged from my main battery system. I keep my Lion Energy battery full because it acts as my backup battery. An empty backup battery is worthless.
This article is about how I maintain the chassis battery by transferring power from the house battery system to the chassis battery.
My solution is unique to my RV and was created to overcome some of the system’s designs.