Your RV Battery Questions Answered: Alternator Charging, Battery Storage, and RV Storing Tips
- Todd Henson
- Nov 13
- 3 min read
Welcome back to Todd’s Two-Minute Tech Tip Tuesday, brought to you by Big Beard Battery—your go-to source for off-grid lithium power and RV solar systems. In this session, Todd answers three of the most common questions RV owners ask about DC-to-DC charging, battery storage voltage, and solar maintenance during winter.
Whether you’re driving across the country or parking your rig for the season, understanding these fundamentals can make the difference between a smooth start-up in spring and a dead system when you need it most.
Question #1: Is My Alternator Already a DC-to-DC Charger?
One viewer—who goes by the name “Meat Robot”—asked a smart question:
“The alternator in my truck charges my batteries as I drive. Isn’t that a DC-to-DC charger?”
Technically, yes—but there’s a big difference between your alternator’s unregulated output and a true DC-to-DC charging system.
A standard 7-pin trailer connector does pass DC voltage to your RV batteries while driving. However, that charge is unregulated, meaning the voltage can fluctuate depending on your alternator load. If you’re running your truck’s A/C, lights, or other systems, you’ll likely see a voltage sag—and your lithium batteries won’t charge properly.
That’s where a dedicated DC-to-DC charger makes all the difference.
Benefits of Using a DC-to-DC Charger:
Regulates voltage coming from your alternator
Prevents undercharging or overcharging lithium batteries
Steps up voltage when alternator output dips under load
Optimizes battery health with proper charge profiles
Todd recommends setting the charger to around 14.2V while driving to avoid fast-charging your lithium batteries to 100%. Let them reach a near-full charge, then let the absorption stage finish the job safely.
Question #2: What’s the Best Voltage for Storing Lithium Batteries?
Another viewer, Samuel “L.” Tucker, asked:
“When storing my LiFePO₄ batteries for winter, should I leave them full or at 50% charge?”
The answer: Store them at 12.8 volts.
That’s the nominal voltage of a lithium battery—right around 3.2V per cell—which is ideal for long-term storage. At this voltage, the batteries hold a healthy charge without being over-pressurized or chemically stressed.
Todd explains:
“When cells are fully charged, they begin to push on the outer casing. We don’t want that pressure during storage. 12.8 volts keeps them relaxed and ready to go.”
Stored at this level, your lithium batteries can safely sit for up to six months without a recharge.
Question #3: What Should I Do with My Solar System in Winter Storage?
Finally, Dman3324 asked:
“I have a 200W solar panel on my camper, but I’m storing it under cover for winter. What should I do?”
If your RV is under cover and the solar panels can’t see sunlight, the panels won’t maintain your battery bank. In this case, you have two options:
Turn off your batteries and system disconnects.
This prevents phantom draws and allows your lithium batteries to rest safely at 12.8V.
Plug into a 15A outlet if you need some 12V systems to stay active (like alarms or monitors).
If you expect freezing temperatures, it’s important not to charge your lithium batteries while cold. Instead, disconnect them and store them in a temperature-controlled space if possible.
Pro Tip from Todd
“Lithium batteries don’t need babysitting. They just need proper voltage and protection from overcharging or freezing. Follow these steps, and your system will be ready to go when the season starts back up.”
Why Trust Big Beard Battery
At Big Beard Battery, we’re more than just a lithium manufacturer—we’re your partner in designing and maintaining complete off-grid power systems. From custom solar builds to DC-to-DC charging solutions, our certified experts ensure your RV stays powered, protected, and performing at its best.
If you have questions about batteries, charging systems, or storage solutions, visit BigBeardBattery.com and fill out our Solar Design Form. One of our certified solar experts will give you a call to help design a safe, efficient system that fits your RV lifestyle.
Because when it comes to powering your freedom—Big Beard Battery gets it right the first time.