RV Battery Basics for Newbies
Before you determine how to charge RV batteries, know what type of batteries you have in your RV. RV batteries, as a general rule, come in three different standard types.
The Different Kinds of RV Batteries Include:
- Lead acid: Most flooded lead acid batteries have little caps you pop off to refill with distilled water (to minimize adding impurities).
- AGM: This stands for “Absorbent Glass Mat”, which has to do with the construction of the battery. These are sealed, maintenance-free, and won’t spill. (They can also contain a gel-based substance, too.)
- Lithium: These are also known as LiFePO4, or Lithium Iron Phosphate batteries. While usually the best choice, they do have their disadvantages too.
Aalmost all RVs are designed as 12V systems. The combination of batteries, whether wired in series or parallel, will output 12V. There are exceptions, however.
The biggest advantage of lithium batteries is their ability to discharge almost completely without incurring any damage. AGM and lead acid batteries start to get damaged when they are discharged to 50% or more. In addition, AGM/LA batteries will output a lower voltage as they discharge. But lithium batteries will maintain a constant 14 volts output almost to 5% remaining. (This can vary by manufacturer and model.)
The biggest downside to lithium batteries is they shouldn’t be used in freezing cold weather. Internal BMS (battery management systems) will usually prevent charging in low temperatures. This is to avoid damaging the devices.
All of these battery types, however, require recharging after a discharge to replenish the stored power they need to spend for your use.
All battery systems are direct current (DC). Shore power and electrical plugs are alternating current (AC). Depending on the configuration of your battery bank, it will usually be 12 volts DC, but could be 24 volts or even 48 volts. It is important to know how your bank is set up. For the purposes of this article, we will use a 12V battery bank as a reference.
How to Charge RV batteries
Method 1: Shore power combined with a converter
The majority of today’s RVs are equipped with a converter. This is a device that converts AC from a shore power connection. Then it converts it to DC that is suitable to recharge a battery. The converters are usually buried out of sight in a storage compartment or underbelly. But they are also usually close to the battery bank. Sometimes a converter will also be an inverter. It depends on the device. (Inverters change DC power to AC power for your plug-in appliances.)
If your batteries aren’t charging from your shore power connection, have a qualified electrician test this device for proper function. These also may be wired to a breaker in your power panel. Ensure the breaker has not tripped. If a reset trips it again, have a technician test and/or replace the converter.
Method 2: Camping generators
As RVers, many of us like to get away from the crowd and boondock on public lands or other suitable locations. In these situations, you won’t have any shore power. Some RVs come with generators on-board. Sometimes your seller can install one as an option. For those smaller rigs, portable generators are a way of life.
There are also generators that are considered “contractor grade”. These tend to be larger and are rather noisy. We wouldn’t recommend one. Your neighbors won’t thank you if you use them.
Some of the better generators not only generate DC power to recharge your batteries. But like the example above, also have “inverter” outputs to directly power AC appliances. If equipped with proper connections and cable, a generator can be used to charge batteries directly. Otherwise, connect your shore power cord to the generator’s AC outlet for charging RV batteries. (Always be sure any inverter generator is a “pure sine” (not “modified sine”) version to keep today’s sensitive electronics safe.)
These generators typically use gasoline as fuel. But they can sometimes be converted to also use propane as a source. Some onboard generators for larger RVs may be powered only by propane. This will almost always be the same propane source as your stove, furnace, and other propane appliances. Watch your levels!
Method 3: Solar power
With the continuing price reductions in solar panels and solar kits, the RV industry is seeing many more solar power implementations than just a decade ago. Some manufacturers will install “solar ready” kits, meant for portable solar panels, while other, newer rigs may even have solar panels pre-installed on top.
The best benefit of solar recharging is that, once installed, using the sun is truly free. Many RVers start small with a lower-output panel, and increase the quantity or output size as their budget and needs grow.
Installing solar will require a good understanding of electricity and how it works. For example, you cannot just wire a solar panel directly to your batteries! Solar panels can range in their output from very low high amperage. A properly installed complete solar power system includes a “controllers” which will monitor and adjust amperage for safely charging batteries.
There are two types of controllers used in modern configurations: PWM and MPPT. The PWM tend to be less expensive, but not as efficient as MPPT. Either of these, however, must be sized correctly to your battery bank and electrical system. Consult a qualified solar installer to ensure you get the right matchup for your battery bank and your budget.
Method 4: RV vehicle engine
Many of today’s larger Class A and large Class C rigs, and also some Class B rigs, have integrated charging the battery bank from the vehicle’s engine itself.
This means that when you are driving the rig from one place to another, the same engine that is causing the wheels to turn is also acting as an on-board generator! It doesn’t matter whether the RV is powered by gasoline or diesel, this configuration will keep your batteries topped off, as long as everything is functioning as it should.
Method 5: Tow vehicle 12v feed
Similar to #4 above, this only applies to travel trailers and fifth wheels. These types of RVs have trailer wiring connections to ensure that lights and turn signals operated in the tow vehicle also cause the trailer to match. Many of the larger trailers will have a 7-prong connection.
One connection in the outlet and trailer cord plug connect to send an “auxiliary power” connection. When wired correctly, this can provide a 12-volt power feed from your tow vehicle’s alternator (the same one that charges your truck battery) and sends additional power back to the RV.
When this is connected correctly, your travels will be topping off the batteries so when you arrive, you’ll be ready to turn on the lights and fire up the laptop. Some tow vehicles can even be installed with a separate, dedicated alternator just for this circuit.
These are the five most common ways to recharge your RV batteries. If you know of more ways, leave a comment below and share with others!
RVers looking for valuable how-to information have learned to go to the experts. Forums such as iRV2.com and blog sites like RV LIFE, Do It Yourself RV, and Camper Report provide all the information you need to enjoy your RV. You’ll also find brand-specific information on additional forums like Air Forums, Forest River Forums, and Jayco Owners Forum.
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