The terms “RV converter” and “RV battery charger” are often used interchangeably, but what are the differences between them? How do they stack up against one another, RV converter vs battery charger? The term “battery charger” is pretty self-explanatory… it charges your RV batteries. But there’s a bit more to it than that. Likewise, an RV converter can charge your rig’s batteries, but it does much more than that.
So, what are the exact differences between the two? And do you need both? Let’s charge in and find out. 😉
- 1) What is an RV Converter?
- 2) What is an RV Battery Charger?
- 3) What Are the Differences Between an RV Converter & Battery Charger?
- 4) What’s the Difference Between Older Converter/Chargers and Newer Ones?
- 5) What Are Charging Stages?
- 6) Do I Need a Converter/Charger When My RV Is Connected to Shore Power?
What is an RV Converter?
First, a little history:
When converters were first introduced in the RV market, they didn’t charge the rig’s battery/batteries at all (because in those early days, RVs didn’t even HAVE their own batteries… they relied on the towing vehicle’s battery when connected). Instead, the converter was simply there to convert the 120V AC shore power to 12V DC to power the lights, water pump, vent fans, etc. when the RV was disconnected from its towing vehicle (we’ll dig a little deeper into older vs more modern converters in just a bit).
If you’ve seen our full post on RV power converters, you know that the job of a modern RV converter is to convert 120V shore power to usable 12v DC power and charge your rig’s batteries. This is why, these days, they’re most typically called a “converter/charger” since they include a battery charger along with the ability to convert the 120V AC power in your RV to 12V DC power for the onboard loads.
- Converters 120VAC shore power into usable 12VDC power
- Capable of charging your RV's battery while also powering low voltage lights and appliances
This piece of RV equipment does double duty, providing 12V DC power supply for the electrical loads while connected to shore power AND allowinh your 12V RV batteries to be charged when plugged into shore power. Both functions are critical to keeping your lights, vent fans, appliance electronic control circuits, and some other accessories working, whether you’re hooked up to shore power or while you’re off the grid (not connected to shore power or running a generator).
What is an RV Battery Charger?
As you might glean from the term “battery charger,” an RV battery charger charges your RV’s batteries.
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Modern RV battery chargers use more advanced, multi-stage charging cycles that are designed to more completely (and more efficiently) replace the energy that’s been used from the battery. This has the added benefit of more properly maintaining the battery’s health, thereby increasing its service life and reducing the need for regular replacement.
Battery chargers can be portable units that you can move from one battery to another, stand-alone units, built-in models (often combined with a separate, dedicated converter module), combination converter/charger units that serve both functions from a single device, or even combination RV inverter/chargers.
What Are the Differences Between an RV Converter & Battery Charger?
The fundamental difference between an RV converter and a battery charger is found in their ability to control their output voltage/amperage. At its simplest, a converter supplies amperage at a fixed voltage (typically 13.6 volts) to supply the needed power to onboard loads. However, the output voltage can drop if the power or amperage demand exceeds the converter’s capacity to supply.
Another difference between a converter and a charger is that a converter can sometimes provide a slower charge rate than a charger. However, if it’s left connected for too long, it could overcharge the batteries. A battery charger, on the other hand, can adjust its output voltage & amperage according to the battery’s state of charge. A good 3-stage charger will cycle its output through each stage in order to provide the most thorough and safe charging, which will extend the battery’s life.
A lot of confusion has arisen due to the combination of these two functions into single converter/charger units.
What’s the Difference Between Older Converter/Chargers and Newer Ones?
There’s actually a significant difference between older converter/chargers and more modern ones. Older converters and chargers (sometimes called “single-stage” chargers) will top up your RV’s batteries while you’re plugged into a power source. They’ll also charge your batteries pretty quickly if you’re running on generator power.
This is an older 2-stage converter charger in a 1998 Roadtrek Class B RV.
However, the efficiency of older units is so poor that they can damage your batteries under certain conditions. For example, if you keep your RV plugged into shore power for extended periods, an older single-stage unit can overcharge the battery.
Newer units, on the other hand, charge more efficiently and intelligently. Not only do they properly charge your RV batteries, but they also provide the proper degree of charge in stages.
This modern 3-stage RV power converter/charger could be a replacement for the 2-stage unit shown above, provider better, smarter, multi-stage charging.
What Are Charging Stages?
RV chargers (or converter/chargers) generally offer 2- or 3-stage charging. For example, with a 3-stage charger, the charging stages for standard 12V flooded lead-acid batteries are:
Bulk Charging
This is the first stage of charging, which supplies a high voltage & high amperage charge to the battery(ies). This stage generally restores your depleted battery to 70-80% of its original capacity. The bulk charging stage ends when the battery voltage reaches about 14.6V.
Acceptance/Absorption Charging
Once the bulk stage has ended, the 14.6V is held constant while the charger slowly reduces the amperage it supplies. This stage returns the remaining 20-30% of depleted battery capacity. Acceptance/absorption charging ends when the current has been reduced to approximately 1% of the battery’s capacity (for example, if you have a 100 amp-hour battery, it would be fully charged when the absorption charge current is reduced to 1 amp).
Float Charging
The float stage begins once the charging amperage drops to a defined target rate (typically down to 1% of the battery bank’s capacity). In this stage, the charging voltage is reduced to 13.6V to maintain the battery’s charge at 100% of its capacity.
Most lead-acid battery manufacturers recommend a 3-stage charging process as the best and most efficient way to recharge a battery to its full capacity, while also extending battery life.
Some older RVs have only 2-stage (bulk & float) converters/chargers. The problem with these is that they never completely charge the battery to its full capacity. This is because, as we noted above, the bulk charging stage can only return about 80% of the depleted charge. Over time, this constant under-charging of the battery leads to sulfation and a shorter life.
Another problem with 2-stage chargers is that, because they spend longer in the high-voltage “Bulk” phase, they tend to boil off the water from the battery’s electrolyte solution, leading to more battery corrosion and contributing to reduced battery life (if the battery isn’t properly maintained).
Do I Need a Converter/Charger When My RV Is Connected to Shore Power?
You absolutely do, for several reasons. First, as we’ve already noted, if you don’t have a working RV power converter (or charger) onboard, your batteries will drain, and you won’t be able to use any of your rig’s 12V accessories or appliances (remember that some RV appliances like refrigerators, water heaters, and your RV’s propane furnace use a small amount of 12V power for their control circuitry, even if they’re propane appliances).
You need a working converter/charger AND at least one battery in good condition, even when you’re plugged in to shore power.
It’s also essential to have at least one battery charged and in good condition in the system to act as a buffer to keep the power provided by the converter/charger “clean”, which is essential to the health of the electronics in the system. If your RV battery were dead or inadequately charged, the charger would try to compensate by sending more power to it, which would be hard on the entire electrical system (fluctuations in system voltage due to the different charging stages can cause increased wear on wiring and circuitry). This is why you should never use an RV converter/charger without a good battery connected to the system.
As a final note, if your RV’s converter were to fail and you wanted to temporarily resolve the issue until you could replace or upgrade it, you could visit any Walmart or auto parts store and purchase a portable multi-stage battery charger, such as this one. At a minimum, it would allow you to continue enjoying your trip without worrying about your batteries dying, at least until you return home and can get the unit repaired.
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Rob
Friday 15th of August 2025
Thanks for that explanation. I am upgrading a 2005 Casita travel trailer from a few hundred pounds of 6V lead acid batteries installed on the trailer tongue by a previous owner to a single 100Amp LiFePO4 battery. The trailer has a Parallax 7345 converter/charger that, as far as I can tell with their lack of transparency, is a 2 stage unit with output voltage too low to fully charge my new batteries. The easiest option would be to swap the converter/charger to a PD 4645 which can charge Lithium Iron Phosphate batteries, but it is $250 and is not smart or adjustable as far as I can tell. So I was wondering if I could just trash the old converter/charger and replace it with a smart battery charger to take care of both charging the batteries and running the trailers 12V needs? I don't plan to be plugged in too often. You mention a Walmart charger as a temporary solution. I would probably go for a Victron or one sold by LiFePO4 battery vendors. Is the temporary part of your advice because permanent use would stress a battery charger or because the voltage supplied to the 12V loads would not always be optimal? I would think the voltage would be the same as using solar panels and always running off the batteries? Perhaps there is another smarter converter/charger that I could install right in the existing power center where the present converter/charger lives? I'm just trying to get a good understanding of all this before taking any action so I don't do anything stupid! Thanks for any advice you can provide!
TheRVgeeks
Saturday 16th of August 2025
Hi Rob. All good questions (hopefully we get 'em all). Looks like the PD4645 replacement module would likely be the way we'd go in your situation. It can get tricky with how different RVs (and different power centers) handle supplying charging to the battery(ies) and having constant 12V power available for household use. In our old motorhome, the system ONLY worked by supplying power to interior house loads through the batteries... so the charger was just a charger. But in other rigs, particularly towables, that's not always the case... in some of them, the power center wires things in a way that the converter/charger can supply 12V power for house loads WITHOUT a battery being in the equation at all. Without knowing the intricacies of your Casita's wiring, we can't say for sure how the Parallax 7345 works. Which is why the Progressive Dynamics PD4645 replacement seems like the best route. The only thing we see about it that you'll want to be sure you confirm if/when installing it is that there's a hard-to-find, possibly-not-well-documented jumper that needs to be modified in order to switch the charger into Lithium battery mode.
BTW... looks like the 7345 is actually a 3-stage charger (good for flooded lead-acid), and the PD 4645 is as well. But... (there's ALWAYS a "but" right?!?!) that's not really that important with lithium batteries. Not knowing which brand you plan to intall, whatever you get SHOULD have an onboard BMS to handle the finer details, so charging really just becomes a matter of supplying high-enough voltage (the replacement PD4645 supplies 14.6V to charge lithium batteries). For lithiums (with BMSes), charging can actually be quite dumb. No special charging curves needed... they like receiving high voltage until they're full. Then nothing. So the PD should be just fine.
As for the portables, it's not so much an issue of burning them out (though they DO tend to be lower amperage, which would mean larger charging times that COULD affect them over time) as much as lack of convenience, since most use alligator clips to attach and aren't designed for a permanent installation.
Hope this all helps!
Primo Rudy
Friday 11th of July 2025
Rv authors talk about "older converters" and "newer converters." I know the converter in my "old" fiver was a three stage and I know that the converter in my "new" fiver is a 3 stage but I have no idea where the difference is made between "old" and "new"/.
TheRVgeeks
Friday 11th of July 2025
Good question, Rudy! There's not a hard-and-fast date for when manufacturers switched over to installing more-capable (i.e. 3-stage) chargers (and/or converter/chargers) in RVs. It actually varied a lot depending on the manufacturer and class of RV (for instance, high-end diesel pushers got it first, while lightweight travel trailers were probably last). BUT... that said... we'd put a stake in the ground of around the year 2000. BEFORE that, it was quite likely your RV had an "older" (i.e. less capable, likely single- or dual-stage) converter/charger. Between about 2000 and 2010, it was iffy. Again, depending on the manufacturer and class of RV, you COULD have a 3-stage, but might not. After about 2010... you could pretty much gurantee that all RVs had a 3-stage charger in them. Give or take. 😉
Clear as mud now, right? LOL!
David F.
Friday 19th of July 2024
I have a 2017 RV. How do I know if I have a 2 or 3 stage converter/charger?
TheRVgeeks
Monday 22nd of July 2024
Hi David... the most certain way would be to look up the model on your converter/charger and check with the manufacturer and/or owner's manual. But, if we had to guess, we'd say a 2017 is very likely to have a 3-stage converter/charger (though manufacturers can sometimes cut corners here and there... the converter/charger being one place they can shave a few dollars off).
Bruce
Friday 12th of July 2024
To properly charge a lead-acid battery you need to monitor both battery voltage and current. Most battery chargers are designed to charge an unloaded battery, in other words the battery alone is the only thing connected to the charger. However in the RV world most 12V house electrical systems operate as a "loaded battery". The 12V lights and other devices are connected in parallel with the battery. Therefore whatever you using to charge the battery has no idea if the current it is supplying is charging the battery or powering some other device. So even the "smart" 3 stage battery chargers/converters can use only a timed charging routine. It charges in Bulk mode for a set period of time, then changes to Absorption for a further period of time, then folds back to Float.
In my business (radio communications) we used deep cycle batteries to for backup power at Fire Halls etc. The chargers we used had separate connections for the batteries and the loads so the charger could properly measure the current going into the battery while charging.
LiFePO4 batteries are actually easier to charge as a loaded battery. The converter/charger has a target voltage to reach before it changes to "absorption" If there are lights ON etc, the battery will simply take longer to reach that target voltage. Absorption is best done by measuring the current to the battery, but depending on the target voltage the battery is already near full charge (95% or so) so it usually just times out in 15- 30 minutes first. The charger then goes to Float. With LiFePO4, Float is only needed to carry the connected loads because unlike Lead Acid, these batteries have a very low self discharge rate.
Dan
Friday 12th of July 2024
@Bruce, thank you for your reply and information.
Tony
Saturday 15th of July 2023
Thanks for the article, guys. Question: What about the latest converter / solar charger on most trailers nowadays? In other words, while in storage, mine has 100-W panel on the roof and a solar controller between it and the two batteries that runs constantly. So when I hook up to shore power, does both the converter and solar controller charge the batteries? Or does one take over?
TheRVgeeks
Saturday 15th of July 2023
Typically, Tony... the solar wiring and charge controller are completely separate from the rest of the RV's 120V AC and 12V DC systems. It operates in parallel with your onboard converter and charger, combined converter/charger, charger and separate inverter, or combined inverter/charger.
There's no harm in the two systems (solar and shore power) operating simultaneously. Both are attempting to bring the battery(ies) up to full charge and will kick out when that happens. Having both operating just means it will happen sooner. ???? In some systems, depending on how they're wired, the charge going to the batteries from one or the other system will raise the voltage that the other system "sees" the battery as being at... which may lead one or the other to kick out sooner. But, again, no harm.