I get some version of this question almost every week from someone mid-build: “My old converter died, should I just replace it, or should I upgrade to one of those inverter-charger combo units?” It is a fair question, because the two terms get used loosely in RV forums and even by some dealers who should know better.
They are not the same device, and for a lithium bank the difference actually matters for how well your batteries charge and how long they last.
The quick version
- A converter only turns AC shore power into DC to charge your batteries and run 12V loads, nothing more.
- An inverter-charger does that job plus converts battery DC back into AC power when you are off-grid, in one chassis.
- Both need a genuine lithium charge profile (no float creep, no forced equalization) or they will undercharge or annoy your battery management system.
- Converters are cheaper and simpler; inverter-chargers save space and wiring but cost significantly more.
- You likely already have a converter in a factory RV. The decision is usually whether to replace it or absorb its job into a bigger inverter-charger.
What a converter actually does
A converter is a one-way AC-to-DC power supply. Plug your rig into shore power or a generator, and the converter steps that 120V AC down to roughly 13.6 to 14.6 volts DC, depending on the charge stage, to run your 12V lights, fans, and water pump while also charging the battery bank.
Factory units from companies like WFCO and Progressive Dynamics are the most common example. They sit inside your power distribution center, usually a metal box behind a cover panel near the main breaker panel, and most stock units from the last 15 years use a simple three-stage lead-acid profile: bulk, absorption, float.
That profile is the whole problem for lithium. A lead-acid float stage sits around 13.2 to 13.6V indefinitely to trickle-maintain the battery without boiling off electrolyte. Lithium does not want a float stage at all in the same sense, and it does not need the multi-hour absorption times lead-acid demands. I cover the actual voltage targets in more detail in our breakdown of the right charge voltage for LiFePO4, but the short version is that a generic converter often stalls out shy of a full charge on lithium, or dumps a load-shedding relay clunk into your system when the battery management system briefly disconnects.
What an inverter-charger adds to the equation
An inverter-charger, sometimes called a multi-function inverter, combines a charger with a true or pure sine wave inverter in one enclosure. Plug it into shore power and it charges your batteries exactly like a converter would. Unplug from shore power, and the same unit flips to inverter mode, pulling DC from your battery bank and producing 120V AC for your outlets and appliances.
Popular examples in the lithium RV and van world include the Victron MultiPlus and MultiPlus-II line, the Xantrex Freedom XC and Freedom eGEN, and smaller setups using a Renogy inverter-charger. Most of these ship with, or allow you to program, a lithium-specific charge curve, often something close to 14.2 to 14.6V absorption with a short hold time and a true float or storage voltage near 13.6V.
Tip: If you are shopping inverter-chargers, check whether the lithium profile is adjustable or fixed. Victron’s units let you dial in exact absorption and float voltages and even accept a VE.Bus BMS connection for a true managed shutdown, which matters a lot if you are running Battle Born, Li Time, or Ampere Time batteries without their own separate communication bus.
The scenario that makes the choice obvious
A guy I helped last spring had a 2016 travel trailer with a dead WFCO converter and a 400Ah Battle Born lithium bank he had just installed. He was ready to spend $1,800 on a Victron MultiPlus-II because a forum post told him inverter-chargers were “the only real option for lithium.”
His trailer already had a separate 2000W modified sine inverter under the bed that worked fine. All he needed was a charging source that understood lithium. We put in a $260 lithium-programmable converter instead, kept his existing inverter, and he was charging correctly that same weekend for a fraction of the cost.
That is the mistake I see constantly: assuming inverter-charger because the word “lithium” gets attached to it in marketing, when the actual gap is just the charging profile.
Side-by-side comparison
| Factor | Converter | Inverter-Charger |
|---|---|---|
| Primary job | AC to DC charging only | Charging plus DC to AC inversion |
| Typical price (lithium-capable) | $150 to $400 | $900 to $2,500+ |
| Common brands | Progressive Dynamics, WFCO, Renogy | Victron, Xantrex, Renogy inverter-chargers |
| Install complexity | Usually a swap into existing power center | New AC wiring, transfer switch or built-in bypass, often new location |
| Best fit | Rig already has a separate inverter you want to keep | New build, or replacing both an old inverter and converter at once |
| Space and weight | Smaller, lighter | Larger footprint, heavier |
What to check before you buy either one
- Confirm the unit has a documented lithium or “LiFePO4” charge profile, not just a “lithium compatible” sticker with no spec sheet
- Match the charger’s amperage to your battery bank size, generally no more than 0.5C for most LiFePO4 cells unless the manufacturer states otherwise
- Check whether the unit needs a BMS communication link (CAN bus or similar) for full charge control, or runs open-loop on a fixed voltage curve
- Verify your existing AC wiring, breaker sizing, and any transfer switch are compatible if you are moving from converter to inverter-charger
- Look at physical space and ventilation requirements before ordering, inverter-chargers run warmer under load and need clearance
When replacing your converter is the right move
If your rig already inverts fine and the only failure point is charging, replacing just the converter is almost always cheaper and less invasive. We walk through that exact process, including which lug goes where and how to avoid frying your existing wiring gauge, in our guide to replacing an RV converter for lithium. It is also worth checking first whether your current converter can be reprogrammed or is secretly already lithium-friendly, since some newer WFCO and PD units ship with a switch or dip setting for it. That question gets its own deep dive in our full explainer on whether your RV converter will charge lithium at all.
When the inverter-charger upgrade makes sense
Combo units earn their keep in a few situations. New builds and van conversions running all new AC and DC wiring benefit from single-box simplicity: one set of cooling, one programming interface, often a built-in transfer switch so shore power and inverter power share the same outlets automatically.
Boat owners doing a full lithium retrofit also lean this way, since marine inverter-chargers like the Xantrex Freedom often include galvanic isolation and better corrosion-resistant hardware than a bargain RV converter. If you are also running shore power charging regularly, it is worth reading how that charging path interacts with a lithium bank in our guide to charging lithium on shore power, since the same absorption and float logic applies whether the charger lives inside a converter or an inverter-charger.
Sizing and voltage details that trip people up
Whichever path you take, understand the charge curve you are buying. Lithium wants a firm bulk charge up to roughly 14.2 to 14.6V, a short absorption hold of 30 to 60 minutes rather than the 2 to 4 hours lead-acid expects, then a drop to storage voltage rather than a true trickling float. The reasoning behind why lithium needs so much less absorption time is covered well by Victron’s lithium battery compatibility documentation, worth a read before setting any charger’s parameters manually. The chemistry itself is summarized on Wikipedia’s lithium iron phosphate battery page if you want the electrochemistry side of it.
Warning: Do not assume a “smart charger” label means lithium-safe. Plenty of smart converters just cycle faster between the same lead-acid stages. Pull the actual spec sheet or manual PDF and look for a stated LiFePO4 or lithium iron phosphate profile with real voltage numbers before you buy.
Making the call for your rig
Ask yourself one question first: do you need AC power from your battery bank when unplugged? If yes, and you do not already own a separate inverter, an inverter-charger combo is worth pricing out, since two separate lithium-capable units often cost close to the same as one combo unit anyway.
If you already have an inverter you like, or rarely run AC loads off-grid, a dedicated lithium-programmable converter gets your batteries charged correctly for far less money and a simpler install weekend. Either way, the part that protects your battery investment is the charge profile inside the box, not the badge on the front of it.
