Lithium has gone from a premium upgrade to the default choice for serious touring setups, and the price has dropped far enough that the old "is it worth it?" question has largely answered itself. But the real reasons to switch aren't the ones the marketing leads with. Here's what actually changes when you move from AGM to lithium — and the cases where AGM still makes sense.
The one number that matters most
Forget the headline capacity for a moment. The figure that changes your life on the road is usable capacity. A lead-acid or AGM battery should only be drawn down to about 50% before you start shortening its life. Lithium (LiFePO4) happily gives you around 85% — some quality units more.
So a 100Ah AGM gives you roughly 50Ah you can actually use. A 100Ah lithium gives you about 85Ah. That's not a small edge — it means a lithium battery of the same rated size does about 70% more work before it needs charging. Put another way, a single 100Ah lithium replaces close to two 100Ah AGMs for usable power, at a fraction of the weight.
Switch the battery chemistry in the calculator and watch the recommended battery size change. The same daily load needs a much bigger AGM bank than a lithium one, purely because of how deep you can safely discharge each.
Weight — the reason that surprises people
Lithium is roughly half to a third the weight of an equivalent AGM. On a 4WD where every kilo over the GVM matters, replacing a pair of heavy AGMs with a single lithium can free up 20–30kg. That's weight you can put toward water, recovery gear, or simply not carrying. For a camper or van it's the difference between sagging suspension and sitting level.
Our 2019 MDC XTT came with 2 × 100Ah AGMs. Switching to 2 × 120Ah LiFePO4 freed up around 30kg of payload — real weight back in the bank on a camper that earns its keep as the group's base camp. On a build where every kilo counts toward water, gear and staying under weight, that's not a number on a spec sheet, it's a genuinely more usable trailer.
Charging speed and how it holds voltage
Two things happen when you charge lithium that AGM can't match. First, it accepts charge far faster — it'll take close to the full output of your DC-DC or solar right up until it's nearly full, where AGM tapers off badly in its final stage and wastes your driving hours. Second, lithium holds a near-flat voltage as it discharges, so your fridge, lights and inverter get full performance down to almost empty. AGM voltage sags as it drains, and sensitive gear can misbehave before the battery is truly flat.
In practice this means a lithium setup makes far better use of a short drive between camps, and a modest solar array goes further because none of its output is wasted on a slow absorption taper.
The bigger usable buffer is what changed how we actually camp. On a 4-day trip we could run the smaller compartment of our CFX95 as a freezer — ice blocks and desserts for the kids — which the old AGM setup would never have carried alongside everything else. A 300W Kings folding panel through a Victron SmartSolar MPPT 100/20 kept it all topped up, and the lithium takes that charge fast enough that a bit of sun through the day was enough to run movie nights, camp lighting and everyone's device charging off the camper as the group's base.
Lifespan — where the cost argument flips
This is where the sticker price misleads. A decent AGM might give you 300–500 full cycles before it's tired. Quality LiFePO4 is typically rated for 2,000–5,000 cycles. Even at a higher upfront price, the cost per cycle — the real cost of the power you use — usually lands well in lithium's favour, often several times cheaper over the life of the battery. You buy it once instead of replacing AGMs every few years.
The honest downsides
Lithium isn't the right answer for everyone, and it's worth being straight about the trade-offs:
- Upfront cost. Still more expensive to buy, even as prices fall. If your power needs are tiny and occasional, an AGM may never cycle enough to justify the difference.
- Cold weather. LiFePO4 should not be charged below freezing. Most quality batteries now have low-temperature charge protection built into the BMS, but it's worth checking if you tour alpine areas in winter.
- Charging setup. To get the benefit you generally want a lithium-aware DC-DC charger and solar controller with a lithium profile. Charging lithium off an old fixed-voltage setup won't fill it properly.
- The BMS matters. A lithium battery is only as good as its battery management system. Cheap units with weak BMS ratings can't deliver the continuous current a big inverter demands, even if the Ah figure looks fine.
On that last point: if you run a high-wattage inverter, the battery has to supply serious current — a 2000W inverter can pull around 190A at 12V. The calculator flags the BMS continuous rating you need, not just the Ah, because capacity alone doesn't tell you whether a battery can feed your inverter.
So — should you go lithium?
For most people running a fridge, lights, device charging and any kind of inverter, and wanting to camp more than a night or two off-grid: yes, and the main regret people report is not doing it sooner. The usable capacity, the weight saving, the charging behaviour and the lifespan stack up into a genuinely different experience, not just a spec-sheet upgrade.
AGM still earns its place in light-duty setups, tight budgets, or as a cheap starting point you plan to grow out of. But if you're building a system you intend to rely on, lithium is the foundation most serious touring builds now start from.
For how we use the camper — a base for the group, fridge running as part-freezer, movie nights and a mob of devices to keep charged — the lithium switch paid for itself in capability, not just numbers. The extra usable power and the 30kg off the payload made it a genuinely more capable setup. If you're running more than a fridge and a couple of lights and you camp for more than a night or two, it's the upgrade I'd make first.
Want to see what it means for your own build? Put your gear and travel pattern into the 12V calculator and compare the lithium and AGM recommendations side by side.