This is the question we field more than any other: should I switch to lithium? The honest answer is "usually, but not always," and the reasons matter more than the headline. Below is how we actually weigh it when we spec a build — no oversell, just the trade-offs we'd walk a customer through in person.
Usable capacity is the number that matters
Battery labels list nominal capacity, but the number you can actually use is smaller, and it differs sharply by chemistry.
- A flooded or AGM lead-acid bank should not routinely go below about 50% depth of discharge. Take it deeper and you trade cycle life away fast. So a 200 Ah AGM bank gives you roughly 100 Ah of working capacity.
- LiFePO4 (lithium iron phosphate) tolerates much deeper cycling — commonly 80% to 90% of nameplate day to day, and close to 100% when you need it. A 200 Ah LiFePO4 bank gives you roughly 160 Ah or more of usable energy from the same nameplate rating.
That's the core of it. On paper a 100 Ah AGM and a 100 Ah lithium look equal. In the rig, the lithium delivers close to double the usable amp-hours. When people say "I doubled my battery and barely noticed," the fix is often chemistry, not capacity.
Cycle life and cost over the life of the bank
Cycle life is where the upfront price gap closes.
- AGM typically delivers 300 to 1,000 cycles, and how deep you discharge it largely decides where in that range you land — shallow cycling stretches it toward the top, regular deep discharges cut it toward the bottom.
- LiFePO4 typically delivers 2,000 to 5,000 cycles, and shallow daily cycling pushes it toward the high end.
For a rig that gets used regularly, you may replace an AGM bank several times before a single LiFePO4 bank wears out. Lithium costs more on day one — often roughly two to three times the per-amp-hour price, though it varies with brand and whether the pack is self-heating — but the cost per usable cycle usually lands in lithium's favor over the life of the system. Lithium is also more efficient round-trip (commonly around 95% or better, versus roughly 80–85% for lead-acid once charging losses are counted), so more of what your solar and alternator produce actually lands in the battery.
Weight and space
For a van or trailer where payload and floor space are tight, this is decisive. A LiFePO4 battery weighs roughly half its AGM equivalent for the same nameplate capacity — and since you need fewer amp-hours of lithium to match a lead-acid bank's working capacity, the real-world weight and volume savings are larger still. On a retrofit it's common to reclaim a battery box and a meaningful chunk of payload just by switching chemistry.
Charge acceptance: faster recharge from solar and alternator
Lead-acid is fussy about how fast you push current into it. Practical charge rates sit around 0.1C to 0.2C — a 100 Ah lead-acid bank wants something like 10–20A — and acceptance tapers off as it fills, so the absorption stage drags on for hours. That's exactly when an afternoon of sun or a short drive runs out before the bank is full.
LiFePO4 accepts charge at a much higher rate, commonly 0.5C and up (a 100 Ah lithium battery can often take 50A), and holds that acceptance nearly to full. In practice that means a rooftop array or a DC-DC charger off the alternator refills the bank far quicker. If your charging window is short — a couple of cloudy days, or a 40-minute drive between camps — lithium captures energy that lead-acid simply leaves on the table.
Voltage stability under load
Lead-acid voltage sags steadily as it discharges and dips noticeably under heavy draw — an inverter running a microwave or an induction cooktop can pull the bus voltage down enough to trip low-voltage cutoffs early. LiFePO4 holds a much flatter curve, sitting in the 12.8–13.2V range across most of its discharge before dropping off at the very end. Sensitive electronics and big inverter loads run more cleanly on that stable bus.
Cold weather — the real caveat for lithium
This is the one we make sure every customer understands. LiFePO4 cannot safely accept a charge when cell temperature is below freezing (32°F / 0°C). Forcing current into a frozen cell causes lithium plating — permanent, irreversible damage. Discharging in the cold is fine; charging is not.
Reputable lithium batteries handle this two ways:
- A BMS low-temperature cutoff that blocks charging below freezing. Protective, but it means no charging on cold mornings until the cells warm.
- Self-heating packs with internal heating pads that warm the cells before allowing charge, usually drawing a small amount of power to do it.
Cheap lithium often lacks low-temp protection entirely — a real hazard for anyone chasing a Nevada winter or a high-desert night. Lead-acid is more forgiving here: it has no plating-failure mechanism, so it tolerates cold charging far better, though best practice is still to reduce the charge rate below freezing, and a deeply discharged lead-acid bank can have its electrolyte freeze. For a cold-climate rig, this forgiveness is a genuine point in lead-acid's column, and at minimum it means specifying a self-heating lithium pack or a heated battery box if you go lithium.
A retrofit is more than swapping batteries
Dropping lithium in where lead-acid lived rarely ends at the battery. To do it right we usually look at:
- The BMS, and whether your charge sources play nicely with its cutoffs.
- A DC-DC charger so the alternator charges lithium at the correct profile and stays within its own thermal limits.
- Charge profiles on the solar controller and any shore/converter charging, set to lithium voltages.
- Fusing and cable sizing, because lithium's higher charge and discharge currents change what your wiring has to carry safely.
Skip these and you either underperform the new battery or stress your charging hardware. The battery is the easy part.
When lead-acid still makes sense
We won't push lithium on a rig that doesn't need it. AGM is still the sensible choice when:
- The budget is tight and you want a working system now.
- The rig is used rarely — a few weekends a year — where lithium's cycle-life advantage never gets spent.
- The rig lives or travels in sustained sub-freezing conditions and a self-heating lithium pack isn't in the budget.
- Loads are modest and a simple shallow-cycle bank covers them comfortably.
Lithium earns its price through use. If you're not cycling the bank, you're paying for cycles you'll never draw.
If you're weighing a retrofit and want someone to size it against how you actually camp — your loads, your charging window, your climate — see our lithium upgrades page, or talk through your build and we'll give you a straight recommendation.