Lithium vs AGM, minus the hype
Two batteries can wear the same 100Ah sticker and give you very different nights. What the Megawatt battery math assumes, and what to read before you swap.
2 min read · Updated
Two batteries can wear the same 100Ah sticker and give you very different nights. The sticker is the nameplate. What you can pull out before you shorten the battery’s life is the part that matters.
Why the calculator talks in watt-hours
Every battery the Megawatt calculator recommends is a Vatrer lithium (LiFePO4) pack. It converts each one to watt-hours at 12.8 volts, the usual nominal voltage for that chemistry. A 12 V 100Ah pack reads as 1,280 Wh. A 300Ah pack reads as 3,840 Wh.
Watt-hours are easier to plan with because your appliances are rated in watts. Amp-hours only mean something once you know the voltage.
Vatrer 12V 300Ah lithium battery
3,840 Wh in the calculator's math. This is the same short link the battery calculator uses for its 300Ah step.
Check the current price on Amazon.
Where AGM fits
AGM is a sealed lead-acid battery. People plan around a smaller usable slice of its rated capacity, because deep discharges wear it out faster. How small depends on the battery and how long you want it to last. That’s why the battery runtime calculator asks you to enter the usable fraction yourself. Leave it blank and it won’t guess.
We won’t quote cycle life, weight, or cold-weather charging limits here either. Those belong to one specific battery, and they live on its maker’s spec sheet.
When 12 volts runs out of room
The calculator also picks your system voltage from how many watts you run at once. Up to 3,000 continuous watts it stays at 12 volts. From there to 5,000 it moves to 24. Past that, 48. A residential fridge plus air conditioning is usually what pushes a coach over the line.
Vatrer 12V 460Ah lithium battery
5,888 Wh at 12 volts, for coaches that stay under the 3,000 W line.
Check the current price on Amazon.
Vatrer 24V 200Ah lithium battery
5,120 Wh at 24 volts, for when your peak load crosses 3,000 W.
Check the current price on Amazon.
Before you swap anything
Read the converter’s charging profile and the battery maker’s manual side by side. The 2019 Fleetwood Class A manual warns that the coach electronics are voltage sensitive. Lithium wants different charging voltages than lead-acid, and a swap that ignores that is how circuit boards get cooked.
