Lithium and AGM, without a fake scorecard
Every battery the original Megawatt calculator recommends is a Vatrer lithium pack. The watt-hour figures are printed in that widget: a 12-volt 100Ah pack is treated as 1,280 Wh, 300Ah as 3,840 Wh, and so on. That is 12.8 volts times amp-hours, which is a common nominal voltage for LiFePO4, not a lab test Megawatt ran.
AGM is a lead-acid battery. People plan a smaller usable slice of its nameplate amp-hours because deep discharge shortens that chemistry. This site’s battery-runtime calculator lets you set that usable fraction yourself. It does not ship a default and call it a measured fact. If you leave it blank, it does not invent one.
What this guide will not do is quote cycle life, weight, or cold-weather charge rates. Those belong on the manufacturer’s spec sheet for the exact model. The 12-volt 100Ah short link on the old calculator did not even resolve to a product page when this site was crawled on October 1, 2026, so that link is preserved as-is and not given an ASIN.
The calculator also picks system voltage from continuous watts: stay at 12 volts at or under 3,000 watts, move to 24 volts through 5,000 watts, and 48 volts above that. Those cutoffs are the published widget, not a code citation. A higher-voltage bank is a different charger, a different inverter, and usually a job for someone who does this work.
Match the pack to the calculator’s net storage number, then read the battery maker’s manual for charging voltages. The Fleetwood house-electrical chapter says the coach electronics are voltage sensitive. A lithium swap that ignores the converter’s charge profile is how coaches get cooked boards.