AGM or lithium: choose for the system you’re building
Rayne Automotive generally recommends AGM for lighter builds needing less than 40Ah of usable battery capacity and no inverter. If you want to run an inverter or need more usable storage, lithium is usually the better route. The point is not to buy the biggest battery: it is to size the storage alongside the loads and the ways you can recharge it.
An AGM battery’s rated Ah is not the same as the energy you would normally plan to use. As a practical planning rule, limit regular discharge to around 50% of its rated capacity. Lithium typically offers more usable capacity for the same rated Ah, but its usable amount and charging limits depend on the battery model; usually 80–100% of rated capacity is usable. Use the System Builder for a recommendation based on your own equipment rather than relying on a one-size-fits-all capacity chart.