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At a campsite at dusk, the phone is dead, the fridge in the van has stopped humming, and the battery that ran it all day is the part that matters. Types of 12v battery come down to chemistry and build: sealed lead acid, including AGM, and flooded lead acid, with lithium as a separate chemistry the listings here do not cover in figures. The listings in this guide state capacities, rates and uses for lead acid types, so the choice follows the figures rather than the label.
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The quick answer
A 12v battery for solar, RV or cabin use is usually a deep cycle battery, built to give steady power over hours rather than a short burst. Sealed lead acid batteries, including AGM, hold the acid in the case and need no water added, while flooded lead acid batteries hold liquid acid and vent gas as they charge. The Mighty Max listing in this guide states a 12V 35Ah sealed lead acid AGM battery, and the U.S. Battery listing states a set of 4 12V 155Ah flooded lead acid deep cycle batteries, so these listings show the size gap between a small sealed battery and a large flooded bank battery.
Types of 12v battery at a glance
| Type | Example listing | Stated capacity | Stated use |
|---|---|---|---|
| Sealed lead acid, AGM | Mighty Max ML35-12 | 35Ah | Trolling motor, solar generator, power chair |
| Flooded lead acid, deep cycle | U.S. Battery US12VXC2 | 155Ah at the 20-HR rate | Utility vehicles, floor scrubbers, ride-on sweepers |
Both listings state 12V, and both are deep cycle types built for steady discharge. Lithium types, including LiFePO4, use a different chemistry and need their own figures; this guide states no lithium figures, so compare lithium listings on their own stated capacities.
Sealed lead acid and AGM
The Mighty Max ML35-12 is a 12V 35Ah sealed lead acid battery, described in the listing as a deep cycle AGM solar battery. Sealed means the case holds the acid inside, and the listing calls the battery spill-proof, with a high discharge rate, wide operating temperatures, long service life and deep discharge recovery. The listing states dimensions of 7.5 by 7.75 by 5.0 inches in the spec table, while the bullets list a different size, so check the listing before ordering, since the figures do not match. The listing states the battery replaces 33Ah, 34Ah and 36Ah batteries, and lists uses from trolling motors and solar generators to power chairs and mowers.
A sealed battery suits a cabin or van where the battery sits inside a living space or a locker, since the case keeps the acid in and the battery needs no water added. The listing states the battery comes with screws only, and no wire harness or mounting accessories, so the cables and mounts come from elsewhere. Check the stated capacity against the loads, and check the stated dimensions against the battery box or locker before ordering.
Flooded lead acid deep cycle
The U.S. Battery US12VXC2 (on Amazon) is a set of 4 12V 155Ah flooded lead acid deep cycle batteries, BCI group GC12. Flooded means the cells hold liquid acid, and the listing states a 12-month manufacturer warranty. The listing states a 5-HR rate of 122Ah and a 20-HR rate of 155Ah, with capacity minutes of 292 at 25 amps and 77 at 75 amps. The listing states a weight of 86.0 pounds, and applications in utility vehicles, floor scrubbers, ride-on sweepers, floor buffers and carpet extractors.
A flooded battery suits a bank that stays in a vented space, since the cells vent gas as they charge and the acid level needs checking. The set of 4 suits a larger bank, while the Mighty Max 35Ah battery suits a smaller setup, so match the stated capacity and the stated rate to the loads. Check the stated warranty term, the stated weight and the stated dimensions on the listing before ordering, since a set of 4 weighs and measures more than a battery bought alone.
How to read the capacity figures
Capacity in amp-hours changes with the discharge rate, so read the rate with the figure. The U.S. Battery listing states 122Ah at the 5-HR rate and 155Ah at the 20-HR rate, which means the stated capacity is higher when the battery discharges slowly. The listing also states capacity minutes: 292 minutes at 25 amps and 77 minutes at 75 amps. A higher amp draw gives fewer minutes, so match the stated minutes to the amp draw of the loads.
Do not mix figures from different rates. The Mighty Max listing states 35Ah with no stated rate, while the U.S. Battery listing states 155Ah at the 20-HR rate, so the capacities come from different listings with different stated rates. Compare batteries on the same stated rate, and treat a listing with no stated rate as a gap. The listings here state no cycle life figure, so this guide gives none.
How to match a battery to the job
Match the battery to the loads and the space. A trolling motor, a solar generator, a power chair or a mower needs a battery that fits the compartment and meets the stated capacity, and the Mighty Max listing states 35Ah in a 7.5 by 7.75 by 5.0 inch case for those uses. A utility vehicle or a floor scrubber needs a larger bank, and the U.S. Battery listing states a set of 4 155Ah batteries for those uses. Check the stated dimensions, the stated capacity and the stated rate on the listing before ordering.
For solar use, compare AGM and flooded lead acid on the figures the listings state. See our AGM vs lead acid battery for solar guide and our AGM vs sealed lead acid battery guide for the chemistry split. For deep cycle uses, see our deep cycle and RV batteries guides.
What this guide does not cover
This guide gives no prices, because prices change by seller and by season, and the listings used here state no prices. This guide gives no wiring steps and covers no home wiring systems; a licensed electrician should install any battery that connects to home wiring. This guide also gives no lithium figures, since the listings here are lead acid, and no cycle life figures, since the listings state none.
FAQ: power away from the grid
What is the difference between AGM and flooded lead acid?
AGM is a sealed lead acid type. The Mighty Max listing states a 12V 35Ah sealed lead acid AGM battery, while the U.S. Battery listing states a 12V 155Ah flooded lead acid battery. Sealed batteries hold the acid in the case, while flooded batteries hold liquid acid and vent gas as they charge.
What does 35Ah mean on a 12V battery?
Ah is the stated capacity. The Mighty Max listing states 35Ah at 12V, and the U.S. Battery listing states 155Ah at 12V at the 20-HR rate. A higher Ah figure at the same stated rate means more stored charge.
How long will a 155Ah battery run a load?
It depends on the amp draw. The U.S. Battery listing states 292 minutes at 25 amps and 77 minutes at 75 amps. Match the stated minutes to the amp draw of the loads.
Do 12V deep cycle batteries come with a warranty?
It depends on the listing. The U.S. Battery listing states a 12-month manufacturer warranty. The Mighty Max listing states that a manufacturer’s warranty can be requested from customer service, with no stated term.
Related solar guides
See the AGM vs lead acid battery for solar, the AGM vs sealed lead acid battery, the deep cycle and RV batteries guides and the LiFePO4 batteries guides.
