Solar panels batteries are not designed for quick bursts of power. They are designed to provide a long-duration low current. This design enables multiple charges and discharge cycles with only minimal damage to the battery. Lead-acid deep cycle batteries are much more tolerant of discharge to 50% of their “full” capacity than are modern batteries. Fifty percent discharge lowers the lifespan of the battery to a few hundred discharge/recharge cycles.

So far I have not seen the inverse mistake, a lead-acid deep-cycle battery used as a starter battery, probably because deep-cycle batteries cost more than starter batteries. Getting specific, I also prefer lithium-iron-phosphate deep-cycle batteries. This article is not addressing that issue but you can get more information about that here.

THE FOUR BASIC LEAD-ACID BATTERY TYPES

Here are the general differences in the lead-acid battery variations. Understanding the difference will help you choose the correct deep cycle RV battery for your application.

FLOODED CELL

The oldest style of lead-acid batteries is flooded cell batteries. They may be lead-acid starter batteries or deep cycle lead-acid batteries. The key identifying feature is the caps on top of the cells where you can add distilled water. Today in 2021 most batteries with caps are deep cycle batteries.

SEALED FLOODED CELL

This is the modern lead-acid start battery. The caps on top of the cells are missing from these batteries. There are two styles of these batteries. One type has extra fluid built into the case. Under normal circumstances, the fluid will be depleted as soon as the warranty expires. The second type is a valve-regulated vent battery that may be installed in toys or mobility scooters. I have not seen a “full size” valve-regulated battery.

AGM BATTERIES

AGM Batteries are sealed lead-acid batteries. They have fiberglass between the cells. Almost always AGM batteries are deep cycle batteries. Some AGM batteries are starter batteries and they are expensive. The fiberglass mesh between the lead plates isolates each plate from the adjoining plate. I have owned six sealed lead-acid AGM batteries. The four I still have and are doing fine. Two I sold with my previous RV; last time I checked they also were fine. Since these batteries are more expensive to make than lead-acid start batteries they will always say AGM on the label.

GEL BATTERIES

Gel Batteries are advanced sealed lead-acid batteries. The electrolyte is a gel rather than a liquid. Many people will drop the word “gel” when selling a sealed battery that doesn’t have any gel in it. True gel batteries are as expensive as AGM batteries. Some gel batteries are very good deep cycle batteries and these require special treatment. Unless you know what you are doing don’t replace flooded lead-acid batteries with gel batteries.