Lead-acid batteries are one of the oldest and most widely used types of rechargeable batteries. They are commonly used in vehicles, backup power supplies, and other applications requiring high values of load current. These batteries are made up of lead plates and an electrolyte solution of sulfuric acid and water.
The lead–acid battery is a type of rechargeable battery first invented in 1859 by French physicist Gaston Planté. It is the first type of rechargeable battery ever created. Compared to modern rechargeable batteries, lead–acid batteries have relatively low energy density. Despite this, they are able to supply high surge currents.
Personally, I always make sure that anything connected to a lead acid battery is properly fused. The common rule of thumb is that a lead acid battery should not be discharged below 50% of capacity, or ideally not beyond 70% of capacity. This is because lead acid batteries age / wear out faster if you deep discharge them.
One concern is overcharging AGM batteries, which already have very little water reserve, and so there is risk of dry-out. However, most chargers sold today are “smart” chargers and will shut off after the battery is fully charged. Myth: Any charger should work perfectly okay with any type of lead acid battery.
Myth: The worst thing you can do is overcharge a lead acid battery. Fact: The worst thing you can do is under-charge a lead acid battery. Regularly under-charging a battery will result in sulfation with permanent loss of capacity and plate corrosion rates upwards of 25x normal.
This means that if you (accidentally) short-circuit a lead acid battery, the battery can explode or it can cause a fire. Whatever object caused the short-circuit, will probably be destroyed. Because lead acid batteries can supply such high currents, it's important to assure that you use the right wire thickness / diameter.