The electrolyte in a lead acid battery may freeze under very low temperature(eg, -40℃). Especially under partial state of charge. For example, at a flooded battery at 40% state of charge, electrolyte will freeze if the temperature reaches approximately 16.0°F. The freezing temperature of the electrolyte in a fully charged battery is -92.0°F.

The state of charge of a lead acid battery is most accurately determined by measuring the specific gravity of the electrolyte for a flooded battery. This is done with a hydrometer. Battery voltage also indicates the level of charge when measured in an open circuit condition after fully charged. This should be done with a voltmeter. For an accurate voltage reading, the battery should also be allowed to rest for a period sufficient to let the voltage stabilize.

Lead acid batteries do not develop of memory like a Ni-Cd battery.

All chemical batteries has self-discharge reactions. The rate of self-discharge depends both on the type of battery and the storage temperature the batteries are exposed to. However, for a good estimate, wet flooded deep cycle batteries self-discharge approximately 4% per week at 80°F. And around 2-3% for a VRLA battery.

When charging lead acid batteries, the temperature should not exceed 120°F. At this point the battery should be taken off charge and allowed to cool before resuming the charge process.

Lead acid batteries are 100% recyclable. Lead is the most recycled metal in the world today. The plastic containers and covers of old batteries are neutralized, reground and used in the manufacture of new battery cases. The electrolyte can be processed for recycled waste water uses. In some cases, the electrolyte is cleaned and reprocessed and sold as battery grade electrolyte. In other instances, the sulfate content is removed as Ammonia Sulfate and used in fertilizers. The separators are often used as a fuel source for the recycling process.

Batteries in portable consumer devices (laptops and notebooks, camcorders, cellular phones, etc.) are principally made using either Nickel Cadmium (NiCad), Nickel Metal Hydride (NiMH) or Lithium Ion (Li-Ion) technologies. Each type of rechargeable battery technology has its own unique characteristics.

The main difference between the two is the fact that NiMH batteries (the newer of the two technologies) offer higher energy densities than NiCad’s. In other words, pound for pound, NiMH delivers approximately twice the capacity of its NiCad counterpart. What this translates into is increased run-time from the battery with no additional bulk to weigh down your portable device. NiMH also offers another major advantage: NiCad batteries tend to suffer from what is called the 'memory effect'. NiMH batteries are less prone to develop this dreaded affliction and thus require less maintenance and care. NiMH batteries are also more environmentally friendly than their NiCad counterparts since they do not contain heavy metals (which present serious landfill problems).

Li-Ion has quickly become the emerging standard for portable power in consumer devices. Li-Ion batteries produce the same energy as NiMH batteries but weigh approximately 35% less. This is crucial in applications such as camcorders or notebook computers where the battery makes up a significant portion of the device's weight. Another reason Li-Ion batteries have become so popular is that they do not suffer from the memory effect AT ALL. They are also environmentally friendly because they don't contain toxic materials such as Cadmium or Mercury.

Ni-Cd batteries, and to a lesser extent NiMH batteries, suffer from what's called the 'memory effect'. What this means is that if a battery is repeatedly only partially discharged before recharging, the battery 'forgets' that it has the capacity to further discharge all the way down. To illustrate: If you, on a regular basis, fully charge your battery and then use only 50% of its capacity before the next recharge, eventually the battery will become unaware of its extra 50% capacity which has remained unused. The battery will remain functional, but only at 50% of its original capacity. The way to avoid the dreaded 'memory effect' is to fully cycle (fully charge and then fully discharge) the battery at least once every two to three weeks. Batteries can be discharged by unplugging the device's AC adapter and letting the device run on the battery until it ceases to function. This will insure your battery remains healthy.