What makes one battery better than another?

Lead-acid is the oldest rechargeable battery in existence. Invented by the French physician Gaston Planté in 1859, lead-acid was the first rechargeable battery for commercial use. 150 years later, we still have no cost-effective alternatives for cars, wheelchairs, scooters, golf carts and UPS systems. The lead-acid battery has retained a market share in applications where newer battery chemistries would either be too expensive.
Lead-acid does not lend itself to fast charging. Typical charge time is 8 to 16 hours. A periodic fully saturated charge is essential to prevent sulfation and the battery must always be stored in a charged state. Leaving the battery in a discharged condition causes sulfation and a recharge may not be possible.

Lead-acid does not like deep cycling. A full discharge causes extra strain and each cycle robs the battery of some service life. This wear-down characteristic also applies to other battery chemistries in varying degrees. To prevent the battery from being stressed through repetitive deep discharge, a larger battery is recommended. Lead-acid is inexpensive but the operational costs can be higher than a nickel-based system if repetitive full cycles are required.

Depending on the depth of discharge and operating temperature, the sealed lead-acid provides 200 to 300 discharge/charge cycles as compared to 1000 cycles for a Flooded Lead Acid Battery. The primary reason for its relatively short cycle life is grid corrosion of the positive electrode, depletion of the active material and expansion of the positive plates. These changes are most prevalent at higher operating temperatures. Cycling does not prevent or reverse the trend.

The lead-acid battery has one of the lowest energy densities, making it unsuitable for portable devices. In addition, the performance at low temperatures is marginal. The self-discharge is about 40% per year, one of the best on rechargeable batteries. In comparison, nickel-cadmium self-discharges this amount in three months. The high lead content makes the lead-acid environmentally unfriendly.

Plate thickness

The service life of a lead-acid battery can, in part, be measured by the thickness of the positive plates. The thicker the plates, the longer the life will be. During charging and discharging, the lead on the plates gets gradually eaten away and the sediment falls to the bottom. The weight of a battery is a good indication of the lead content and the life expectancy. 

The plates of automotive starter batteries are about 0.040" (1mm) thick, while the typical golf cart battery will have plates that are between 0.07-0.11" (1.8- 2.8mm) thick. Forklift batteries may have plates that exceed 0.250" (6mm). Most industrial flooded deep-cycle batteries use lead-antimony plates. This improves the plate life but increases gassing and water loss.

Witch Well Energy carries Crown batteries which are manufactured in Ohio.  The extra thickness of the lead plates can actually increase the lifetime usefulness of nearly double that of a traditional name brand battery such as Trojan.  Trojan is a good battery and we have sold a lot of them.  The extra plate thickness of the Crown battery also means that the specified rating of the battery more closely resembles reality near the end of life, than other brands with thinner plates and consequently a cheaper battery.