Sealed lead-acid (SLA) battery charger:

Yuasa, Kobe, Sonnenschein and Varta are but a few of countless manufacturers of sealed lead-acid (SLA) batteries. Although these batteries have been around for many years, their use in amateur and hobbyists circles has seen an upsurge recently because of price cuts in the surplus trade, at car boot sales and flea markets. The compact, easy to handle 6-volt and 12-volt types with capacity ratings up to 30 Ah can be picked up cheaply and appear to be the most popular. SLA batteries require a simple but fairly unusual charge algorithm for which a low-cost circuit is described in this article.