On 12 November 2014 06:15, Dwayne Reid wrote: > I'm just starting a project which is powered by a 12V 18AH AGM Lead > Acid battery. The customer greatly desires a display that shows the > amount of charge remaining in the battery. > What Byron and Battery University and similar say. Most certain method is intelligent gas gauging, where you consider enough parameters to work as well as you need it to. eg if load was constant current or power you MIGHT be able to use time used since last charged + a self discharge factor, or at the other extreme may need a battery model based on measured rate, temperature, prior charging aspects, battery age, cycle history, time since charged, ... . Loaded terminal voltage gives you 'some' indication at relatively constant load and not too excessive temperature variations. R. --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .