At 05:11 PM 1/8/2014, Josh Koffman wrote: >I have a couple of 12V 7Ah gel cell batteries. They've been sitting >for probably about 3 years. Any thoughts on if they'd still be good? I >need to power a 12V 4A load for about 20 minutes at a time. Decent-quality gel-cell batteries can live for many years *if* they=20 have been stored fully-charged. If they have been on a charger for=20 all of that time, they will be good / great *if* the battery voltage=20 has not exceeded the float value for more than a tiny percentage of time. However, if they are put away while discharged (terminal voltage less=20 than 12.0V for a nominal 12V battery)), they are most likely garbage. The homemade gel-cell chargers that I build always go into equalize=20 mode every time the charger is powered up, then drops to float mode=20 as soon as the battery voltage reaches the equalize voltage=20 value. The batteries last in excess of 5 years with reasonably-heavy use. I have dug out old batteries that appear to work as if they were=20 brand-new. But they were stored after being charged fully (to the=20 equalize voltage). Cheap gel-cell batteries appear to have significant self-discharge=20 rates and they go dead all by themselves with no load=20 attached. These are generally garbage after being stored for more=20 than a few months. Bottom line: just measure the Open-Circuit voltage of the=20 battery. If the O-C voltage exceeds the nominal battery voltage,=20 odds are the battery is good. dwayne --=20 Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax www.trinity-electronics.com Custom Electronics Design and Manufacturing --=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 .