Just add a thought here....make sure the volt meter you are using puts a load on the system....most digital voltmeters for commerical use like Flukes will not put a load on the batteries...all it tells you is the voltage...not whether the batteries will last under a load....as said above an expanded scale voltmeter will load the batteries as will some digitals for RC use...mine has a selectable load .5, 1, or 2 amp load.....Plus they're cheaper than commerical voltmeters