To properly test a battery it should be done with either a load on it or by using battery-testing equipment. as seen here - viewtopic.php?f=2&t=71
Batteries used in scooters or go carts or what ever your project is should not be run down past 10.5 volts or 87.5% of nominal voltage.
Example; 12 Volt Battery X 87.5% = 10.5 volts therefore a 12V battery will stop discharging at 10.5 volts. This also applies to strings in series.
Examples; 2-12V batteries in series will produce 24 Volts. 24 X 87.5% =21V This string should be disconnected from the circuit at 21V.
4-12V batteries in series will produce 48 Volts. 48 X 87.5% =42V This string should be disconnected from the circuit at 42V.
Never replace a partial string of batteries! This is not an old wives tale, it's true! When you put new batteries in a string with old batteries they will take on the characteristics of the older batteries and will require replacement much sooner and cost more in the long run. The charger will see the string as a single battery and older batteries may cause over or under charging of the new batteries causing premature failure. It will also cause the equipment to be less reliable.
this was taken from a battery suppliers website, it explains why we have seen an increase in battery prices. since i have started this addiction, battery prices have doubled.
Lead prices are rising! In the past year costs of lead have risen over 120%. So far we have seen up to 4 price increases for some manufacturers this year alone. All of the manufacturers we carry have or are increasing their prices again this month or in months to come! We are doing our best to keep prices down but have been forced to raise prices accordingly. We apologize for any inconvenience this may cause and hope you will continue to let us supply you with your battery needs.
Speed, Distance, Torque... Pick any 2