BU-701: How to Prime Batteries – Battery University
Discover what a battery needs to get going and attain a long life
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Not all rechargeable batteries deliver the rated capacity when new, and they require formatting.......
“What’s the difference between formatting and priming?” people ask. Both address capacities that are not optimized and can be improved with cycling. Formatting completes the fabrication process that occurs naturally during use when the battery is being cycled. A typical example is lead- and nickel-based batteries that improve with usage until fully formatted. Priming, on the other hand, is a conditioning cycle that is applied as a service to improve battery performance during usage or after prolonged storage.
Formatting a lead acid battery occurs by applying a charge, followed by a discharge and recharge. This is done at the factory and is completed in the field as part of regular use.......Lead acid typically reaches the full capacity potential after 50 to 100 cycles.
Deep-cycle batteries are at about 85 percent when new and will increase to 100 percent, or close to full capacity, when fully formatted. There are some outliers that are as low as 65 percent when tested with a battery analyzer.
The function of a starter battery lies in delivering high load currents to crank the engine, and this attribute is present from the beginning without the need to format and prime. To the surprise of many motorists, the capacity of a starter battery can fade to 30 percent and still crank the engine; however, a further drop may get the driver stranded one morning.