All About Sealed Lead-Acid Batteries

— Sizes and/or capacities:

Most commonly used lead-acid battery sizes/capaities in electric bikes are 12V9Ah, 12V10Ah, 12V12Ah, 12V14Ah and 12V20Ah. Usually, the bigger the Ah number (capacity), the larger the size and the heavier the weight, except for 10Ah and 12Ah ones which share same dimensions.

For electric bikes, the most significant bottleneck is the battery, especially on hills where the power demand will be several times higher than on flat while battery voltage drops dramatically (battery gauge needle drops). Bigger batteries will definitely do better on continuous power supply and battery life span because of less chances of large-current discharge.

— Recharging:

Lead-acid batteries do not have memories so we do not have to drain the battery first before recharging. Or we probably should say "NEVER DRAIN THE BATTERY!!!" since low battery level will result in the crystallization of PbSO4 on lead plates and reducing the electric conductivity of lead plates.

Then when should we recharge the batteries? Usual recommendations are right after every use. It's better to wait a little bit longer (half an hour?) and let the battery cool down, then recharge the battery. The electrolytes perform better when it's under cool temperature (but certainly not cold temperature!). Same for using the bike, it's recommended to wait for some time to let the battery cool down, instead of right after recharging.

When should we stop recharging the batteries? The obvious answer is when the light on the charger turns to green. But there is exceptions! If one or more of the battery cells are damaged, we'll never see the green light on the charger. Instead, we will see a heated battery which means we should stop recharging right away.

— Battery dead or not?

If you see the green light on the charger shortly after you started recharging an empty battery, then the battery is dead. If it takes forever (more than 10 hours) to recharge a battery, it could be dead or one or more cells are damaged. Unfortunately, we have to change the whole set in either case.

— Battery good or not?

An easy way to test a battery set is by measuring the voltage of each individual cells. The voltage difference should be within 0.1-0.2%. Otherwise, never put them together in series.

 

Other useful battery topics:

— How to test a lead-acid battery?