Checking and Charging Motorcycle Batteries

How are Motorcycle Batteries Rated?

The amp/hour (AH) capacity is the basis for rating motorcycle batteries. For example, a 12AH battery can produce one amp of current flow for 12 hours, or two amps for six hours. In order to calculate the amount of time needed to use up a fully charged motorcycle battery by turning the lights on, we have to take power in watts, and divide it by voltage, which gives us the current draw in Amps. Therefore, a 72 watts beam and tail together, divided by 12 volts equals a 6-amp draw. So in 2 hours, the 12AH battery is dead.

Checking Motorcycle Battery:

If you decide to check if your new motorcycle battery is done correctly, follow this actual factory-recommended service procedure.

If the battery is not a maintenance-free type which doesn’t have a vent tube, unwrap the battery, unkink the vent tube and snip about a half-inch off the end. Fill it with electrolyte midway (between the high and low level markings on the case) and leave it undisturbed for one or two hours. Remember, the battery will still be at only 65% of full charge at this point. Add electrolyte again if required.

If your battery is a refillable lead-antimony type, it should be charged at one-third of its rated capacity in amp/hours for four to five hours to get it to full charge. Maintenance-free type battery should be charged with a constant-current charger that can drive the charge with as much as 16.9 volts. This should be closely supervised so as not to exceed full charge.

Next, recheck the electrolyte level and add water if required. Let the battery cool so the case contracts enough to fit into its typically tight little holder. Run the new breather tube, if the battery comes along with one, carefully through the original factory routing.

Things to Remember when Charging the Battery:

1. First of all, it is important to remember that Red is positive and Black is negative in order to avoid any accidents such as short-circuits and nasty shocks.

2. The charger should be compatible with the motorcycle battery, and give a greater output than the battery voltage but not too high.

3. Make sure the connections are clean and the electrolyte is at the upper level, and don’t fill the cells up to the very top of the battery.

4. You can either use an optimizer on the battery which can effectively switch off the battery when it’s charged and prevents overheating, or disconnect it manually.

5. It is recommended to put your battery on charge every two or three weeks.

6. An upper and lower level battery should have all the cells on the upper level, not over and never under the lower level.


8. The minimum charge for a new batter should be at least for 8 hours.

9. If you have a dry battery, fill the cells slowly and leave the battery for around half an hour.

Source by George Royal

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