It is generally not possible to properly test scooter batteries ability to hold a charge using equipment you might have at home. A regular voltmeter does not have the ability to test scooter batteries under the same load conditions that a scooter would place on the batteries. Scooter batteries that read 12 volts may not be good and scooter batteries that test much less may just need to be charged.
A car battery tester, while able to test a battery under load, can only test large car batteries, not the smaller 12, 20, 35 amp-hour batteries used in most scooters.
Bringing your batteries to an auto parts store of battery store where they have a battery tester is also not a satisfactory way of gauging the condition of your batteries. Car battery testers cannot properly test deep cycle scooter batteries.
Most scooter servicers use a specially designed SLA battery tester such as the ACT 612 tester. But they are costly to purchase.
Also, the battery indicator built into most scooters will only provide an approximation of the condition of the battery.
One way of estimating the condition of your batteries is via a ride test. Here are the steps:
1. Charge your scooter battery pack for a full 8 - 12 hours.
2. A rider of no more than 85% of the maximum scooter weight capacity would then ride the scooter on a level, smooth surface like an unbroken sidewalk at full speed for 15 minutes without stopping.
At the end of the 15 minute test, in MOST CASES, if the battery indicator is still "in the green" (green lights still lit, needle in the green, etc.) or in the right-hand area of the yellow range, the batteries are in good condition. If after, your 15 minute ride, the indicator is in the left-hand area of the yellow range, your batteries are in fair condition. If, after your 15 minute ride, the indicator is in the red, your batteries are mostly depleted and should be replaced soon.