1. Look at the old and new battery:

In fact, this is a very good judgment. Generally, you can judge whether there are scratches or scratches by looking at the appearance, and then see whether there is rust on the positive and negative metal parts of the battery.

2. Use professional voltage measurement tools to determine whether the battery has an internal short circuit (bad battery):

After riding for a while or after charging the car and letting it stand for several hours, measure the voltage at the charging plug. If it is 48 volts or higher, it is a normal battery (regardless of old and new). If it can only reach 46 volts or below, it means that there is a short circuit in one battery (the 48 volt car has four groups of batteries, each of which consists of 6 2 volt batteries connected in series to become 12 volts), and the 10 volt group is a bad battery.

3. Judge the useless battery:

1) After the battery is fully charged, if you suddenly accelerate the ride and the battery meter needle drops less than half a mark (a small mark), it is a new battery.

2) Just after being fully charged, if you suddenly accelerate the ride and the battery gauge needle drops one mark, it is a half-new old battery.

3) After the battery is fully charged, if you suddenly accelerate the ride and the battery gauge needle drops 2-3 bars, it is an old battery that is about to be scrapped.

4) Just after being fully charged, if you suddenly accelerate and ride more than four bars, the battery is scrapped. (If you don't ride a full charge for a week, the battery will self-discharge and run out).