I recently purchased a tao tao 125D atv. After 30 minutes of riding I heard a loud pop from under the seat. I took off seat to find the battery acid cover had popped off and all acid had boiled away. I checked voltage at battery and read 16.5 volts when rpms were at riding level. This seemed way high to me so i though the voltage regulator was bad so i bought a new one and replaced, but still reading 16.5 Volts when rpms are up. After idling for about 2 minutes you could hear the battery boiling. What else could cause this high voltage at battery?

 

Someone else on here had the same problem, don't think they resolved it. Some bikes just have a rectifier, so whatever voltage the alternator puts out is converted to DC and shoved into the battery. Most have a rectifier/regulator which converts to DC and controls max voltage down to 14.5v. The other poster tried several "regulators" from Tao-Tao and all were producing more than 14.5v so either they are just rectifiers or Tao-Tao has bought a batch of crap regulators.