ATV charging system Chinese 110 CC Loncin engine

I have an Eagle ATV for my kids with a 110CC Loncin engine. Its about 3 years old now. I have replaced the battery 3 times. I always use a trickle charger when not in use. After the last battery failed I was told my regulator must be bad, that it is overcharging the battery, and I should check it. The voltage seemed high, like 18+ volts at the battery when revving. I bought a new regulator from the many suppliers on eBay, looks identical and pluged right in. Now when idling the ATV is around 12V, and the voltage steadily increases to about 18 volts when revving.

Is this normal or is something not right with this 18 volts at high RPM and will that fry any new battery?

Thanks  

you could try an inline capacitor from radio shack rated @12v.this will only let 12v.come into the battery ,cheap fix  
08/ Raptor 700 SE.
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18 volts is way high. The charging system should read 14.5 volts at speed.  Whether 18 volts will fry a battery depends on how much time is spent at high RPM versus low RPM.  Overcharging a battery will result in a very hot battery, and loss of fluid in the six individual cells.  Have you noticed any of that?

So if you turn the headlights on and then run up the engine speed, what voltage do you measure then?

Pop out the main fuse and insert your meter across the fuse terminals.  Set the meter to read current on the 10 amp scale (you will have to move the red lead to the 10 amp current jack as well as setting the dial to DC 10 amps).  Now you will measure the actual charge/discharge current into or out of the battery.  The measured current polarity changes when changing between charging to discharging.  How much current do you measure going into the battery with the headlights off and the engine rev'ing?  How much current do you measure with the engine rev'ing and the headlights on?

Make sure the battery inside your meter isn't low.  Most meters will read a too high voltage when the battery is near dead, but otherwise seem to work fine other than the low battery indicator flashing.  This has got me more than once.  Pay attention to that low battery indicator on the meter.