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ST2 frying regulators - high batt. voltage - new RR50 fitted - HELP !

Dear All,

I’ve a 1998 ST2 which has a habit of destroying regulators , four so far with the Electrex RR50 lasting the longest at 3 year.

New Electrex RR50 and battery fitted :- with the engine running at 3,000 revs. and lights on or off it runs hot, I’d estimate over 60 deg. C.

Voltage across the battery at low revs. around 14, lights on or off, but at 3k. ramps up to 16 with near 20 with lights off, no ST2 components at excessive temperature.

The battery voltage of my 900 Supersport is between 13 and 15 under the same cycle as above with the regulator temperature substantially lower than the RR50, same battery being swapped between the two.

With the engine running and regulator - alternator disconnected the alternator output measures between 30 to 80V. A.C., same for ST2 and 99SS.

All voltages measured with two Avo 8V meters which I’ve had from new, identical readings in both.

If I continue as is the new RR50 will have a very limited working life.

Perhaps the answer would be to replace the 420W. alternator with the 350 unit of the 900SS however that seems like treating the symptom rather than the cause.

Any help would be very much appreciated, thanks Lads.