Fh020aa

[Larry D]

I'm curious if the FH020AA R/R is as good as the SH775AA ? What is the difference between these two ? Is one, as good as the other, for our bikes ?

Thanks.

[tom203]

I'm curious if the FH020AA R/R is as good as the SH775AA ? What is the difference between these two ? Is one, as good as the other, for our bikes ?

Thanks.

You want the series SH-775....it's much easier on the stator

[Larry D]

Not doubting you , but,.....easier, in what way ? Obviously, my R/R is out on the 450S. I've been doing a bit of reading and it seems both of these R/Rs have been highly recommended by folks on the interwebs.
Just wondering what makes one better than the other.

[Rust_to_Redemption]

Not doubting you , but,.....easier, in what way ? Obviously, my R/R is out on the 450S. I've been doing a bit of reading and it seems both of these R/Rs have been highly recommended by folks on the interwebs.
Just wondering what makes one better than the other.

The FH020AA is a mosfet (shunt) type R/R that puts stress on the stator, the SH775 is a series R/R and does not. As I understand it, when there is no demand on the battery, the voltage is shunted directly to the ground on the shunt type R/R. In the Series style, the voltage regulator turns the charging system off. Therefore reducing stator current and thus heat build up.

EDIT: I am not 100% sure on the accuracy of the underlined, so someone more knowledgeable may come along and correct me, but to my understanding that is the difference

[Larry D]

Gotcha. I was thinking that they were both series type R/Rs.

[roeme]

Shindengen's documentation is a bit convoluted and hard to find, but yes, the SH775 regulates by disconnecting the generator, whereas the FH020AA shunts.

Not sure if the monikers 'series' and 'shunt' are the correct english technical terms.

[Steve]

Yes, those are the correct, or at least common, terms.

Larry, to put it in another light, a shunt-type regulator, whether stock or aftermarket, like the FH020 or the FH012, regulates by diverting the output. Some say it goes straight to ground, others will say it goes back through the stator, but either way, the stator is putting out as much as it can, all the time. What the bike 'sees' is a bit less because it is interrupted quite often, so the average output is proper.

A series-type regulator, like the SH775 or a Compufire, will also regulate by interrupting the output, but it does it by simply opening the circuit, not diverting the output. That reduces the average current through the stator to something less than full output all the time. That is what reduces the load on the stator, helping to keep it cooler.

Be careful shopping, though, there are a LOT of regulators that look like an SH775, but are not series-type regulators.

.

[Larry D]

I am happy to report that after installing a new Caltric stator and a SH 775 R/R, the '81 GS450S is charging at a solid 14.8 volts at 4000rpm and at about 14.1 at idle.