R80GS electrickery...

[Steve R]

Despite owning a whole series of Airhead G/S and GSs, most of which couldn't effectively keep the battery charged under a wide variety of conditions, I still know very little about electrickery. I bought a meter and managed to switch it to the right setting to see my new, newly charged and fitted battery in my '96 Kalahari giving out 12.46v with the bike switched off. The bike started (!) and straight off tickover the voltage across the battery jumps to 13.5ish and remains steady. At tickover it drops to 12.8 or 9 and there's a slight glowing of the charging light on the dash but touching the throttle restores 13.5v immediately and the light goes out. So far, so good.

The previous battery died sudddenly, 54 weeks after I bought it. Thing is, I don't know whether I killed it or not. I run with my headlight on, ZumoXT sat nav, phone charger and often heated grips on low. Occasionally, on motorways, the heated grips warning light flashes denoting low voltage. Altogether now... "Not surprised". Thing is, that never happens if I'm pootling around the Peak District at low revs.

The bike is fitted with an electronic Speedwell/Siebenrock aftermarket speedo which has a voltmeter read out. I noticed as I was riding along that the voltage dropped from 13.5 to 12.9 when I switched the headlight on. Replaced the bulb with an LED. Drop is now only to 13.2 or 3. Putting the sat nav on drops it by 0.1 and putting the grips on low drops it also by 0.1, leaving me with a charging voltage of 13ish.

Questions could be:

Why does it seem to charge less effectively at motorway speeds than at pootling around speeds? The bike's done about 80,000 miles and not had much done to it. Rotor/stator might be knackered.

Is 13v enough to keep the battery charged? Too open a question to answer definitively I know.

Anyway, has anybody else been here / done this? Does anyone know what their bike puts out and what they safely run off it? Has anybody had experience with the high output rotors that are available? I know about the high output voltage regulators.

Any thoughts would be very welcome.

Cheers.

 

[mikeyboy]

From my experience,
I rarely see over 14v from standard systems
If I recall the standard output is quoted at 220w which in theory should be sufficient to run headlamp etc and maybe heated grips.
Perhaps the brushes are poor resulting in lower output at high revs,
Or perhaps a poor connection resulting in a voltage drop somewhere.
I guess the 1st step is to check the output voltage directly at the diode board.

 

[Gelandestrasse]

Steve, if your BATTERY voltage level with the engine off is 12.46V and when the engine is running the SYSTEM voltage is 13V, you are charging your battery. As the SYSTEM voltage drops, your VR should up the field (rotor) voltage so that the stator gives more juice to the diode board and hence back to the SYSTEM, which the VR monitors. If you want a higher SYSTEM voltage then the VR is a good place to start. But it seems ok at the moment? If you have poor wiring/connections/corrosion/crap on your commutator, worn brushes, tired brush springs (like Mikey says) then that isn't going to help.

It will be interesting to find out what change had the most effect!

 

[MickDB1]

I had a similar problem with an old PD I had.
It turn out to be a diode on the board which must have had 1 didode bad soldered and it kept moving away from contact when warmed up on a decent run.
Also with the standard generator and regulator my even older g/s didnt like trailriding or put putin about at slow speed with the lights on.
With the first problem I did get a slight glimmer on the "red charging light"
1 of these (well similar) was helpful and not just on the bikes
https://www.ebay.co.uk/itm/12V-24V-...686251?hash=item595dbbecab:g:x44AAOSwqqdfu47R
PS I was told they are not really puttin owt back into the battery till at 13v

HTHY