Beemer Airheads, as Fiona and Brigitta are known affectionately by the riding cognoscenti (don't listen to the K-Bike Riders, they're just jealous); are also known to have anemic charging systems.
280 Watts of electricity is what they put out I believe and it's barely enough to power all the needs of the motorcycle and perhaps one extra electrical accessory.
The voltmeter I used on Fiona had always reported a maximum of 13.2 Volts when at charging RPMs (higher than 2000 rpm). 13.5 volts, I've come to learn, is basically "float charging" voltage used by battery chargers to keep a battery "topped up".
This 13.2 voltage, wasn't really enough to keep the battery charged up during slower riding and with frequent stops; especially in cold weather which is hard on batteries.
RichardM, Alaska Rider and Wrencher, upon hearing of me complain of this, offered me the voltage regulator he'd upgraded his Beemer to before completely upgrading his charging system with something even better.
The more modern, solid-state, voltage regulator from RichardM.
Note the small screw in the blue square. You can adjust the output
from 13.6 to 14.5 I believe.
Its a Transpo IB301A and its available for $19 +$5 shipping from Amazon here: LINK
For the BMW purists out there, the BMW part which I replaced (mine had a 12/83 date stamp on it), BMW wants $128 for one. Just saying...
The regulator got here today and within minutes was easily installed in place of the stock BMW Voltage Regulator which was larger and less reliable and only apparently putting out 13.2 volts for charging!
Usually, the voltage regulator on an Airhead is mounted under the gas tank. However, the previous owner of Fiona had displaced the regulator and a relay onto a bracket mounted on the bolt that secures the upper front support bracket of the sidecar frame. This made it very easy to remove the old and install the new regulator.
View of the old regulator in situ, it was wrapped in silver tape,
hinting it had been taken apart before? Note its bulk.
The smaller rectangular box on top is just a relay
far as I can tell.
New to me voltage regulator installed, much smaller eh?
I fired up Fiona's engine and revved it up to charging RPMs. I was getting between 14.2 to 14.3 volts!
Success! About a whole volt more involved in the charging process, hopefully this along with cutting out the main headlight and sidecar running light; will help keep the battery charged up when doing frequent stopping for pictures in cold weather.
Views of the cheap plastic cover used to keep water away
from the relay and the voltage regulator.
My thanks to RichardM for his generous donation of the voltage regulator! Until I can really justify the expenditure of around $500 for an upgraded charging system with more output wattage, this will have to do.
One test ride later, I realized I had been getting the 14.3V in the garage because I'd disabled the headlight and sidecar running light. Doh. Still, at cruising RPMs I was getting 13.7-13.8V! A gain of over half a volt and with peaks to 14V at one point in the ride.
I was even able to turn on the auxiliary headlights that came with Fiona and the voltmeter still registered 13.4V....at below 20 mph....good stuff.
Later on, I decided to turn the adjusting screw clockwise to increase the output. I was only able to turn it perhaps 1/8 of a turn and then it stopped so I think I've reached the upper limit. I started Fiona's engine and revved it up to about 2500 rpm and saw 14.5V after a few seconds.
RichardM recommends I monitor the battery's temperature, making sure it's not hotter than ambient temperature after a long ride.
One test ride later, I realized I had been getting the 14.3V in the garage because I'd disabled the headlight and sidecar running light. Doh. Still, at cruising RPMs I was getting 13.7-13.8V! A gain of over half a volt and with peaks to 14V at one point in the ride.
I was even able to turn on the auxiliary headlights that came with Fiona and the voltmeter still registered 13.4V....at below 20 mph....good stuff.
Later on, I decided to turn the adjusting screw clockwise to increase the output. I was only able to turn it perhaps 1/8 of a turn and then it stopped so I think I've reached the upper limit. I started Fiona's engine and revved it up to about 2500 rpm and saw 14.5V after a few seconds.
RichardM recommends I monitor the battery's temperature, making sure it's not hotter than ambient temperature after a long ride.
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