Alternator output and goodies

gamecock · Post by **gamecock** » Thu Dec 01, 2005 6:08 pm

I am the proud owner of a '92 907ie and have just joined the DB. Glad to be aboard. Having owned several BMWs I am spoiled by their big alternators. Since I want to commute with this bike, I want to install my motolights (2X35 watts), my XM roady, autocom, and on cold days use my Gerbings jacket (77 watts) and Symtec Dual star heated grips (36 watts). Can I do it, or am I asking for a dead battery or worse?

Thanks!

Andy

pencilbeam · Post by **pencilbeam** » Thu Dec 01, 2005 6:53 pm

Your alternator is supposed to put out 350 watts, and it powers an electric fuel pump, ignition, lights, and that funny little clock, so you may find it a little underpowered for all those goodies. My advice would be to only turn them on when your bike is running and you're about to go. Then keep it on a trickle charger at night. Also, a battery upgrade would be a good idea. Don't know if they make a gel battery for a 907, but that would be a plus.

gamecock · Post by **gamecock** » Thu Dec 01, 2005 8:33 pm

I do keep it on a Battery Tender in my garage. I will check on the gel batteries. Does anyone know how many watts of the 350 that the bike uses? In other words, how much do I have left to play with? Thanks.

DesmoDog · Post by **DesmoDog** » Thu Dec 01, 2005 9:25 pm

pencilbeam wrote:Also, a battery upgrade would be a good idea. Don't know if they make a gel battery for a 907, but that would be a plus.

Keep in mind the 907 uses the same battery as some of the Harley Big Twins, so there are quite a few choices out there for them. I bought a maintanence free (AGM?) battery from my local Harley dealer last time I needed one.

Rogero · Post by **Rogero** » Thu Dec 01, 2005 10:44 pm

Maintenance free? If you've got a Datatool alarm fitted there is no such thing as a maintenance free battery, these things drink more juice than an African Elephant.

Big Harley Batteries do fit though.

Finnpaso · Post by **Finnpaso** » Sun Dec 04, 2005 3:31 pm

"gamecock", DONT do that!!! That 350 alternator is JUST enough for all that injection stuff, what is most important to have enough voltage to work well..... I put to my 907 double headlight with another 55W bulb, and just after that i need to ask one Honda driver to push me to jump start after 100 kms drive with all lights on!!! I had new battery, so NOT enough from 350W alternator to anything else, than heated grips and mobile charger !!!!! I know... I am electrician

Anyway good idea to put 12V socket with fuse to charge battery and power outlet to mobile charge, GPS, etc.. low current devices.

Antti
Paso 750
Paso 907IE
ST4S

Post by **jcslocum** » Mon Dec 05, 2005 9:39 pm

The charging system was designed for an output of 350 watts max and the running loads are approximately:

Load...........................................Watts

Low/high beam...........................55
High Beam (off)...........................0
Sidelight......................................5
Tail light / brake light..................10 (21 when braking)
Turn Signal (off)...........................0 (10 when used)
Number plate light.......................5
Instrument cluster.......................2
Fuel Pump (clean Filter)...............60
Horn (off).....................................0 (60 when used)
Cooling Fan (off)..........................0 (60 when used)
Electronic Ign..............................48
Computer....................................24

Total...........................................209 (under normal cond there is some variability)

Max possible..............................350

As you can see you have only about 140 extra watts left over during nornal running and if you have and if you have any of the extras kick in you can easily overload the alternator/electrical system. The fule pump can draw significantly more if the filter is dirty.

I have a 750 Paso and regularly ride in the cold weather with an electric vest that works just fine. Obviously the cooler weather and the fact that I don't have a fan, fuel injection or fuel pump (Dellorto carbs) makes a huge difference!

To run any extras I would inspect all of the charging system connection and get them very very clean. Particularly the connector from the alternator to the regulator.

Finnpaso · Post by **Finnpaso** » Tue Dec 06, 2005 11:15 am

In 750 Paso there is plenty of "reserve" in charging system, but NOT in 907IE :toofar: That all injection stuff takes sooo much current.

Antti
Paso 750
Paso 907IE
ST4S

90_907ie · Post by **90_907ie** » Thu Dec 08, 2005 4:04 pm

I can attest to 350w being barely enough, my 907ie when running normal, the lights dim when I put my brakes on and everything blinks when I am turning. I probably need to check some wiring connections, but the point is there is almost no margin.