odyssey batteries for R100RS?

[ricochetrider]

howdy guys,
just got a new battery, an odyssey PC680 for my K100, and over on the flying brick forum page everyone was talking about the odyssey PC925L being the hotter battery for running extra lights, heated accessories, etc., with plenty of juice for all and some to spare. there was some chatter concerning whether or not it would fit into the battery tray however.

my recently acquired 93 R100RS has heated grips and PIAA running lights. the battery that is in it now seems to draw down when i run the lights and if i run the grips and lights at the same time, i only get about 10 volts on the volt-meter. since i just got the bike i have no idea what is in it or how old this battery is. one night i did have a problem with the bike not starting after a stop, and had to jump-start it, after pushing the bike up a small hill.

i'm thinking of a new battery, certainly will get a new one sometime this summer. will the odyssey PC925L fit? if not, which battery should i get, for the most juice to handle all the accessories?

 

[manicmechanic]

On any car/truck/bike, the battery is nothing more than a storage device. When the machine is running, the charging system (alternator/generator) provides the power to operate the machine, and any leftover capacity can go into recharging the battery. So in your case I would check to see that your charging system is up to the task, because if it's not, it doesn't matter what size battery you install. The same thing will eventually happen.

 

[robsryder]

If you want to make more electrical current for heated grips, lights, etc. then the bike's charging (electrical generation) system may need to be enhanced. Having a healthy battery will help with starting the bike and with the bike's operation when the charging system isn't making enough "juice" (i.e., at lower rpms).

There are several aftermarket (non-BMW) systems available to enhance the airhead charging system. It is worthwhile to ensure that the existing charging system is functioning properly. This can be done by making certain that the various connectors are tight and free of corrosion. Use of a grease or dielectric compound can help preclude corrosion (vaseline can also be used). Another thing to check are the carbon brushes over the rotor and the grounding and functionality of the diode board.

An excellent reference for the airhead charging system is available from Motorrad Elektrik. This book is called "Classic Boxer Charging, version 2". Here is the link -
http://www.motoelekt.com/goodstuff.htm

If one wishes to increase the output of the charging system, one of the available systems can be obtained from Motorrad Elektrik -
http://www.motoelekt.com/charging.htm

The Enduralast charging system from Euro Moto Electrics is another enhanced airhead charging system. -
http://www.euromotoelectrics.com/SearchResults.asp?Cat=58

On the AirList folks that have installed these systems have reported good results. Both systems appear to be reliable and well supported by the vendors.

Following are links to other discussions on airhead charging -
http://www.airheads.org/content/view/177/49/
http://www.advrider.com/forums/showthread.php?t=111189
http://forums.bmwmoa.org/showthread.php?t=10558

 

[ricochetrider]

thanks for the info guys.
since i have had the bike (a couple months) i have had to keep it on the street so can't keep a tender on the battery. i know the bike sat for a while over the winter, but don't know for how long, so it's a pretty safe bet the battery has lost some of its heart.

i have been riding it a lot lately, putting a couple thousand miles on. the voltmeter often reads out at about 13 volts but sometimes dips to as low as 10 or 11, and i did have the issue late one night on the long commute home from work...

so....will the PC925L fit the bike?

i will check the charging system and make certain it is up to snuff. i know the original system only charges at above 3,000 RPMs so i have been mindful of that...some of the aftermarket stuff may be in my future...
thank you,
tom

 

[beemerman77]

pc680 verses pc925L install

owner of 1978 r100 rt, ran pc680's for the longest time.last time around purchased a pc925l. yes it will fit in the battery tray. pc925l is a bit taller. when using the oem battery hold down with the tool tray in place it was difficult to close / latch the seat close.without the hold down seat closed perfect. i fabricated a different hold down that goes across the back of the battery along the top edge. using the oem threaded hold down posts. works good , the battery posts on the 925l will be vertical instead of horizontal this posed little problem to get the cables connected, ended up milling some brass stock to convert vertical to horizontal . yes pc925l will fit but it is not really a drop install.

 

[ricochetrider]

thanks beemerman

what was your reason for switching to the PC925L, if you don't mind my asking?

 

[keelerb]

PC925L was a drop-in replacement on my 84 R100RT. It's a bit tall, so tall box sits higher on top of it, but it fits.