• Welcome, Guest! We hope you enjoy the excellent technical knowledge, event information and discussions that the BMW MOA forum provides. Some forum content will be hidden from you if you remain logged out. If you want to view all content, please click the 'Log in' button above and enter your BMW MOA username and password.

    If you are not an MOA member, why not take the time to join the club, so you can enjoy posting on the forum, the BMW Owners News magazine, and all of the discounts and benefits the BMW MOA offers?

It WAS the battery, but then again, was it just?

Ted Perch

New member
My first post in November was about my 1995 R100RT Classic and its 4yr old battery that suddenly crapped out, an event, the timing of which, made me take a serious look at the entire charging system and its limitations. The battery WAS old and I shouldn't have been surprised when it died, but now I am left wondering should I update the 280 Watt system to a 450 Watt kit ($600 +), renew the present system or leave it alone? Do I fix what ain't necessarily broken? Has dry rot begun to set in? A previous bike was an 82 Honda 750VF Sabre; a terrific machine except the electrical system began failing in expensive episodes. I couldn't afford it and sold it for parts. In the 3 yrs I've owned the RT I have had to replace the regulator but otherwise it's been trouble free. I've been spooked by electrical systems ever since. I'm not looking to accessorize the RT, but I don't want to be stranded on the road with a dead battery either.
 
I, too, had an '82 Sabre...wish I had it back. :(

You have a relatively young RT...compared to some of us!! I wouldn't be so quick to jump to a newer system. 280 watts is pretty sufficient for a large majority of riders. You really only need the higher wattage if you want to run a host of farkles. At this point, you just need to be attentive to your existing system and possibly cleaning connections periodically. Will you never have problems again? Doubt it, but you should have many trouble free miles if you take care of the bike and the systems.

As for being stranded...just have your cell phone, Anonymous book, and a credit card with you. That will get you home.
 
I don't have any experience with the aftermarket (Omega, EME, etc.) 450 watt kits, but I think if it were me and I wanted to save my money, I would go through the current (no pun intended... ok, maybe a little) system and be sure that the battery cables and electrical system wiring are in good shape, connections are clean throughout, brushes are good, etc. I also recommend using a low (2 amp) smart charger like the battery tender or equivalent regularly. I hook mine up about once a week to keep the battery up- my Panasonic is about 6 yrs or so old now and still plugging along. I think a good quality battery is a good investment also. You can search the forum for recommendations- I like the 28 ah Panasonic from Mottorad Elektrik. The charging system on a stock bike without alot of additional accessories should be good enough to keep the battery up while riding if it's in good repair and the battery is in good shape.
 
Unless you have a really large electrical demand with multiple add-ons, you don't have need for a 400+ watt system. The 240/280 watt Airhead system will run your bike and a lot of additional stuff. Your bike is a baby. I've got a '74 and an '84, both over 100k miles. The '74 needed a new rotor and diode board about 3 years ago. Both of these bikes run batteries for about 6 years (Panasonic 28AH SLA) and then I've been replacing them just proactively not because they've shown any voltage drop. You should have approximately 100 watts for accessories as long as you are running 4k rpm. If you are riding in-town stop and go traffic, you are likely draining the battery. If that's your typical ride, then the 400 watt systems might be what you need.
 
I don't have any experience with the aftermarket (Omega, EME, etc.) 450 watt kits, but I think if it were me and I wanted to save my money, I would go through the current (no pun intended... ok, maybe a little) system and be sure that the battery cables and electrical system wiring are in good shape, connections are clean throughout, brushes are good, etc. I also recommend using a low (2 amp) smart charger like the battery tender or equivalent regularly. I hook mine up about once a week to keep the battery up- my Panasonic is about 6 yrs or so old now and still plugging along. I think a good quality battery is a good investment also. You can search the forum for recommendations- I like the 28 ah Panasonic from Mottorad Elektrik. The charging system on a stock bike without alot of additional accessories should be good enough to keep the battery up while riding if it's in good repair and the battery is in good shape.

At the risk of inviting ridicule, it is also important to keep the motor RPMs above 3000. In town, this means choosing a lower gear to achieve the desired speed. The alternator output will be at maximum around and above that motor speed.
 
At the risk of inviting ridicule, it is also important to keep the motor RPMs above 3000. In town, this means choosing a lower gear to achieve the desired speed. The alternator output will be at maximum around and above that motor speed.

I can't find the link (maybe it was out of an old ad?), but the manufacturer's of upgraded charging systems show that ~ 2800 rpm is needed for the stock charging system to begin putting out more current than the headlamp and ignition system use. Around 4k rpm gives a safe margin with the maximum stock output > 5k rpm. So, yea, 3000+ rpm around town is needed for a (good condition) stock charging system to keep the battery charged.
 
One of the better things you can do for your electrical system is fit a "euro" on/off switch for your headlight.

It's what your bike was designed for.
 
One of the better things you can do for your electrical system is fit a "euro" on/off switch for your headlight.

It's what your bike was designed for.

This might help with starting, but most of the later models have a circuit that temporarily turns the headlight off during starting. Then one must also be aware of the laws in your state or states you travel through regarding headlight use. Many states require headlights to be on for motorcycles built after a certain year.
 
I have an '83 R100RT and had been considering one of the aftermarket charging systems as well. I put in a digital voltmeter (Datel) to see what the battery voltage really was as the stock voltmeter is usually off by a bit, and the euro switch lkchris mentions and haven't had a problem even with heated gear and heated grips. The reading on the voltmeter is enough to know when the extra stuff needs to be turned off. I may still upgrade the electrical system but it's now on the "want" list rather than the "need" list.

Other electrical system changes are an Odyssey PC925 and an adjustable regulator set at 14.4v as recommended in the Odyssey literature.
 
This might help with starting, but most of the later models have a circuit that temporarily turns the headlight off during starting. Then one must also be aware of the laws in your state or states you travel through regarding headlight use. Many states require headlights to be on for motorcycles built after a certain year.

Well if you live in a state where you can get away with it it will help with more than starting, because your battery is more likely to be recharged after a short trip with the headlight off than after a short trip with the headlight on. This was my point, as I'm well aware that with the correct headlight relay the headlight is cut off when starter motor is running. For those bikes '78-'84 when the switch is retrofitted a '77-style relay must be retrofitted as well, as otherwise the headlight will come on during starting if it is off at the switch.
 
Thanks everyone. From another thread I found two good suggestions; clean and/or replace the alternator brushes and get a spare rotor. Ted Perch Easthampton, MA.
 
I think the idea outlined above about going through the system, making sure you don't have corrosion at connections, that you have good bare metal grounds, that your brushes are new and your rotor slip rings cleaned up is great advice.

The only real expense will be the new battery. Other than that, it is a can or two of electrical contact cleaner, some di-electric grease, and a small wire brush. You might end up finding some corrosion in the cables, like the battery cables and the three wire bundle that comes off of the alternator, and need to replace a couple of wires, but maybe not.

It will be a great exercise to get familiar with the charging system. Then you can run it for a year or two and see if you really need to upgrade.

One possible middle ground course of action is to replace your diode board with the newer kind that comes as part of the Motorrad Elektrik Omega charging system. On older bikes like mine where the diode board has almost 40 years of baking away in the front cover, that seems like a reasonable step. Not sure about your late model bike though. Your board may be as good as they get.

Barron
 
Back
Top