More amps!

[pmdave]

If this topic has already been discussed before, please let me know.

There has always been a quest for the holy grail of airheads: a charging system that really works. OK, my old R75 seems to have acceptable charging for the smallish battery, but my 1980 R100 (that I'll soon be getting back from my son) has always had charging problems. I only had a few complete failures (open rotor, bad diode) that I remember, but on numerous occasions I meticulously cleaned contacts, added ground wires to the diode board, replaced diode boards, sanded the rotor slip rings, changed brushes, changed voltage regulators, cleaned up the charge light circuit in the instrument cluster, etc. etc.

Whatever, it always seems to charge weakly. Last time I rode it, the voltmeter could barely stay above 0 unless I turned off the headlight.

So, I'm thinking of doing some sort of major surgery to the charging system when I get the bike back. Perhaps one of those new aftermarket alternators. Or (trust me here) sawing a hole in the cover and adding an automotive alternator on the outside.

So, what are your experiences with aftermarket charging systems?

pmdave :type

[R100RS]

My stock 280W alternator works for me just fine. The two easiest/best improvements to the charging system (IMHO) are switching to a police model voltage regulator (starts charging at 1500 rpm) and a sealed battery (less voltage loss after sitting unused). Of course, I don't have any heated clothing or heated grips or extra lights.

[Bob_M]

Greetings
My 84 R100 has the 400W alternator as provided by Motorrad Elektrik. It works as advertised. The thing starts charging at 1600 RPM and is at full power at 4000 RPM. I had a resistence problem that prevented the system from working properly and Rick at the company has been very generous with his time in helping trouble shoot the problem. (the fuses had a dust of oxide on them :doh ) The installation was easy for a fairly capable wrench. I run a pair of driving lights and a vest at the same time with no problem. It is strongly advised to not overload the system. The system runs about $675 so it is expensive, but the rotor and diode board swap out with no other modifications. No regrets :type
Bob

[lkchris]

Best favor you can do for your charging system is to install a switch to turn off your headlight. Then you'll be running your bike as BMW designed.

[pmdave]

I'm not looking for ways to bodge the weak system to get around it's problems. I want some AMPS! 400 watts sounds about right. I have heard about some failures with the aftermarket system.

BTW, in states such as WA and OR, state laws require the headlight to be on even during daylight hours. ("any time the vehicle is in operation") So, even though the old R100 has switches to turn everything off, that doesn't help get through a series of stoplights on a dark rainy night.

I'm currently test riding a Ural 750cc that has a nice auto-type Japanese alternator driven from gears in the cam box. I don't see any easy way to attach one on an airhead, but I am a little jealous of an alternator (with built in rectifier and regulator) that works as well as in the automobile from which it was transplanted. Hey, I don't have any worries with my Toyota electrics.

Anyone else have experience with the Motorrad Elektric aftermarket alternator? Can it handle the heat, tucked inside that cover? Does the rectifier hold up? Is there any reason NOT to build a custom diode board with independent replaceable diodes? (etc. etc.)

Believe me, I'll be looking seriously at attaching a belt-driven automobile alternator, say hanging from the frame on the R side, or directly on the front of the crank inside a modified cover. Hanging it out in the breeze should help it's lifespan. I'm looking for serious amps and 100% reliability here.

pmdave :thumb

[Bob_M]

During the Spokane ralley we had some heat. I ran all over the place during the event. On the way home to Portland I hung about a half a mile behind a pair of K bikes running 90/95 for more than an hour. My old R had every chance to run hot. That bike has no fairing so it Alternator cover is in the wind stream.
B

[R100RS]

I'm not looking for ways to bodge the weak system to get around it's problems. I want some AMPS!
Clearly, you have more money than I do! ;)

[kbasa]

Greg Hutchinson in the NorCal club has an arrangement that places an automotive 1KW alternator up on top of the case. It's driven by an automotive belt from the original generator location. All the electrics are moved out of the front cover and located elsewhere. To the casual observer, it's totally invisible as the alternator is way up under the tank.

I think he's got a kit going for it, but I don't know much about it. But having a 1Kw alternator on an airhead allows you to use lights, heated gear and a GPS all at the same time.

[pmdave]

Yeh! Yeh! that's what I want. KILOWATTS. Anybody have a photo of this setup? A contact perhaps? A phone number?

And, in terms of money, I don't think it's clear that I have money burning a hole in my picket. In financial terms, I've already spent maybe $1,000 on various repairs and replacements to the stock BMW charging system. You can spend a lot of those greenbacks trying to bodge a reluctant bike system into action, and then discover it STILL isn't reliable or adequate. I'm not knocking the original design, after all it's 35 years old. I just want something better now.

I haven't priced a typical oriental auto alternator (say from a Subaru or Toyota), but I'd be amazed if we're talking more than $350 for a new one. Car parts are typically much cheaper than bike parts, remember? OK, there's some futzing required to add one to an airhead--some machining, welding, etc. Mostly, it's an expenditure of time. Obviously, if you're not mechanically inclined, this is not for you.

KILOWATTS! KILOWATTS! Add some lights and make a glow in the sky!:clap

pmdave

[YB in IN]

I'd go for it man. One of the main reasons that I switched from an airhead to a K-bike was basically the same reason as yours of wanting more amps. I can now run lights, and heated clothing without thinking twice about it.

[kbasa]

Sent you a PM, dave. :D

[BMWzenRider]

Hey, KBasa,
I would be interested in info about a automotive alternator conversion too. I am running extra lights & electrics on my '81 R100RT w/hitchhiker sidecar, and have big problems with the stock charging system keeping up.

I have been looking at the Ohmega 400watt system too, but haven't heard anything about how reliable they are compared to stock.

PM, the other route to go for in the short term is upgrading the wiring in your charging circuits. There are discussions about that on both the airhead and IBMWR sites in the techy sections. Old small gauge & corroded wiring sucks a lot of power in resistance.... A new ground strap and sealed battery did a lot to help me, but my voltmeter needle still dances all over when I turn on a signal or hit the brakes.... :(

[widebmw]

I have had the Omega 400 watt system for over 2 years (35,000 miles), and I have not had any problems.

[pmdave]

I appreciate the advice about upgrading the wiring, but I've already done what I could, and it's still not enough. For whatever reason, the charging system on that particular machine has always been wimpy.

The Omega system does have the advantage of tucking neatly inside the front cover, just like the original alternator. That's probably the way to go for those who need more juice but don't want to do surgery on the stock covers and castings. The failure reports I have received involve the voltage regulator, not the alternator itself. I don't know the specifics, but with experience I'd assume the Omega folks will cure the problems.

I'll be following up on what's required to graft an auto alternator onto an airhead, and will report back on what I find. The advantages of an auto alternator are that they are obtainable at auto parts outlets, many are totally self-contained (including rectifier and regulator), they are designed to power an automobile with all it's lights and systems, and they are typically more robust than motorcycle parts.

pmdave :type

[nrpetersen]

Remember that automotive alternators run at pretty high RPMs, hence they get a lot of output even at idle..

As the operating RPM goes down, the strength of the rotor magnetic field has to go up. Try measure the voltage being deliveredacross the rotor slip rings by the regulator. It should approach 12 V at lower engine speeds. Measure the reistance of the Rotor thru the slip rings and compare to a new unit. That will probably identify the source and possible fixes of your problem as to whether it ithe regulator or the alternator.

[Bob_M]

Here is a link to an article on the subject

http://www.icss.net/~squirts/stator.htm
The photo displays one persons idea of pretty

[pmdave]

Thanks for the suggestions, nrpetersen,

However, even if all the components in an R100 stock charging system were in perfect condition, and augmented by extra ground wires, it's still weaker than I would prefer, and less reliable.

I also wonder about the idle speed of various engines. Seems to me that today's car engines idle at about the same RPM as bike engines. I'd wonder more about max RPM of car engines vs. the airhead, although I don't recall ever exceeding 7,000 RPM. Of course, the pulleys can be selected to provide a different alternator speed than engine RPM. As I recall, cars seem to have a large pulley on the crank, and about half that size on the alternator.

I have observed on a Ural sidecar rig (with a Japanese "car" alternator) that there is obviously higher voltage at speed than at idle. It shows in the rate of turn signal winking. However, there seems to be more than adequate voltage to keep the battery charged even if allowed to idle.

However, just out of curiosity, I'll be checking the RPMS of different vehicles.

pmdave :thumb

[pmdave]

OK, I've wussed out of the auto transplant. Those GL photos really turned my stomach. I've ordered an Omega aftermarket alternator, after some discussion with a BMW parts man who runs the Omega on his personal airhead.

Yes, there were some problems with early diode boards, but Motorrad Elecktrik has taken care of any failures promptly. In general, the Omega seems to work very well, and very reliably, about the same as a K bike alternator.

Give me a year or so, and I'll report back. Hey, I'm still awaiting the arrival of old Blackberry Blue from the right coast, so I don't have anything to fix yet.

pmdave :brow

[The_Veg]

I installed an Omega back in August in my 1995 R100R. 1000 miles later the diode board failed. It for some reason overheated which softened the solder joints on the field diodes enough for one of them to fall out of it's mounted position (they are mounted verticvally), and a second one was almost out as well. This stranded me in rural OKlahoma where my cell phone doesn't work. My anonymous book earned it's keep that day! Rick replaced that board promptly and said he's bash his supplier over the head with it. When I received the replacement board, I set the field diodes in blobs of JB Weld (which is non-conductive and can take high temperatures) so that should the board overheat again, the diodes will still hopefully remain in contact even with most of their solder gone.
But my troublres were not over. My charge lamp was doing odd things, not being on or off at the right times and I was burning regulators quickly. LOTS of troubleshooting, LOTS of consultation with Rick and with my expert pals at the Boxerworks forum. Everything kept testing good, including all charging system wiring. Eventually Rick decided that since the rotor was the one moving part, why not try it? He sent one right away at no cost to me. That turned out to be it. Seems that the rotor that came with the kit was testing OK when sitting still but would short once spinning. Rick did a postmortem on the rotor and determined that it was assembled with too much pressure on the halves. He showed it to me when I visited him a few weeks later while passing through that part of the country (nice guy BTW- we had a good time talking Beemers and other stuff).
Since then I have have ridden a few thousand miles and had no further problems. Rick absolutely stood behind his products. He claimed that out of nearly 400 Omegas in the field, mine was the first to have a rotor die early.
Would I buy Omega again? Absolutely. I paid $575 (*not* 675) for it. I have seen the same system advertised by European suppliers for much less but I can't say what it would cost to ship to USA and I doubt that their product support would be as exemplary as Rick's.

[R100RS]

Here's an 800W alternator with a really clean installation...

http://www.geocities.com/jimmywanger/alternator.html

http://www.geocities.com/jimmywanger/bareengine.jpg

Don't know anything more about it.

[The_Veg]

I see two problems here. One is that I doubt that that kit includes a modified cover to keep the elements out. Also, and this is the bigger one, from the sizes of those pulleys I'd say that the alternator in that setup rotates at cranks speed. This is one primary reason why the stock alternator isn't so strong. Automotive alternators are designed to rotate at twice cranks speed to charge as much as they do, so would this setup really be much of an improvement?