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Thread: Charging question

  1. #1
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    Charging question

    OK, going through my 83 R100s, 70K miles that I recently purchased, one system at a time. Have a new battery, keep it on a bike charger when parked. When fully charged it goes to a float charge mode. Red light on dash goes out at just over idle. Checking the voltage at the battery running at 4k rpm was 13.25V so I suspected the voltage regulator might be bad. I did the test where I disconnected the connector to the voltage reg and jumped the 2 sockets in the connector and tested the battery voltage again at 4K rpm and found 14.5 to 15 volts so I go buy another regulator (Hella set at 14V) and install and now the voltage at 4K rpm is 13.5V on a fully charged battery. Does this mean that the battery can't absorb any more voltage so it's only up to 13.5V or should tested voltage be higher like 13.8 or 14 when at 4k rpm? BYW, I checked the Voltage at the alternator and it was 15V plus at 4K rpm Any electrical guru's out there know if I'm worrying for nothing, or is something wrong. Thanks in advance,

    Brad

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    RecycledRS
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    Liaison 20774's Avatar
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    13.5v at 4K RPM doesn't sound too horrible, although it might if be hard to maintain a charge if you do a lot of stop and go driving. You might want to check the voltage at the B+ terminal on the diode board and compare to what you see at the battery. This terminal is the output which is routed via a wire to a lug on the starter and then on to the +terminal on the battery. You could be having some corrosion on the starter lug, which is reducing the voltage at the battery.

    Transpo has a voltage regulator that is adjustable and is good for situations where there's a lot of stop-n-go rather than sustained highway miles. There was a recent thread regarding the Transpo...the poster didn't know how to adjust it. Do a search with the word "transpo" and see what you find.

    Consider getting a charging booklet from Rick at Motorrad Electrik. It has all the additional charging system checks.

    Also check out (settle in, it'll be a long read!) Snowbum's discussion for troubleshooting the electrical system.

    http://bmwmotorcycletech.info/trbleshootALT.htm
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    Registered User miairhead's Avatar
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    testingvoltageregulators.htm

    http://bmwmotorcycletech.info/testin...regulators.htm

    I got an adjustable from Bob's I think, 13.95, my bike know stay charged. I attach a battery tender when I come home, it green (not charging) on attachment. It use to be yellow for a little while.
    Last edited by insertdisk; 08-17-2009 at 11:10 PM.
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    Registered User skiteach's Avatar
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    If you are charging at 19.5 volts, you are trying to blow up your battery( cheaper than a regulator, leave testing jumper in plug)! You will at the very least boil any fluids right out of it. The reason regulators are use is to limit the charging system to around 14.5. Any higher voltage is way beyond the capabilities of 12v systems. Now, if you are running 24v system, you're a little low.
    '73 R75/5
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    Liaison 20774's Avatar
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    Quote Originally Posted by skiteach View Post
    If you are charging at 19.5 volts,
    I read that as the cost was $19.95...
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

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    Registered User skiteach's Avatar
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    Hope so!
    '73 R75/5
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    So what you are saying with this post is there's nothing wrong with my charging system?

    Quote Originally Posted by RecycledRS View Post

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    Stage Crew beemerPhil's Avatar
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    Geez-loueeze!



    First, if you really did the test with a FULLY charged battery, and there wasn't some heavy load on the system....
    If you get less than 14v at anywhere above 2550 rpm, something is wrong.

    Period.

    13.anything WILL NOT RELIABLY MAINTAIN A "12" volt battery.

    Second. You DON'T want an adjustable regulator. It's a cool idea, but it's lots more trouble than you think to set it accurately. The Transpo part number for the NON-adjustable regualtor is IB-301, and you can get one from Rick at Motorad Elektrik, or from any decent auto-electric shop. If the battery isn't damaged already, and there isn't something over-loading the system, this will solve your problem.

    Been all over this, for many years- trust me. The primary reason for premature battery failure on the /6-/7 bikes was that the solid-state regulators they were equipped with cut out at below 14v- typically 13.8v- which will insure short battery life and lots of push-starts in cold weather! (Curiously- maybe- the mechanical 'points' type regulators on earlier bikes generally charged to 14.2 volts. Maybe they weren't selling enough batteries?)

    This is not news, or rocket-science; those of us who dealt with these bikes first-hand in the cooler climates have known this since the bikes were in the showroom.



    The punchline is that the Transpo will cost you less than half the price of the BMW part that doesn't work in the first place.....

    I probably will NOT go into a discourse on the boxer/delco charging system unless someone really steps in it, other than to say that when introduced, it was ahead of its time in the m/c industry, perfectly adequate for the loads it was expected to encounter at the time, and, if it's not abused, over-loaded, or neglected, ithe design is about as reliable as a brick; although in production, some weak points were added by the cost-cutters.

    Buy Rick's book- he knows the subject as well as anyone you'll find, and it's a good read if you're interested.


    NOTE:

    After re-reading the original post, there's something else you should check. If during your full-field test, you had 13.5v at the battery, and 15v at the alternator B+ terminal, yoiu have excessive resistance in the circuit from the alternator to the battery. This could be in the hot side, most likely at the starter terminal where the wire from the alternator meets the wire from the battery, or in the ground side, most likely either at the battery ground wire or at the diode board ground wires. (the ones that jump the diode board rubber mounts. These are a notorious weak spot- the terminals are crimped, and should've been soldered. You'll likely find this area shows burned/hardened insulation from the excess heat)

    Normal voltage drop between the alternator and the battery should be in the neighborhood of 1/2 volt or less, unless there's a very heavy load on the battery.

    Again: NONE of these results are certain to be valid unless you've insured that the battery is fully charged and the system isn't overloaded.
    Last edited by beemerPhil; 08-16-2009 at 01:23 AM. Reason: Re-read the original post!
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  10. #10
    It's my belief that the original equipment regulators were set low to protect the Werle diode boards. Now that even Werle seems to make a decent board, there's no reason to use the OEM regulator.

    An unnamed person at BMWNA (who should have known better) once said, "We're going to shorten the warranty on batteries. We give them (new bike owners) a battery chager, so there's no reason for battery failures".

    My response was, "Do you plug in your car every night?".

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    Stage Crew beemerPhil's Avatar
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    Could be, Lostboy- bet I know who that un-named DSPM was!

    Sounds distinctly like BMWNA, although I think the crummy regulator pre-dates the crummy diode board by a few years.

    Maybe they had shelf stock they had to get through!
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    Thank you. That was the advice I needed. I do have Ricks book, "Classic Boxer Charging". I'll check the wire connections as recommended above but probably will not be able to get to it until next week. Brad

  13. #13
    Heartbeat of my R100GS Guenther's Avatar
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    13.5 V seems to be fine

    My R100GS produces 13.5 V max. For the last 20 years I had to replace a battery every 6 years and never had a discharged one. No trickle charging. Over the winter pause I put a 2A charger on for 8 hours twice during that whole period.

    So from my experience (using a high quality voltmeter) I think 13.5 is just fine.

    /Guenther

  14. #14
    Stage Crew beemerPhil's Avatar
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    Outstanding!

    Where did you measure the output voltage? With what equipment? Was the battery fully charged? What load(s) were connected?

    What year is your G/S? Later boxers with the French/Spanish-made Japanese-style starter will draw about 1/5 as much current as the older Bosch starters; look at the comparative size of the ground wire between 70s and 90s bikes!

    Does your G/S have a clock, etc?

    Last(maybe) but not least, how do you ride? Short trips on weekends, or a 30-mile daily commute? Riding habits have everything to do with battery longevity.


    Either way, you've done well- 6 years is, in my experience, about the service limit for a boxer battery. That's what I get- I don't commute daily, I don't even usually ride every day, but lots of my rides are a couple hundred miles or more. I live in Vermont, so lots of cold-weather starts and a long winter rest. I don't think my winter charging habits are 100%- maybe about the same as yours. Sometimes I disconnect the ground, sometimes I forget- and all my BMWs have clocks. My three older (70s/80s) boxers have old-style Bosch starters; two K-bikes have the newer low-current starter and alternators. All my BMWs also are equipped with 80/100 watt headlights- only one has the Euro switch that allows me to turn it off, and I really never use it. I run electric grips, vest, and chaps when it's cold enough to warrant.



    For most riders, and average riding patterns, 14.2 is appropriate regulation voltage, and you'll find that almost all aftermarket regulators will emulate this. The noteable exception is the early OEM BMW regulator; for reasons BMWNA has never explained, they run a half-volt below the rest of the pack.

    They sell lots of batteries.

    I've been replacing BMW regulators with (mostly) Transpo units since the 80s- the number of weak starting bikes that have been rehabilitated thus is huge, not only in my shop, but in countless quality airhead shops, where this is practically a knee-jerk response to poor cold starting and weak charging system problems.

    I've had one Transpo IB301 fail on the road. Fortunately, it was mine, on my 1978 R100S, on my way to Lima for the National. I was not able to find a handy replacement in upstate NY, so I stopped at an Aubuchon's Hardware and contrived this arrangement on my left hand-grip. For about 500 miles, I was the voltage regulator; watching the voltmeter, when it got a bit low, I'd press the contacts together with my finger. When it got a bit high, I'd let go. Worked like a charm, except that in the rain, I got a tiny shock whenever I'd let go! Of course, Rick was at the rally, and I got a replacement there without any trouble.



    I played with the IB301A adjustable regulator for quite a while in the 90s, while I was experimenting with higher-output wiring tricks, but found them to be fussy and hard to set accurately, and therefore not worth the extra effort- the fixed rate units work fine. FWIW, the fixed-rate Transpo runs up to 14.25 volts, plus or minus a tenth or so from unit to unit.

    Again; Riding style has everything to do with battery life. Your mileage will almost certainly vary; I based my statements and conclusions upon my experience with these issues over the last 35 years.

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    Last edited by beemerPhil; 08-16-2009 at 05:43 PM. Reason: added photo
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  15. #15
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    Update: OK, I removed the diode board and checked the diodes with the procedure from Ricks book and it checked out OK. Checked and cleaned the ground connections from the diode board and also checked and cleaned the connections to the starter. Everything looks OK. Put it all back together and checked the charging output. At 4,000 RPM it was 13.55 volts. I did notice something that I want to ask about. The fully charged battery read 12.9 volts before starting and at idle after starting the voltage read 12.6 volts. Is this normal voltage drop at idle? Anyway, still trying to figure out why I'm not getting 13.8 V to 14.0 V at the battery at 4000rpm. Thanks.

    Brad

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