The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: jamestnewsonr65 on June 17, 2015, 04:05:06 PM
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When I refurbished the bike I replaced the gen light for an LED version and installed a resistor in the headlight assembly. To be honest I think I might return to the normal filament bulb version.
Since replacing it with the LED I have never been sure that it is completely working as it should. The light seems to stay on longer than it should and sometimes just stays on for a while then goes off randomly. I guess this could be a loose connection or something but I doubt it as I made sure all the connections were solid.
I've recently replaced the battery with an AGM version and noticed the other day that the CTEK battery tender I have attached was showing that the battery was losing it's charge. Tried to start the bike and the battery died. This leads me to believe that the charging circuit is definitely not working.
Is there any way to check the circuit is either working or my case not working with a volt meter?
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Is there any way to check the circuit is either working or my case not working with a volt meter?
Yes, just measure the voltage at the battery with the engine running. You should see the voltage rise to something in the region of 14.0 Volts as the engine is revved. Ideally the charge voltage for an AGM should be higher but it will still charge at 14.0 volts
You can also measure the state of charge of the AGM battery with a voltmeter, in fact it's the only way. Expect 12.8 volts or even a little higher. It varies so set your own benchmark by fully charging the battery then let it sit overnight before measuring the voltage. Whatever you read that's the voltage to expect when it's at 100% charge. Every 0.2 volts below that = approx 25 % discharge so if 100% charge = 12.8 volts then 75% charge will be 12.6 volts and so on.
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Was this GEN light problem an issue prior to you modifying the circuit?
Where and how did you add the resistor?
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And, what value ohms and wattage resistor did you install?
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Was this GEN light problem an issue prior to you modifying the circuit?
I didn't use the bike before it was refurbished, but the light went out on the dash when revved.
Where and how did you add the resistor?
I added it in the headlight bucket connected to the wires originally for the gen light. (Blue & Green)
And, what value ohms and wattage resistor did you install?
330 Ohm, 1/2 watt
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Was this GEN light problem an issue prior to you modifying the circuit?
I didn't use the bike before it was refurbished, but the light went out on the dash when revved.
Where and how did you add the resistor?
I added it in the headlight bucket connected to the wires originally for the gen light. (Blue & Green)
And, what value ohms and wattage resistor did you install?
330 Ohm, 1/2 watt
That all sounds correct. Might try going back to the OEM-style bulb. If that doesn't fix the issue, then there's probably something else amiss.
:(
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I'll check the voltage at the weekend when I have some spare time and see what I get. I might try connecting the regular lamp to just to see if it works.
Will report what I find.
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So Ive been out on a run this morning for about an hour and took the voltages which came out as follows:
- 13.2V when the bike is turned off measured at the battery.
- 12.4V or thereabouts when idling, with the gen light on/flickering (idle flicks around 900/1000)
- 13.8V or thereabouts when revved so that the gen light goes out.
This all seems fairly normal to me, but I have noticed it takes a while for my gen light to start functioning (i.e. turning off when revved) when out on a ride, but once it starts it works fine.
Fine to me is off when riding and then flickering/solid when idling.
Should I worry about this at all/change the gen light or just keep an eye on the battery charge to ensure it stays around the 13V mark when off?
Thanks.
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Should I worry about this at all/change the gen light or just keep an eye on the battery charge to ensure it stays around the 13V mark when off?
It is normal although I would like to see higher than 13.8 volts especially with an AGM battery. I would keep an eye on the battery voltage to make sure it maintains a voltage that indicates full charge. If the engine has been run or the battery has been charged always measure after an overnight rest or you get a false high reading.
The explanation of the slight change in behaviour is simple enough. There are likely two effects contributing to this:
For the gen light to extinguish the alternator output voltage has to equal or exceed the battery voltage and the new battery voltage at 13.2 volts could be 0.5 volts higher than the old battery so it takes a few more revs before the alternator output reaches this higher voltage and extinguishes the light.
The 2nd effect is that by substituting the original gen lamp with an LED and resistor you have reduced the excitation current that flows through rotor. The original lamp would have provided at least 250mA where as the resistor and led will be something in the region of 70mA (30mA for the LED and 40MA for the resistor). The net effect is to increase to revs before there is any output from the alternator although at higher revs there will be no change in output.
To be clear I'm not say the resistor value is wrong, it's in the accepted range of values for this LED mod. There is an issue of heat dissipation if you use a resistance equivalent to the original lamp which would be in the region of 50 Ohms. You can use such a low value resistor but it would have to be a higher wattage type mounted so that it is able to safely dissipate the heat.
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It seems to be pretty normal behavior to me - you may want to check your connections from the diode board and brushes/slip rings, and also the voltage regulator under the tank to make sure that you don't have a loose or dirty/corroded connection which is causing slightly less than optimal charging voltage.
Be sure to disconnect the battery cable (at the very least the GROUND battery cable, but either/both will do) before removing or installing the front cover just in case you accidentally bump an exposed terminal connection under there with the metal front cover - this can cause a short that takes out the diode board.
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When you have the bike out for a ride, or your usual commute, is it lower speeds with traffic lights, or higher speed motorways ??
The charging system on these bikes don't put out enough power in the lower rpm range to provide the power to run the bikes electrical system and charge the battery .
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This bike is a bit of a toy so when I go out for rides it's a varied mix of traffic lights and 50mph runs.
Im going to run it on a couple of commutes this week, 16 miles through central London and see how it behaves. I have a bit of time next week so I think I may switch over to the non LED gen light and see if I get any improvements.
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I got oil on my brushes on my r65,my fault.The gen light took ages to go out.I assume a bit of heat was required to break through the coating of oil to complete the charging circuit.Changed the brushes for new ones and cleaned the rotor/ stator of the oil,worked perfectly.HTH
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I don't entirely agree that the charging system is inadequate if properly set up with all the electrical connections clean.
Due to other commitments, for the last month I have ridden the bike only 4 miles to work and 4 miles back Mon, Tues Wed. The bike has then sat until the following Monday. I have not had to charge the battery at all and I don't mean by that it starts the bike OK I mean it has maintained very close to a full charge with rested voltage never falling below 13.0 volts. The gen light goes out at 1000 RPM idle and stays out. The key to that performance besides a well maintained charging system is having the voltage regulator set correctly for an AGM battery at 14.5 volts cold.
I don't run a full head light though only a 10W halogen daytime running light. And the points ignition is using less current than the electronic ignition bikes.
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I swapped my GEN light for an LED and a resistor and I noticed a difference. I always just assumed it had to do with the different characteristics of the lights.
With the filament bulb in place it would be brightly lit once started and at about 900 rpm start to slowly fade out until it was out at about 1050-1100 rpm. With the LED it is brightly lit once started and stays bright until around 1050-1100 rpm when it goes out instantly. I always attributed it to the instant on/off of LEDs.
With the filament bulb it would flicker dimly as the rpm's dropped into the 1000 rpm range. With the LED it is off until it hits it designed rpm then comes on fully.
I have never had an issue with a less than fully charged battery but I also changed every bulb on the bike to LEDs to lessen the voltage draw. Short trips or long I have never had an issue.