Hello, i'm new to the forum and to bike building/restoration. Current project is a '73 Bonneville 750 T140V, which I'm modifying to a "bobber".
My question: when the ignition is "off", the battery reads over 12V. Once switched "on", the battery immediately begins to quickly drop until the ignition is switched back "off". Once switched "off", the battery goes back up, slowly, to 12+V. The battery is new. Any ideas or suggestions?
Second, since I'm going the bobber route, any thoughts on switching to a Boyer Power Box? Thinking this might eliminate most electrical problems and clean up the overall look. Cheers!
Disconnect the brake light switch and try ignition...Keep disconnecting electric till you find the source of the drain..Could be a pinched wire under the seat..Boyer is a good sound conversion as long as charging system is up to snuff..you will not start this bike with a battery below about 9 or 10 volts and a Boyer..ya can with points..
The first thing you want to check for is if your showing a voltage loss from a closed set of points. Leave the meter on and turn the motor over slowly. You should see the voltage jump back up to 12 when both sets of points are opened. If this does not happen, follow Dave's route above.
,_o _ -\_<, (*)/'(*)
Re: Battery Mystery#90503 04/12/0610:44 am04/12/0610:44 am
Get the battery load tested or maybe hook a headlight bulb up to it and see how long voltage drop takes. I would think that any fault that would drag a good battery down that quickly would make smoke. 12V is not an indication of a fully charged battery, 12.7V is closer to the mark. One thing that will drag a battery down slowly is a damaged diode in the rectifier, if so : http://physiology.usouthal.edu/restore/diode/diode.html
Hey Guys, thanks for all the great suggestions and ideas. I have all afternoon open tomorrow, so I'll be testing and applying your suggestions. Will let you know what I come up with. Thanks again for all the great advice, and for making this rookie feel welcome. I've learned a lot already. What a great group!
Battery voltage without a load means squat. When the ignition is turned ON, you've applied a load and the voltage SHOULD drop.
The real question then is... just how much does it drop? Because the "dropped voltage reading" is the REAL battery voltage.
What we've decided on this forum as simply a "standardized home test" is to leave the headlamp ON low beam for 2 minutes. Your battery (after being trickle charged for 24 hours) should start out between 13V and 12.6V, then after 2 minutes with the headlamp ON should drop no lower than 12.0V (measured with headlamp still ON).
For your particular case, since you suspect ignition issues, you may unplug the WHT wires from BOTH ignition coils there under the seat. They won't make a big difference with the larger load of the HL being ON. (Just remember to reconnect them after the "test".)
I suspect your battery voltage will be at 11V or lower. If you had an electronic ignition you MUST replace the battery. Since you seem to have a standard points-type ignition this is not a big deal. Your bike will still crank and run very well. However, your headlamp will be a dull yellow at night (not very safe) and your battery will continue to go "down hill" until you can't see “diddley” at night. [Not that Bo Diddley is highly visible at night anyway. :rolleyes: ] Your battery will not have a miraculous recovery; it is a natural aging process of the lead-acid battery.
If you pay for a "load test", this is exactly the procedure they will follow. However they will use a device that will allow this to happen in a matter of moments, and then charge you money for the privilege. And then after you pay, since you'll be at the local Honda or Kawa-yama-suki-Davidson shop, all laugh at you for having a Triumph. Our plan is equivalent and much less damaging to your ego.
Lacking an ammeter to put in place of the fuse, you can place a small12 volt 2 to 3 watt bulb in place of the fuse. If there is a drain on the battery, due to a short or load load created by a failing diode, etc., the bulb will light. If the bulb is lit, disconnect wires from different circuits until the bulb goes out.
If the ammeter indicates zero amps, or the bulb does not light, you do not have a drain on the battery from a short or load created by a failing diode or the like. It is time to look at the battery AND the charging system.
Due to modern battery technology, which allows it to be put into service in a much shorter time, a "new" battery is always suspect. Mechanical problems that happened in production or shipping will not show up in a new battery until it is put into service. Also, if the vent cover is accidentally removed, it lets out the gas that protects the plates from being damaged during dry storage. This has been covered on this site several times.
The common voltages seen on a battery are: 13 plus volts just after it is taken off the charger. It will hold this voltage for a short period of time after the battery is removed from teh charger. 12.8 (indicating a full charge) which is the voltage you always like to see. 11.8 volts indicating that the battery is fully discharged.
As Richard mentioned, measuring a batteries' OPEN CIRCUIT (no load on the battery) voltage has little diagnostic value. All this is telling you is: the portion of the batteries' plates that are able to hold a charge are fully charged. It is not telling you that 90% of the batteries abillity to hold a charge has been compromissed due to a mechanical problem or sulphation.
What the OPEN CIRCUIT voltage indicates in this case is that the 10% portion of the battery available to hold a charge, is fully charged. So instead of the 10 amp battery you paid for you now have a 1 amp battery.
Boyer ignitions do not need a new battery, but a good battery.
I followed Mike's advice (since it was listed first and appeared to be the simplest) of disconnecting electric until there was no drain on the battery. Tried several with no luck. I unplugged the White/Yellow (kill switch wire) inside the headlight. Doing this the battery stabilized. So, I'm deducting that the kill switch wire is the culprit.
So here is another rookie question for ya: I tested continuity from the kill switch to where I unplugged it, and it read "0". So, I tested from where I unplugged it back to where it plugs into the right coil (which I had disconnected for this test). Again, it read "0". The system was not under any load when I tested it. Do I need to perform a similar test with the system under load? If so, how do I do this? Or, could the coil be the problem? If so, how do I test the coil? Does the white/yellow end at the coil? I do not see it going any further on the schematic. Finally, if I cannot track down the ground, can I just leave the kill switch wire unplugged, or will this cause the bike to always be in "kill" mode? Whew, that was a lot, eh?
Hope I'm not confusing everyone! Let me know if you need more details and I'll see if I can confuse you more
You know I answered your question without asking...was or is this bike a runner?? does it start?? If not the coil could be shorted thru the switch if it set for any time..I do not use the kill switch on my Triumph as they have a bad reputation for staying that way (killed)..
The bike had sat for over 10 years, however, over the last few weeks I've gone through some of the systems, mainly the fuel, and I had her running. That is until she died and the electrical problem came up. I sure appreciate your help.
I think I'll just leave the kill switch unhooked as you have done.
Thanks for all the help. I had the battery trickle charged. Put her back in the bike. Fired her up and ran for several minutes with the headlight on. Road through the neighborhood at various rpm's. Seems to be holding charge just fine. Running around 12.7amp when not running, around 11.5 while running, at idle with the headlight on.