'68 dream loses charge quickly

DeaneKY · Post by **DeaneKY** » Mon Aug 23, 2010 12:15 pm

Thanks, Wilf. I'll try that, if not tonight, then tomorrow evening and post what I find.

jensen · Post by **jensen** » Mon Aug 23, 2010 1:07 pm

Hi,

Rectifiers or diodes always "leak" current, but in normal situations this is very low, typical values are a few nanoamps. However, the current leaking in these old rectifiers can be a bit higher. In normal cases a rectifiers does work, or doesn't work.

Another problem could be a leaking current in the wiring or somewhere else (ignition switch ?), but a bad battery is the most logical and suspected reason, just test the battery outside the bike on a loader, and check the voltage after the battery is fully loaded, and repeat this every day the same time.

Jensen

DeaneKY · Post by **DeaneKY** » Mon Aug 23, 2010 2:35 pm

Thanks Jensen. I've tested the old battery after removing it from the bike and over the course of 3 or 4 days it's only dipped about .02, so even though it had a few years on it, I don't think it was the problem. The new battery hasn't rectified (bad pun, I know) the situation.

jensen · Post by **jensen** » Mon Aug 23, 2010 3:05 pm

Hi,

If the battery is ok, check with your meter the resistance seen from the battery leads (disconnect the battery first). The reading should be a very high resistance (mostly depending on the quality of the meter) when the switch is in the off position. But when it shows a few kilo ohm to 100 kilo ohms, check were the "short circuit" is with the meter.

If you use a 9 ampere hour battery which is fully charged and it looses capacity, let's say 1 Ampere hours, over 10 days. It loses 1 ampere hours over 10 * 24 hours is 240 hours. That means that you (per hour) 1/240 = 0.0042 amp hour. Your system is 12 Volts, so start looking for something with a resistance of 12/0.0042= 2880 ohms (3 kilo ohms).

The above is only an theoretical example (without the battery's internal losses, the 0.2 Volts in your case) , but it gives a rule of thumb of what to look for,

Jensen

e3steve · Post by **e3steve** » Thu Aug 26, 2010 8:11 am

Dean, please post your engine-running voltages, at the battery terminals, thus:

Lights OFF, engine circa 4000rpm
Lights ON, headlight dimmer switch centred (leaving just front & rear parking lights on), engine circa 4000rpm
Lights ON dipped beam, same rpm range

DeaneKY · Post by **DeaneKY** » Sun Aug 29, 2010 9:01 pm

I haven't forgotten about this thread. Work has picked up and grad school started back, so I've just continued charging the battery every 2-3 days until I can get my head back in the game to properly diagnose the issue. I'll post results as soon as I get the chance. Thanks, again.

e3steve · Post by **e3steve** » Mon Aug 30, 2010 9:27 am

I had a similar problem to yours on my first CB, whereby it would run all week, daily use, with the lights ON (additional charging coils get 'added in' to support the current required by the lighting); it turned out to be a broken wire on the main stator coils. Re-soldered the yellow wire and all was well.

If it's the brown that's high-resistence / discontinuous, then you'll get no lift in voltage with the engine running, even with the lights ON (combo-switch 2nd detent c/w from OFF?); if it's the yellow, then chances are that's all the problem is -- just a bad connection at the stator, or even at the bunch of connections from the main harness to the motor (bn, y, pk: stator; l-gn/r: neutral switch).