Battery charging issue

Hi All,

I was out for a ride yesterday and noticed that my voltmeter was not showing the same values (ie : 13 to 14 volts) as usual ,when running at 3 to 4 Krpm. Then the engine died and I had to shut off the headlight to start it again and ride back home.

The battery was loaded at about 8 volts. After a night of re-loading, it showed 13,7 volts this morning. So I assume the battery is OK.

The loading system consists of a Lucas RM21 alternator, a Boyer Powerbox 12 volt / single phase (PBOX00108), a 12 volt / negative ground battery and a voltmeter (which seems to be OK as it gives the same readings as my workshop multimeter).

I've also checked the 2 wires of the alternator with an ohmeter (one wire of the ohmeter connected to (eg) wire 1 of the alternator; other wire of the ohmeter connected to the frame): no resistance when grounded.

All the (soldered) connections to/from alternator, Powerbox, battery, voltmeter look OK.

When running the engine at about 2000 rpm, the alternator provides about 18 volts of AC (more when higher RPMs, less when lower).

Having reconnected the alternator to the Powerbox, running the engine at about 2500-3000rpm, the voltmeter shows no sign of loading current coming into the battery (still shows a stable 12,7 volts, no rpm-sensitive).

My current thoughts are that either the Powerbox is dead, or I'm missing something.

Do you know if there is another way to test the P-Box than the one I used?

Thks for any other help.

Laurent

pretty unlikely the power box has failed but possible

more likely is that the black wire coming out of the power box that goes to charge the battery is bad

as in maybe fractured or not well secured to the battery

you say you have a negative ground battery, assume you mean a standard battery but your bike is still positive ground?

if so then the wire from power box goes to the negative battery terminal to provide charging, that how it is?

Thanks for your prompt reply.

I switched from Positive to Negative ground because of my new tachometer which is Neg. ground only. So my bike is in Negative ground configuration.

And of course I changed the Powerbox wiring accordingly (i.e. red wire to Positive socket of the battery, black one to negative one).

It has been working fine in that new configuration for about 1000 miles, until yesterday ...

ok, thanks for the explanation

so it sounds like you have verified AC to the power box but the volts do not rise when you put a volt meter on the battery when motor is running and raise rpm's up above say 2000?

then the problem has to be one of two: either box has suddenly gone bad or the wire from the box to the positive battery terminal to enable charging is a bad connection, correct?

the easiest test right now is the wire, have you verified it is tightly bolted to the positive battery terminal, and that
the other power box wire is secure to the negative terminal, and not to a frame point?

if you think so, then I personally would cut off both power box wires a couple inches from the box and attach new wire to those and new connectors back to the battery terminal, do the volt test again

and if that does not result in increased voltage (charging) then you can conclude a new box is needed?

If your multi meter has a diode checking function you may be able to confirm your regulator is dead. Select the diode function if you have it, be cautious as some meters require you push an additional button or swap the test leads into a different socket.
Test between the AC leads and the DC output leads, one at a time swapping the DC leads and then reversing the test leads. You should have a reading one way but not the other for each AC lead. This will only tell you if a diode has failed which in my case was the problem (podtronics clone). The AC and DC leads of the regulator are internally attached to a bridge rectifier.

http://en-us.fluke.com/training/trainin ... meter.html

Thanks Gents.

Quite instructive document about testing the diodes Jim. I'll try that tomorrow.

1up3down: I don't understand why you highlight the fact that the P-Box black wire shoudn't be connected to the frame but to the negative terminal of the battery (which is grounded to the frame). Results of both types of connection are similar, aren't they?

I stress connecting ALL ground wires directly to the battery terminal dedicated ground simply out of personal experience

In fact after repeated electrical failures over many years from various frame grounds I got fed up and made a thicker wire to the battery ground with a number of thinner wire connections for the various component grounds in order to eliminate the weaknesses that I saw in frame grounds versus zero possibilities of ground failures direct to terminal

having done so some years back my electrics have been bullet proof

in your situation you have a charging problem that is either box or wiring related, given the info you have disclosed

in trying to make sure it is not a box replacement solution I am suggesting the possible wiring solutions that I personally have employed on my Nortons through the years to try to solve your problem easily and surely ?

Crystal clear. I'll follow your advice.

L.

" ... I got fed up and made a thicker wire to the battery ground with a number of thinner wire connections for the various component grounds "

This is obviously a good idea, 1up3down, but I'm having trouble imagining exactly how it's done.
Care to share any tips?

Ive tested the diodes as you told me Jim. Readings show a problem with one of the 2 AC (yellow) wires. Thks again for your help!

L.