charging problems

steveKs. · #1 10-29-2007, 03:27 PM

While cruising the alternator stops charging and I start losing voltage. If I switch on the landing lights the alternator will begin charging again at around 20 amps. Switching the lights back off the alternator will show 4 amps or so then back to zero amps.
I pulled the alternator and it checks out fine. The battery checks out ok also. If I let the RV sit for a week the battery usually is very low to the point of not cranking the engine over.
Any thoughts??
I am thinking of installing a new battery just to rule out a quirky battery.

steve

John Clark · #2 10-29-2007, 03:45 PM

What sort of voltage are you seeing as this is happening?

John Clark
RV8 N18U "Sunshine"
KSBA

steveKs. · #3 10-29-2007, 05:29 PM

When the amps go to zero the volts will begin declining. When showing amps of charge the voltmeter will climb to 13.5 after charging for a bit. When the ampmeter shows zero the voltage will continue to decline to about 10 volts.

I will try flying tomorrow and leave the landing light on to see if it will keep the alternator charging.

The alternator repairman that checked out the alternator said sometimes a bad battery will cause similar symtoms.

Another guy told me that a battery with a dead cell will take a charge and appear to be normal but will lose that charge with out a load.

It seems strange. The alternator will continue to charge strongly after I turn on the landing light but will drop slowly, maybe to zero then back up to 2 amps then 4 or 5 then finally fizzle out to zero.

Ironflight · #4 10-29-2007, 05:44 PM

I think you might be on the right track suspecting the battery....how old is it? I have had shorted cells in car and truck batteries before, and they act very, very strange. I find voltage much more useful than amps for troubleshooting charging problems - generally, you either have good alternator output voltage, or you're draining the battery at discharge voltage.

For strange symptoms, you might also look for a bad/corroded crimp or joint somewhere.

Just shots in the dark....

Paul

grover · #5 10-30-2007, 10:22 AM

internally regulated alternator?

steveKs. · #6 10-30-2007, 11:25 AM

Yes, internally regulated.

I put the battery on a tester and loaded the snot out of the battery then charged the snot outta it.
Reinstalled the alternator buttoned everything up and now it works perfectly!!??

When I reconnected the sensor leads back on the alternator I felt the plug in snap into place, got me to wondering if the plug in was not quite attached securely and giving the alternator less than adequate commands.

Thanks for the input. This one had me really guessing.

steve

Mike S · #7 10-30-2007, 11:31 AM

Quote:

Originally Posted by steveKs.

I put the battery on a tester and loaded the snot out of the battery then charged the snot outta it.
Reinstalled the alternator buttoned everything up and now it works perfectly!!??

You obviously had a snot problem.

And here I was suspecting a regulator problem.

steveKs. · #8 10-30-2007, 04:39 PM

Yeah Mike and all the time I was thinking it was the alternator as well.
Was it the alternator?.. no it's snot.

gmcjetpilot · #9 10-30-2007, 11:02 PM

What kind of ammeter do you have?

Sounds like he's ammeter is a LOAD METER verses a Charge/Discharge Meter.

A load meter shows out put of alternator right. 20 amps is high for landing lights (usually about 4 amps each, may be 5 amps so 10 amps total). However once you turn the lights of the amps go down again with LOAD, right. The 4 amp to 0 amp does not sound right.

If its a charge/discharge (*bat*) meter than your alternator is not keeping up with the lights, but providing 4 amps to charge the battery again? However that would be a negative 4 amps and than zero as the battery reaches full charge.

steveKs. · #10 10-31-2007, 07:03 AM

I was reading amps and volts off a Visionmicrosystems 1000.

Normally I will see approx. 6-7 amps charge with strobes, nav lights with all the avionics on. When I turn on the landing lights I usually get at least 20 amps of charge. I am very electrically challenged but 7 amps plus another 8 for the lights should only be drawing 15 or so...correct?

My battery is a PC925 Odyssey and the alternator is a internally regulated Denso 48 amp.

Like I mentioned, since I put everything back after testing everything works perfectly.

If I let the RV8 sit for over a week the battery is drained to barely cranking the engine over. I will pull the postive cable and test to see if I actually have a small load draining the battery or if the battery is going down on it's own.
The master should kill everything but if I am correct the battery will still be connected to the alternator and that may be a possible source for the drain.

steve