voltage slow to come up

GeorgeC

GeorgeC

Administrator
Management Council Member
Joined
Dec 5, 2010
Messages
5,151
Display Name
Display name:
GeorgeC
2 year old Concorde battery, never abused. Voltmeter has always snapped into the green until maybe a week ago, when it started coming up very slowly, into the red or maybe yellow.

Master solenoid going south?
 
I've never seen a variable solenoid response. Either the battery has issues or possibly your voltage regulator. Does it help to goose the engine a bit?
 
Plane power alternator on an O200, no belt. I'm talking about with the master on with the engine off. Once started, it runs normally. Didn't observe much ammeter deflection after start so I don't think the battery was discharged. Is it possible to get a voltage drop across a corroded contactor?
 
GeorgeC said:
Is it possible to get a voltage drop across a corroded contactor?
Click to expand...
Yes. But that requires some current flow.
Now, to be clear, you switch on yea olde master switche, the volt meter comes up slow, but it does come up. If the battery were low, it would not come up until the alternator started charging. If you had enough resistance in the master to cause a noticeable voltage drop with almost no load, then she ain't gonna crank for poop.
My money is on the mechanical voltmeter movement getting sticky.
Get a real voltmeter and compare voltage somewhere with what your aircraft quality voltmeter is doing.
 
Capt. Geoffrey Thorpe said:
Get a real voltmeter and compare voltage somewhere with what your aircraft quality voltmeter is doing.
Click to expand...
Yeah, I'm going to bring my multimeter next time and connect it directly to the battery. FWIW, the digital voltmeter on my engine monitor said 11.4V when I updated its firmware on Friday, so I'm not sure it's the analog voltmeter in the panel.
 
Last edited:
Do you have an engine analyzer? Many of them have a voltage readout (possibly may have to step through the displays to get to it).
 
I just went through this. Battery was indicating 11.8 volts. Voltage at cigarette lighter was 11.6. Found a Zeftronics ACU troubleshooting guide and tracked it down to a bad alternator. New one on order. You may want to check things out and make sure your ACU and alternator are working correctly for charging the battery.
 
Rcmutz said:
I just went through this. Battery was indicating 11.8 volts. Voltage at cigarette lighter was 11.6. Found a Zeftronics ACU troubleshooting guide and tracked it down to a bad alternator. New one on order. You may want to check things out and make sure your ACU and alternator are working correctly for charging the battery.
Click to expand...
Easy enough to do. The voltage when running should be a couple of volts higher than when not running. Even a lazy voltmeter should show that. An ammeter will definitely show it.
 
Dan Thomas said:
Easy enough to do. The voltage when running should be a couple of volts higher than when not running. Even a lazy voltmeter should show that. An ammeter will definitely show it.
Click to expand...

Agree. But it could be an issue with the ACU, the field wire from the Alternator to the ACU, or a problem with the alternator itself.
 
Ye olde voltmeter sayeth OCV=12.41, which is a little low according to the Concorde documentation. Master on, alternator field off, panel voltmeter read 11.5. Avionics on, the G2 said 12.2.
 
12.4V OCV is about 40% discharged. So the question is why is your battery not fully charged? Could be the battery is sulfated or otherwise in poor condition, or your charging system is not working properly. What is the bus voltage when the alternator is charging? Should be 13.8-14.2V. If you are undercharging your battery, for example, it can lose capacity due to persistent sulfation. A fully charged battery should be 12.8-12.9V OCV.
 
13.3 in flight.
 
GeorgeC said:
13.3 in flight.
Click to expand...
Get it checked with a calibrated voltmeter and have it adjusted. Can't rely on just any voltmeter when we're working with narrow tolerances. Too low sulfates the battery. Too high boils the electrolyte. Both ruin the battery, and boiled-off electrolyte eats airplanes.

If adjusting the regulator won't bring it up, the alternator brushes and slip rings are likely contaminated with grease from the rear bearing. Easy to find: take the field lead off the alternator and check the resistance between the terminal and case. Should be 3 to 5 ohms. Move the prop some; it shouldn't change the resistance much at all. Disconnect the sparkplugs before you move that prop.
 
GeorgeC said:
13.3 in flight.
Click to expand...

That's almost a volt low. Should be 13.8-14.2 V. I had this issue a couple of annuals ago, and the ancient voltage regulator had to be readjusted up to the proper value. The solid state regulators are better. I still have a working old style mechanical one.
 
I found an old photo of it at 13.9, so something must have gotten dorked up between then and now.

Concorde has a nice table of voltage regulator settings:
concorde.png
 
MIF. Checked the logs, looks like they adjusted it at annual. Got it adjusted back to 13.9.
 
So if it took ~10 hours for the state of charge to decay enough for me to notice, how long should it take to juice the battery back up?
 
If it got sulfated by undercharging over a long period of time it may not come back at all without special discharging/charging. Depending on how deeply discharged it is, it could take an hour or two of flying to come up to full charge.You could always remove it and put it on a smart charger to see if you can fully charge it or desulfate it if necessary.
 
The voltage never came back up after flying it all summer. A self-powered desulfator didn't seem to help. After a week on the batteryminder, however, the resting OCV is now around 12.7, or >80% SOC, so maybe it was not significantly damaged.
 
Both. When it was in the plane, I was checking the (analog) panel voltmeter and the (digital) engine monitor with the master on, and also a DMM poked into the charger pigtail with the master off. I recently replaced the Concorde with an Odyssey.
 
I should test it again now that I have a new battery.
 
RG25XC
 
Those ( R25XC) are pretty good batteries. I run the 35 version and a Concorde charger/ maintainer. At least you stayed away from the pink nightmare !

It sounds to me like you have a sticky voltmeter, and your voltage regulator might be set a bit low...with that being said, I am not your A&P....best of luck with your new installation and Happy New Year !
 
Welp, that looks like it may be a 1950 part.contactor.jpg
 
Half a volt difference between master off and master on.
 
GeorgeC said:
It has high standards and needs a darned good reason.
Click to expand...
Have you put a DVOM in parallel with the aircraft voltmeter circuit and is the DVOM slow to indicate as well?
 
GeorgeC said:
Half a volt difference between master off and master on.
Click to expand...
Hypothesis busted, the voltage drop persists despite a new solenoid, and the voltage is still slow to come up. Something else must be sucking some current with the master on.
Bell206 said:
Have you put a DVOM in parallel with the aircraft voltmeter circuit and is the DVOM slow to indicate as well?
Click to expand...
I'll try that next time.
 
GeorgeC said:
Hypothesis busted, the voltage drop persists despite a new solenoid, and the voltage is still slow to come up. Something else must be sucking some current with the master on.

I'll try that next time.
Click to expand...

Then pull all circuit breakers or remove all fuses. Turn on master and reset each breaker one at a time till you see a voltage drop, or better yet get a clamp on ammeter and check each circuit. The ammeter will show the current flow to each circuit. Keep a log of your readings.
 
Old battery cables will drop voltage. Clean all the terminals. I also run the Plane Power Alternator in my C150. I run at 14.0v. Same battery.
 
You're likely dealing with a ****ty voltage regulator that is on its way out.
I have experienced the exact same, the original voltage regulator and overvoltage protector went their own way.
Mind you the voltage regulator provides the "field voltage" to the alternator to tell it what of its production to provide.
I don't mean to stress you but it is something you want to take care of, especially if it is an original one and get this.
If you have it done, its about a 1000 exercise but worth it. I had the regulator fail during flight one time, running on battery only with retract gear
man I tell you the stress add it gives.
The battery voltage doesn't rise over time, it is likely your regulator/alternator that is affect here.
And the concord batts btw are solid, I had to replace one after 5 years of usage, as I was running it dry especially in winter time though it recovers nicely
WITH a good alternator/regulator. Look at those first.

Simple test you can do is to hook up a voltage meter on the field lead of the regulator/alternator and see what it says, I betcha that one is not going to show what you need (is 13.9V)

xander
 
xander75 said:
Simple test you can do is to hook up a voltage meter on the field lead of the regulator/alternator and see what it says, I betcha that one is not going to show what you need (is 13.9V)
Click to expand...
You'll never see full battery voltage at the field terminal. There are resistors in the regulator that prevent that. There should be maybe around 10 volts if the engine isn't running, and it should drop as the RPM comes up and rise as you add loads by switching on lights and other stuff.
 
Dan Thomas said:
You'll never see full battery voltage at the field terminal. There are resistors in the regulator that prevent that. There should be maybe around 10 volts if the engine isn't running, and it should drop as the RPM comes up and rise as you add loads by switching on lights and other stuff.
Click to expand...
Maybe I should enhance my write up that you'd want to see the 13.9 when the engine is running and the alternator is working.
I agree with you that the batt only voltage needs to be 10+ in order to start the engine, but from my experience if your battery is on the way out it shows a drop on the initial voltage when you flip on master and of course dropping definitely during start.

Point I was making is merely to look at battery and alternator separately...
x
 
You must log in or register to reply here.
Back
Top