bsacks05

bsacks05

Well Known Member
I have been flying my -9 for 7 years and 800 hrs. The ignition is wired mostly per Vans simple schematic. I just installed a new PC680 battery, started the engine, the voltmeter rose above 16 and the alt breaker popped as it should. Shut down and restarted as always with the master and alt on, then hit the starter. Same thing happened twice more. Assuming I hooked up the new battery correctly, and I can't see anything amiss, why is this happening?
The old battery was barely able to turn the prop, but the new one turns it with authority, as it should.
The alternator is externally regulated. I ordered a new voltage regulator, circuit breaker, and master/alt field toggle switch. They should be here in a few days.
It is hard to believe that one of these components would give up at the same time I installed a new battery and I'm thinking its something I did wrong while installing the batt, I just can't imagine what that could be.
Any ideas?
 
Sounds like the regulator simply failed. Could have been on its way out anyway, and the installation of the new battery was just what pushed it over the edge. One of the best choices for an external voltage regulator is an automotive unit for a mid 1970's Ford LTD with big V8 engine... about $27 at most auto parts stores. That's what I replaced mine with.
 
I got nothing - -

If it was low initial charge, then the voltage would not run away.

Voltage on the wire going to the regulator should be the same as measured by your instrumentation. If it is not, then the regulator would not be getting the correct signal. The only thing that comes to my mind is a bad ground to the alternator that completes the circuit. (or wire back to ground through the engine)

Is there a single ground wire on that side of the battery?

I would go back and check all the connections one step from the battery to be sure they are tight.

Let us know what you find, as a tech teacher, you probably already know this.

Good Luck.
 
bsacks05 said:
......... I just installed a new PC680 battery, started the engine, the voltmeter rose above 16 and the alt breaker popped as it should. .......
Click to expand...

I have always thought that CB's "popped" due to over-AMPerage, not over-Voltage.

OTOH, if you have an over-Voltage protector that crowbar's the system, then the CB will pop. Not due to the voltage, but due to the crowbar, which is essentially a SHORT across the system. The Short causes extremely high AMPerage, which in turn trips the CB.

Can you describe your entire electrical charging system?

A new battery shouldn't change anything.
 
Bruce,

I am inclined to think that you have a coincidental failure.

Pete is correct. Breakers pop on amps, not volts. That being said, with ohms law we see that with a given resistance amps will rise commensurately with a rise in voltage.

That being said, i am guessing that there is no crowbar installed?

Conversely, start your engine with the alternator offline. Turn on the alt field and, watch your amps closely. What instrumentation do you have for that? See if it pops immediately. Is there a slow rise?

There is a possibility of a dead short, a high resistance short, over-voltage allowed by the voltage regulator or a bad alternator.

Do this with the old equipment and replace the regulator first.

Repeat the steps with each change.

Your battery voltage is probably fine based upon the enthusiasm for which the engine ignites, but putting your new battery on a charger while you are tinkering on the other components will ensure its longevity!

Keep us posted!

:confused: CJ
 
This may not help you, but just in case you can use this info:
Don't know what battery/charger system you have but I was just doing some avionics tinkering on another plane that has an Odyssey PC680 and the Odyssey charger. I had the charger hooked up while I was piddling and the voltage kept going down and down. So I called Odyssey and asked why the charger would not keep the battery up and charged while I had the master on.

They said having the charger hooked up with the master on would only shorten the life of the charger and that it would not keep my battery charged during the time the master switch was on.
 
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Running your avionics on a battery charger is defintaely NOT RECOMMENDED.

When you done "playing", turn everything off and then charge the battery.
 
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If you have too much resistance in the field circuit or bad connections this will lead to an overvoltage protection trip.

This is more likely to happen with a discharged battery, since that's when the alternator is drawing the most field current. The greater the field current, the larger the voltage drop due to the previously mentioned resistance.

It's likely that your new battery was somewhat discharged on startup, so the first thing to try is to charge it right up. Being a new battery, it will be able to accept charge at a higher rate than your old battery. Your alternator will see this as a larger load, similar to a discharged battery.

So a new, slightly discharged battery is quite stressful on your alternator/regulator wiring compared to your tired old battery. It's not a coincidence, it's science.

Cheers
 
Walt said:
As blueflyer eluded to, running your avionics on a battery charger is defintaely NOT RECOMMENDED.

When you done "playing", turn everything off and then charge the battery.
Click to expand...

...not sure why you quoted me?

I never said to run avionics on the battery charger.

Walt, I see that you savvy yourself a professional.

There are plenty of those!

Thanks for your two cents!

:cool: CJ
 
I would put in the old battery with a charge and double check the system with the old setup. That would eliminate chasing around if the new battery was the culprit some how. :)
 
CJ:
I quoted "blueflyer" not you but sorry if I stepped on your toes, that wasn't my intention, my point was merely that it's not a good idea to run your avionics on a battery charger.
I edited out the quote in my previous post to avoid any confusion/misunderstanding on what I was attempting to convey.
Walt
 
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I had to dig out my wiring diagram and there is no crowbar installed for over voltage protection. I will install a new regulator in a few days and top off the battery charge. It is a simple system and I'm confident I will find the culprit. Thanks for the suggestions. I wired my plane so long ago and have had no problems so it is taking me a while to relearn how everything works.
 
thanks for the tip.

Walt said:
CJ:
I quoted "blueflyer" not you but sorry if I stepped on your toes, that wasn't my intention, my point was merely that it's not a good idea to run your avionics on a battery charger.
I edited out the quote in my previous post to avoid any confusion/misunderstanding on what I was attempting to convey.
Walt
Click to expand...

thanks for the tip. tonight I wired a float charger connection to the aircraft.
 
Problem solved.
A new voltage regulator solved the problem. My best guess is that I accidentally induced a short in the old regulator as I was wrestling with the old battery in order to remove it. My regulator is positioned above the battery and one of the tools I was using must have contacted the + terminal and the regulator at the same time. That's my best uneducated guess. I also topped off the new battery with a full charge and maybe that helped as well.
Happy again and back in the air!
 
Bruce, thanks for the follow up and final solution. Your explanation makes sense.
 
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