Ammeter shows a full load at start up.

Unit74

Unit74

Final Approach
Joined
Mar 8, 2014
Messages
6,989
Display Name
Unit74
After engine start, the ammeter shows a full right deflection and stays there for a few minutes. I've cycled the alternator, left the avionics switch off and it eventually settles down on its own timeframe. I'd say within 8-10 min it's settled to a normal load indication.

It has a Plane Power alt and regulator if that helps. Plane is flown almost every weekend.

Any idea what is up? :dunno:
 
Sometimes one very weak cell in the battery will cause the voltage to sag a lot and force the alt into a high charge mode for a while. Before starting next time do an electrolyte check with a hydrometer and see if the cells are all pretty close.
 
Unit74 said:
After engine start, the ammeter shows a full right deflection and stays there for a few minutes. I've cycled the alternator, left the avionics switch off and it eventually settles down on its own timeframe. I'd say within 8-10 min it's settled to a normal load indication.

It has a Plane Power alt and regulator if that helps. Plane is flown almost every weekend.

Any idea what is up? :dunno:
Click to expand...

normal operation, it is simply showing the battery being charged after start.
 
If this was a bad cell in the battery, the engine would be hard to turn over with the lower voltage and thus current through the starter. The OP did not state that so it is hard to judge. But even then, the battery should not take 8-10 minutes to recharge at full charging current.

How much current does the amp meter show afterwards? Does the gauge have any numbers?

Otherwise, I'd agree with an out-of-calibration gauge. They use a shunt, they do not stay exactly precise over multiple decades.
 
What does max deflection represent and what can your alternator produce? It's not uncommon for an alternator to be at full output after start, especially if you sat there for a bit with everything fired up programming everything before starting. If you have PP alternator and factory gauge, you may have an alternator with twice or more the capacity of the stock one, so burying the gauge may not be abnormal, though I agree that if you start experiencing other electrical issues, it is an indicator for a sulfated cell in the battery, although then the load will never drop to 'normal' as there will always be an unaccounted for extra load. You may not be able to see this on a crudely calibrated instrument.

At this point I would just keep my eye out to make sure the situation remains consistent (allow for fluctuations in temp) and you have no other symptoms of electrical problems. If nothing shows, I would think it something that does not require fixing.
 
No, no other symptoms. Plane will turn over quickly and not lug like it has a dead battery. The middle of the gauge shows 35 amps and in NO, it sits right there or slightly above it.

I usually fire it up and then program the GPS to bring oil temps up.
 
Unit74 said:
After engine start, the ammeter shows a full right deflection and stays there for a few minutes. I've cycled the alternator, left the avionics switch off and it eventually settles down on its own timeframe. I'd say within 8-10 min it's settled to a normal load indication.

It has a Plane Power alt and regulator if that helps. Plane is flown almost every weekend.

Any idea what is up? :dunno:
Click to expand...

Has there been a change or did you just start noticing it? It sounds normal to me from back when I had original gauges. Part of the reason I changed gauges was that those swinging needles didn't tell me jack.
 
Unit74 said:
No, no other symptoms. Plane will turn over quickly and not lug like it has a dead battery. The middle of the gauge shows 35 amps and in NO, it sits right there or slightly above it.

I usually fire it up and then program the GPS to bring oil temps up.
Click to expand...

mine does this also.....I suspect my battery might be a tad weak and the alternator works a little after startup to restore the battery.
 
Unit74 said:
No, no other symptoms. Plane will turn over quickly and not lug like it has a dead battery. The middle of the gauge shows 35 amps and in NO, it sits right there or slightly above it.

I usually fire it up and then program the GPS to bring oil temps up.
Click to expand...

You don't have any indications of a problem I would be looking to address. I would add up my operating loads though and see if they add up to 35 amps.
 
Checkout_my_Six said:
mine does this also.....I suspect my battery might be a tad weak and the alternator works a little after startup to restore the battery.
Click to expand...

Actually it works the opposite, the old batteries get sulfided and the plates become smaller. they will discharge quicker and charge quicker.
 
Tom-D said:
Actually it works the opposite, the old batteries get sulfided and the plates become smaller. they will discharge quicker and charge quicker.
Click to expand...

Tom is right on. There's nothing to see here.
 
Unit74 said:
then program the GPS to bring oil temps up.
Click to expand...

I wish I could program my GPS to do that... maybe time to upgrade.

I do wonder if it is a normal charge with the ammeter reading a little on the high side. I don't know what you are equipped with but on my PA28-180 we run a little over 20 amps; a later model Arrow I fly with fairly extensive avionics seems to run around 30. 35 seems high to me unless you have a really loaded avionics stack and/or so power hungry landing light(s) running.
 
If I apply a load of 200 amps for 5 seconds to a battery while cranking the starter how long will it take an alternator to recharge the battery at 35 amps?

There is nothing wrong here.
 
Tom-D said:
Actually it works the opposite, the old batteries get sulfided and the plates become smaller. they will discharge quicker and charge quicker.
Click to expand...

Until you get a sulfation bridge, then the battery never charges and always is draining itself.
 
Henning said:
Until you get a sulfation bridge, then the battery never charges and always is draining itself.
Click to expand...

When you do the battery maintenance as required by the ICAs for the battery, you never see this.
 
bnt83 said:
If I apply a load of 200 amps for 5 seconds to a battery while cranking the starter how long will it take an alternator to recharge the battery at 35 amps?

There is nothing wrong here.
Click to expand...

Trivial question. You have used 1000 amp-seconds. It will take a 35 amp alternator about half a minute to put out 1000 amp-seconds.

Jim
 
Tom-D said:
When you do the battery maintenance as required by the ICAs for the battery, you never see this.
Click to expand...

:rofl::rofl::rofl: People doing battery maintenance...:rofl::rofl::rofl:

Usually what I do when I come across one is drop on concrete from about 6" a couple of times. Typically you can save and refresh a sulphated battery 3 times this way by knocking the crap off the plates to the bottom.
 
Tom knows that properly charging the battery on a modern smart charger will take care of any sulphated plate issues and will rejuvenate the battery very effectively.
 
Stewartb said:
Tom knows that properly charging the battery on a modern smart charger will take care of any sulphated plate issues and will rejuvenate the battery very effectively.
Click to expand...

It sure will, yet still...:dunno: Even using a charger with a desulfation pulse, if you have a bridged cell, dropping it and breaking the bridge still helps.
 
I think dropping it to the floor.....just short of busting it up would be fun though. :lol:
 
Make sure the Bendix on the starter isn't hanging too. If it suddenly comes back quickly versus a slow return is the way to tell.
 
Last edited:
You must log in or register to reply here.
Back
Top