Plane Power Alt doing weird stuff...

I have seen lots of discussions about PP and other alternators here on VAF and learned a ton from them.

The PP alternator in our -7A recently started sending 55+ amps to the shunt as soon as we turned the switch on. The VPX showed it going to the Battery. (Did this with the old battery and the new EarthX). We replaced the regulator with a new one and Allen at PP hooked us up with a new plug to eliminate variables. ALLEN is the man and has been AMAZING to work with. He really cares about his customers.

Per Allen?s direction, in an effort to verify that the VPX was reading correctly, we wired in a mechanical gage and verified it was in fact sending all that power to the Shunt.

It settles down anywhere from 1-4 minutes after the switch is turned on and is functioning properly when loads are added (lights, strobes) or removed. I remember my old 172 having a large draw at first... however this didn?t happen with this plane until recently

It freaks me out seeing all the alarms on the Dynon go off when I turn the alt on.... recently is taking longer to settle down and is going above the 60-amp output the alternator is rated for. Have seen 64 amps.... doesn?t blow the 60-amp fuse on the panel

I would love some good old VAF wisdom on this one.... and if someone here in Oregon has a PP alternator we could use to test prior to just purchasing another that would be amazing!

Thanks

David ?Red? Hyland

David,

Apples to oranges, maybe --

For a LiFePo battery (e.g. Earthx), you will see a current draw at the shunt (provided that the shunt is inline between the Alternator and the Battery) of roughly ~60A for several seconds - a minute, right after the engine has started and the alternator is brought online. It's quite disturbing if you've been using a lead-acid, or RG, or drycell battery (eg. PC680).

This behavior is described in the EarthX manual, page 28.

Hmmmm

What's the OVP doing when all of this is going on?

AMPs not Volts...

OVP should only act if the VOLTAGE exceeds a predetermined limit -- say 16VDC.

In the OP's case, I suspect that the Voltage is right around 14.5V when the alternator is running...

HGIC said:

The PP alternator in our -7A recently started sending 55+ amps to the shunt as soon as we turned the switch on.

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At what voltage?

(Did this with the old battery and the new EarthX).

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As noted, a lot of amps initially would be expected with a lithium iron battery. As for the lead-acid battery, if the alternator's output voltage is normal, I think it was simply rather dead.

I'm running the same alternator and EarthX ETX900 battery, and I frequently see 40-50 amps for the first minute after start, quickly tapering down as the battery voltage comes up to normal and levelling off to hold it.

If the voltage is not rising out of nominal, I would tend to call this normal behavior.

Where does all that juice go?

Assuming the Voltage regulator keeps it at 14v where do all those amps go? In most systems the Flap motor and other things like lights may be ON or are "connected to be always On" They may not be moving but what does the Amperage do to those systems? Or does the battery just eat those Amps?

Battery

RV7ForMe said:

Where does all that juice go?

Assuming the Voltage regulator keeps it at 14v where do all those amps go? In most systems the Flap motor and other things like lights may be ON or are "connected to be always On" They may not be moving but what does the Amperage do to those systems? Or does the battery just eat those Amps?

Click to expand...

The EarthX LiFePO will do that. That chemistry has little hysteresis for discharge/charge curves so a dip in SOC can demand a lot of amps with little voltage difference from the battery free state. The constant voltage charging system is not well matched to that LiFePO characteristic, but very suited to the PbA chemistry.

BillL said:

The EarthX LiFePO will do that. That chemistry has little hysteresis for discharge/charge curves so a dip in SOC can demand a lot of amps with little voltage difference from the battery free state. The constant voltage charging system is not well matched to that LiFePO characteristic, but very suited to the PbA chemistry.

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sorry to re-ask... Does that mean all equipment is safe? and this is "OK"?

Trying to understand the situation here. A couple of posts said after engine start and you brought the alternator online. Are you not starting the engine with the alternator online already? Could that be a problem?

when I flew 2RD home from Safford, AZ there was no AMP surge like it has now and the PC680 battery was newly installed during our pre-purchase.

This condition began after we had our A&P install our Smoke System and Supertracks. It sat for a week, not on a tender. I didn't fly it home that night, put in on his charger and when I picked it up that next day, when the alt was turned on the amps went to 55.... and lowered back down to normal within 1-min. We continued to experience this and learned that the newly installed battery was dated 2016 and had been on the shelf for nearly 4-yeas.... so we bought the EarthX

Our checklists, and various POH's I have researched show starting the engine, then turning on the Alt.... open to suggestions here...

I also run an EarthX battery, with B&C alternator.

I start the engine then turn on the alternator.

After cranking, it is normal to see 40-50+ amps for a short time as the battery is recharged.

As someone mentioned above, this is spelled out clearly in the EarthX manual, as it is a common question for them. And gave me concern the first time I saw it!

also... the VPX shows Volts are normal and the AMPS are being directed to the Battery (both with the new and old battery)

HGIC said:

also... the VPX shows Volts are normal and the AMPS are being directed to the Battery (both with the new and old battery)

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Volts <> Volts
With your VPX or other system, the bus voltage measured will vary depending upon where and when the potential is measured. e.g. With the engine/alternator off with a fresh/charged PC680 battery, you should expect to see a voltage of ~12.2V, until you crank the engine and the volts will drop to 10V or so, and then once the alternator is spinning & turned on, the volts will go to > 14.0V (14.5V)....With an EarthX battery, the resting fully charged voltage is ~13.2V, dropping to 11V during cranking and then rising to 14.5V once the engine/alternator are running.

Charging:
Charging occurs when the Battery is connected to a circuit/bus with a higher potential (voltage) than the battery itself.

The chemistry of the battery, the number of cells in the battery, the internal resistance of the battery, and voltage potential state will determine how much current is drawn (sunk) by the battery.

The C rate of LeadAcid, AGM, Gel, ALC, etc.(e.g. Odyssey PC680) is between .1 and .05C, compared to a C rate of almost 1C for LiFePo4 (EarthX). So you should expect the charging current of an EarthX battery to be quite a bit higher for shorter periods than your PC680.

On Alternators:
Look at the Plane Power spec sheet that came with the alternator. You will notice that the 60 AMP alternator (AL12-EI60) is really capable of producing current >70A following a curve that's proportional to the alternators rotor speed.

Someone asked if this was safe for the equipment. Yes, this is safe, normal, and expected.

Good reading material at https://batteryuniversity.com/learn.

DanH said:

At what voltage?



As noted, a lot of amps initially would be expected with a lithium iron battery. As for the lead-acid battery, if the alternator's output voltage is normal, I think it was simply rather dead.

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+1

If my alt was pumping out 50 amps for a few minutes after startup and then settled down, I would assume that my lead acid battery was failing and due for replacement. A failing battery often struggles to hold a charge. This is normal for a lithium.

Larry

Thanks for all the information! Coming from the Cessna world I have a lot to learn and I really appreciate all of your help.

leave it on

HGIC said:

...Our checklists, and various POH's I have researched show starting the engine, then turning on the Alt.... open to suggestions here...

Click to expand...

Seems people have had good luck with both methods.

Our checklists, and various POH's I have researched show starting the engine, then turning on the Alt.... open to suggestions here...

Click to expand...

This (similar) alternator and internal regulator system was used in small 4 cylinder cars in the 80's (Suzuki Samurai & others). I dont know of any car owners that turned the alternator on AFTER starting the car do you? A Lycoming with the same system is no different. Save yourself some grief and turn the Alternator "excitement" (internally regulated alternator) power on when you turn the master on and BEFORE you start the engine. Easy

For a short while I was turning on only the battery side of master to start the engine then turning on the alt. I had read this sends a couple more amps to the starter. Soon after my alt failed. I have to idea if it was related. Then I read something in a post here on VAF for a reason NOT to leave alternator off during start up and it sounded good so I stopped and went back to what I had always done. I don't remember what the posters reason was to keep alt on during starts. Anyway just my experience.

What engine RPM are you energizing the alternator at?
My recommendation is to start the engine with alternator "off",
then, after engine is running smoothly and oil pressure has stabilized, pull the throttle to idle and THEN energize the alternator.
Two good things result:
1) Less stress on alternator belt
2) alternator isn't spinning fast enough to spike overvolt, or produce maximum output.
After the alternator has been brought online, then ease the engine rpm up until you see that the regulator (alternator controller) is maintaining proper buss voltage.

I start the engine and then set the idle around 800-900 rmp then engage the alt. I went out and started it today with it on just to see if there was any difference and there was not. It did the same thing.... which I am now believing is normal / acceptable

I have not seen the voltage do anything out of the ordinary... with this regulator or the old one.


Several good things have come from this experience. I have learned a lot... and I now have an extra regulator and an extra plug that is apparently made of solid GOLD judging by the cost to replace via Aircraft Spruce

Li battery

If I remember right, Li batteries normally use a constant current charge, whereas lead acid typically use a constant voltage charge. But for our planes, we only have a constant voltage charge system.

Because of this, I think the immediate high current charge of the Li battery should be minimized. Maybe the best way is to either leave the alt on during start so that the low rpm after start limits the immediate charge current, or the alt is turned on after start when the rpms are low. Just my opinion. Its worth what you paid for it.