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PlanePower Field

D

ddnebert

Well Known Member
I have been flying my -10 for over a year but have noticed a progressive problem with the alternator field. Increasingly, the annunciator light from the PlanePower alternator illuminates on take-off and in cruise, meaning that charging of the battery has stopped. I have an EXP Bus II switch and solid state breaker panel and I have bypassed its overvoltage detection (jumper) since the alternator already has protection built-in and I wished to isolate the problem. I can get 5-30 minutes of charging again after cycling the alternator field switch, but it is a constant hassle to reset while in flight.

I've shed all possible load to determine if there was some excess draw on the charging circuit, but can find no offending item. Charging shows as around 13.3V when the charging circuit is active, which is normal, but drops below 12V eventually when field drops, which is also normal, but it shouldn't be dropping.

PlanePower tells me that the sensing circuits are thermal, detecting overvoltage by excess heat on the wire. Given that I have bypassed the switch panel's detection, my current diagnosis is that the sensing device at the alternator is experiencing too much heat - possibly from the engine exhaust radiant heat and not from the line load, rather than from load. Or, it is possible that the sensor is defective.

Have any of you -10 operators with the standard PlanePower alternator also experiencing charging field loss like this? If not, does it make sense that the alternator might need some heat-shielding? Or, is it probable that the alternator is simply defective in its OV-field processing?
 
I am planning on installing a ss heat shield on #1 exhaust. Also you could try installing a cooling blast tube to rear side of alternator. Our agm batteries can absorb alot of energy quickly.
 
Sounds like your charging voltage is low, the AGM odyssey batteries require 14.2 - 14.7 volts in order to reach full charge.
 
So, perhaps I should measure the voltage coming directly off the alternator (I think I used a #8 wire) for the charge and be sure it is sufficient or replace it. In that case it wouldn't be too much load but insufficient charge. That wouldn't explain why the circuit keeps breaking since I see a constant surplus charge (13V+, greater than 12V) charge when it is charging. It sounds like there might be two things going on here - assuring sufficient charge and not triggering an inadvertent cutout.
 
I installed 6 ga from alt to start contactor with 60a fusible link at s/c. The 6 ga bacl to main bus fuse block. #2 to 925L Odyssey battery.

It is possible that normal avionics & misc loads in addition to a large recharging load is too much for the 8 ga wire.

Is it possible for us to change pp alt output voltage or would it have to go back to pp? I have not started up yet so have no idea what my voltage will be.
 
I usually don't bother with sparky issues, it's too much like my day job. :) And always, the metrology issues... ugh. :D

But I'm bored today, so here goes..

Charging shows as around 13.3V when the charging circuit is active, which is normal...
Click to expand...
No, it's not normal. As Walt indicated, 14.2v to 14.7v at the battery posts is what you want. 14.4v is the typical norm. If you don't see this, your charging system or your metrology is defective.

At 1500 rpm, with all loads (except battery charging current) switched off, measure the voltage at the battery posts with a known good DMM. Voltage should indicate as above.

Enable all the loads in the airplane. A voltage drop of more than a few tenths is bad. Incorrect voltage regulator sense point wiring or inadequate wire gauge can cause this. If the voltage at the alternator post is more than a few tenths higher than the battery posts, you have this sort of problem.

For best charging happiness, the following conditions must be met:
Voltage difference between battery and alternator posts less than 0.3 volts.
Voltage at the regulator sense terminal is the same as the alternator post.
Voltage difference between battery negative post and all other grounds in the system less than 0.1 volt.
Current requested from the alternator is within specified limits.

If these conditions are met and the output voltage is still low, the alternator or regulator is bad. If possible, measure the alternator field voltage. If it is 11 volts or greater and the alternator output is low, the alternator is bad.

...I have bypassed its overvoltage detection (jumper) since the alternator already has protection built-in ...
Click to expand...
This seems to me like an undervoltage problem. What makes you think any overvoltage circuits are activating? :confused:

It's possible that your alternator is shutting down due to a thermal issue, but since you see the issue at take-off, where presumably the alternator has not had time to reach an excessive temperature, it doesn't seem likely.

Metrology note: use extension wires, properly secured, to keep you and the DMM in the cockpit, far away from the whirly choppy thingy. :D
 
I would bypass the EXP buss and install a 7.5 amp breaker for the field. I've seen a number of PP alternators pop the 5 amp breaker, IIRC the PP alt draws around 4 amps for the field so a weak breaker or one on the low side of the spec will nuisance pop.
 
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I think what I am hearing is that the normal charge voltage of 13.8-14.2 volts, which is what a normal regulator is usually set up for, is too low for the Odessey batteries. If this is the case, does any one know if the PP alternator internal regualtors can be adjusted to a higher charge output, or confirm that 14.4 is correct for the Odessey AGM Batteries.
Bill
 
From the Odyssey Literature: Link to Document

In summary here is what Odyssey says about charging

The message to be taken from this graph is clear ? in deep
cycling applications it is important to have the charge
voltage set at 14.4 ? 15.0V. A nominal setting of 14.7V is a
good choice, as shown by the test results.

If the voltage output from the charger is less than 14.2V or
more than 15V for a 12V battery, then do not use the charger.

Standard internal combustion engine alternators with an
output voltage of 14.2V can also charge these batteries.
The inrush current does not need to be limited under
constant voltage charge. However, because the typical
alternator voltage is only 14.2V instead of 14.7V, the
charge times will be longer than those shown in Table 5
 
Walt,
Great post and information. Thanks! BTW, do you have any idea if the PP voltage reg. adjusted upward if required?
 
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