I could use some suggestions on what could be causing the subject issue with my airplane and what diagnostics we might do to narrow down the possibilities. I've already emailed my local shop, but know that they are swamped with other big ticket install work and short staffed, so anything I can do ahead of time could be the difference between a quick resolution and weeks on the ground.
Below are two graphs of charging amps and battery voltage for my Tiger. One is from a ca. 30 minute flight and is representative of what I expect (i.e., normal). Charging current (light blue trace) is high and positive immediately after starting (when the black, voltage trace jumps to ca. 14). Current then drops as the battery charge withdrawn during charging is replaced by the alternator. Eventually charging current stabilizes at about 1 amp and voltage is kept between about 13.9 and 14.1.
Startup for the abnormal profile is generally normal with high charging current initially falling as the battery is recharged. This time, however, shortly after the plane was airborne charging current went negative (discharged). I caught the anomaly at about the 5 minute mark and recycled the alternator side of the master switch. Current dropped to about -8 amps with the switch off, then back to positive (briefly) with the switch back on. Battery voltage appeared normal, though, and neither it nor current changed systematically with pitot heat or radios on/off (sorry, I did not record where I did those tests).
Since voltage was holding, I decided to continue the flight. Voltage remained within 13.9 -14.0 (maybe biased down 0.1 V vs. what I considered normal) despite about 10 minutes of a ca. 2 amp discharge reading. Near the end of the flight charging current increased from -2 to ca. -1, then to ca. +1 for a couple of minutes, then back to down to -1 as the battery voltage increased from 13.9 to 14. Voltage continued to rise and reached 14.1 despite showing a discharge current.
I later restarted the airplane hoping that power cycling the CGR-30P would eliminate the problem, but it did not. Current went negative in about 2 minutes, and after about 5 minutes it dropped to -15 amps for about 2 minutes, then back to -2 amps, then back to ca. -15 amps, then back to -2 amps, then stabilized around zero. Battery voltage was about 13.8 Volts during this time, but rose to about 14.1 Volts after about 2 minutes at zero charge current. I checked the battery voltage immediately after shutdown and it was 13.6 V. It was 12.8 V after resting for about 8 hrs.
For background, voltage and current readings are from an EI CGR-30P with its current shunt wired to show battery charge/discharge current. Battery is a 3 year old Concorde sealed AGM RG-25. Voltage regulator is a 19 year old solid state Zeftronics. I don't recall the brand or age of alternator.
What could cause this behavior. Failure of the CGR-30P voltage reading that is translated to discharge current is an obvious potential culprit. But this is a relatively new (ca. 3 years old) solid state device which appears to be working normally otherwise. Any suggestions on how to test whether it is the Volt or Amps reading(s) that is (are) in error? Could battery failure somehow explain this behavior? Or loose/dirty connections? Or worn alternator brushes? I don't see how, but also don't claim particular expertise. Are there readings I can take which will help narrow down the cause?
Thanks in advance for your assistance.
Below are two graphs of charging amps and battery voltage for my Tiger. One is from a ca. 30 minute flight and is representative of what I expect (i.e., normal). Charging current (light blue trace) is high and positive immediately after starting (when the black, voltage trace jumps to ca. 14). Current then drops as the battery charge withdrawn during charging is replaced by the alternator. Eventually charging current stabilizes at about 1 amp and voltage is kept between about 13.9 and 14.1.
Startup for the abnormal profile is generally normal with high charging current initially falling as the battery is recharged. This time, however, shortly after the plane was airborne charging current went negative (discharged). I caught the anomaly at about the 5 minute mark and recycled the alternator side of the master switch. Current dropped to about -8 amps with the switch off, then back to positive (briefly) with the switch back on. Battery voltage appeared normal, though, and neither it nor current changed systematically with pitot heat or radios on/off (sorry, I did not record where I did those tests).
Since voltage was holding, I decided to continue the flight. Voltage remained within 13.9 -14.0 (maybe biased down 0.1 V vs. what I considered normal) despite about 10 minutes of a ca. 2 amp discharge reading. Near the end of the flight charging current increased from -2 to ca. -1, then to ca. +1 for a couple of minutes, then back to down to -1 as the battery voltage increased from 13.9 to 14. Voltage continued to rise and reached 14.1 despite showing a discharge current.
I later restarted the airplane hoping that power cycling the CGR-30P would eliminate the problem, but it did not. Current went negative in about 2 minutes, and after about 5 minutes it dropped to -15 amps for about 2 minutes, then back to -2 amps, then back to ca. -15 amps, then back to -2 amps, then stabilized around zero. Battery voltage was about 13.8 Volts during this time, but rose to about 14.1 Volts after about 2 minutes at zero charge current. I checked the battery voltage immediately after shutdown and it was 13.6 V. It was 12.8 V after resting for about 8 hrs.
For background, voltage and current readings are from an EI CGR-30P with its current shunt wired to show battery charge/discharge current. Battery is a 3 year old Concorde sealed AGM RG-25. Voltage regulator is a 19 year old solid state Zeftronics. I don't recall the brand or age of alternator.
What could cause this behavior. Failure of the CGR-30P voltage reading that is translated to discharge current is an obvious potential culprit. But this is a relatively new (ca. 3 years old) solid state device which appears to be working normally otherwise. Any suggestions on how to test whether it is the Volt or Amps reading(s) that is (are) in error? Could battery failure somehow explain this behavior? Or loose/dirty connections? Or worn alternator brushes? I don't see how, but also don't claim particular expertise. Are there readings I can take which will help narrow down the cause?
Thanks in advance for your assistance.