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Eis and GRT EFIS voltage

texdog

Well Known Member
I'm reading 13.8 eis voltage. I have the EFIS alarm set at 12 volts. Today at 6500 ft. 72 degrees OAT. The EFIS voltage would vary between 11.8 and 12.3 and set the alarm off. Odessie680 battery, Plan Power alternator. Is this normal? Could it be the voltage regulator? The Odessie battery is 2 years and 300 hours old. Any ideas are appreciated.

Thanks,
Fred
 
13.8V is marginal for a flooded cell battery; too low for an AGM. You're lucky the battery is still working. If voltage is down to the 12V range with engine running, the charging system isn't working. Could be the regulator or the alternator itself.
 
13.8V is marginal for a flooded cell battery; too low for an AGM. You're lucky the battery is still working. If voltage is down to the 12V range with engine running, the charging system isn't working. Could be the regulator or the alternator itself.

+1
You should set your alarm at 13.5 volts or so, so you immediately get an alarm if the alternator goes off line.
 
Hold on. This may not a battery or charging system problem if what you reported was 13.8 EIS and 12 on the EFIS at the same time. I also assume it has been this way since the beginning. It would be either an electrical system architecture issue (diode locations or style selection, or backup battery loocation) or a poor connection issue.

Are you the original builder and do you have intimate knowledge of the wiring or detailed records of same?
 
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Eis EFIS voltage

Thanks gentlemen, I'm not the original builder and the GRT's were added after the original build. It has worked perfect for the last four years. I thought I would start this morning with the battery voltage and follow Plane Powers trouble shooting guide. I will be the first to admit that I'm weak on electrical. I think it's charging, because I've flown it 8 hours since this started. It maybe a lose connection or corrosion. I appreciate ideas.
:confused:
 
EIS VS EFIS VOLTAGE

I know more now. The alternator is charging and the battery is staying charged.
The big issue is differential voltage. EIS is 12.5 static, battery, the EFIS is 11.5 or 11.6. GRT technical support is on vacation, but I was told the voltage should be similar. Also the standby battery, which I can't find, is 12.3. I have reset all of the cannon plugs. I would appreciate and suggestions.
Thanks,
Fred
 
My recomendation would be to start tracing the efis power feed line from the efis going upstream and measure the voltage at each connection point (switch, fuse, diode, etc) and find the point that the voltage goes up to 12.5 like the EIS reports.
 
Kahuna was correct

Kahuna is the man, he said it was the charging system! I replaced the Plane Power alternator with a different alternator and everything is back to normal. No help from Plane Power on this, they don't really support the alternator anymore.
I'm good, thanks.
 
Congratulations on the fix.

I am very curious what the two systems are reporting for voltage now.
The reported split between the EIS (13.8) and EFIS (12) should not have anything to do with the charging system.
 
EIS vs EFIS

first run up, EIS was 14.2 EFIS was 13.8. It did vary a little .1 or .2. I installed a Nippon Denso part number 213-8331, pigtail was from a old part number 14824. I'm leaving for Wyoming next week, we will see how it goes.
 
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