Bubblehead

Bubblehead

Well Known Member
I landed at Jacksboro for fuel and my batt voltage is too low to start the engine. Anyone close that came give me a jump? I have a charger connector accessible from the cockpit if you have that style connector. Call 512-850-8339 if you can help.
 
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Back home ok

Thanks to the people who called and offered help. I hitched a ride in a Cessna 172 to Hicks where my wife picked me up with tools and battery chargers and we drove back to Jacksboro.

Now the embarassing part, offered here for either your enjoyment or education.

I pulled the rear seat and battery access cover and charged the battery. Still no go.

I pulled the rear baggage floor to check the battery terminals and connections. Everything beautiful, just as it was at the condition inspection in April. Still no go.

I crawled under the panel and checked the wiring to the starter switch. Everything looked good, still no go.

I took off the upper and lower cowls to cehck the wiring to the starter and solenoid. Everything tight and clean. Still no go.

So I'm sitting in the cockpit wondering what to do next, or actually what brand and strength of alcohol to buy to drown my sorrows, when I notice a circuit breaker is tripped. I push it in, and the engine turns over! UGH. All that work and a Saaturday wasted and I should have double checked all the breakers!

I'm not sure why the alt field breaker tripped, and did not know the starter solenoid circuit was on that circuit too. I'm not the builder. I need to break out Aeroelectric info and check the starter circuit out again.

The interesting thing is that on the way to Jacksboro there were the cockpit indications that the field had tripped. I was flying along with little electrical load and the EIS 4000 gave me a low amp alarm. I get that from time to time when there is little or no load on the electrical system so I pressed reset and did not think twice about it. From there on I was apparently not charging only drawing from the battery.

My current sensor is on the alternator cable not the battery. I am now considering changing it to the battery cable so I will know when the battery is discharging. I think I'll also reread the threads on where to locate the current sensor too.

So I had a couple of short but nice flights and a nice education on Saturday.
 
It sounds to me like your alternator field breaker tripped in flight. You then ran your battery down. See, your Saturday wasn't wasted after all! :)
 
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I too have an EIS 4000, you should probably turn on the warning for batt voltage <13V. That will _really_ show that your alternator is now offline. I've found the current based sensor from GRT is not as reliable.
 
Guy - You're right. Saturday was not wasted because I learned something new about the plane.

Kevin - good idea. I just checked my notes and I still have the low voltage alarm set to the 11.0 V like it came from the factory. I will raise that before the next flight.

13.0v? What do other people have their low voltage alarm set to?
 
12.8V is some magic number :) I think I saw it from 'lectric Bob in one of his notes.. too low for alternator, and too high for battery alone..

It is OK to have a low-voltage warning when engine is not running!!! but if it comes up in flight.. something's up..
 
Setting the low volt alarm to 13V sounds kinda weird on a 12V system, but it works. My PC680 battery has a normal "static" voltage of around 12.4 volts, but when the engine and alternator is churning the voltmeter shows 14.4 volts. Find out what your usual output voltage is and set the alarm somewhere just below so you'll instantly know when the alternator quits. I think mine is set at around 13.5, maybe 13.8. With the alarm set at 11V, you might not know the alternator is gone until you've been running on battery alone for awhile and it's well on it's way to draining down...
 
Where you set the alarm does depend on how your system is built, and what the "normal" voltage reads at the point you pick off the voltage measurement. For instance, if you cross an isolation diode, you might have a .5 - .8 volt drop right there. I'd look at what you normally get when everything is working well, and set the alarm a little below that. An arbitrary number won't necessarily work on every plane.

Paul
 
I looked at the data from the EIS and the normal system voltage is 14.4 to 14.6. I may try a setpoint of 13.5 so I get as early as indication as possible.

In another post I'll tell more but Saturday's flights were the first two flights with the EISMate software and a Palm T2. In a nutshell, the screen is too small to be of much help but it does include a data logger. That's the main reason I bought it.

My original mounting position was a little too low also. I will change it this weekend and try it again. Someday I'll have an EFIS with datalogger but for now this will have to do. It was nice coming home and checking the data to see what went on with EGTs and CHTs vs fuel flow and to look at battery voltage. I could not really tell when the alt field tripped. I did not have any electrical loads on except avionics and battery voltage stayed above 14 volts throughout the last part of the flight. When I turned the master switch on for startup I only saw about 12.6 volts though. The battery will get changed now. This is the same battery that was in the plane when I bought it 2 years ago, and the log books do not show a battery change so this may be the original Concorde RG-25XC from the plane's test flights in 2001.
 
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