What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Is My Battery Going Bad?

Bill_H

Bill_H

Well Known Member
Patron
170 Hrs, Battery arrived in late 2011 so ~4 years old.

So recently I didn't fly for about 5 weeks. I leave the battery on a maintainer. I get in and master on - and the voltage is low, about 11.8. It barely cranks but she starts up and the voltage goes up and it charges in flight. Made three short hops that day - 15 min, 15 min, 15 min, and the the charging current started out high and went down. No problem with the subsequent two starts and voltage was above 12.

Popped the cowl and all connections are good.

Ending voltage with engine off was good - 12.3 or so. So I plugged in the maintainer again (after "rebooting" it just in case.) After a few days, the battery voltage (maintainer disconnected) is now 12.2.

I turn on the master, with fuel pump on, and it drops to 11.8. With avionics master off, Skyview shows 4 amps being drawn, which is typical for that condition before engine start.

Master off, the voltage is back to 12.2 at the battery.

Comments?
 
Fully charged voltage should be close to 13 volts. Based on reading other forums, I do not think that it is good for an Odyssey to be left on a maintainer. The 13.8 volts from the Ducati regulator is almost 1 volt less than the Odyssey recommended charging voltage. After flying, I connect a Schumacher 1562 chager/maintainer to the PC680 while downloading flight data. I leave the charger/maintainer on overnight and remove it the next day. AGM type batteries do not need to be continuously connected to a maintainer. The PC680 will hold a charge for weeks. My battery is still good after 5 years.
 
Last edited:
My original battery still going strong after 5 years. I rarely put a charger on it. Airplane just sat for 2 months between flights while I had the lenses upgraded in my integrated optical sensors. Started right up at about 30 degrees F with no preheat.
 
Fully charged voltage should be above 12.5 but when you turn on master there is a load and it will be less. Check voltage with no load, I believe your battery is ok.

Your system must have a keep alive load when master is off. I deliberately made sure mine does not and voltage stays up for weeks with not charger. The parasite load may be the EFIS system, some require it to provide short start boot up. My GRT requires about 2 minutes without keep alive power, no big deal takes at least that long to get temps up anyhow.

These batteries are good for long term service, I have one close to 10 years and it is still a good bench checker of stuff.
 
One of the advantages of AGM batteries is their exceptional shelf life. Odyssey claims their battery can maintain 12.0v open circuit for up to two years on the shelf. It has been my experience the key to long life with the PC680 is to routinely fly once a week, make sure there is no keep-alive drain, and don't use a maintenance charger.
 
Be sure to read the currently active "Battery Chargers Not Approved" thread on this site.

I had some initial problems with understanding and learning to live with the Odyssey battery in my RV-12. My battery seems to be working fine after 20 months and 250 Hobbs hours. I have the Odyssey Ultima 6-amp charger, but I use it sparingly. I do not think that the charger does the battery any favors if you use it as a full-time maintainer. My RV-12, like any airplane, really likes to see regular use -- I fly 2-3 times a week usually for @ 45 minutes minimum. The charger only seems to kick-in and work in recharging the battery if, in fact, the the battery is low on voltage. If the battery voltage is "sort-of-OK", then the charger indicates that the battery is charged and goes right to the maintainer mode which doesn't seem to actually recharge the battery any significant amount. These are MY impressions -- your findings may vary!

ps -- I have somewhat given up on using the voltage and amp readings shown on my ROTAX/Dynon SV panel for definitive electrical system performance information. If I consistently see 13.8-13.9 volts and 1 amp in flight at cruise RPM with everything operating, I am a happy camper!
 
I had similar symptoms. After a new battery only lasted 150hrs/18months, I looked closer and found that I had a parasitic load on the battery with the master off. The P680 does NOT like parasitic loads.

I removed the parasitic load, and she starts strong Every time now. Almost a year and 100hrs.

Also, I tried to deep cycle the battery with no luck. Voltage seemed to be fine, but no capacity/ cranking amps.
 
Last edited:
How to find parasitic load
Click to expand...
Shut off the master switch. Disconnect the cable from the negative battery terminal. Connect a milliammeter in series between the negative battery terminal and the cable that you took off. The current should be zero.
Caution! Connecting an ammeter directly to a voltage source will blow its internal fuse.
 
I recently replaced my battery. FWIW the new battery had an open circuit terminal voltage of 12.9V after topping off the charge, and with a 100 amp Harbor Freight load tester the terminal voltage was 10.5V on the new battery.
 
Scott and everyone - thanks for the links and the excellent advice. I found that, did some more reading. I did 2 discharge-to-10V-then-recharge-with-6-amps recharge cycles (although neither actually heated up the battery) and it seems to have recovered, on a good three-leg test flight today. Think I caught it early! No more maintainer. GREAT RESOURCE!
 
Last edited:
You must log in or register to reply here.
Back
Top