PC680 batteries

[chaskuss]

Originally Posted by NinerBikes

My buddy replaced his 680 in his RV-12 in Oct of 2018. It was dead by May 2019. Probably 34 hrs of flying time in that period. Dead cell. Air Spruce replaced it under warranty. New battery was dead by early Sept this year. Dead cell ,voltage falling of 0.1 to 0.2v per day. Lasted 4 months. Air Spruce replaced it again under warranty. Had to pay return shipping.

RV-12, and it charges normally, at 14.3V after start up, at about 8 amps and quickly falls, if on a Rotax 912, the rpms for warm up are kept at 24-2500 rpms. At 2000 rpm, the battery is -2 amps /hr.

I saw another post from someone also mentioning short battery life on their 680 recently.

The symptoms you are reporting and the very short life spans of these batteries coincides exactly like the symptoms of an alternator that has one or more shorted rectifier diodes. 95% of the time when a rectifier diode fails it fails open circuit. You then generally lose one sixth of your alternators output for every diode that fails. So it's fairly easy to determine that you've got a bad alternator. However when a rectifier diode fails shorted, the alternator will still pass charging testing. However what is happening is that that diode is allowing AC current to pass to the battery. Alternating current will destroy a battery in very short order. Unless the charging system is tested with a high quality tester that has the capability to find this issue, the test won't find anything wrong.

Charlie

[emsvitil]

Originally Posted by chaskuss

The symptoms you are reporting and the very short life spans of these batteries coincides exactly like the symptoms of an alternator that has one or more shorted rectifier diodes. 95% of the time when a rectifier diode fails it fails open circuit. You then generally lose one sixth of your alternators output for every diode that fails. So it's fairly easy to determine that you've got a bad alternator. However when a rectifier diode fails shorted, the alternator will still pass charging testing. However what is happening is that that diode is allowing AC current to pass to the battery. Alternating current will destroy a battery in very short order. Unless the charging system is tested with a high quality tester that has the capability to find this issue, the test won't find anything wrong.

Charlie

Would putting a 'noise filter' and additional diode on the alternator output help?

High Capacity diode
Large Capacitor
Maybe even an inductor

?

[Walt]

To test for a shorted diode (rare) just put you meter on AC with the engine running, should be '0'.

[revenson]

Originally Posted by Walt

To test for a shorted diode (rare) just put you meter on AC with the engine running, should be '0'.

Walt: Where does one do this AC voltage test? At battery + and -?

[emsvitil]

To see the AC ripple voltage output of an alternator you need to connect as close to the alternator as possible.

Connect - to alternator case, + to alternator output.

The battery acts like a large capacitor. If you test at battery, you may not see the AC ripple.

[BobTurner]

Most inexpensive multimeters just use an internal diode for ?ac?. Procedure: connect multimeter to ?hot? wire, near alternator. Connect other multimeter lead to ground. Set multimeter to ac. Turn on electrical power but leave engine off. If voltmeter reads zero, good. If it does not, reverse the leads. It should then read zero. Start the engine, alternator on, read any ac voltage present.