Master Relay

[Pat Stewart]

So I left the Master turned on last weekend and found a dead battery yesterday. No problem just charge the battery and go fly. Well that did not fix it. Tried to start and it acted as though the battery was completely flat, not a sound and nothing powered up after turning the master switch on. Then I noticed that when I turned on the master switch I did not hear the master relay, looks like leaving the master on somehow damaged the relay at least I think.

[DanH]

It's more likely that you did not charge the battery.

Most chargers incorporate a polarity check circuit. The charger won't start if terminal polarity is reversed.

A completely dead battery doesn't supply enough power to operate the polarity check. The initial charge time usually requires a second, live battery jumpered in parallel with the dead one, just to fool the charger.

[vic syracuse]

Agree with Dan. Your battery is so dead that the chharger doesn't know which way to go. Hook up a high amp charger for a few minutes and see if you can get it started taking a charge. It may take a couple of hours to see it happen. I have been able to bring them back to life overnight this way.

However, if it is the only battery in the airplane and you fly IFR, I would consider getting a new battery.

Vic

[AlexPeterson]

And the learning continues - I never knew that, or if I did, I'd forgotten it.

The old charger I have for auto use is probably too ancient to have it (40 years?).

[Pat Stewart]

I put a trickle charger on it yesterday and it took several hours but at least the charger said charged. I will take another look.

Thanks

[Carl Froehlich]

Originally Posted by Pat Stewart

I put a trickle charger on it yesterday and it took several hours but at least the charger said charged. I will take another look.

Thanks

You caused irreparable damage to the battery. You might beat some life into it, but whatever reserve capacity you had is gone forever. Replace it.

Carl

[Special Delivery]

Here ya go, Pat... it's time for a new battery.

BatteryMart.com
$109.95 No Tax Free Shipping

[Pat Stewart]

Thanks Ernie, found it for 104 with free shipping from Amazon. Just ordered it, thanks everyone for the quick response.

[chrishalfman]

I have a ‘friend’ who had left his master on for days and completely wiped out the PC680 battery. Twice. He has a different procedure for shut-down, now. :-) And the Odyssey is a deep cycle (that probably means different things to different people, not sure it means killed dead) battery.

Here here are a couple Odyssey docs for year reading pleasure:
http://www.odysseybattery.com/docume...gedODYSSEY.pdf
http://www.odysseybattery.com/docume...M-002_1214.pdf

The first time was at AirVenture. I left, I mean, my ‘friend’, left the master on after turning it off after being reminded by the nice folks working ground crew. Didn’t see it until 4 days later when we were ready to leave. Took it to the emergency repair shop, put it on a charger for a few hours, got enough volts into it to to barely crank the engine over, but the voltage jumped up from the alternator, and flew it home. (I had stopped by a couple vendors in the hangars. Plan B was a new battery.) The voltage grew from 12-something to 14.4 by time we were back to Omaha. BUT-the battery never really recovered. I kept using it another 6 or 8 months before replacing it. You could flip on the master and see the voltage drop over the course of less than 30 seconds. It started at 12.7 or so and would slowly drop to 12 or less. During start-up, voltage would head south of 10 volts no matter the ambient temp. When you’d crank, the first blade would stop for an instant before going though. Always started, though. Tried different chargers, but the battery was spent. Never had issues with voltage in the air (I have only 5 or 6 amp load). But it was toast. Finally decide enough was enough. Replaced the battery and was amazed at the new-found speed of the starter!!!!

The same ‘friend’ left his master on after a trip (after the previous event. He’s a slow learner…..). Luckily it was in his hangar at home when it happened. I, I mean my ‘friend,’ went to the local giant auto parts store and bought a 400A lithium-ion battery booster/starter. Hooked it up. The voltage went up to 10-ish volts (if recollection is correct) in like 15 minutes. Left that thing on for an hour maybe, trying to hit it with a lot of volts/amps. NO idea the battery got hot or not. Never removed it from the firewall or pulled the cowl. Put the trickle charger on over night. Went out the next day and it was fully charged. Now when I head out there, the voltage is 12.8V before start-up and haven’t really paid attention to what the voltage sags to, but its like the battery was never drained. And, no, I don’t put a maintainer on it.

So…. depends on whether or not you want to mess with it and what's an acceptable level of risk for you. They are a deep cycle battery. With all that being said, I’m a VFR only guy. My plane doesn't 'need' electrical accessories (no electrical only fuel pumps, ignition requiring external power, etc) to typically fly. But it does make it a lot nicer! I might have a different opinion if I was in the clouds. As everyone on here says- YMMV.

[Bubblehead]

Autozone, Batteries Plus and other places will load test your battery for you free of charge. Take it to two places if you want a second opinion. I had an Odyssey that I had used for 7 years. !!! I pulled it and when it was tested had 1 bad cell. Voltage would be almost right but that one cell reduced capacity. I've got a new battery on the firewall now and should be good for 3 to 5 years. I don't think I'll push it to 7 again.