I need tech support! :)

I have an O-360 in my 6A. Yesterday after my flight, I somehow forgot to turn off the Master. When I got the the hangar today, I had obviously no power.

We started the engine manually and I still didn't had any electrical power. I let it run at idle for 5-10 minute (increasing/decreasing RPM regularely) as I though that after a couple minutes running, the ALT would pump enough juice into the system for it to kick in. Didn?t worked.

Any of you guys have experienced a dead battery before? Did it had the same symptoms?

field voltage

I suspect your voltage was so low on what was left of your battery, the alternator field circuit couldn't excite your alternator. Your alternator is not a permanent magnet and therefore requires voltage to "get it going".

Jason Smith
Aerotronics Inc.

That makes a lot of sense. Battery was completely dead.

Charging

I left the master on in my -6 one time and had the same problems. The battery tender unit would not charge the battery. I needed to use an auto charger for a few minutes to bring the voltage starting up and then used the battery tender to bring it back to normal voltage. Gotta love them Odyssey batteries....

Odyssey full discharge

I "killed" my Odyssey 3 times over the year before first flight when I was working on the electrical system. Was always able to bring it back to life using an auto charger. However I've read that these glass mat batteries can be permanently degraded by full discharges. I used it with no problems during the first year after first flight. I went ahead and replaced it rather than risk getting stranded away from home.

A generator will produce power without a field, but not an alternator. Dead battery will not excite the field on an alternator. All you would need to do however is apply 12V to the field to flash the alternator then it should work fine as it charges the battery.

rv9av8tr said:

All you would need to do however is apply 12V to the field to flash the alternator then it should work fine as it charges the battery.

Click to expand...

Until it burns up that is... This is considered serious alternator abuse, your alternator was not meant to be used as a battery charger on a dead battery (on the other hand I guess it good for business and helps support the economy).

I've done it without incident. Not to say its OK, but it worked. Alternator output is protected from over current, (that's what your alternator output breaker / fuse does. But I would think the greater "risk" is possible battery damage from overheating/warping by a sustained high current inrush. Initially it wouldn't be any different than using jumper cables from a charged battery to a dead battery, it still looks like an initial dead short between them and that's done all the time with cars.

How to avoid dead batterys!

What I do is put a BIG red light on the panel that is wired to an oil pressure sensor on both my homebuilts. I label the red light oil pressure or low oil pressure. The real purpose of the light is tell me if the master is left on after I turn the engine off. In over 2200 hours I have never had a dead battery. More than once I have looked at the panel while exiting the plane and seen the red light on. It has saved we more than once.

Steve

not quite the same

rv9av8tr said:

I've done it without incident. Not to say its OK, but it worked. Alternator output is protected from over current, (that's what your alternator output breaker / fuse does. But I would think the greater "risk" is possible battery damage from overheating/warping by a sustained high current inrush. Initially it wouldn't be any different than using jumper cables from a charged battery to a dead battery, it still looks like an initial dead short between them and that's done all the time with cars.

Click to expand...

When you go from charged battery to deadbattery it's only 12.6 volts. And alternator puts out at least 13-14volts (else it wouldn't charge your 12.6volt battery).
So using a charged battery or an alternator to charge a dead battery is not quite the same.

All the other posts about the alternator needing at least enough voltage from the battery to excite the alternator field is spot on.

Great posts

Steve Barnes said:

What I do is put a BIG red light on the panel that is wired to an oil pressure sensor on both my homebuilts. I label the red light oil pressure or low oil pressure. The real purpose of the light is tell me if the master is left on after I turn the engine off. In over 2200 hours I have never had a dead battery. More than once I have looked at the panel while exiting the plane and seen the red light on. It has saved we more than once.

Steve

Click to expand...

Here's Van's part number: IE SPDT PRES-15 SW

Mine came with a wiring diagram on how to hook up the warning light. Serves three purposes: enables hour meter (if installed), low pressure warning, forgot to turn the master switch off.

captainrichhill said:

When you go from charged battery to deadbattery it's only 12.6 volts. And alternator puts out at least 13-14volts (else it wouldn't charge your 12.6volt battery).
So using a charged battery or an alternator to charge a dead battery is not quite the same.

All the other posts about the alternator needing at least enough voltage from the battery to excite the alternator field is spot on.

Great posts

Click to expand...

Lead acid battery full charge is 12.6 V however an AGM battery full charge is 12.9 V. And 50% discharge is 11.5 V.