Dead Electrical System (was Need Help, Please)

Damn, I like this Board!

Good post and explanation Pete.

Thanks,

Keven
________
THE CIGAR BOSS

[Ernie Martin]

Pete, thanks so much for your answer. I would caution, however, that flight immediately following such a restart is not advised and may even be against regulations. Setting aside the regulations, let me suggest a couple of things before taking off.

First (and this is subject to Pete being in accord), I would check water level in the cells and add distilled water before jump starting the rear engine.

Second, I would run the rear engine 5-10 minutes after disconnecting the jump (external) battery and then (gasp!) turn it off to see if the battery accepted some charge. How close is the battery voltage to 24 volts with the master switch on (so that there are some loads connected). If there is no voltage meter on your panel, measure the voltage across the aircraft battery posts with an external voltmeter. You might also turn on some heavier loads (lights, maybe flaps, but not cowl flaps due to their sensitivity and cost) and see if the battery has juice to operate them. The purpose of this step is to determine whether the battery had drained down to nothing but is good (i.e., will accept a charge) or is totally gone, incapable of charging. Don't you want to know this before you get going? Even if you have to take off (after re-connecting the jump battery and following Pete's procedure for restarting both engines) don't you want to know whether there will be a) some or b) no battery on board? For instance, if you lose an engine or an alternator. Or, in my 337G, with a powerpack for the gear, I know my gear will hang up in mid-travel when there is little or no battery left (because the last few seconds of gear travel demands so much power that the alternators alone can't hack it), so, if I choose to go, I'm going to leave my gear down.

Third, once I have both engines going, look at your idiot lights to make sure that both alternators are putting out. I wouldn't take-off with a bad/dead battery and a bad alternator. If your idiot lights are bad or unreliable but you have a voltage meter on your panel, you can determine alternator output by looking at the meter as you turn each alternator off and then on.

Finally, depending on your findings as to the condition of the battery and the alternators, it would be most prudent if you had a hand-held aviation radio on board before take-off.

Ernie
(Sorry if the above was too obvious/detailed/pedantic for the savvy -- it's meant for the average owner or pilot.

[Pete Somers]

Ernie
Yep, the procedure I gave is really a 'get home last resort' and if you are really stuck.

Now if you jumper the battery on the older Skymasters and do a start on the rear, and run it , from memory i do not think you will be able to start the front due to the small alternators on the older models (i am sure i have tried it).
The 60 amp systems are no problem.

And as you say Ernie, if you have to take off with a low battery, leave the gear where it is down, raising the gear uses a lot of power and it does not make all that much differance to the speed anyway.

Battery maintenace is just as important as the servicing of the engines. The UK CAA called for a capacity check on these batteries every 3 months until everyone complained that it was destroying the batteries rather than doing good, but that is one of many backward idea's of our system.

Just checking the water level and maybe put it on charge now and again will keep a battery good.

Remember a lot of the system rely on the electrics, so if you see or hear something you are not sure of get it looked at.

If you need any help on the electrics let me know!!

Good comments Ernie!!

Happy flying

Pete

[Paul Sharp]

Read the followup comments, and would like to add a couple of my own...

First, I'm glad I simply bought a battery and got on with it. I think that 3 years is around a good life-cycle for a battery - which is what I had gotten on the old one even though it hadn't been showing any signs of being done with - but due to that amount of life on it I'm not unhappy about putting in a new battery. Up in West Yellowstone, with no A&Ps and no shop available, it was much easier just to put a new one in and be done with it. Took less than a half hour to install, button up, and be doing the preflight for the trip home.

Second, on the idea of not being able to sart the front from the rear only running, that would be an interesting experiment to try some time with a known weak battery. I have been able to start the rear first and then the front when I tried it before, but that wasn't with a flat battery.

Third, I made myself a set of special jumper cables for starting the bird remotely where there might not be any 24V sources. What I did was to create a small jumper that can connect between the minus side of one 12V battery to the plus side of a second 12V battery. Then I have the standard 2 cables which can be connected from the one remaining plus post and one remaining minus post. So by connecting in series I can get 24 volts.

But - aha - for me that would only allow me to get them started; I'd have to do something else about getting alternators back on line, since my early model has no "restart" DC pack to do that. I guess I could simply connect to the battery posts instead of using the exterior connection cable, though.

Others might consider that little trick who are sometimes way out in the boonies. If there are any cars around you can probably beg/borrow 2 batteries long enough to get 24V with a series hookup.

Last, my plane has dual hydraulic pumps. I wonder if it needs to "borow" battery power to get the gear up (assuming they're both working)? Would be interesting to know.

[Ernie Martin]

On your last point, Paul, I don't think that models with gear hydraulic pumps (like my old 337D) have any significant electrical power draw (which models like my current 337G with a powerpack do). You probably need some electrical power for switching, but it's negligible.

Ernie