Dead Battery P-MAGS

[guidoperez]

Hi everybody.
I have installed dual P-mags on a TITAN IOX-360 180HP engine with Skytech lightweight starter on it. I did only a first start to Run-In and check parameters. Then I did a very short test flight too and guess I will begin to fly the 40 Hours test flights soon. The engine runs great with both P-mags configuration.
I have in mind start to do backcountry flights and I have doubt about start the P-mags with a car portable Jump when battery is dead by discharging or failure.
I know the P-mags will start only if energized. So, in case of battery dead I will need to have an alternate way energize P-mags for engine start.
Reading P-mags install manual I did´t find mention to use or not use a Battery jump to start the engine as external power. Another way to excite P-mags is with 9v battery but, This only will work doing a hand prop start and I would like to avoid this start procedure.
Well. I apreciate opinions and experiences concerning to this topic.

Thank in advance.

Guido.

[stewartb]

If I attach a Jump Pack to my battery, how would Pmags behave any differently than with the normal battery? I have no intention of hand propping my Cub engine. I carry a Jump Pack in my day pack for that day I may need it.

[skywagon8a]

I foolishly left my battery switch on and ran the battery dead. Using a EarthX jump pack, the engine started normally with two P-mags. Get a light weight jump battery to carry with you.

[guidoperez]

Hi Stewratb and skywagon8a.
If battery jump works well for you, I guess will work good for me too.
I have a good quality compact jump. So, I will use it.
Yours posts were very helpfull for me
Thanks!!

[Cub Builder]

You may find that unless you are using an high amp capable battery, your engine will spin over nicely and not fire; especially under cold weather conditions. This is due to the Skytech starter pulling the battery voltage down below the threshold needed to excite the Pmags while driving the starter. It is not an unusual problem. I've resolved this issue a couple of times by replacing the Oddyssy batteries with EarthX for more cranking amps. Just a FYI, especially if you are operating in cold weather.

-Cub Builder

[skywagon8a]

... This is due to the Skytech starter pulling the battery voltage down below the threshold needed to excite the Pmags while driving the starter.

-Cub Builder

That's interesting since the Pmag instructions say you only need a 9 volt battery for hand starting.

[wireweinie]

You may find that unless you are using an high amp capable battery, your engine will spin over nicely and not fire; especially under cold weather conditions. This is due to the Skytech starter pulling the battery voltage down below the threshold needed to excite the Pmags while driving the starter. It is not an unusual problem. I've resolved this issue a couple of times by replacing the Oddyssy batteries with EarthX for more cranking amps. Just a FYI, especially if you are operating in cold weather.

-Cub Builder

If this is an ongoing issue for you guys operating in extreme cold, you can use a 'split battery' system for startup. In it's most basic design, two batteries are connected, in parallel, through a normally closed relay. The larger, main battery is directly connected to the main bus and powers the starter motor while cranking. The smaller, secondary battery is connected to any electronics concerned with firing the spark plugs (in this case the P-Mags). When cranking the engine, the key switch/starter button will energize the start relay to turn the engine over and at the same time, open the relay between the batteries. This will allow the starter to draw power from the main battery only. While the engine is cranking, the P-Mags will draw from the secondary battery only. Since this is the only draw on that battery, the voltage drop will be minimal. When the key/start button is released, the relay between the batteries will close, connecting both batteries in parallel and allowing both to recharge from the alternator.

Web

[mvivion]

Interesting conversation. If what I’m reading is accurate, I sure wouldn’t even consider P-Mags on any plane. That said, the only battery I ever had a problem with in Fairbanks, Fort Yukon, Bettles, Galena, etc was the crappy “Gel” battery that Aviat’s used to install in Husky’s. Replaced that with an Odyssey and never looked back.

Turn your strobe light switch on and LEAVE it on, always. If you get distracted and forget the master, hopefully that strobe will get your attention.

But if you actually can’t start a P-Mag equipped airplane with a jump pack…..maybe there’s a good reason we still use old tractor parts.

MTV

[tedwaltman1]

Dual P-mags working awesome for me for 1,100 hours now. Same battery. 9-volt circuit wired in for hand-prop in an emergency. Never had to use the 9-volt though. And, as you all know, I fly in seriously remote places. No worries on the battery or P-mags for me.

[Colorguns]

One Slick one Emag can hand prop on the Slick and at about 1500 RPM the Emag will kick in per the paperwork on my Certified -12.
Doug

[stewartb]

The OP has an injected engine. A battery dead enough not to energize Pmags isn’t going to power the electric fuel pump. It’s a simple problem to manage with today’s tiny and lightweight portable battery packs.

[JohnnyR]

One of the reasons I upgraded to an EarthX 900 series

You may find that unless you are using an high amp capable battery, your engine will spin over nicely and not fire; especially under cold weather conditions. This is due to the Skytech starter pulling the battery voltage down below the threshold needed to excite the Pmags while driving the starter. It is not an unusual problem. I've resolved this issue a couple of times by replacing the Oddyssy batteries with EarthX for more cranking amps. Just a FYI, especially if you are operating in cold weather.

-Cub Builder

[mvivion]

The OP has an injected engine. A battery dead enough not to energize Pmags isn’t going to power the electric fuel pump. It’s a simple problem to manage with today’s tiny and lightweight portable battery packs.

That is why EVERY fuel injected plane should also have a manual primer. Simple, cheap insurance. I’ve started a few with manual primer and hand prop. Did that with a Stoots converted 170 a year or so ago, to complete a flight review. Pilot didn’t realize he still had a primer…..

MTV

[stewartb]

Nope. The EI would still be an issue. Jump packs are the answer. Simple.

[skywagon8a]

That is why EVERY fuel injected plane should also have a manual primer. Simple, cheap insurance. I’ve started a few with manual primer and hand prop. Did that with a Stoots converted 170 a year or so ago, to complete a flight review. Pilot didn’t realize he still had a primer…..

MTV

I haven't had a need to try this, so just for discussion purposes. High wing airplane (gravity feed fuel to engine pump) with fuel injected Lycoming, P-mags with 9 volt aux battery, dead aircraft battery. Mags off... mixture full rich ... throttle wide open....pull prop through by hand many turns for priming purposes.... throttle cracked...Pmags on with 9 volts... spin prop by hand. Isn't it likely the engine would start? No need for a manual primer.

[stewartb]

Call me a sissy. My 10-1 IO-390 is not fun to pull through. I need to do a compression test today or tomorrow and the thought makes me cringe. I’m not propping my plane when other easier alternatives are available. I think most guys with EI/FI hot rodded engines with lightweight props will agree. Oh hell, I’m not propping my low compression carbed/mag’d Continental, either. No need to these days.

[stewartb]

In case anyone wonders how a JumpPack will perform with a TOTALLY dead battery? I left my master on after upgrading the G3X a few days ago. No indication of power. Hooked up my old 12v JumpPack, primed with the electric fuel pump, and started the engine (Skytek and Pmags) without hesitation. Easy peasy.

[JohnnyR]

Which jumppack? The little one?
How many cranking amps?

I’ve been following this discussion with interest. Not sure why folks don’t just carry a jumppack and use that to power their PMags instead of the 9v route.

In case anyone wonders how a JumpPack will perform with a TOTALLY dead battery? I left my master on after upgrading the G3X a few days ago. No indication of power. Hooked up my old 12v JumpPack, primed with the electric fuel pump, and started the engine (Skytek and Pmags) without hesitation. Easy peasy.

[skywagon8a]

This is the one I have, which appears to have been discontinued. With a dead battery, it started the engine with P-mags and powered all the electronics for about 1/2 hour before it ran out of juice. The airplane ran fine after that until I landed when the engine quit due to low rpm. Had to paddle ashore. At the time the airplane had no generator.
This is Earthx's current model: https://earthxbatteries.com/product-...y-accessories/

[stewartb]

The original (discontinued) one. I have the newer 12/24 volt version and it’s a POS. I needed to jump my tractor this morning and the freshly charged 12/24v Pack wouldn’t start it. My NOCO GB50 spun it with ease. I used my oldest JumpPack on the plane. No issue with initiating a charge once started, either. All’s good.

I know some guys who like NOCO boost packs better than EarthX. As far as the new ones go? I wholeheartedly agree!

[JohnnyR]

I also have the old model. Maybe I’ll disconnect the battery on the experimental Cub and conduct an experiment.
J

[cubflier]

Which jumppack? The little one?
How many cranking amps?

The NOCO GB50 is my all time favorite NOCO. I own a pile of NOCO jump packs spanning the bulk of their product line and the GB50 is the sweet spot for small GA type aircraft IMO. The biggest plus is that you can recharge it with one of those light weight back pack type solar panels in a reasonable amount of time. Another plus that it's override mode in not timed. As far as cranking amp claims from all manufactures, most are fairy tales anyway.

Jerry

[stewartb]

For guys who may be curious about Pmags and self-generated power, my plane idles smoothly with master off down to 875rpm. At 850 it develops a stumble. At 800 it quits, then the prop spins backwards for 6-8 blades. After the reverse run I was startled so restarted it and it ran fine. I won’t be doing that again.