I am going to jump start the PT6 in a Piper "JetProp" in the morning. I have the proper jump cable to fit the AUX power in, and will be using my electric golf cart.

The golf cart has 6 quality 8V batteries. What would you think of starting with 4X8 for 32v, or 3X8 for 24v. It is a 28v system.

Actually, with the 3 batteries I am getting about 25.5 volts, so the 4 would probably be around 34V.

His batteries are not completely discharged, but may have 80%, and are being replaced with new at the next stop.

Best....................from the desert of Washington State.

Go with the 24v

Without any doubt.

It's a 24V system that is charged by 28V. The airplane is "expecting" 24V from the batteries. Don't risk letting the magic smoke out by feeding it more.

You can, however, feed it from 2 x 3 x 8V for more starting capacity (2 parallel strings of 3 series 8 V batteries).

Next most important thing, note what the voltmeter does during the start- hopefully not dip too far into the teens initially on starter engagement and recovers to about 20 as the engine is coming up to idle. Then you'll know you got a decent combination of the aircraft's degraded battery and your jump start rig.

If the voltage first dips into the low teens (and if this airplane doesn't normally behave that way on battery starts), you might have a hot start a few moments later.

We start ours with a fast start system that provides 48 volts and get starts that are cooler than the idle temp of the engine. When we used to use a golf cart as a supplement, we were wired up for 30 volts and it worked great.

I forgot what might be the most important "gotcha" of all- if your friend's battery is moderately discharged, then that's one thing. If it's too deeply discharged (and consider it will be more discharged after the start), then recharging it can make it dangerously hot. Practically speaking, the loose number I've usually seen is below about 18-20 volts with the master on but otherwise minimal load (no lights, avionics, fans, etc.). Lower than that for a 24V lead acid battery and it is better to put it on a conditioner to recharge it.

Disclaimer: not an A&P, just a lot of pilot experience in PT6 and other electric-start turbines.

And if NiCad batteries, pull them out and take to a battery shop for the recharge.

8 volt batteries??? are you sure??

I suspect they are 6 volt batteries and if you check them while or shortly after charging, you are reading the higher charging voltage.

How many cells are in each battery? probably 3, if so they are 6 Volt.

If so, then you need 4 in series to start a 24v aircraft.

I as going to ask what kind of cart. Many carts are now 48v

https://www.golfcartgarage.com/8-volt-g ... ng+CPC+PLA

Rick,

Most new golf carts are 48 volt, they use six batteries (four cell).

Kevin

His aircraft batteries are some kind of Concorde 35 batteries, and not completely dead. But they will only spin his PT6 to 10%.

My batteries are six(6) 8V batteries like pictured in the link that Rocky posted.

It is 7:10 here now, and freezing cold outside in the desert of Washington. AND I just dreamed up the best scheme................since my JetProp friend will be gone, and my mechanic will be here Monday to annual my Cherokee...............I'm going to borrow his always floor heated hangar to do the annual. I LOVE my hanger right on the taxiway here, but it is COLD right now!!

So my plan, since Craig uses 48V, is to spin the PT6 with 24V, and if we don't, say 17%, shift up to 32V.

I like Jim's idea of the parallel/series rigging, except that I need to get in the golf cart right after start...............to get out of the way...........and it need to run.

So, okay, I'll check back here, now with about 2 hours to go, for any late ideas. Thanks, I'll let you know how it goes.

If they are regular old group 35 lead acid batteries, is it possible to clean the posts and verify tight terminal connections and charge them up as much as possible prior to starting?

Why don't you put the Jetprop in the heated hangar with a charger on it? You are scaring me with your McGyver ideas on the 500k engine

I have rigged my electric tug so I can plug in my connector for 12 or 24 volts.
Great for starting or ground use for systems.

I love that idea and I am going to look into doing that with my upcoming battery change.