Andrew Bird

Today I went flying at my field (FBF in Brooklyn). It was pretty cold - around -1 deg C.

I have a 4800 fromeco 7.4 Li ion pack on my ECU. The turbine shuts down if the battery voltage dips below 6v.
After a couple of flights, the turbine would start its start up procedure start loading the pack and the voltage would drop below 6v so the procedure would be aborted.
The pack is new but the model was second hand (with very little run time on it). I seem to have had various problems with these packs not taking the loading the turbine is putting on them (have replaced the pack once before).
Is it just a bad choice of pack? I'm keen to keep weight down and have faired well with lipos in the past. Are lipos just better at sustaining the necessary voltage output? I come no where near to using the capacity of this 4800mah pack.
Any thoughts?

Andrew

Airforce7

My Feedback: (31)

How was the flow of propane to the turbine during the startup? On my P-120 in the cold, I need to keep the propane warm prior to startup. Otherwise, the propane doesn't flow evenly out of the can and it takes multiple start-up routines which drain the battery delivering an error to the GSU. What turbine are you using?

Andrew Bird

I keep the propane bottle connected through the start process. It's an artes Falcon.

I didn't keep the gas warm, it was just sitting outside with the model. I have had a problem with flameouts in the past which I traced back to the original ECU pack. Unfortunately, I made a direct replacement of identical pack and my confidence in them is not high!

flyinfool1

My Feedback: (2)

A good High C rated LiPo pack will do a better job of supplying amps than a Li-Ion pack will.
All batteries loose capacity in the cold, lithiums are real bad.
I have a P70 kero start that I fly off skis. When it is warm out I can get 5 flights with no problem. In the cold I can get 2 flights and that is pushing it. In the cold I now charge just before each flight at the max rate that is safe fore the battery. This warms the battery up a little to help its power output.
Another option is to put a chemical hand warmer by the battery to keep it warm. I would remove the hand warmer for flight since a rupture of the bag would be very bad for the on board electronics. I use the hand warmers to keep my Tx warm at the field.

Richard-RCU

My Feedback: (21)

Fly your simulator in cold weather....mine is at a comfortable temp of 72 degrees....while I wait for spring

Richard

Andrew Bird

It looks like I can face up to the cold weather better than these li ions can - they are bound for the trash can!

flyinfool1

My Feedback: (2)

I would not trash them. They make great RX packs. I have them in most of my aircraft.

Andrew Bird

Ok - maybe they won't go straight to the bin!

But - I'm currently building a composite super Bandit (the old fasioned way from a kit that involves some cutting, wood and painting!)

I've just taken the battery set up intended for that one and put it in to the Bandit ARF. Previously I had 3 x 4800 li ion packs - 2 saddling the main tank and the other at the back of the engine compartment. I have had to put lots of lead in the tail, so I replaced the two rx packs either side of the main tank with 2100 TP lipos. Removed lots of the lead from the tail, although some is still left, and got an overall weight reduction. ICS pack is being replaced by a TP 4200 2c pack, which weighs in pretty much the same. I still have plenty of capacity and a set up I have more experience with.
The Li ions will eventually find another project.

Andrew

Tom Antlfinger

My Feedback: (24)

Hi Andrew:

Info on liths has been around for a long time.....I started noticing poor cold weather performance on my non-rechargeable lithium batteries that powered my ELT(emergency locator transmitter) in my full scale plane more than 15-20 years ago.....pre-flight check of the ELT would often be inop if the outside temp was hovering near the -20 deg F mark...that battery was in the aft fuse, not in the warm cabin......the FAA subsequently made their use unlawful because of fire hazard and poor cold weather performance.....

I also pursue Amateur Radio and have a hand-held 144/440 Mhz transceiver in my car with Li-Ion battery.....after leaving it out all night in the cold, now down to 20F in my garage, I can only get 1 watt power output, whereas in the summer, I get the full rated 5 watts.....and it lasts for only a few minutes on transmit, whereas in warm weather, it is good for more than 30 minutes.....

There are charts on the Google Lith sites showing the rapid drop off in performance based on lowering temps.....worse than NiCd or NiMH.....

I never fly any of my big jets with Lith, either Ion or Li-Po when ambient temp is below 32F, just to be safe......

Our club experience here in the winter is that Ni/Cd/Mh bats hold up quite well down to almost 0 deg F.......

Tom