[Dutkoski]

Hi guys,

Here's the problem, when first assembled last year, the 50 mm edf's produced what was expected. 420 watts each and then when paired, they did produce around the 840 watts, maybe a little less.

I'm using two Turnigy Delux 40 ESC's and they seem to work well with no apparent over heating. The amp draw on the motors are as advertised, 28 amp full throttle each.

I'm using a pair of two cell 3300 Nano Tech batteries hooked in series to act as a 4 cell.

The other day, I launched the Arrow and noticed it was not very sprite off the bungee and wasn't really going as fast as usual. I landed safely and tested the system with the watt meter and found the system was producing only 720 watts of power, which is just over 100 watts of power loss.

Brought it back to the house and tested the system with a fresh battery. I ran each EDF unit separately and both units produced their advertised power of 420 watts. Now when I reconnected them to work as a pair, again, I lost 100 watts of power.

Kinda frustrating. Any thoughts.......if I have to, I'll stick in two separate 4 cell batteries but trying to not have to buy 4 more lipos if I don't need too.....

[cassat]

I don't know. Mathematically, it calculates out just like you said.

Formula P = I x V Power equals Current times Voltage
Power = 28 (amps) X 14.48 ( volts)
Power = 405 Watts This is the maximum power you can get from the 4 cells unless you are a magician

So, your load is two motors. How can each motor get the same amount of power? The only way would be if each motor is parallel to each other but I believe they are not.

Cassat

[4stripes]

Powering each fan individually doesn't put as much load on the battery. Double the load, and it will not produce as the voltage will sag. If you doubled the capacity or used high C rated batteries, some of the loss will be mitigated. Try running a cheap battery monitor with beeper on the balance leads during the run. You will see right away if the voltage sags in one or many cells.
I always fly running a monitor as it will expose a weak battery or prevent me from running it too far down in voltage.

[Dutkoski]

A 4 cell fully charge is actually more than the 14.8 volts, the volt meter shows 16 so that's where the extra watts come from. The manufacturers alway try to show more than what is actual. But that being said, the two esc's and motor are being fed parallel off the same battery supply.

The system works great but the power loss is just frustrating me. As I indicated, last summer the power was up to spec, just last Sunday it seemed to be less and sure enough it was. The Sunday before all seemed good.

[Dutkoski]

Thanks 4stripes, I'll try that. I think I have a couple of monitors in the tool box. Both sets of two cells were purchased last May. They are 45C rating so I cannot see how 58 amp draw total should have that much affect but they are 9 months old with about 20 to 30 flights on them.

I have a few bigger 4 cell packs with me, might charge one up and give it a try and see what happens.

[airbourne]

This might be slightly off-topic but I have noticed EDFs perform much poorer when flown in cold conditions. Less flight-time, slower speeds, less performance in general.

[Dutkoski]

You are correct, lipos do perform not as good in the cold.......fortunately for me, I'm wintering in Palm Desert, Southern California. Today the temperature was in the mid-80's......sorry...... I here it's nippy in the GTA.
My wife is home in Toronto and keeps me advised, I don't want to go home........

[dashpuppy]

Originally Posted by Dutkoski

You are correct, lipos do perform not as good in the cold.......fortunately for me, I'm wintering in Palm Desert, Southern California. Today the temperature was in the mid-80's......sorry...... I here it's nippy in the GTA.
My wife is home in Toronto and keeps me advised, I don't want to go home........

You really don't want to go home, the weather is 100% different LOL like opposite LOL!

it was 7-deg out here today, almost went and did a few flights HOWEVER Vancouver Island has been hit hard with thick soup fog for the last week

[Soulfly]

Take a look at your wiring? Pinched wire? Broken wire(s) or strands?

You may have had a connection in the 'Y' harness come loose or a solder joint loosen up?
Also, If they are push in connections, pull them apart and give them a clean?
Oxidization will rob you of some wattage..

[Dave Holmes]

Originally Posted by Soulfly

Take a look at your wiring? Pinched wire? Broken wire(s) or strands?

You may have had a connection in the 'Y' harness come loose or a solder joint loosen up?
Also, If they are push in connections, pull them apart and give them a clean?
Oxidization will rob you of some wattage..

That's the first thing that occurred to me as well. A bad connection will heat up, raising its resistance causing more voltage drop, etc.