DavidR8

The weather was ultra calm and not pouring rain this morning so I decided to take the rebuilt Super Cub out for its semi-maiden flight.

I had replaced the fuselage and used the super-slick brushless motor mount from Heads Up RC.

Loaded up a 2200 pack, did a control and CG check. Maybe a bit tail heavy but ok for a first go.

3/4 throttle and a solid throw. Heads off to the right. Some left rudder and we're ok but are tail heavy. Bring it back and tape some weight to the nose. Launch again and she tracked straight away from me, climbing nicely at 3/4 throttle.

I climb and do a series of circles and figure 8's and landing approaches to get accustomed to the feel as this is the first time I've had this much time between crashes.

At 21 mins my radio starts beeping, I look down and see the TX battery voltage is down to 8.5v! I turn her around and bring her back and land about 10 feet away.

For reference, it's a 3S pack, an Emax 2215 motor turning a GWS 9050 prop. I was at 1/2 throttle for virtually all of the flight.

The radio battery was fully charged before I started so it looks like I'm in the market for a new, bigger capacity TX pack.

CHELLIE

Wow, a 21 min flight, thats unreal to be on the safe side, limit your flight to 15 min to prevent a possible brown out, Take care and have fun, Chellie

DavidR8

I checked the pack voltage when I arrived home. 3.7, 3.71, 3.71. So definitely on the edge. I will change the timer setting to 15 mins

Brick

15 minutes air time is still awesome !! like CHELLIE says, don't push that battery too far and loose power

solentlife

Hey Guys ... and Ladies ...

He said TX was 21 mins ... not flight pack ... >


Hey "DavidR8" ... do you mean MODEL FLIGHT LiPo is 21 mins ?

That's awesome - but if you meant TX battery pack - that's terrible !!

Nigel

DavidR8

When the low battery signal for the TX battery timer sounded, the flight timer on my TX was at 21 mins. For what it's worth I ran through a 2200 pack yesterday in a static test and it went 20 mins before it hit 3.7v. This is the motor I'm running, and I'm using the second prop in the list, a GWS 9050: http://www.headsuphobby.com/Emax-BL2...otor-D-662.htm

So yes it was flight time of 21 mins and also TX battery life of 21 mins. The Futaba 7C TX has a 600 mah battery. They are notorious for their small battery capacity, plus the radio is new to me so I don't think the nicad pack was well treated. So I'm looking for a way to up the capacity.

stemo99

21 minutes on a 400 class motor with a 2200mah battery, yeah right.

fhhuber

Your transmitter should go 2 hours MINIMUM on a charge of its battery. If that TX pack is not providing 30 min you need a new battery.

Since you got less than 1/4 what you should have from the TX pack.... change the battery before flying again. Max Blose at the Waco Hobby Stop, Waco TX can make a pack for you with higher capacity cells. http://www.wacohobbystop.com/ (or maybe someone on your side "of the pond" can do it)

Many of the 2.4 ghz radios can go more than 8 hours of operation on a charge.

*************

As for the plane getting 21 min. Easily believable. I have a couple of planes that can get 15 min at full throttle. With some throttle management and chasing some buzzards to find themals I can keep one flying for hours.

******

Chellie... brown out isn't going to happen until long after LVC shuts down his motor.

DavidR8

Other than I know the TX timer is accurate, it is setup correctly and at 21 mins in, the plane was still in the air. I landed because the TX battery hit the low voltage cutoff. Once it hits the cutoff, it will continue to operate for 5 mins. Because it drained so quickly I had no confidence that I had actually 5 mins left.

On Sunday replicated the time in a static ground test to check a battery I felt was suspect. It went 20 mins as well.

The test went like this:
simulate launch and climb for 45 secs @ 3/4 throttle
simulate cruise for 120 secs @ 1/2 throttle
simulate climb/roll etc. for 30 secs @ full throttle
simulate cruise for 120 secs @ 1/2 throttle
I repeated this until I hit 20 mins.

After a rest of 30 mins, the battery voltage was 3.7-3.72 across all three cells.

I used two iPhones as timers for the intervals and the TX timer for the sum.

DavidR8

Last night I found a Sanyo 2000mAH Eneloop pack from Canuck Engineering.

JetPlaneFlyer

21 minutes sounds about right. The Super Cub weighs about 1.6lb, for gentle cruising around it will use about 30-40W per lb. If we say 35W x 1.6 lb = 56W required to fly

56W / 11.1v = 5 Amps

2.2Ah /5A = 0.44 Hours = 26 minutes

Given that the battery had 3.7V on landing that indicated about 80% depletion which looks spot on where you would expect it to be.

solentlife

OK - understood ... no prob.

Just have to be careful how you word things as some people here don't read properly !!

Yout Tx battery is easily solved ... there are plenty of battery pack makers in US as well as rest of world ... you can find them on ebay or just google ..

They can make to order or if its a brand name radio - often they will have pre-made purpose packs that a) are better than original, b) usually greater capacity.

My JR original was 500mAh similar to yours ... a UK battery maker supplied me a 2600mAh pack to fit - same size and design with plug ready to just drop in for 75% the cost of JR's replacement less capacity pack. They even incl. shipping in that.

Nigel

Brick

those eneloops are great...gonna be my next TX powersource !

raming

I also strongly endorse the Sanyo AA Eneloop 2000mAH batteries for Transmitter battery packs. For the cheaper Spektrum transmitters with a 4cell Battery back such as the DX5e or DX6i, I use the Eneloops.

Here are the benefits that I have enjoyed:
1. This type of NiMH battery has much lower self-discharge over time. So, the Transmitter can sit idle with a high charge setting in the batteries and will still be safe to use months later. (They will hold 80% of charge over a year of storage at room temperature).
2. If charged properly, the battery will last for hundred's of cycles. (I use Sanyo's USB Charger that can charge 1-2 cells at a time through my PC's Charge Port. Each cell is charged separately so when 4 are combined in the Transmitter battery compartment they are all within a few mV of each other). I have Sanyo's that are still going strong after 3-4 years of continuous use.
3. The 2000mAH rated Batteries in the 2.4Ghz Spectrum's will easily last for several outings of flying.
4. I can audit each cell voltage to make sure all the cells are matched. The 4 cells in a Receiver Battery pack can also be checked on the Wattmeter. By the way, the DX6i battery voltage readout reads about 0.2V high, so I don't use this to check the batteries state of charge.

My motto: "Trust but Verify"

Rhondas

how low van my 72 MHz transmitter with a 3 cell 1,400 mah lipo battery ?

Angler-Hi

You're still here!!! Missed you, lol!