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45 minutes per charge

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Old 01-15-2004, 11:59 AM
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HoboDog
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Default 45 minutes per charge

I finally timed my video setup. It gets a good 45 minutes before the battery voltage drops below 7.3 volts. It is a Blackwidow 600mw transmitter with a BW Panasonic CX161 camera. It is powered by a 700mah 2 cells in series Li-Po regulated to 5 volts by a Kokam voltage regulator board.
Just some trivia...
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Old 01-15-2004, 01:53 PM
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IA-Flyer
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Default RE: 45 minutes per charge

Have you checked your setup with a amp meter yukondog?

The 600mw TX I have draws 290mA @5v
The CX161 draws 130mA on my meter.
For a total draw of 420mA.
I was going to ask Bill what a good average should be when I had a chance.
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Old 01-15-2004, 04:12 PM
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Default RE: 45 minutes per charge

Hi Jim,

Your current readings sound about right. Keep in mind that yukondog has a 5v linear vreg in there so he's eating some power in the form of heat.

Now stop sitting around playing with your meter and go fly the damn thing

Bill
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Old 01-15-2004, 05:27 PM
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IA-Flyer
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Default RE: 45 minutes per charge

But... But... But...

My plan was to get all the parts together and design a new plane around the parts. Still need a Co-Pilot but everything else is here (U-NAV 10 & 20, GPS, Your Video system, 12oz camcorder).
Ok, I'll strap it on something and fly it.

Jim
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Old 01-15-2004, 06:15 PM
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Default RE: 45 minutes per charge

Are you going with the new copilot/receiver unit, the FS8?

I have one in my Graupner Terry (pretty small electric plane) and it has operated great so far.

I just ordered a second one for my Twinstar, which is already set up for full autonomous flight, but does not have a failsafe receiver in it. The new unit will really help tame the rats nest of wires in my current installation.

Bill
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Old 01-15-2004, 06:41 PM
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Default RE: 45 minutes per charge

That’s why I was holding off on the co-pilot.
When I talked to you last you said you were getting on of the new ones and I was hoping you would tell us how it worked out sometime but I didnt want to seem pushy

I was going to use a futaba PCM receiver and the old style co-pilot. But if your report is good, the new system looks very attractive especially the Z sensor.
Dave at U-NAV said I should use his system or the co-pilot for elevator control, and I'm not sure the you can use "just" aileron leveling with the new co-pilot system. I may have found a way around the problem if you cant disable elevator control, put the Co-Pilot sensor on a pivot and let the U-Nav tilt it to control bank angle and altitude using servos and a servo driver board for neutral points. Not sure it would work though, I've never used a co-pilot before and hate to spend that kind of money on a test.

73
Jim
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Old 01-15-2004, 07:11 PM
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Default RE: 45 minutes per charge

It gets a good 45 minutes before the battery voltage drops below 7.3 volts.
I thought that 7.3V (under load) represented a LiPO that had plenty of charge remaining. Why not allow it to go to the usual 6.0V under load? That lower voltage is still very safe. BTW, unloaded voltage specs are much higher. But even so, the 7.3V seems to suggest a LiPO pack that has more to give.

Assuming your setup draws 420mA, you should be able to gain lots more run time. Even with a 5V LDO linear Vreg, your 700mAH pack should offer over 1-1/4 hours of use. Perhaps even more if you push the pack to the {safe} rated end-of-discharge voltage (2.7V/cell).
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Old 01-15-2004, 07:39 PM
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Default RE: 45 minutes per charge

You are right mr.rc-cam,
At 7.3 volts there should be time left before the cells are driven into the danger zone. The reason I stated the time at 7.3 volts is because of the way the Kokam VRLI Sport voltage regulator works is this. It has 3 LEDs on the board. Green on at 7.3 volts, Yellow on between 7.3v and 6.0v, Red on at less than 6.0v. To be safe I figure I need to charge it when yellow shows up. At 45 minutes until Yellow I can get all the video I need for one charge. I'm even considering a LiPo at 360mah to save weight and still get all the video I need during the charge duration of the motor battery. Currently I'm getting 10 to 15 minute flight time with 45++ minutes video time.
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Old 01-15-2004, 08:46 PM
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Default RE: 45 minutes per charge

the new system looks very attractive especially the Z sensor.
Dave at U-NAV said I should use his system or the co-pilot for elevator control, and I'm not sure the you can use "just" aileron leveling with the new co-pilot system.
There is no reason that you shouldn't be able to give control of the elevator to the unav device. I think this is what cyberflyer did. When the unav altitude control is off, then control would effectively be turned over to the copilot.

Regarding the Z sensor, it might not be what everyone thinks it is. From reading the documentation it does NOT do "continuous calibration" as has been suggested. Instead, it serves two purposes... it allows you to calibrate with the plane sitting on the ground (no more holding the plane nose down) and it gives the copilot a clear understanding of "which way is up". According to the doco, if the plane is inverted when copilot is engaged and the Z sensor is installed, then elevator compensation is supressed while the plane is upside down. Instead, it uses roll control to get the plane upright. Without the Z sensor, the copilot would command hard up elevator to loop the plane to level, and many airframes can't handle this level of stress.

Regards,
Bill
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Old 01-15-2004, 10:06 PM
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Default RE: 45 minutes per charge

mr. rc-cam,
Thanks for the informationm & great advise, as always. I was a little concerned at how low to let the voltage drop on my pack also. Those Li-Ion / Po packs aren’t very forgiving if over discharged! I have seen way to many portable computer Lithium-whatever packs fail, seemed like NiMH lasted way better in real world conditions.

yb2normal,
Wow, I’m glad I asked! The "in the air" calibration updates from the z-sensor is what was leaning me towards the new system. If my plane gets upside down I'll have bigger problems than a z-sensor could fix. Thanks again!

Yukondog
Sorry I got off topic in your post!
Where did you get your Kokam regulator, it sounds nice.

Jim
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Old 01-16-2004, 01:42 AM
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Default RE: 45 minutes per charge

Too bad the LED monitor does not offer low voltage cutoff. That would solve the nagging problem of harming the LiPO pack.
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Old 01-16-2004, 03:07 AM
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Default RE: 45 minutes per charge

Sounds like a good RC-Cam project!
LDO regulator, fet?, comparator and a remote voltage programmable warning LED (in the video field of view) to warn you before it shuts off.

I wonder if some of the battery packs made for camcorders and digi-cams have the circuit built in. I used a pack from a Nikon camera (650mA 1.5oz), but never let it discharge far enough to find out.
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Old 01-16-2004, 12:26 PM
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Default RE: 45 minutes per charge

IA-Flyer: I got the regulator from FMA Direct.

mr.rc-cam: Yes, it is too bad it has LEDs and no Low Voltage Cutoff. Being desinged to power the receiver and servos I bet they figured LVC would be counter productive. Save the battery while the plane flys away on its own.

Doug
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Old 01-16-2004, 12:30 PM
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Default RE: 45 minutes per charge

Sounds like a good RC-Cam project!
I had thought about creating such a gadget for the e-flight folks, but they did not seem to be excited by the weight gains from a tiny circuit (every gram counts to them). If my schedule allows it, I may just find a reason to do this for our camera app.

I wonder if some of the battery packs made for camcorders and digi-cams have the circuit built in.
Perhaps, but I imagine that many cameras have shifted the low voltage cutoff responsibilty to the camera itself. If the pack's internal protection board has a low voltage cutoff, then you may have to sacrifice a battery to find out.
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