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Battery Current Ratings

Old 04-23-2005, 06:59 PM
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Default Battery Current Ratings

Hello everyone,

I was hoping someone could shed some light on how batteries behave at high current draw.

1) I fly a Zagi 400X with an Astro 020 with a 6x4 prop. I run this setup with the stock zagi batteries, which are rated at only like 12A or so, yet, my batteries don't seem to be excessively hot after a flight (performs well too). This also happens with my kokam 1500 (10C, 11.1V) pack that I have...good performance, battery doesnt get too hot.

I would assume that I am (attempting to) draw over the max current rating for both of these batteries, so what is going on? Is the pack voltage dropping so that the current draw goes down?

2) I am building a unicorn, and putting a Mega 16/15/3 in it. I will continue to use the 6x4 prop. I was thinking about using the kokam 2000 (15C 11.1V) pack on it from towerhobbies. Supposedly this pack can do 30A continuously. Does anyone know how well this thing works?

Thanks!!

-Dan
Old 04-29-2005, 11:37 AM
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Default RE: Battery Current Ratings

cinntax,

That setup is drawing a lot more amp than your 1500 can deliver. It may damage your battery in short order! I ran motocalc, it claims you are trying to pull 38 amps!!! what is your esc rated for? The new Kokam 2200 would definatly give you much greater performance.

I dont know the current rating for your motor, or esc, You need to check that first. But DAMN! If you can pull 30+ amps, then you have one hot little motor. Motocalc claims 26oz thrust, 80 mph propspeed, and 1800 fpm RofC. By the way this setup is not very efficient, but very fast?

without know which esc, I would try a 5x3 prop(22amps). It will be way more efficient, and plenty fast. a 5x2 (17amps) would work very well also. I still cant believe how many amps you are trying to draw! Can that motor take it? Your batteries wont even come close to giving it.

Give me more numbers, I will give you free advise, based on throwing dollars thrown into crashing every plane I build...lol

theharpmandan


theharpmandan
Old 05-01-2005, 10:15 AM
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Default RE: Battery Current Ratings

Thanks for the replay Dan!

The motocalc setup you describe sounds like it might be from the Mega 16/15/3 setup. Is this right? In that case, I do have a phoenix 45 ready to handle 38 Amps. I'm more worried about the motor itself getting overheated than anything. I've pretty much come to the conclusion that unless I want to spend $100+ dollars on a lipoly battery, that the answer is a good 9 nicd/nimh cell pack. I'm looking at the GP2000 4/5A cell, but it seems to be out of stock in a lot of places [].

As for the Zagi setup, the astro 020 pulls quite a bit less current.... the motor is rated at 20A. I have essentially a phoenix 25 powering it. Motocalc says that I'm drawing about 18 amps at full throttle (6x4 prop). I'm guessing that maybe since my batteries are rated only slightly below that, maybe I am pushing them a little too hard when I'm at full throttle. Since I don't always fly at full throttle, I guess I'm OK .

If you know where I can get some GP2000 cells (that are in stock), I'm all ears!

-Dan
Old 05-01-2005, 11:11 AM
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Default RE: Battery Current Ratings

try www.cheapbatterypacks.com they should have it. If not there are better battery packs to choose.
Old 05-02-2005, 09:29 AM
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Default RE: Battery Current Ratings

Better than the GP2000's? Which ones? Some of the Sanyo Ni-Cd's maybe? Considering how difficult it is to get my hands on these GP cells, it looks like sanyo is becoming a better option anyway. (Cheapbatterypacks is out of stock on the GP2000's).
Thanks!
-Dan

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