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        Qualcomm's Won't work in the GWS,EDF-50

#1 mtflyr Jun 14, 2002 07:00 AM

Qualcomm's Won't work in the GWS,EDF-50
 
Hey Guys,
Thought I'd bench test the Qualcomm 2 cell lithiums in my Fan-Tastic MiG-15.
I knew it might not work given the 3 amp circuit cut off and the GWS 50 fan pulls 3 amps +-.
If I could limit the throttle to 3/4 or 1/2 it would work but I'm not going to risk it...
These are great batteries if used within their limitations

Pete

#2 Propeller Head Jun 14, 2002 07:34 AM

What about flying without the protection circuit. I realize that this would shorten the life of the battery but it may still be worth a try.

#3 mtflyr Jun 14, 2002 07:53 AM

I know my luck it would blow my plane up or me...
Yeah if someone out there more knowledgeable than me could advise I'd give it a try since I've only made up one pack.
But then how do I charge them? I got the charger that uses the circuit board...
Any ideas?
Thanks,
Pete

#4 Propeller Head Jun 14, 2002 08:05 AM

Charging would be a problem. There are a couple of simple circuits on the internet that can be built from radio shack parts. I went this way because I wanted to run three cell packs on my Piccolo (micro heli). The Piccolo draws just over 2 amps at hover but this goes up to 4 during a hard climb. I've been running the same pack for a week now with no problems.

As for the danger of them blowing up: I guess I'm taking a risk there but at these rates, the batteries are barely getting warm.

#5 mtflyr Jun 14, 2002 08:44 AM

PropHead,
Where did you find the charger info.? Is it on the Qualcomm info.?
Thanks,
Pete

#6 Propeller Head Jun 14, 2002 10:15 AM

I found a nice site HERE .
The first half of this circuit is used to bump up the voltage from a 12V source so that you can charge three cells. I have a 14V power supply so I was able to omit this part. This really makes the circuit simple. The only limitation with this circuit is that it does not have a cuttoff at the end of the charge cycle. I just keep an eye on the lamp. When the lamp goes dim, you know that you're in the second stage of the charge. From that point, I just time it so that the batteries charge for another 15 min.

You can get really fancy without much more effort/cost by using THIS chip. It's a single chip lithium battery charger with built in smarts for ending the charge cycle. It even does low voltage recovery of cells that have been discharged too low. Page 12 of the spec sheet has an example of a simple circuit using this chip.


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