battery charger for smartech skylark
 

Hello again:
I seem to have fried a my batteries because of not really monitoring the dumb charger that the factory provides for my little heli. I am going to buy new batteries, but I don't know if anybody have any siggestions or knows where to buy a more intelligent charger, which won't kill my battery packs. Sometimes is really not possible to monitor the batteries while they are charging...
Also, if I stick with the dumb charger, whats the best way to monitor the batteries. I know one is the temperature, but what should the voltage be when the pack is all charged?

thanks again,

guillermo

RE: battery charger for smartech skylark
 

gmozavala,

There are many types of battery chargers out there. Depends on how much you want to spend, or how fancy you want it.

I am using the supplied wall charger, and am a Comp Engineer. The magic number is:

If your wall charger specifies say 500ma, then just divide your battery capacity over 500ma.
My setup is:

750ma battery 7 cell AAA pack
500ma wall charger (9v radioshack ac adapter with the modified connector)


So 750ma/500ma = 1.5 hours of charging.
That will do you very well.

Some assumptions must be made however:
1. The voltage rating of the WALL ADAPTER/CHARGER really should match the total voltage on the battery pack. (or must be slightly higher by 1 or 2 volts, no higher. and certainly not lower.)
2. you've drained your pack to the point where the heli will no longer spin fast, but not dead. dead is bad for nimh.

I often wait for the batteries to cool after a run (probably 10 minutes after a flight) before charging them. Just buy a few packs and you'll be WELL off. Don't settle for one battery pack, trust me, I've been there and it s**ks.

Good luck

-Dan

RE: battery charger for smartech skylark
 

thanks:
the charger I have is 9V and 350 mAh, so it should take a couple of hours to charge. My battery pack is 8.4 V and 700 mAh.
However, if I measure the voltage with a voltmeter (output of the power adaptor) it indicates 13 volts, which is rather high. Thats been very confusing to me because when I have mesured other AC adaptors their voltages always seem much higher that the rating. I don't know if there is something wrong, of if the voltage will go back down when a load is applied.

guillermo

RE: battery charger for smartech skylark
 

Yes you are correct.

The measured voltage is because the "cheap" wall chargers are not designed to handle much loading, so a small load will cause the voltage to fall lower. Although the measured 13volts does seem a bit high for 9v. I can see 10.5 to 11.5 volts, but 13?

That's probably due to the lower 350 ma that it outputs. That would mean that the transformer(wall charger) has a higher impedance or resistance so a smaller shunt load (in this case the battery) will bring the voltage down.

Hope this helps,

Dan

RE: battery charger for smartech skylark
 

thanks:
I checked the voltage again while the battery was connected and measured 10.7 volts, which seems a little more reasonable.
any suggestions to buy a smarter charger for that battery?

thanks

guillermo