Newbie SPAD/Plane Question About Batteries

[slinker]

Hey everyone, I'm pretty new to RC planes and SPADs, in fact I just built my first one the other day (Defender). Anyway, I'm using the battery that came with my Sky Scooter Pro II to power the electronics, its a 600 mAh, 8.4 volt 7-cell rechargeable battery. I was wondering what type of life I could expect out of it on a gas plane. Is there a way to check how "full" it is when gasing the plane up? -- hook it up to a multimeter, maybe?

Thanks for your time.

- Slinker

PS :
I havn't gotten to fly my defender yet, because I havn't been able to start the OS .25 engine I bought for it. I thought I could chickenstick it, but it seems I need an electric starter... dang it. Maybe this weekend. I'll post some pics and talk about my experience. I'm kinda scared. Doesn't seem like it should fly. ;)

[rlt55]

That's too much voltage. Your radio needs 4.8 volts.
Get a new pack at the LHS.

I've always used an electric starter. They work great.
(Make sure your glow plug cell is fully charged)

Buy a 1000 or 1500 mAh 7 cell (Sub-C) pack ($14 to $18) and cable-tie it to your starter. That gives you a portable starter that you can re-charge with your SkyScooter charger.

[slinker]

rlt55,

Thanks for the extra info. I'm actually using the little transformer thing that came with the sky scooter to put out 5v to the reciever, so it should be fine. I'm really using all of the electronics from the sky scooter. But, even if I got a different battery, how do I know how long it should last, or check how full it is?

Slink

[rlt55]

A meter can measure the voltage, but can't tell you how long a pack will last.

There isn't anything that will tell you that, without completely discharging the pack. (That actually tells you if the pack is able to take a good charge or not).

You charge it over night and then sit down and watch TV for a couple of hours with everthing on.
As you watch TV, keep moving the sticks so the servos drain the pack.
When the servos start moving slowly, check the time.
Divide the total test time by 2 and that gives you a nice number to use for flying.

I would not recomend using those little HS-55 servos on the control surfaces of .25 sized glow plane. They don't have the power. You will need larger Servos.

Larger servos need more current than the HS-55s. Your radio has a BEC (Battery Eliminator Ciruit) and it regulates the 8.4 V down to 4.8. and that extra 4 volts (x current) is wasted as heat.

So, not only won't your larger pack last any longer than a normal 4.8V 600mAh pack, your radio might heat up with standard sized servos and start smoking. :(
The higher the imput voltage to the BEC, the more likely it will overheat.

[woodsy]

I'm really using all of the electronics from the sky scooter

BAD IDEA, your SS reciever and servos are NO WHERE near powerfull enough for the Defender, the Defender will be at least 10 times quicker and 10 times harder to fly.