RCU Forums - Servos and Batteries

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Servos and Batteries

I'm confused ... I'ved used 3004 Futaba servos on my trainer, my 4*60, and my WM T-34 ... no problems. I'm stepping up to a more aerobatic plane and I've heard that its a good idea to get a stronger servo for the elevator ... I was looking at the 3010. There is a warning regarding battery size and draw ... I'm lost ... I've always just used the regular Futaba NR4J Receiver NiCd Flat 4.8V 600mAh J battery ... do I need a different one? Should I use a different one?

I have no idea about different batteries, draws, and servo torque and I thought there might be others who could use a quick lesson from those of you who know. Anyone have time to give me a quick education?

By the way, I'm getting a WM Cap 232-46s ...

RE: Servos and Batteries

Kevin--I'm no expert, but have learned that more powerful servos draw more current, especially digital servos. Why not go to a 6V battery. A nickle metal hydride at 1200mah does not cost very much and will give your servos quicker repsonse and more torque--even standard servos. Just make sure you charge it sufficiently. If you are using a 50mah wall wart charger (like what came with your radio) you need to charge for at least 24 hours. 1200/50=24.

Good luck.

Greg

RE: Servos and Batteries

That charge rate assumes 100% efficiency (which is not the real world). For NiMH in particular, multiply the mAH rating of the pack by 1.4 then divide by the charger's output.

So 1200*1.4=1680. 1680/50=33.6 hours for a fully depleted pack. If you have a 120mHA wallwart charger then 1680/120=14 hours. The 120mAH wallwart charger would be a C/10 rate for the 1200mAH pack. 50mAH will work but takes a lot longer to "fill up" the pack.

RE: Servos and Batteries

Thanks PipeMajor--I knew it takes a long time at 50mah. Isn't that what most of the wallwart chargers put out? I'm surprised the there is that much efficiency loss. I use a Sirius Charge Pro for all my charging and have been very satisfied.

Greg

RE: Servos and Batteries

I guess I'm still not sure what to do here ... is the 9010 servo I was looking at a good choice? Do I really need to step up the Rx battery? Is the only step up going to a 6V? What are the 1500 mah 4.8v or the 1000 mah 4.8v going to do for me that the 600 mah 4.8v doesn't?

RE: Servos and Batteries

Quote:

ORIGINAL: Kevin1963

I guess I'm still not sure what to do here ... is the 9010 servo I was looking at a good choice? Do I really need to step up the Rx battery? Is the only step up going to a 6V? What are the 1500 mah 4.8v or the 1000 mah 4.8v going to do for me that the 600 mah 4.8v doesn't?

A bigger 4.8 battery would be fine. It will also save you having to buy a 6v charger, something the others failed to mention. A higher capacity 4.8 pack will also take longer to charge UNLESS you get a better 4.8 charger. What will a larger pack do? It will give you more safe operating (flying) time. Even with a bigger pack, monitor pack health before each flight.

RE: Servos and Batteries

Quote:

ORIGINAL: Kevin1963

I'm confused ... I'ved used 3004 Futaba servos on my trainer, my 4*60, and my WM T-34 ... no problems. I'm stepping up to a more aerobatic plane and I've heard that its a good idea to get a stronger servo for the elevator ... I was looking at the 3010. There is a warning regarding battery size and draw ... I'm lost ... I've always just used the regular Futaba NR4J Receiver NiCd Flat 4.8V 600mAh J battery ... do I need a different one? Should I use a different one?

I have no idea about different batteries, draws, and servo torque and I thought there might be others who could use a quick lesson from those of you who know. Anyone have time to give me a quick education?

By the way, I'm getting a WM Cap 232-46s ...

I've flown a 900 sq in 4 channel trainer using S3004 servos for several years on a standard 600mAH NiCD pack. I'd get about 4 flights before my voltage dropped down to where I decided to stop. Three years is about average for life of a pack so I replaced this with an 1100mAH NiCD. We recently put 8 flights in succession a few weeks ago.

Aerobatic planes with MORE servos (my H9 US40 has SEVEN servos) will deplete your capacity quicker. I am starting out with a NiMH pack rated at 1650mAH.

Unless you're flying BIG stuff I don't see a need for a more powerful servo than a standard sized one. You can always try 6 volt packs for more "ooomph" if you wish.