I plan on running a 2s 7.4V lipo battery on a 6V regulator in my 76" Edge540 to power the receiver and servos. Receiver will be Spektrum AR7000 and servos will be 4xHS-645 and 1xHS-5955. What battery capacity would be considered ok for this setup to get half a days flying out of the battery ? I was thinking maybe a 3300mAh might be enough but I'm just not too sure about the drain these servos would put on the battery.

Also if I'm not using a power expander/box and just running a single receiver is there any added benefit in running dual batteries on different switches, if you can do such a thing? Can someone give me some examples of a good power setup that doesn't require a power expander/box ?


Thanks, FJ

oh i forgot to add, i'll also be using a smartfly ignition cutoff as well and a standard servo for throttle

My opinion only.

I would rather run dual 2100's than one 3300 or 4400. I run dual batts on all big planes just for redundancy and safety. Price is abou the same. Dual switched plugged right into the AR7000. ONe inthe battery slot, one in any open slot. see my pic

Now that said, my recommendation is to go to Troybuilt models website and use their Lithium Ion batteries that they sell if you want to use a regulated system. I would recommend miracle switches in that setup. OR if you havent made the investment, you can use A123 M1 Lion batteries without a regulator. read up on them. they require a special charger, but I like them alot. they are 3.3 volts per cell instead of 3.7 nominal.

Why: you can scale up to larger plane with same setup.You can use the same charger. I am not a fan of LIPO's on a plane like this.

I am not a fan at all of the 645 servos, so if you haven't bought them, I would recommend something else. the 5955 is a great servo. 5985 is a great servo, JR821 is a good servo for sport. I personally prefer coreless motor servos, they are more crisp. my opinion though. I have 635's and 645' on a plane and they dont center well and are slow to me. JR8411's are also great, they were the standard not long ago.

http://www.troybuiltmodels.com/Servos.htm go here and study. then go to JR-radios.com and look there too. I try to remain upwardly mobile on servos. my personal preference is 5955's and 8611A's. I use them on everything large. I know its over kill but they friggin work, and theyare fast and strong. A 73 inch plane can use smaller servos though Im concerned about flutter on 645's. I think there are better choices. by the way, TBM has about the best prices on gear.

good luck.

thanks for the info goosef22.

I already have the HS-645's so I'll have to stick with those and see how it goes.

As for the dual batteries I didn't realise you could plug the battery into any old slot on the receiver, I'll definately run dual batteries/regulators/switches now for safety. With a dual battery setup like that I assume that power is drawn equally from each battery?

I've been reading about the A123 batteries and they do look promising but the batteries are rated at 6.6v. I thought recievers/servos could only take a maximum of 6V? If you don't use regulators won't you be overloading the receiver/servos?

Do not skimp on the regulators. We have had had two crashes of new models at out club which were traced to the regulator voltage dropping when a power surge occurs and triggering a fail safe condition.

I am not going to name the regulator manufacturer but they were not mainstream.