Rcpilot

My Feedback: (78)

I'm assembling the World Models giant Extra 300S--80" wingspan. I'm considering runnng 2 RX batteries and switches.

I'll be running JR8231 Digital servos on both ailerons and both elevators. I have a JR8411 Digital for the rudder. A JR537 on choke and a JR3021 on throttle.

Hitec Supreme 8CH RX

JR Matchbox for elevator servos-- powered by the RX battery.

I have a 50cc gasser. 1400mah NiCd 4.8V on ignition.

I have concerns about battery redundancy on the RX. I have a 6V niMH 2700mah for the RX. I'm considering a second battery of the same size and voltage. I would run it with a seperate switch.

This would mean that the plane would actually have 3 batteries and switches. 1 battery and switch for the ign. and 2 batteries and switches for the RX.

Is this a good idea- or just wasted weight?

I've read a lot about using 2 RX batteries on some of the expensive planes. This might seam like a cheap plane to some of you, but for me, this plane is at the high end of my budget. I want to do everything I can to help this plane survive for a long time.

I know that it can't hurt to have it, but would running 2 RX batteries and switches on this plane just be wasted money and weight?

Thanks

BobPhx

Personally, I'd run dual batts and switches, although 2700 each might be a bit much. I run 2 2000's in my 33% cap. I might try two 1650's. That way they are still AA size, not much heavier than 1 2700 pack, probably. Make sure you gently cycle the packs a few times to "shape" them.

This is the cheapest, easiest and one of the best ways to get battery redundancy on 33% and smaller planes. There's a wiring diagram on the "33% Cap" section of my page if you're interested.

You'll get lots of different opinions on this question (fail safe switches, Li-ion, ni-cd, etc, etc.) this is just mine. Good Luck!

Rcpilot

My Feedback: (78)

I've been over to the battery clinic and read his recommendations for dual batteries on the RX.

I wouldn't bother with any fancy doides, fuses, links, etc... with my setup. I would simply run each battery on a switch and plug into the open ports on the RX.

I realize that the 2700mah packs is a little overkill, but I already have one. I wanted to keep the packs the same size. I could run a pack with same voltage and less mah rating, but I wanted to keep everything the same.

My current pack is brand new- never flown. I always run the packs through a few cycles before flying them. It seams to take about 3 or 4 cycles for a NIMH to come up to full capacity. I slow charge them at 125mah charge rate for 30 hours; then discharge them at 50mah drain. Only the 2700mah pack gets this treatment. Other smaller packs get charged less according to their mah ratings. I do this at least 3 times and sometimes as much as 5 times to assure that they are up to snuff before flying them.

Thanks for the quick response.

BobPhx

Based on my experience, it sounds like you are doing everything right. Red is the expert. I agree that you want to keep the packs the same size, capacity-wise. You'll get lot's of flying in with two 2700's! Please post some flight reports, I'd like to hear what you think of the plane.

Flyfalcons

Why are you using a matchbox on the elevators? Can you do twin elevator servo mixing with your radio?

Rcpilot

My Feedback: (78)

I'm using the JR652 6ch radio. Unfortunately, it will not properly mix the 2 elevator servos. I can slave one servo and use the other as a master- but trim functions won't trim both servos in flight. Wish I had an 8103. So, I gotta use the Matchbox.

I'm sure that a combined mah rating of 5400mah will be plenty for a day of flying. I'll have to keep an eye on my ignition battery more than the RX batteries.

I've gotten lazy with this ARF. I haven't touched it in 2 weeks. I still need to install the Rudder servo and pull-pull cables. Also need to install the throttle and choke servos and pushrods. Elevator servos and H9 Pro Links are installed. Ailerons servos, horns, and H9 Pro Links are installed. Tank is installed on the CG. Engine is installed and cowl is cut.

I really need to get off my butt and finish the rudder, throttle and choke. Then I could fly it- if the weather would cooperate. It's been cold here for a week.