Reborn IC'er

[Frank Day]

Just picked up a first IC model in many and I mean many years. Giving it a thorough overhaul as its been pre-enjoyed.

 

Looking for advice on RX battery, composition, Mah, prefer to go 6V. Model is a 1.8m Piper Cub, Futaba standard servos  4 channel.

 

I have a 6v unbranded pack but cant remember the capacity and the 4.8v that came with it charged from dead to full in about 10mins! so to the bin I think. Looking at 2600 to 3300 or is that too much.

[payneib]

On a plane that big I'd be tempted by 3000mah of 2s lipo, regulated to 6v. Preferably split between two independent battery feeds. 

 

You've got more than enough space and weight capacity. 

[Martin Harris - Moderator]

We used to fly models like that on 700mAh NiCds (and less) all afternoon but my choice would be 2S LiFe batteries as they can be charged in situ. To take the edge off the voltage, I’d use a silicon diode between the switch and the receiver. 
 

For belt and braces, you can use twin packs, as advised above. The diodes will add additional protection without the complexity of a voltage regulator. 

 

Total capacity won’t need to be more than 1000 mAh - any more is carrying unnecessary weight in my opinion. 

[martin collins 1]

What diodes would you recommend, do model shops sell them or is it an online job?

[Martin Harris - Moderator]

I’ve used these but others may be in a better position to advise:

 

https://uk.rs-online.com/web/p/schottky-diodes-rectifiers/4863029?gb=s

 

I have got some higher capacity ones recently but 5A should suffice. 

 

Phil Green recently warned against vibration and strain effects on the pins.  I’ve soldered leads in switch harnesses without any problems but he might have envisaged diodes being soldered onto switches? 
 

Don’t put the diode between the switch and the battery or you won’t have much luck trying to charge the battery!

[Andy Stephenson]

1 hour ago, Martin Harris - Moderator said:

Phil Green recently warned against vibration and strain effects on the pins.  I’ve soldered leads in switch harnesses without any problems but he might have envisaged diodes being soldered onto switches? 

I agree with Phil, the wire ends on that 5A diode are far too thick and heavy to be soldered directly to the switch terminals any movement could cause the solder joint to crack or it could even tear off the lug. Far better to solder it into the wire, properly finished in heatshrink sleeve.

[Martin Harris - Moderator]

Yes, that's exactly what I've always done.

[Wookman]

5s 2000mah AA Sanyo Eneloop LSD Nimh.

Simple and reliable.

Make sure the servos are rated for 6v.

If not use a 4s as above.

[David Davis]

We used to fly all day on 500 and 600 mAh nicads back in the Eighties. I would be happy to fly this model on 2000 - 2500 mAh Nihms. It keeps things simple. Which engine do you have in it?

Edited August 16 by David Davis

[Frank Day]

SC52 4s  OS 52 clone, checked, all the servos are good for 6V, replaced the 4.8v sanwa which was the odd one out rated at 4.8V only

[Frank Skilbeck]

My choice would be a 4 cell sub C pack around 3300mah, it wouldn't even blink at the max load all the servos could pull, where as high capacity AA cells will see a voltage dip.

 

Also check that the switch is in good condition and not an inline resistor.

[Engine Doctor]

14 hours ago, Frank Day said:

Just picked up a first IC model in many and I mean many years. Giving it a thorough overhaul as its been pre-enjoyed.

 

Looking for advice on RX battery, composition, Mah, prefer to go 6V. Model is a 1.8m Piper Cub, Futaba standard servos  4 channel.

 

I have a 6v unbranded pack but cant remember the capacity and the 4.8v that came with it charged from dead to full in about 10mins! so to the bin I think. Looking at 2600 to 3300 or is that too much.

Bin the battery or just use it for setting up. Taking a Charge that quick suggests low capacity /damage due to being discharged for so long. If you want Nimh 6 v packs use the latest type that come ready charged. Only use packs AA packs up to around 2000 mah . Higher capacity AA cells are too fragile internally. Sub  C type 3300 mah  will be fine and give plenty of power without voltage drop.

[Nigel R]

1.8m of Piper Cub will fly on a 0.25 two stroke, so I'd be keeping this as simple as possible, I'd fit a 2000mAh Eneloop AA pack, just one of them.

 

Do get a new pack and bin that old one!

[Robin Colbourne]

Given how we used to fly this size model on a 450mAH 4.8v nicad, the capacities (3000mah+) being suggested are very high.  I would be looking to go for redundancy as opposed to more capacity.  The switch is the weak link in the system, particularly if hard-mounted to the fuselage side, with the welded joints in the battery pack in second place.  Two smaller AAA or AA battery packs with separate switch harnesses would be the belt and braces approach.

[leccyflyer]

Also worth noting that there have been reported issues with high capacity AA sized NiMhs, such that anything much above 2200mah 4.8v, really do not have that great a reputation in terms of delivering their claimed capacity. The Enerloop cells in the 2000-2200mah range are pretty much bullet proof, but go above that into really high capacity and those AA sized cells don't really cut the mustard. If convinced that you need 3amp hours for the radio alone then it might be worth going to Sub C cells instead, but as pointed out, we used to fly a lot of standard club-sized models on 4 cell NiCds of 500-600mah capacity and were happy to do so all day.

[Frank Day]

Thanks for all the replies,  the enerloop option keeps popping up so I'll take that recommendation. As for capacity I simply wasnt sure what was needed as I've just been on electric and they are spent very quickly.

[Jonathan M]

A 2000mAh 4.8v will be fine for your 6ft Cub.  I use a 2000mAh 4.8v Eneloop in my IC Gangster 63 with standard servos. Half a dozen or so 12min flights, call it 1.5hrs all told, which is a lot of big aeros flying over a half day session, uses no more than half the capacity (noting what I put back in when recharging).

 

Even though it's a NiMH rather than a Nicad, I do like to cycle the pack frequently (charge back up after flying, slow discharge to 1.0v per cell, then charge back up again).

 

 

[Don Fry]

I quote the instructions on building a Flair DR1 Triplane, 6 foot span, for 120 size motors. We recomend using a larger battery than standard. We suggest 1200 mAH. 
Just shows how much capacity we think we need nowadays.

[Frank Day]

9 hours ago, Jonathan M said:

A 2000mAh 4.8v will be fine for your 6ft Cub.  I use a 2000mAh 4.8v Eneloop in my IC Gangster 63 with standard servos. Half a dozen or so 12min flights, call it 1.5hrs all told, which is a lot of big aeros flying over a half day session, uses no more than half the capacity (noting what I put back in when recharging).

 

Even though it's a NiMH rather than a Nicad, I do like to cycle the pack frequently (charge back up after flying, slow discharge to 1.0v per cell, then charge back up again).

 

 

Thanks everyone, I've ordered a Eneloop 2000mah 6v hump pack. and a new rx switch with charging port rather than having to dismantle for a recharge or run a random extension lead and have it flapping about.

[Frank Day]

The instructions for this older model- World Models 1.8 Piper Cub simply say a suitable rx battery so little help for the inexperienced so to me that's see what's available and err to the larger capacity, the pack that came with it is 4 cell 4.8 so an extra AA isnt going to make any difference weight wise and offers the servos a bit more power,  needed or not. The Eneloop was recommended by a few, I opted for the standard 6v rather than the Pro.

[Jonathan M]

Good call Frank, and I also like switches with an integrated charging port.