Nicad or NiMH for Rx Pack?

[FlyingW]

All,

What is better for large radio/servo setups? I have the following:

Ailerons - 2 HS-635s
Elevators - 2 HS-635s
Rudder - HS-645MG
Flaps - 2 HS-645MGs

I am currently using an Rx pack made from four (4) Gold Peak 2000mah cells.

Any opinions on whether or not I should use a Nicad battery instead for the radio?

Thanks,

Paul

[kris_pwnz]

Hi.
Well, if You have so large setup, You better use NiMh cells, because they can hold more mAh, than the NiCd. I use Nickel-Cadmium cells in my own radio and rx. NiMh cells have higher discharge rate when they are not being used. My opinion is to use high capacity NiMh cells for Your large setup.

[kenhiraihnl]

just my .02...i use similar servos in my gp giant ss...i was using a hydrimax 2000mah panasonic nimh 4.8v pack...voltwatch showed major voltage drops when working the servos...i had a few lockouts due to the berg7 taking brief naps because of undervoltage--until the tsr took hold again (my theory)...now i use a 3s2200 lipo connected to a hyperion bec with 6v output...no problems...ken

http://www.aircraft-world.com/shopexd.asp?id=4637

[margaret.roberts]

NI-CADS tend to hold higher voltage when cold winter flying.

[Larry3215]

You will save weight and get more consistant servo action (no voltage sag) with a lipo pack and regulator.

Costs a lot more tho.

Larry

[FlyingW]

Thanks All,

The point about cold weather operation of Nicads rang a bell in my distant memory. I just remember them be less finicky than NiMHs.

Also, I thought about using Lipos and a regulator (I do that on another plane, 3s into a UBEC).

I will test fly on the 4xGP2000s and monitor the Rx pack performance closely.

If the plane is successful and called on regularly, then I may upgrade to a LiPo/regulator arrangement.

Paul

[margaret.roberts]

If you are willing to go to the weight of GP 2000's, why not get GP 2200's for a few grammes more, you are not going to have any issues regards volts/current/fast charging.
There are loads of cheap li-po packs these days, my favourite source is real157@cox.net that is Richard Edmonston of Florida, top quality/price HECELLS.

Maggie.

[GWRIGHT]

As stated above, a little more costly, but a small lipo pack and regulator gives constant voltage,.. and a lot of capacity for a given weight. I use the U-bec's from koolflightsystems. On smaller stuff up to 1000 or so watts, I use a single one off the flight pack, on some larger stuff I have the dual setup (two u-becs feeding seperate plugs in the reciever for redundancy, they make dual setups with diodes and such so they won't back-feed each other). On an 85" YAK I'm finishing up that will use 12S at over 4000 watts, I'm using a dual u-bec setup , each with a seperate 3-cell 910mah lipo so I have redundancy in the rx batteries as well as the regulators. This plane has 5 digitals, 4 of them 9155's at 192 oz/in and one 9152 (rudder) at 278 oz/in. , so I wanted the dual setup for both redundancy everywhere, and to handle lots of current.

[kenhiraihnl]

excellent points made, gary...reading about your setup got me thinking...i've accidentally knocked my switch on while loading my plane in the car, and arrived at the field with a discharged battery...however, with my lipo/regulator setup that shouldn't be a big problem anymore...here's my point...should i install a better switch? i hate to have an electrical failure because of a switch...is something like this worth it? ken.

http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXXA49&P=7

[margaret.roberts]

Just mount switch internally away from switch killers like dust/water/oilspray from engines and use a pull'pull system with thread to each side of fuz. drill small hole in switch actuator. Cannot then be accidentally switched.

[kenhiraihnl]

thanks...i've mounted switches internally, i.e., on the servo tray, but never thought about a pull-pull system, as you described...i'm now trying to think of a neat and clean way to actuate the slider on the switch... :)
-ken

[margaret.roberts]

I sense a smirk but ref to oilspray is in connection with being downwind of glow models. :)
Maggie.

[GWRIGHT]

I'm not using switches at all. I plug the batteries into the u-becs on each model. No switch, so there isn't a switch to fail.

[kenhiraihnl]

hey gary...you gave me a fantastic solution...my polyquest 3s2200 lipo pack already had a deans ultra female on it...i soldered a deans ultra male on the input side of the bec...i could plug the bec output directly into channel 3, and bypass the switch, which will be a 'dummy' switch--serving no purpose, other than to confuse someone watching me prep for flying... ;)...thanks...

paul...sorry for hijacking your thread, but i learned a lot from gary and maggie...ken

[FlyingW]

That's fine; I'm learning a lot from it as well - especially now that the thread has come alive.

Ok, now that Gary Wright has put it on the table, can we see a schematic of the dual regulator with anti-backfeed diode arrangement?

I agree with not using a switch; I also just plug the battery into the UBEC when prepping the plane for a flight. Plug the Rx pack in first, check the radio, then plug in the motor battery.

[GWRIGHT]

I've used switches in the past, and like to use them,.. their convenient and you don't have to have a hatch off at the flight line to plug things in,..but it makes more sense from a dependability standpoint to plug in and out rather than using a switch. Sort of the KISS principle at work <G>

As for the duals,..910mah 3-cell (could use any size of course), deans plug since I use them in power systems also and have quite a few. Solder deans onto ubec, plug u-bec into any un-used channel. Repeat for other u-bec. Then connect 12S pack to ESC.All the positives and negatives on a reciever are like a bus-bar,.. all connected, so you can use any channel to plug power in.

[callen]

I'm not using switches at all. I plug the batteries into the u-becs on each model. No switch, so there isn't a switch to fail.

But isn't the plug and unplug just about as unreliable as a poor switch. Connectors fail more than switches if pluged and unpluged a lot. However I will never second guess you, just trying to widen the conversation. Will we get to see your talents at SEEF again this year?

I have many of the Kool Flight UBEC's and have never had one fail. Run them off of 10s lipos also. No backup. Maybe I'm pushing my luck.

[GWRIGHT]

You're assuming my planes last longer than the plugs,..which isn't normally the case <G>

I've got a few things to bring to seff this year. Planning on driving up wednesday, playing some golf, then flying for 4 days. If the sailplane thing has the field totally occupied thur, we might go hit some more golf balls into the woods that day too.
I'm very anxious to get the yak done for seff,..should be around 250~270 watts per pound <G>

[margaret.roberts]

[QUOTE=GWRIGHT]You're assuming my planes last longer than the plugs,..which isn't normally the case <G>

NICE ONE,HA.
M.