If you had the choice what trype of pack would you go for?

the last time around I went for a 5 cell NiMH pack and was pretty please with the results, but with the greater demand of more powerful servos, what now?

Is NiCd better for the current draw is is NiMH better for lower pack weight?

I still don't think I trust Lipo for a flight pack, but maybe one day I will..

Read this. It may help you make up your mind.

http://www.hangtimes.com/weightcompare.html

No problems with lipo.. I use a 2 cell 780 mah battery and regulator..I use hi speed hi torque digital servos and can get 14 flights before charging... I know at the NATS guys where using 340 mah packs.. Now don't forget I'm flying electric and don't have the current draw like IC planes..

Scott Anderson

If you don't go lipo + reg, I'd say NiMH....I use them on a glow set-up that consumes around 200 mAH on a P07, and can't see any effect on servo performance throughout the flights.
Some of the modern NiMH cells have quite a high discharge ability(mine claim 20C),and seem fine on my all digital servo 2M plane at10 1/2 lbs. dry.
I have used packs as small as 600mAH when weight has been an issue(recharging at 1C after each flight),but currently use a nominal 1100 pack,which I recharge at 1C after 3-4 flights----there wasn't any flying problem with the smaller pack, but bench reading of the voltage drop under load was a little worrying.

I'll be drawing a fair whack of current methinks.

ANd there AINT NO WAY i could pull 14 flights in one day not have bubbling stew for a brain.

Shoot my brain would also be a mess with 14 flights in one day... When going to a contest I charge that Thursday prior and fly Friday a practice flight or let one or two others try the electric, then a 6 round contest over the weekend with out having to charge again..

Anyhow just part of my planes diet plan

Scott

Scott,

Is there a recommended discharge capability if going the lipo/regulator route?


-mark

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780Mah / 14 = 55.7Mah per flight???
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Must be really short flights!!!
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Don't forget it is being regulated down to 6V from 7.4 (or whatever the Lipo voltage is), so you gain that in capacity.

7.4/6 = 1.233 times as much capacity based on the voltage step down.


Mark

Flights aren't really much shorter, just tremendously less vibration in an electric setup. The electric setups are routinely using only 55 to 60 MAH per flight. Tested and verified more than once.

What I am not seeing here is the use of LiIo technology unless it is being confused with LiPo. LiIo is much more stable but heavier than LiPo, but not as heavy as NiMh. Almost all our planes are now on LiIo w/ a regulator. Other than using a LiPo/ LiIo capable charger I don't treat them any differently than the other technologies. LiPo however needs to be monitored more closely while charging and we take the battery out of the plane to charge.

The flights are the same length as normal and even doing FAI in the TEN minutes the mah draw is like stated above 50-65 mah per flight.. Thats why a 340 mah pack at the NATS was used..I'm using a 2 cell Tanic 780 mah pack with 15c and 20c burst in to a voltage regulator at 6volts..no problem and I know a bunch doing the same.. Yes charge outside the plane or like me I have two packs for RX and can fly alot if needed.. The scare of lipos and charging is just that.. Get good cells and a good charger.. The latest fire by lipo is where the pilot put on charge and forgot about it and had a issue, must have not been a good charger..
I'm not looking to put the flame suit on for above, just know what works for me and many others doing the same..
The other issue is less wear and tear on servos with electric planes, the servo pots are not wearing out..

well need to charge packs and go do a flight demo today..

Cheers..

Scott Anderson
Team Tanicpacks.com
Team Castle Creations

And what about using Futaba digital servos with LiPo packs, (7.4v reduced to 5.5v)? I ´m asking because in some servo pakage said use only with NiCd and 4.8v.

We use Futaba digital servos on 7.4 regulated down to 6.0 volts. No problems.

I use NICAD´s . Digital servos recomend to use these type of batteries, why dissagree whith the manufacturer?

i use 6V 1.700 MAH, it last 6 or 7 flights.

I think that the Lithium Ion batteries are being confused with LiPo. Most of the guys I fly with use the Lithium Ion batteries from Central Hobbies regulated down to about 4.9 volts, and when I finally get my hands on the Genesis I'm about to buy, that's what I'll be using.

I have used Lithium packs for more than several years, puffed them, blew them up, tested them to see what their limits are in the context of RC planes. At one time, I was carrying more than 9000MAh on my GP 1/4 scale Giles just to amuse myself and get great reaction faces from my flying buddies. The cells were 3 sets of 7.4v at around 3000MAh each and regulated to 5.4v.
A few of things I noticed. First and foremost, Lithium technology failure results in an OPEN circuit. Zero volts. This is akin to NiMh technology but NiCd shorts closed so if a cell in a 6v pack dies, you still get 4.8v. That's why I double up on my rx and servo batteries.

From what I have experimented with, while both LiIon and LiPo batteries are both great, the new LiPos can deliver much more current than LiIon cells. LiPo cells can now deliver 30C or more if needed without killing itself. The most I was able to get from LiIon cells were less than 2C...more than that and you're looking at an early demise. Saying that, I make packs that are 3000MAh 7.4v so I can safely get 3 amps.

Also, LiIon cells can't seem to take "abuse". Drop one from about shoulder height and you'll see when you try to measure for voltage. Zero. When broken as in a crash, the do sometimes catch fire. This is unfortunately, first hand knowledge :-( They are basically high pressure vessels that is held tightly by the casing.

Even though I may have "bad mouthed" LiIon batteries, I still use them because I have several packs already made up. I just double up on the cells and encase them in foam inside the plane. Also, if you're a DIY guy, you can "liberate" excellent 1100MAh batteries from Canon packs. Right now, my Canon 300D has an external battery pack that is 7.2V, 4500MAh made from the infamous Sony cells from Notebooks. You can also get good cells from "bad" notebook packs. Usually, notebook packs are 3S3P, 10.4v at xxxxMAh. When they go bad, often you will find 6 or more good cells if they are not dropped. I used to do this on old, "broken" Toshiba packs. There's a plus side too. These packs usually come with a built in charger although you need to have some soldering skills.

When I make my packs, I run a continuous test of 1C charge and 1C discharge for about 10 cycles just to make sure I didn't thermally ruin the packs and whatnot.

Given a choice, and money, I think I would prefer LiPo packs only because they are lighter and can handle physical, electrical, and thermal stresses better. I will still use 2 in parallel for safety.

Unfortunately, the question in this thread is NiMH vs NiCd. I prefer NiMh only because it is a proven technology, much lighter than Nicad (by capcity) and does not develop memory. Then again, Nicads generally handle more current better. I said generally. I haven't used NiMh and Nicad in a few years except in F5B planes. More power can be applied to digital servos as needed without dropping the voltage to unacceptable levels. I said generally. I haven't used NiMh and Nicad in a few years except in F5B planes.