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Old 12-13-2012, 02:59 AM   #1
tr4252
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Question Battery weight; state of the art?

A question popped into my mind today, and I thought I'd put it to the membership here. I don't see this discussed much, in my limited reading of the forums.

Are there significant differences in weight between various brands of batteries which are of the same type? I'm building a plane at the moment, and thinking of ways to keep it light. I realized that the battery (2 cell 600 mA) is the heaviest single component in the plane. These average about an ounce in weight, and if I could get one which was equal in every other aspect, I know I'd pay a higher price if it was considerably lighter.

Are the manufacturers displaying any interest in promoting lighter cells? Can it be done?

Thanks,
Tom
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Old 12-13-2012, 05:47 AM   #2
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Originally Posted by tr4252 View Post
A question popped into my mind today, and I thought I'd put it to the membership here. I don't see this discussed much, in my limited reading of the forums.

Are there significant differences in weight between various brands of batteries which are of the same type? I'm building a plane at the moment, and thinking of ways to keep it light. I realized that the battery (2 cell 600 mA) is the heaviest single component in the plane. These average about an ounce in weight, and if I could get one which was equal in every other aspect, I know I'd pay a higher price if it was considerably lighter.

Are the manufacturers displaying any interest in promoting lighter cells? Can it be done?

Thanks,
Tom
Methinks that an extremely light weight battery might not have the same output voltage capability under running loads than a battery with more "normal" weight.

There are a LOT of battery suppliers out there. My local club has had good luck with those Gens Ace batteries, but they tend to be out of stock.
http://www.hobbypartz.com/gensace25c1.html (Just about every battery in this web page is OUT OF STOCK!)

DennyV
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Old 12-13-2012, 11:31 AM   #3
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TP Pro-lites? Never used them myself.
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Old 12-13-2012, 04:29 PM   #4
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Most battery development over the years has been to create ever lighter batteries. Basically we use LiPo's because they are the (commercially available) 'state of the art' in terms of energy stored to weight. So it's certainly not that battery manufacturers haven't tried to create batteries with better energy to weight. We would be trying to fly model airplanes with lead-acid batteries if that were the case!

Some LiPos are a bit lighter than others. As a rule lower 'C' rated batteries are lighter than higher 'C' rated. Some manufacturers offer special lightweight ranges of batteries such as the TP Pro-Lites, Flightpower Nano Ultra-Nite, and the Turnigy Zippy-compact.. The difference between the lightweight and standard batteries of the same rating is usually very small because they are all restricted by using the same technology.
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Old 12-13-2012, 07:34 PM   #5
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I've been using some Zippy Compact 3S 2200 batts from Hobby King for a couple of my EDF's. I chose them more for their smaller size, but they are a bit lighter as well than the non-'compact' batteries I've looked at. I strain them pretty hard, but they've done well so far.

On HK's site, I only see 2S 500mAh 25c Zippy compacts (no 600's) in their USA warehouse. 29 grams:

http://www.hobbyking.com/hobbyking/s...dProduct=25518
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Old 12-13-2012, 08:25 PM   #6
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In the air
en.wikipedia.org/wiki/Lithium-air_electrochemical_cell

edit:
The above link is obsolete now. New link:
en.wikipedia.org/wiki/Lithium-air

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Old 12-17-2012, 10:29 AM   #7
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Interesting question.
I must admit power to weight ratio has always interested me. For example when I swapped over my NiMhs for my first LiPo

A Turnigy 2200mAh 3S 25C Lipo Pack weighs 188g, whereas
A Turnigy 2200mAh 3S 35C Lipo Pack weighs 199g.
So C rating has an impact on weight as well as capacity. But does brand?

A ZIPPY Compact 2200mAh 3S 25C Lipo Pack weighs 163 grams though.

A Thunderpower 2200 3S 25-50C weighs 170g.
A comparable battery is the Nanotech 25-50C, which weighs 187g.
The TP costs about five times as much as the above batteries, and only weighs 10% less than the nanotech. I'm not sure I'd want to pay an extra 500% to save 17g. So for competition flying I might look at the expensive batts, but then again I could spend that money on other upgrades, performance increases or weight savings too...

Dynam Spitfire, Dynam P-51, Electrafly Camel, scratchbuilt foamboard F-15 and full fuse Spad XIII, paper airplanes, rubber bands, anything I can fly.
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Old 12-17-2012, 12:27 PM   #8
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Originally Posted by SuchIsLife View Post
The TP costs about five times as much as the above batteries, and only weighs 10% less than the nanotech. I'm not sure I'd want to pay an extra 500% to save 17g.
That of course depends a lot on if you believe the specs quoted for batteries. My experience of Hobbyking batteries in particular is that you need do de-rate the claimed 'C' rating by close to 50%. Their 25C batteries might in reality be good for 15-20C, their 45C batteries are good for 25C or so, and on it goes.

I'm not claiming this makes the Thunderpower batteries worth the money, no way I could justify the price Thunderpower want to charge. There are other brands such as Gens Ace whose rating are much more realistic and dont cost much more than Hobbyking.
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Old 12-17-2012, 08:38 PM   #9
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if its all about wingloading, you can go to an even smaller batter if you can slide the battery around, or move it to its cg.

I personally like the extended flighttimes of larger batteries.

I have actually purchased most of my planes around the size of the battery and motor. I like the 1800mah size for park fliers, and you can generally use a 1300, 1500 or 2200mah battery in its place, if you want more or lighter/heavier batteries. Generally the 1500,1800 and 2200mah batteries are about the same length and size, so if you do have your battery set at your cg, then you can use any of them without issue.

I think buying expensive batteries to save a couple of grams is not the best bang for your buck though. For most of us, this is just a hobby, not a competition, or something we want to drop lots of money into, for little benefit. If the price was comparable, i'd be all over the lighter batteries though.
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Old 12-17-2012, 11:26 PM   #10
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Originally Posted by JetPlaneFlyer View Post
My experience of Hobbyking batteries in particular is that you need do de-rate the claimed 'C' rating by close to 50%. Their 25C batteries might in reality be good for 15-20C, their 45C batteries are good for 25C or so, and on it goes.
.
Yeah
Another thread in wattflyer has a battery supplier claiming their batteries are rated to 150C. That is on a 8000 Mah battery that has #12 wire for its leadwires.

Eight amp hours times 150C results in 1200 Amperes. FYI, I've worked with these kind of currents for decades. That kind of current requires cables with conductors near an inch in diameter.

In fact, I used to operate a 600Amp to 5 Amp power current transformer in reverse, and generate over 1000 Amps on AC from a 120 VAC 15 Amp outlet. That level of current would have a 4/0 cable smoking in about two minutes. Came in handy for field fault testing a circuit breaker through its 13 KV bushings without having $$$$ worth of equipment.

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Old 12-23-2012, 02:03 AM   #11
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Does a battery weigh less after it's discharged?
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Old 12-23-2012, 02:42 AM   #12
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Originally Posted by KillerChaos View Post
Does a battery weigh less after it's discharged?
Well, yes. That is if you place a dead short on the battery, it ignites and burns up.

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Old 12-23-2012, 02:56 AM   #13
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Originally Posted by kyleservicetech View Post
Well, yes. That is if you place a dead short on the battery, it ignites and burns up.
Hahahahaha! Good answer!

-KillerChaos
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Old 12-23-2012, 03:15 AM   #14
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Originally Posted by KillerChaos View Post
Does a battery weigh less after it's discharged?
That's a question for Vsauce!

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Old 12-23-2012, 11:45 AM   #15
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Originally Posted by ron_van_sommeren View Post
Obsolete link. New link:
en.wikipedia.org/wiki/Lithium-air

Originally Posted by KillerChaos View Post
Does a battery weigh less after it's discharged?
Yes, due to the wear and tear on the electrons.

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