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Batteries & Chargers Discuss Li-P, Li-Ion, NiMh, Nicad battery technology and the chargers that juice 'em up!

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Old 12-19-2016, 04:43 PM   #1
Spike101
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Default choosing the right size batteries for my 1880mm

I am confused as to what batteries I should purchase for my 1880mm Corvus 3D airplane. Regular sport flying for now.

Motor: 110 brushless 295kv eflm4110a eflite (65amp max burst current 15 sec)

ESC Castle 100 amp cse010010000

Airplane should end up around 11 pounds

I am thinking 4S x 2 to equal the 8S requirement

2 x ZIPPY Flightmax 3000mAh 4S1P 20C?



What would you recommend?

Thanks for your help
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Old 12-20-2016, 12:06 AM   #2
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eCalc ......

Try out different combos till you get the numbers you want .....

Nigel

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Old 12-23-2016, 04:52 AM   #3
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added more info to original post.
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Old 12-23-2016, 04:56 AM   #4
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Did you look at eCalc ?

Honestly - it will answer all for you.

Nigel

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Old 12-23-2016, 02:47 PM   #5
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You'll want the highest C rated batteries you can afford. The 20C Zippys won't cut it at the currents you are going to need. Flight time will probably less than 5 minutes for a typical 3-D style flight. You may want to go up to 4 or 5000 mAh batteries.

I know you said regular sport flying for now, but trust me, that will last for about five minutes and then you'll want to see what the plane can do.

It's never too late to have a happy childhood.
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Old 12-23-2016, 05:15 PM   #6
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Okay I found some Floureon batteries 2 x 5500mah 4S 40C , but damn that is 2.5 pounds of batteries..lol
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Old 12-23-2016, 07:59 PM   #7
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I would seriously look at the Roaring Tops. Great lipos. Compare weights with all the others and I regularly use Admirals, CHL's, Pulse, Zippy's, Gens Ace, you name it, I've tried them. You will be surprised as was I. They're my new best friend.

Just bought a pair of 4S 3700mah 45C's to go into my new 1600mm F7F TigerCat twin. She's a hoss.

Andy has some 5000 70C's that weigh 523 grams. Doesn't get much better than that. Light is good.

http://rcjetwerx.com/product/4s-5000-70c/

US warehouse. Come with Deans connectors attached

Cheers,

Hawk
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Old 12-23-2016, 11:44 PM   #8
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So before a battery can be set - what prop are you going to use ?

This is a 5kg model all up ..... sport flying or 3D .... alters pitch / diameter ....

It is usual to match battery - motor - ESC - prop to get best combo. Just because a manual or sales blurb says 8S does not mean always 8S ....

Nigel

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Old 12-24-2016, 01:32 AM   #9
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Originally Posted by solentlife View Post
So before a battery can be set - what prop are you going to use ?

This is a 5kg model all up ..... sport flying or 3D .... alters pitch / diameter ....

It is usual to match battery - motor - ESC - prop to get best combo. Just because a manual or sales blurb says 8S does not mean always 8S ....

Nigel
Hi Nigel,

18 x 10 prop with 8S to 12S 3300-4400mah batteries is suggested by the manufacturer. I could not get ecalc to work, I will have to try it again.

Ken
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Old 12-24-2016, 02:17 AM   #10
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Ecalc is so cheap to register ... worth doing it properly.

18x10 seems about right on 8S ..... for sport flying and when I put some numbers into ecalc gave me just over 1:1 thrust ratio with 18x8 ...... 4000 pack .... and about 8 mins flight time.

Nigel

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Old 12-24-2016, 08:28 PM   #11
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Originally Posted by solentlife View Post
Ecalc is so cheap to register ... worth doing it properly.

18x10 seems about right on 8S ..... for sport flying and when I put some numbers into ecalc gave me just over 1:1 thrust ratio with 18x8 ...... 4000 pack .... and about 8 mins flight time.

Nigel
Got Ecalc to work and came to the same conclusion as you.
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Old 12-24-2016, 09:16 PM   #12
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Thought about going to 10S batteries, but the Ecalc shows the voltage would be to high for my 100amp ESC rated at 34volts. So, I guess I will try the Turnigy nano-tech 6000mah 4S 25~50C Lipo Pack x 2.
Calculator states I should get around 11 minutes fly time.
18x8 prop gets me 60mph, 18x10 gets me 75mph.
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Old 12-26-2016, 05:40 PM   #13
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Originally Posted by dahawk View Post
I would seriously look at the Roaring Tops. Great lipos. Compare weights with all the others and I regularly use Admirals, CHL's, Pulse, Zippy's, Gens Ace, you name it, I've tried them. You will be surprised as was I. They're my new best friend.

Just bought a pair of 4S 3700mah 45C's to go into my new 1600mm F7F TigerCat twin. She's a hoss.

Andy has some 5000 70C's that weigh 523 grams. Doesn't get much better than that. Light is good.

http://rcjetwerx.com/product/4s-5000-70c/

US warehouse. Come with Deans connectors attached

Cheers,

Hawk
Thanks for that,I will be ordering from them this spring.Dean
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Old 12-26-2016, 07:42 PM   #14
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Originally Posted by dahawk View Post
I would seriously look at the Roaring Tops. Great lipos. Compare weights with all the others and I regularly use Admirals, CHL's, Pulse, Zippy's, Gens Ace, you name it, I've tried them. You will be surprised as was I. They're my new best friend.

Just bought a pair of 4S 3700mah 45C's to go into my new 1600mm F7F TigerCat twin. She's a hoss.

Andy has some 5000 70C's that weigh 523 grams. Doesn't get much better than that. Light is good.

http://rcjetwerx.com/product/4s-5000-70c/

US warehouse. Come with Deans connectors attached

Cheers,

Hawk
Those batteries would save me about 400 grams weight on a 2 pack, but at a cost of $56.00 more than the heavier batteries. That is roughly .14 cents a gram more. I have to decide the value to me I guess.
I suppose I could use the Roaring Tops 4S 5800 35C x 2 and save the weight. It would only cost me 3 dollars more than the Turnigy nano-tech 6000mah 4S 25~50C Lipo Pack x 2. One would think the performance would be about the same.
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Old 12-26-2016, 10:34 PM   #15
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Originally Posted by Spike101 View Post
Thought about going to 10S batteries, but the Ecalc shows the voltage would be to high for my 100amp ESC rated at 34volts. So, I guess I will try the Turnigy nano-tech 6000mah 4S 25~50C Lipo Pack x 2.
Calculator states I should get around 11 minutes fly time.
18x8 prop gets me 60mph, 18x10 gets me 75mph.
Glad to see a happy chappy !

Ecalc really takes the fuss out of this ... and note that it errs on safe side. I usually get more than it shows.

On the subject of increasing cell count. Ecalc is good because it shows that its not the universal answer to just add cells. My Edge 540 - posts on RCG go on about using 6S and pushing the 4250 motor to limits. Ecalc showed I could use 5S ... motor staying well inside design specs .... and get as good or better than they were .... matter of balancing prop to power etc.

Cheers
Nigel

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Old 01-11-2017, 05:15 AM   #16
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I ended up going with two Zippy 5000mah 30c batteries.
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Old 01-11-2017, 08:09 PM   #17
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Default Somtimes you can find big ones

Sometimes you can find big batteries with 5000+ mah. That's really the way to go. Capacity is everything!
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Old 01-12-2017, 05:26 AM   #18
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The starting point is to take your ESC Current Rating and divide by 20.

So if you have a 100 Amps ESC / 20 =5 or 5000 mah. The number 20 is the battery max C-Rate of 20C. If that is to big and heavy bump up to 30 which would give you 3300 mah.
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Old 01-12-2017, 11:08 AM   #19
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Hi Psychron .... you don't say what S rating your 5000 packs are. 3 .... 4S ?

Technically max amps for a pack is : capacity x C rate .... so a 5000 20C pack is supposed to be capable of 5000/1000 x 20 : 100A
But in reality I usually halve that as my setup numbers.

To arrive at capacity pack to use .... I often set my target as 5 mins full throttle ....

Test motor to see what amps is max. Let's say 30A.
I want 5 mins.

Time x Amps / 60

So 5 mins x 30A / 60 mins in 1 hour. Gives an answer of 2.5A/hrs .... or 2500mAh in our parly, but we need to increase as that is full discharged. So multiply number by 1.2 to add a margin of storage.

So for 5 mins full rate we have 2500 x 1.2 : 3000mAh.

Nigel

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Old 01-13-2017, 03:24 AM   #20
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Originally Posted by solentlife View Post
Hi Psychron .... you don't say what S rating your 5000 packs are. 3 .... 4S ?

Technically max amps for a pack is : capacity x C rate .... so a 5000 20C pack is supposed to be capable of 5000/1000 x 20 : 100A
But in reality I usually halve that as my setup numbers.

To arrive at capacity pack to use .... I often set my target as 5 mins full throttle ....

Test motor to see what amps is max. Let's say 30A.
I want 5 mins.

Time x Amps / 60

So 5 mins x 30A / 60 mins in 1 hour. Gives an answer of 2.5A/hrs .... or 2500mAh in our parly, but we need to increase as that is full discharged. So multiply number by 1.2 to add a margin of storage.

So for 5 mins full rate we have 2500 x 1.2 : 3000mAh.

Nigel
Nigel,

I use 3s packs on all my stuff. I have a mini apprentice s from e-flite that came with a 3s - 1300 and I got 5 minutes of flight out of it at full throttle.. and about 18-20 minutes out of it coasting around up there catching thermals if I could etc. Then I switched to a 2250, and I got about 10 minutes of full throttle flight out of it, and coasting around? well.. let's just say after about 35 minutes I wasn't sure if I wanted to stay up any longer.

The real point to think about is that your motors may be drawing 30 amps at full throttle, so you need a battery that'll supply that power obviously. but your longevity is going to be based on the draw at half throttle, or closer to 15 amps. Wherever "hover" is if it's a drone, or cruising speed for an airplane.
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Old 01-13-2017, 05:08 AM   #21
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My point is that we calculate on full - then we know that reduced mixed throttle gives us desired.

It also makes sure that our ESC / battery is up to the job.

Nigel

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Old 01-13-2017, 11:53 AM   #22
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Originally Posted by solentlife View Post
My point is that we calculate on full - then we know that reduced mixed throttle gives us desired.

It also makes sure that our ESC / battery is up to the job.

Nigel
I think we're both saying the same thing.

I always start with full and then any extra time I get from the larger battery is a bonus.

Obviously you wouldn't pair a motor that has a max draw of 30 amps with a 12 amp ESC because you'd fry out the ESC the minute you pushed the throttle all the way up. Your ESC should always be sized larger. I know some guys will put a 12 amp ESC with a motor that draws 10 but I'd probably just throw a 20 on there because it's likely going to cost the same or a dollar more at most and then I can rest easy that it will never overheat or burn out.
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