Battery question, 11.1 v 12,000 mah??? - RC Groups
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Jun 18, 2012, 11:31 PM
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Battery question, 11.1 v 12,000 mah???


Ok I'm building a y6 and the motors I'm using are the hobby king donkey 1,100 kv and the say to use 3s, so I found a good deal on some single cell 3.7 v 4000 mah battery's and I want to run them 3s3p. So would that make them 11.1 v 12,000 mah? And to run all six motors it's going to use 1,680 watts max, is that make my battery too much? I'm really new and this is my first build and just wanted to get some help from some of you guys that know more then me. And the cells are just 10 grams a piece so that's why I'm trying to go this way to have a longer flight time. Thanks in advanced for the help!
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Jun 18, 2012, 11:51 PM
If it ain't broke, fix it.
Hasher66's Avatar
Quote:
Originally Posted by Wilds315
Ok I'm building a y6 and the motors I'm using are the hobby king donkey 1,100 kv and the say to use 3s, so I found a good deal on some single cell 3.7 v 4000 mah battery's and I want to run them 3s3p. So would that make them 11.1 v 12,000 mah? And to run all six motors it's going to use 1,680 watts max, is that make my battery too much? I'm really new and this is my first build and just wanted to get some help from some of you guys that know more then me. And the cells are just 10 grams a piece so that's why I'm trying to go this way to have a longer flight time. Thanks in advanced for the help!
Well, since I don't know what type of motors and props you're using, (or the "C" discharge ratings of your lipos), we'll need to run with the info you have provided wrt peak power consumption.

To be conservative, let's assume that your battery voltage under full load will drop to around 11V or so, (this will depend on the "C" rating of your lipos).

With that as our basis, that would make peak current = 1,680 watts/ 11V = ~153 amps.

153 amps/12ah batteries gives a nominal discharge rating of 12.75C.

Since the minimum "C" rated lipos that I have seen on the market currently are 15C, (most now have a maximum of 20C or higher), you're probably fine. It would still be good to check on the C rating of your lipos just to be safe, however.
Jun 18, 2012, 11:58 PM
Registered User
Hasher, yea it don't say the c rating on the cells. And the info for the motors are;

Kv (rpm/v) 1100
Weight (g) 76
Max Current (A) 32
Resistance (mh) 0
Max Voltage (V) 11
Power(W) 280
Shaft A (mm) 4
Length B (mm) 24
Diameter C (mm) 35
Can Length D (mm) 14
Total Length E (mm)


Also this info was given
Prop Data:
10x4.7 - 11.1v - 21A - 1150g Thrust
9050 - 11.1v - 18A - 900g Thrust
1060 (3 blade) - 11.1v - 23A - 1200g Thrust
Jun 19, 2012, 12:06 AM
Registered User
And I'm using Turnigy TY-P1 25Amp IR HEXFET ESC and the info for them are


Specs:
Cont. Current: 25A
Burst Current: 50A
BEC: 5volts / 2amps
Weight: 42.5 Gram (including wires and plugs)
Battery Plug: XT-60
Motor Plug: 3.5mm Bullet Connector
Jun 19, 2012, 12:07 AM
If it ain't broke, fix it.
Hasher66's Avatar
Quote:
Originally Posted by Wilds315
Hasher, yea it don't say the c rating on the cells. And the info for the motors are;

Kv (rpm/v) 1100
Weight (g) 76
Max Current (A) 32
Resistance (mh) 0
Max Voltage (V) 11
Power(W) 280
Shaft A (mm) 4
Length B (mm) 24
Diameter C (mm) 35
Can Length D (mm) 14
Total Length E (mm)


Also this info was given
Prop Data:
10x4.7 - 11.1v - 21A - 1150g Thrust
9050 - 11.1v - 18A - 900g Thrust
1060 (3 blade) - 11.1v - 23A - 1200g Thrust

Okay, that info was helpful since it reveals the range of props you could use, and none of them will cause the amp draw to go above the ~150 amps I used above.

That being said, I would be a tad concerned about your lipos not having any "C" rating whatsoever. Doesn't the vendor list that info?

Either way, if those cells were made for RC use and were manufactured recently, you're probably okay. If I were you, I'd really want to know the rating of those cells just for peace of mind though.

Good luck.
Jun 19, 2012, 12:08 AM
If it ain't broke, fix it.
Hasher66's Avatar
Quote:
Originally Posted by Wilds315
And I'm using Turnigy TY-P1 25Amp IR HEXFET ESC and the info for them are


Specs:
Cont. Current: 25A
Burst Current: 50A
BEC: 5volts / 2amps
Weight: 42.5 Gram (including wires and plugs)
Battery Plug: XT-60
Motor Plug: 3.5mm Bullet Connector
And you're fine there as well.
Jun 19, 2012, 12:33 AM
Registered User
chuenwe's Avatar
Be careful of the LiPo that don't have C ratings. Most of those are for light electronics like your AA battery in your TX. That's why they are very cheap.
Jun 19, 2012, 12:34 AM
Registered User
Oh, the cells I was looking at looked like AA sized... Guess that kills that cheap idea lol. Ok so then what sized cells should I use? I'm looking to make this for fpv but I'm doing it in stages and working with no budget. But I want long flight times as I can get.
Jun 19, 2012, 12:40 AM
Registered User
chuenwe's Avatar
15C bare minimum. The price is not that big a different if you go 20/30C. I would strongly recommend using AT LEAST the 25/30 or so if you can afford it.

The mAh would only give you longer/shorter flight time. Not really a big factor for your setup.
Jun 19, 2012, 12:42 AM
Registered User
Quote:
Originally Posted by chuenwe
15C bare minimum. The price is not that big a different if you go 20/30C. I would strongly recommend using AT LEAST the 25/30 or so if you can afford it.

The mAh would only give you longer/shorter flight time. Not really a big factor for your setup.
Thanks, but I still don't under stand how to figure out flight time to mah .... I'm sorry like I said I'm new, I pick up fast but this is out of the range of things I know about.
Jun 19, 2012, 12:43 AM
Registered User
Quote:
Originally Posted by Hasher66
And you're fine there as well.
Thank you too!
Jun 19, 2012, 12:43 AM
Registered User
chuenwe's Avatar
How heavy is your Y6 with everything you want on it? Well, without the battery i guess since you don't have it yet. What size of props are you using?
Jun 19, 2012, 12:45 AM
If it ain't broke, fix it.
Hasher66's Avatar
Quote:
Originally Posted by Wilds315
Oh, the cells I was looking at looked like AA sized... Guess that kills that cheap idea lol. Ok so then what sized cells should I use? I'm looking to make this for fpv but I'm doing it in stages and working with no budget. But I want long flight times as I can get.
No, AA sized will not work and won't have nearly the discharge capacity that you need.

These Hobby King 3s 6000mah batteries would work for your rig, and you wouldn't need to parallel them up since they can handle at least 150 amps. Paralleling two together would get you your 12,000mah capacity, but at the expense of much more weight and much less payload capability.

http://www.hobbyking.com/hobbyking/s...arehouse_.html

Price is pretty good and they're stocked in the US warehouse.
Jun 19, 2012, 12:54 AM
If it ain't broke, fix it.
Hasher66's Avatar
Quote:
Originally Posted by Wilds315
Thanks, but I still don't under stand how to figure out flight time to mah .... I'm sorry like I said I'm new, I pick up fast but this is out of the range of things I know about.
First off, "mah" stands for milliamp hours. This tells you your battery's total capacity.

Let's use 100 amps average draw for your intended flight. If you use a 3s 6000mah battery for your rig, that would be 100 amps divided by 6 amp hour battery capacity, (6000 milliamps = 6 amps), for a total of 0.06 hours, or 3.6 minutes. But you never want to draw your lipo down 100%, so using a 20% reserve capacity as a safety margin, multiply this 3.6 minutes times 80% for a flight time of about 2.9 minutes.

100 amps continuous current draw is pretty high though. Unless your rig is really, really heavy, hovering around should be much less.
Jun 19, 2012, 01:45 AM
Registered User
Quote:
Originally Posted by Hasher66
First off, "mah" stands for milliamp hours. This tells you your battery's total capacity.

Let's use 100 amps average draw for your intended flight. If you use a 3s 6000mah battery for your rig, that would be 100 amps divided by 6 amp hour battery capacity, (6000 milliamps = 6 amps), for a total of 0.06 hours, or 3.6 minutes. But you never want to draw your lipo down 100%, so using a 20% reserve capacity as a safety margin, multiply this 3.6 minutes times 80% for a flight time of about 2.9 minutes.

100 amps continuous current draw is pretty high though. Unless your rig is really, really heavy, hovering around should be much less.
So how do I figure the draw from the six motors? Is that the volts,11.1, times the amps, Say 23( largest shown ) to get my watts, 255.3 per motor times 6 for 1531.8 watts Total ??? What would give me ten min flight times then?


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