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Nov 04, 2015, 03:17 PM
Registered User
Thread OP
Help!

Battery differences and charger(4s 2200mah/1800mah)


Hello,

I recently purchased the CF 258 Armattan quad.
Now I need to pick a battery for it. I want to fly it with 4s battery.
I was looking on hobby king and I found mostly what I am looking for.
So my options are the following:
1800mah : https://www.hobbyking.com/hobbyking/s...Lipo_Pack.html
2200mah : https://www.hobbyking.com/hobbyking/s...Lipo_Pack.html
1300mah : https://www.hobbyking.com/hobbyking/s...Lipo_Pack.html

The 2200 and 1300 have 25-50C. I don't know if that is enough for the CF 258.
1800 has 65-130c. That I think is more than enough!

What should I pick? I am looking for max power.
However I am very new to this hobby and can't tell the differences among them.

Any advices or support is more than welcome

Cheers,

Maria

P.S. what charger would fit the battery?
Last edited by iMaria; Nov 04, 2015 at 03:21 PM. Reason: updated question
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Nov 04, 2015, 03:50 PM
Space Coast USA
hoppy's Avatar
Hi Maria,
Need to know something about your quad.
What motors are on it?
What prop size?
How long of a flight time do you want?
How many amps does it draw at full power?
How many amps does it draw at cruise power?

Some threads about quad and batrteries:
https://www.rcgroups.com/forums/show...d#post33068573
https://www.rcgroups.com/forums/show...d#post33058038
https://www.rcgroups.com/forums/show....php?t=1963998

With those packs, the Accucel 6 charger will work OK.
Last edited by hoppy; Nov 04, 2015 at 03:59 PM.
Nov 04, 2015, 04:24 PM
Registered User
Thread OP
These are the motors: http://www.myrcmart.com/rcx-h2208-23...ed-p-8789.html
Props are 6". The standard ones provided from armattan.
The standard model had 1800kv motors 30amps with simonk ESCs http://www.armattanquads.com/cf-258/
However I will replace them with the motors above.

A balance of flight time and max power possible. Would that be 5-7 minutes?
Nov 04, 2015, 05:43 PM
Space Coast USA
hoppy's Avatar
So you want to use the myrcmart motors with 6" props and a 4s pack and 30A ESC's
You will notice the current draws for this combination in the reference below.
100% throttle - 38A This will fry the ESC and motor.
75% - 22A.
50% - 10A
Flying at 50% throttle will give you less than a 3 min flight.
That combination isn't good because of the excess current draw at full throttle.

I would start out with the standard motors, standard props, and the standard 3s pack as described in the review posted above.

Motor A/prop/V comparison here.

On the other hand you can use a 4s pack with those motors if you drop to a 5" prop. Say a 5040.
At 50% throttle, that will give you <4 min flight. If average draw is less, flight time will be longer.

As far as C-rate.....Anything above 30C will be good. See this thread.
Last edited by hoppy; Nov 04, 2015 at 05:57 PM.
Nov 04, 2015, 05:55 PM
Registered User
Thread OP
I don't have the standard motors. I used to use 1800kv motors but I don't like them. I find them not powerful enough. The ones I have are those from mycart. The standard props are 6".
I was thinking that a 4s 1300-1800mah would give me -+2 min flight time. That is why I opened this thread.

CF 258 is an acrobatic quad. Should I go for 3s? If yes how many mah?
Nov 04, 2015, 06:17 PM
Registered User
Thread OP
Quote:
Originally Posted by hoppy
So you want to use the myrcmart motors with 6" props and a 4s pack and 30A ESC's
You will notice the current draws for this combination in the reference below.
100% throttle - 38A This will fry the ESC and motor.
75% - 22A.
50% - 10A
Flying at 50% throttle will give you less than a 3 min flight.
That combination isn't good because of the excess current draw at full throttle.

I would start out with the standard motors, standard props, and the standard 3s pack as described in the review posted above.

Motor A/prop/V comparison here.

On the other hand you can use a 4s pack with those motors if you drop to a 5" prop. Say a 5040.
At 50% throttle, that will give you <4 min flight. If average draw is less, flight time will be longer.

As far as C-rate.....Anything above 30C will be good. See this thread.
I cant understand how the C-rate calculation is done.
Wouldn't it be pointless to use a 4s pack and get smaller props? 5" props on 250 quad?

Let's say a 3s 1800mah. Now as I see it, with one cell less, the power will be less. Weigh will also be less. However this could be used with 6" props without frying the motors or ESCs.
But how much flight time would that give me?

I like the 4s idea but -+3 min flight time would be disappointing. Charge for 2 hour to be able to fly 3 min is pointless.
Nov 04, 2015, 08:46 PM
Space Coast USA
hoppy's Avatar
Your ESC's are rated for 30A, right?
The 4s pack with the 6045 prop draws 38A and will burn out the ESC. That's too high which means you have to either reduce the voltage or the prop size.
A 3s pack with the 6045 draws 30.8A which is right at the max ESC spec.
A 4s pack with a 5045 pro p draws 30A at full throttle which is at the ESC's max rating. (BTW, it is not recommended to use an ESC at it's max rating).

Using more power and longer flights do not go together. The more current you use, the lower the flight time will be. Increasing battery capacity increases flight time.

Basic rules:
The higher the voltage you run the motors at the higher the current draw will be with the same prop..
The higher the kv of the motor, the higher the current draw will be with the same prop.
The larger the diameter/pitch of the prop the higher the current draw will be with the same kv motor.

You have increased voltage and kv which will give you a lot more power and a much higher current draw with a much shorter flight time if that power is used.

The max current a battery can produce is figured by multiplying the C-rate and capacity (in amps) together.
A 20C 1500mah pack can produce 20*1.5 = 30A. A 50C1500mah pack can yield 50*1.5 = 75A. Remember, as current draw goes up, flight time goes down.
Flight time = BatteryCapacity(A) X 60 divided by planes average current draw. If your quad draws an average 40A during flight with a 2000mah (2Ah) pack, the flight time will be 2 x 60/40 = 3min

Read about C-rate and other things here.
Nov 04, 2015, 09:36 PM
Registered User
Thread OP
That clears up a lot of questions. Thank you very much.

So according to what you are saying, which I believe is correct, to be able to have an average flight time and not risk burning the ESC I should go for 3s 1800+mah with 5045?
Is that a good thing for an acro quad?

Edit: How can I know the current my quad draws?
Last edited by iMaria; Nov 04, 2015 at 10:33 PM.
Nov 04, 2015, 10:27 PM
If it flies, I can crash it.
rocketsled666's Avatar
From the MyRCMart page on the motors you're using: This H2208 2300KV Motor is for those who need to maximize the performance for both 5 inch propellers on 3-4S and 6inch on 3S Li-Po Battery. This is good for the Racing Copter and 3D Flipping Copter which speed and responsive are required.

There is also a very comprehensive table of props/battery combinations. On the 6045, as Hoppy indicates, the motor draws 38A with a 4S pack. But remember, that's per motor. There are 4 of them. Even if you had good enough ESCs, you're pulling almost 160A from the pack. That's a lot of power to be pulling. A 2000mAh 4S pack would need to be 80C nominal to survive it.

According to that table, if you want to stay below the 30A ESC limit with some margin, the largest prop you can spin with a 4S is the 5040 and that'll still be pulling 25A, or 100A for 4 motors. But at 50% throttle you're still getting 450g of thrust. Times 4, 1800g of total thrust from 4 motors. The Armattan 258 is pretty small. 1800g of thrust is a high multiple thrust/weight ratio. It will likely hover at much less than 50% throttle. I couldn't find the weight of the 258 anyplace, since there are so many variables (like the motors you choose). Your motors weigh 50g each. A 2000mAh 4S weighs about 170g. So the heaviest components, the motors and battery, only add up to 370g. Call the frame and FC 130g, you're up to 500g and at 50% throttle you've got 1800g of lift. Better than 3:1 at mid throttle. At 100% throttle you're getting 950g/motor, 3800g!! of thrust. Better than 7:1 power/weight.

I would expect the quad to be quite "sprightly" with this setup.

A 2Ah pack will only last about 1 minute at WOT. But there's no possible way you'll be flying WOT all the time. You use WOT in bursts. Your actual flight time will probably be in the 3-5 minute range depending on how violently you fly.

On a 3S, the 6045 pulls 30.8A, which is too close to the ESC's rating to be a good idea. But you get 1170g of thrust per motor, so more than you can get on the maximum 4S setup you're able to run. And the ship will be lighter than the 4S setup, so it'll be more responsive. But it pulls too much current, you can run 6045s. The 5045 pulls 19.7A and gets you 725g of thrust. So less thrust, but the copter is lighter too, so maybe only a little lower performance, but you'll get a 20% increase in flight time.

For 3S, it looks like you really want a prop someplace between a 6045 and a 5045. A 6040 would probably work great at 3S, maxing out the performance for that battery size.
Nov 04, 2015, 10:30 PM
Space Coast USA
hoppy's Avatar
I've just been looking at the capabilities of the batteries, motors and ESC's you are using as I know little about quad performance.
Basically, the prop determines the load on the motor. The more volts you supply to the motor, the more amps it draws. Once you know how many amps the motor draws, you can figure how large a battery you need to provide that current and the amp rating of the ESC.

That's why my original question were :
How many amps does it draw at full power?
How many amps does it draw at cruise power or in your case, hover power.

The idea is to select a prop that will draw at full throttle less amps than the motor is rated for.
In your case, you would want to use either the 3s with a 6045 or the 4s with a 5045 prop.

The 3s/6045 provides 660g of thrust @ 75% throttle - Efficency - 4.13g/W
The 4s/5045 provides 608g of thrust @ 75% with an Efficency of 3.01/W
The 2200mah pack would provide the longest flight time.

I'd suggest looking at what others are using and go with that.
For instance, here's a guy using 2300kv motors with 6 x 4.5 props and a 4s1000mah pack and gets 2 min flying time.
CF 258 2208 2300 KV 4s1000mah (2 min 37 sec)


Check out other youtube videos searching for CF 258 Armattan quad review
Nov 04, 2015, 10:49 PM
Registered User
Thread OP
Ohhh gosh... I thought this would help me but it makes me even more confused.
Thank you both for all the explanation.

Since I have the 6" props I will go for 3s. I think it would be better to start with and learn the quad. I will take the 5045 props as well for tests. Then maybe later I try the 4s.

One last question. Sorry but C-rates are above me.
What C-rate should a 3s 2200mah have with 6045 and what with 5045?
Would about 4s?

Edit: Oups that was two question!
Nov 04, 2015, 10:53 PM
Registered User
Thread OP
Quote:
Originally Posted by hoppy
I've just been looking at the capabilities of the batteries, motors and ESC's you are using as I know little about quad performance.
Basically, the prop determines the load on the motor. The more volts you supply to the motor, the more amps it draws. Once you know how many amps the motor draws, you can figure how large a battery you need to provide that current and the amp rating of the ESC.

That's why my original question were :
How many amps does it draw at full power?
How many amps does it draw at cruise power or in your case, hover power.

The idea is to select a prop that will draw at full throttle less amps than the motor is rated for.
In your case, you would want to use either the 3s with a 6045 or the 4s with a 5045 prop.

The 3s/6045 provides 660g of thrust @ 75% throttle - Efficency - 4.13g/W
The 4s/5045 provides 608g of thrust @ 75% with an Efficency of 3.01/W
The 2200mah pack would provide the longest flight time.

I'd suggest looking at what others are using and go with that.
For instance, here's a guy using 2300kv motors with 6 x 4.5 props and a 4s1000mah pack and gets 2 min flying time. https://www.youtube.com/watch?v=jXByXUhTe3g

Check out other youtube videos searching for CF 258 Armattan quad review
My quad is built upon his build. If he has 2min flight time with 4s 1000mah then with 2200 mah would go around 5 mins.
That is more than enough for an acro quad with max power isn't it? Just asking
Nov 05, 2015, 08:51 AM
Space Coast USA
hoppy's Avatar
Heat is the problem! As long as the motor system components stay cool you can fly forever.
I'd start with the 3s /6045's and after landing, feel the motors, ESC, and batteries.
Anyone of those so hot you can't keep your fingers on them? If so, reduce the prop size. If not, you can try slightly larger props.

Quote:
If he has 2min flight time with 4s 1000mah then with 2200 mah would go around 5 mins.
Flight time with the 2200mah pack will be at or below 4 min due to extra weight. But more important, since you are flying longer, the motor/ESC/battery may be getting much hotter. I'd start with a 1 min flight, check tempertures and if OK fly another min and check again...repeat till the pack reaches 3.7V/cell.
Nov 05, 2015, 10:41 AM
Registered User
Thread OP
Yes but the point is, how many C-rates do I need on my 3s? You said anything above 30c will be good.
What's the difference between getting a 35c and a 75c(same cells same mah).
Why should I go for 75c if 35c is enough?

I see people doing that on internet.

P.S. let's forget the 4s case for the moment, I might try that later. You guys scared the hell out of me!

Edit: about the charger I found the Accucel 6 as you suggested. However I am finding 50W 6A and 80W 10A.
Which one should I go for? I don't want to catch fire with those batteries... Hope it is safe
Last edited by iMaria; Nov 05, 2015 at 10:50 AM.
Nov 05, 2015, 10:50 AM
Space Coast USA
hoppy's Avatar
Yes, 30C would be good for most applications but with the 123A draw of your motors at max throttle, I'd go with the 65C packs like this:
Turnigy nano-tech 1800mah 3S 65~130C

The 3s pack with the 6045 prop will draw 30.8A/motor or 123A total at full throttle. So you need a pack that will deliver 123A for short spurts and say 20A for cruising.
Looking at the HK website, I see a lot of the packs are high C-rate now.
So taking the Turnigy nano-tech 1800mah 3S 65~130C Lipo Pack as an example, theoretically it will deliver 117A continuously and 234A for a burst. (1.8A x 65C = 117A and 1.8A x 130C = 234A). It should be able to handle your loads without a problem..... But, I can't imagine your battery leads handling a 123A current for very long.



But going back to what most modelers have discovered is that those high C-rates are good advertising rather than lab bench obtainable.


Quote:
Edit: about the charger I found the Accucel 6 as you suggested. However I am finding 50W 6A and 80W 10A.
Which one should I go for? I don't want to catch fire with those batteries... Hope it is safe
I'd buy the 80W/10A one for a couple bucks more. Not that you will need the higher charger current capability but because they probably have corrected any problems they had with the 50W model and have uprated the power rating of the components.
Do you have a 12A+ power supply? Something like this Turnigy Reaktor Pro 240W 16A Power Supply (100~240V AC)


As to safety, read this several times..... https://sites.google.com/site/tjingu.../lipo-problems
Last edited by hoppy; Nov 05, 2015 at 11:50 AM.


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