fly24-7

As others have stated, capacity is just that. a 5000mAh pack means that it has enough energy to supply five amps continuously for one hour. 6000mAh is six amps continuously for one hour. You may see some flight performance difference with the larger pack because it's a little heavier. But, it shouldn't be much.

hogflyer

Here's some thing I've learned about batteries: Think of them as a big fuel tank.

Voltage is the size of the hole in the tank that allows the gas to be pumped out faster. The bigger the hole the more gas can come out at any given time.

Amperage is the size of the tank - the higher the amperage is like a larger fuel tank so you'll go further on that tank of fuel.

Something else to consider is the weight of the battery pack. It's a lot more critical for heli's, but something to consider for an airplane. When you increase or decrease the amperage capacity of a battery you'll also be increasing/decreasing the weight of the battery (a 2200mAh battery will weigh less than a 3300mAh battery of the same voltage rating.

Batteries of the same voltage and capacity will have different weights depending on the manufacturer and chemical make-up. Even identical batteries by the same manufacturer will have slightly different weights, but usually not enough to worry about. I've found instances of larger batteries by different manufacturers of the same voltage/amperage having over a 1/2 ounce of difference in weight.

When you start changing batteries between planes that are from different manufacturers it's always a good idea to do a CG check with each battery in the plane to make sure you'll be in good shape.

Hogflyer

jetmech05

Hog you're kinda right, but you make it sound like you can just change voltages at will and that it simply not the case....if you have a system that is set up on 6V you might be able to go to 8v but your risking it...and an 8V battery will be higher fully charged so you'd need a regulator not go over 8V.....Voltage is the key here....since eletricity is lazy you can go up in amp capacity...but voltage will fry your system

guver

My Feedback: (325)

Maybe voltage should be the pressure and the current should be the line size. The two combined would be gallons per minute. Increasing either one would increase the gpm. Increasing both always gives nice increases to power. Capacity of course is the size of the tank.

lopflyers

My Feedback: (12)

Thx again, it was confusing. At this point I was buying the recc battery for the motor/esc, and not interchanging.
The C rate was obscure for me, I was told to buy the biggest C I could afford.

jetmech05

Look at it this way if you had a power plant big enough to power a city in your back yard...this power plant produced 115 v and billions and billions of amps. now this power plant isn't hooked up to anything except a 115v light bulb pulling say 5 amps....when you flip the switch that big ol power plants out put will be 115V 5amps.....
Now same power plant producing the same amps but at 400 V now flip the switch and your light bulb will be very very bright but only for a milli second. I am going to leave it at that. The mAh rating of a battery is to give you an idea of the batteries capacity....as electricity is lazy your only going to pull the amps needed to do the work no more.

CGRetired

My Feedback: (1)

The "C" rating is how quickly the battery can output the power that it delivers. The higher the "C" rating, the more it will be able to supply the current to the load.

This does not mean that it will push out amps at that rate, but it can. Say 20 C. This means that it will be capable of supplying at a rate of up to 20 amps per hour without doing damage to that battery until it is drained. That does not mean that it is good for an hour, it just means that it can supply it at that rate until it is dry.

Think of it as a 5 gallon bucket of water. If it has a nozzle on it that will allow 20 gallons of water per minute to pour out, and you start pouring water out of it, well, if it had 20 gallons of water in it, it could pour out that 20 gallons in one minute. But since it has 5 gallons in it, it will pour at a rate of 20 gallons per minute but for only 15 seconds or 1/4 of that minute because you only have 5 gallons of water.

When I say "push out amps at that rate, but it can", that means that the load, or the motor and ESC will only draw out what the demand is for. Push the throttle more and more current will flow until it reaches the "C" rating. Go over that and strange things begin to happen. The battery will get hot and the ESC will most likely cause the motor to surge. This is why some say to get the highest "C" rating that you can so that you don't get into the position where you are trying to demand more than the battery can deliver.

Guver has the best analogy for voltage and current. Voltage is the pressure, like the pressure of water, and the current is the water. The higher the pressure or voltage, the more current will flow, to a limit... the size of the hose or wire will determine how much can physically flow. It will flow until it is drained at a maximum "C" rating.

CGrl

fly24-7

From my point of view, the key is, selecting the proper sized motor for the plane. From there, the motor manufacturer will typically specify the size speed control, battery and propeller that are needed so that the electronics operate within their range and that enough thrust is produced to fly the model appropriately. If more run time is desired, go to a battery of the next highest capacity.

Horizon Hobby (E-Flite) is good about identifying what type of equipment should be parred together. Even if you don't want to buy from them, you could go to their website, find a plane of similar size/type/weight as yours, and get the specifications of the equipment they recommend. Then shop around for alternatives of equivalent specification.

Fred Dings II

My Feedback: (2)

Hello to all

I am also rather new to electrics, but flew wet sport/pattern/3D for years, and still do. Please explain KV. I have a motor that is 2200 KV. I have read that KV= rpm/volts. 11.1 volts, my battery, divided into 2200 =198.19. I know I have more rpms than that. What am I missing?

Also, I bought a wattmeter and used it to make sure my escape is not over loaded. I guess I can also use it to select the props for my motor, but this is an arf and I bought what the designer suggested. I would like to know more than just buy and fly. If somebody can recommend a publication, I will attempt to find it.

Fred ([email protected])

guver

My Feedback: (325)

Multiply , not divide. 2200 x 11.1

Fred Dings II

My Feedback: (2)

guver

Thanks for the reply. The author used rpm/v which indicates division. Now it makes sense.

guver

My Feedback: (325)

strange yes. It is "rpm per volt" What's more strange to me is the term "kv" To me that means kilo volt.

CGRetired

My Feedback: (1)

Well, Kilo for thousand and Volt - well, you get the idea. So, kilovolt in terms of voltage means thousands of volts. In this case, a little explanation goes a long way. But, I understand where you are coming from, guver.

I've long complained that we 'were' in the dark when it came to comparing electric motors to glow engines... like what motor is a comparable replacement or a glow engine. So, we had to do some homework to figure this out and it was not as easy as one might think.

Along comes Tower Hobbies and Rimfire who shows the motor plus something like .25 to compare that motor with a glow engine that is .25 cu-in displacement as a comparison. Nice, and long time coming, I'll tell you that.

http://www3.towerhobbies.com/cgi-bin...fire&search=Go

This makes it much easier to choose a motor for your plane if doing a conversion or building a glow powered plane using electric power. I did this on a Little Something Extra, but I did the homework in selecting a motor/esc/battery pack. I must say that I did a pretty good job, but some of it was pure guesswork.

Anyway, you can go to Tower and see what I mean (use the link).

CGr.

Gray Beard

My Feedback: (-1)

When I built the two Swoose planes the one I built for my friend was going electric and we ran into the problem of picking out the motor and ESC so we did like CG said and went through Towers motor selection and ended up buying the Tower 50 that compares to the .50 glow engine. Sure got rid of that hurting brain from doing all that math. That system of comparing to a glow engine is a big help for me. They even tell you what battery to use. Very good idea for converting kits and planes designed for glow engines.
Once in a while I think I'm getting a handle on this electric stuff but the more I learn the more confused I get. Reading this thread and having things dummy downed really helps.

CGRetired

My Feedback: (1)

GB - I don't think us old folks will EVER get a handle on the electric stuff. We are so used to putting our glow or gas engines on our planes and flying the things until the tank runs dry. What I really don't like about the electrics is that you will never have the same power after take off, unlike glow where you have the same power level until, of course, you run out of fuel.

One advantage, of course, is that it teaches you throttle management where most of us set the throttle for a cruise level and forget it. Electric, on the other hand, you have to really monitor performance and adjust the throttle accordingly. Then, at about at the half point of the flight, that begins to mean you have to trim to less power and speed.

I have two planes that seem to ignore that. One is the Little Something Extra, and the other is my Seawind. Both seem to fly like the devil right up to when the battery dies, but I seem to land them before that happens (or else the landing becomes a crunch).

Anyway, no matter.. I still prefer my glows.

CGr.