Mah (milliamp Hours) Explained!

Tony

Staff member
Tony submitted a new Article:

Mah (milliamp Hours) Explained!

As most of you know, things come in waves. From motor KV, to voltage, and now, MAH that a battery can sustain. Because of this, I have decided to create a quick article to try and explain what MAH means when you see it on a battery.

Lets talk about one of the most popular batteries out there, the 3s 2200mah battery that is used in most 450 sized heli's. Now, just to be clear, voltage has NOTHING to do with the mah. Well it does, but it doesn't. I will explain below.

When you are talking about MAH, you are talking about the discharge rate that the battery can sustain over a given amount of time. Again, we are going to use the 2200mah as an example. In this example, 2200mah could equal 2.2ah, or 2.2 amp hours. This means the battery can sustain a draw of 2.2 amps for one hour. Yup, it's as simple as that.

Just to be clear, there are 1000ma in 1 amp. This is how I got to the 2.2 amps out of 2200mah. Just divide 2200/1000 to get to 2.2 as I explained in the How To Match Motor | Battery | ESC.

I hope this helps some of you out that were unclear on what mah stood for. As always, if you have any questions, all you have to do is ask. If there is something wrong with this article, let me know and I will fix the issue.

Read more about this article here...
 
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Tony

Staff member
I am quite surprised that there have been no comments on this. Do I need to redo the way the articles section is structured? Can you even find where this article is located? Post up and let me know.
 

EyeStation

Well-Known Member
I saw it too Tony, in my unread threads section. I just didn't see a need to go there. I got a handle on my mAh. lol
 

Tony

Staff member
I'm thinking it's hidden way too much. Tucked into a corner of the articles section.
 

pvolcko

Well-Known Member
I don't know how everyone else accesses this site, but I have a link in my bookmarks to the forum. This site is the forum, for me. I never see or use the articles unless there is a post to the forum linking to it.

That said, another idea for an article, perhaps an expansion of this one, is to give a broader explanation of batteries, wire guages, motors, ratings and what it all means, with analogs to car motors/fuel systems. Something along the lines of:

mA = milliamps = 1000 mA per 1A = measure of current = the flow of fuel at any given moment

mAh = milliamp hours = 1000 mAh per 1 Ah (Amp hour) = amount of fuel in the tank (ie. 2200mAh pack means 2200mA flow rate can be supplied for 1 hour before it is drained completely, or 4400mA for 30 minutes or 8800mA for 15 minutes)

C = capacity = charge and discharge capability in terms of 1Ah per 1C = how much flow the tank can accept (charge) and provide (discharge) at any given time (35C discharge 2200mAh pack can supply at
most 77000mA or 77A at any given time, at this rate the pack would discharge in 60 minutes / 35 = 1.7 minutes, at a 1C discharge rate, or 2200mA it will last for 60 minutes, as said above in the mAh explanation)

V = volts = lipo battery voltage is rated at 3.7V per cell (around it's 20% capacity remaining point), but at full charge they can provide 4.2v/cell = how much pressure the fuel pump can sustain

ga = guage = lower number is thicker wire = size of the fuel lines going to the carb (too small and you restrict flow, starving the carb and motor of fuel at high throttle and possiby leading to a rupture due to excessively high pressure where the fuel pump connects (ie. melting the wires due to high resistance and heat build up) perhaps provide a chart with guages and recommended maximum currents they can support

ESC = electronic speed control, rated in voltage and current it can handle = equivalent to the carborator or fuel injection system, it controls the flow of fuel into the motor (in this case by metering how much voltage/pressure is allowed, thus restricting the fuel flow into the motor so it will not run as fast)

Motor = rated in kV as well as maximum voltage and current handling capability = kV is the number of RPMs the motor will turn per volt applied to it, coupled with maximum voltage this tells you the maximum number of RPMs this motor will turn at full throttle (theoretically, real life inefficiency losses and loads will diminish it somewhat), maximum current times maximum voltage tells us the maximum power (horsepower) this motor will create.

Motor ratings dictate how large our carb (ESC) has to be. It must handle the current the motor will need at the voltage we wish to supply it. Usually we supply the maximum recommended voltage the motor can handle, but sometime opt to use one cell less if our motor is overpowered for the heli/airplane, or perhaps many cells less if we want a very slow flying aircraft. The current draw of the motor (as handled by the ESC) also determined how big our fuel lines need to be (wire size and connector type). Fuel pump (battery voltage) was decided when we decided how much voltage at full throttle we want to provide the motor, up above.

That leaves fuel tank size (battery mAh) and maximum flow supported (discharge C rating). These are linked and dependent on average power use of the motor during flight, how long we want to fly, weight limits of the heli/plane, size restrictions for the tank/battery, etc. A 3 cell (3S) 2200mAh 35C battery, a 2600mAh 30C and a 3100mAh 25C battery will all support the same maximum fuel delivery potential (77A max at any given time) but in an average flight that is only drawing say 10A per minute (4.5C on the 2200 battery, 3.8C on the 2600 battery, and 3.2C on the 3100 battery) will result in different flight times. Maybe 10 minutes on the 2200/35 pack vs 12 minutes on the 2600/30 pack vs 15 minutes on the 3100/25 pack.



or something along those lines... oy. And I wonder where all my time goes during the day. I just get going on something, turning a quick post into a 30 minute long rant. :)
 

Tony

Staff member
hahaha, I think you just did what you were trying to explain to me to do lmao. That post, I will be linking too quite a lot, I can assure you.
 
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