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  1. #1
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    Question A few questions on c and mah ratings

    I was looking into getting a 3 cell lipo (as my first lipo ever ) and I'm having a bit of trouble understanding c and mah ratings. This is what I think I have: The c rating is how quickly the battery can discharge. Does it change the max charging speed? For a not super fancy motor, is 30c enough? I would assume so, but if that was enough, then why would people buy 150c batteries? As for mah, I heard an analogy that it's like the size of a fuel tank, so the more mah(s?), the longer I can run it. What if I have a larger motor? Would a 5000 mah 3s lipo on a brushless motor give me a similar runtime to a 3000mah 7s nimh?

    Sorry for the wall of bad questions, but I'm pretty confused! Thanks for reading this!

  2. #2
    Marshal Double G's Avatar
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    Mah is the gas tank of the battery. The listed C rating is the max it can push. Both are used to determine the amount of amps it can supply. So a 3s 5000mah 50C battery will be able to push 250 amps (5000mah/1000 * 50c = 5 * 50 = 250). If you have an ESC that will pull a max of 125 amps then this battery will handle it with ease. Even a 5000mah, 30C battery will (150 amps); just don't buy a battery that is not able to supply the amps (such as a 5000mah, 10C which will give 50 amps) as the battery will heat up and puff.

    For charging, take the mah and divide by 1000 and that is the amps you can charge which is coined as "1C." Take the battery above with 5000mah and divide by 1000 and you'll get a 1C charge of 5 amps. If the battery says max charge of 2C, then multiply it by 2 and you'll get 10 amps. A 7500mah battery can be charged at 7.5 amps for 1C and 15 amps for 2C. The standard is to charge at 1C for longevity, but if the battery allows you to charge at 2C it'll charge in half the time but at the expense of overall battery life.

    A 5000mah battery (regardless of nimh or lipo) will give more run time than a 3000mah. A 7-cell battery may have a max charge of 10.5v but as soon as it is used that voltage drops and you'll notice performance slows the entire charge of the battery. Lipo have a max voltage of 4.2v per cell so your 3s will be at 12.6 and will drop but you'll see consistent performance of the battery until it is dead (at a recommended low-voltage cutoff of around 3.5v/cell).
    The Super Derecho

  3. #3
    RC Racer
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    Agreed, people will spend a lot of money for 150 c rating lipos just for racing and stuff. You NEED a lipo charger to charge lipos and if you don't use one, bad things will happen... I recently switched to lipo and am very happy with the results. I have 2s lipos, but will switch to 3s soon.
    3000 mah lipo = charge at 3 volts
    5000 mah lipo = charge a 5 volts
    Lipos generally take about an hour to charge at this rate.
    c rating does not effect charging speed. Lipos need to be stored at 3.85 volt per cell. Here is my old lipo thread with my questions that I had. I hope this helps. https://forums.traxxas.com/showthrea...po-please-help!

  4. #4
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    Quote Originally Posted by Double G View Post
    Mah is the gas tank of the battery. The listed C rating is the max it can push. Both are used to determine the amount of amps it can supply. So a 3s 5000mah 50C battery will be able to push 250 amps (5000mah/1000 * 50c = 5 * 50 = 250). If you have an ESC that will pull a max of 125 amps then this battery will handle it with ease. Even a 5000mah, 30C battery will (150 amps); just don't buy a battery that is not able to supply the amps (such as a 5000mah, 10C which will give 50 amps) as the battery will heat up and puff.

    For charging, take the mah and divide by 1000 and that is the amps you can charge which is coined as "1C." Take the battery above with 5000mah and divide by 1000 and you'll get a 1C charge of 5 amps. If the battery says max charge of 2C, then multiply it by 2 and you'll get 10 amps. A 7500mah battery can be charged at 7.5 amps for 1C and 15 amps for 2C. The standard is to charge at 1C for longevity, but if the battery allows you to charge at 2C it'll charge in half the time but at the expense of overall battery life.

    A 5000mah battery (regardless of nimh or lipo) will give more run time than a 3000mah. A 7-cell battery may have a max charge of 10.5v but as soon as it is used that voltage drops and you'll notice performance slows the entire charge of the battery. Lipo have a max voltage of 4.2v per cell so your 3s will be at 12.6 and will drop but you'll see consistent performance of the battery until it is dead (at a recommended low-voltage cutoff of around 3.5v/cell).
    This great info thank you. My daughter just bought a Slash 2WD at the local hobby shop and it with came with the NiMH, but she got a 5000mah 50C lipo.

    Looking on Traxxas' site the XL-5 (if I'm reading this correctly) has a peak forward pull of 100A so the most it'll pull is 100A. So if she got another battery a 30C would be sufficient correct? Is there any benefit of having a 50C over 30C if the ESC can't pull that much?

    Thanks
    Last edited by kantonburg; Yesterday at 09:08 PM.

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