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This question already has an answer here:

I was wondering if the mAh on an battery pack is important or relevant, so you would recognize a difference?

Little bit Off-Topic:

I've read a lot about "Nerf voltage mods" where modders change the standard 3xAA NiMh batteries (1,2v each = 3,6V) against 2 Li-Ion batteries (3,7v each = 7,2v) and one "dummy" battery for better perfomance and range.

Now I'm also thinking about changing to Li-Ion (with around 1500mAh) or just buying better/stronger NiMh batteries with around 2500mAh.

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marked as duplicate by Dmitry Grigoryev, Dave Tweed May 10 '17 at 10:41

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • \$\begingroup\$ Only applies to name brand batteries. If you are buying from no name vendors like on eBay or Amazon iot does not matter because they lie a lot and the stated mAh is very likely going to be incorrect. They will also sell NiHM as Li-ion. Stick to name brand. \$\endgroup\$ – Misunderstood May 10 '17 at 22:16
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The mAh rating of a battery tells you roughly the energy storage capacity of the battery as a function of the terminal voltage. In direct answer to the question "is it important?" Yes. For a given terminal voltage, a battery with a higher mAh rating will last longer as it stores more energy.

However, you cannot directly compare the mAh rating of two batteries which have two different rated voltages. Your NiMH batteries have a rated terminal voltage of 1.2V, whereas the LiIon have a terminal voltage of 3.7V.

If you convert the Ah rating to an actual energy value in Wh you get:

  • NiHM = 3 Wh
  • Li-Ion = 5.5 Wh

What that is telling you is that the Li-Ion batteries, despite the lower mAh rating, actually have a much higher energy density - they store almost 2x as much energy.

If you have 2 Li-Ion batteries in your system that would give you 11Wh of energy. If you have 3 NiMH batteries, that would give you 9Wh of energy. So despite the lower mAh rating, the 2 Li-Ion batteries still store more energy than the 3 NiMH ones.

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More mAh means longer lasting

mAh means milliamp-hours, and is a measure of capacity. Milliamps are a measure of current, i.e. the amount of electricity flowing out of the battery, whereas Volts are a measure of the energy in the electricity. Milliamp-hours are a measure of how long the battery can provide a certain current. A 1000mAh battery can provide 1000mA for 1 hour, or 500mA for 2 hours, or 3000mA for 20 minutes.

Caveats:

  • It's not really quite that simple with a real battery. If the battery is being discharged slowly, then probably you'll get the rated number of mAh. If it's being discharged quickly, then you'll get less. If it's being discharged very, very quickly you'll get a lot less, and maybe a fire. Look at "C" ratings for a measure of how quickly you can discharge a battery.
  • If you replace the 3.6V source the nerf gun was designed for with a 7.2V source, that will probably affect the current it takes. So a 1000mAh 3.6V battery pack will last longer than a 1000mAh 7.2V pack.
  • Be wary of stated capacities. It's not easy to measure, so it's something dodgy retailers lie about. Batteries bought on well-known auction sites may have a much smaller capacity than advertised.
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  • \$\begingroup\$ so its just a matter of "duration" but gainig not more "power" (in this case), right? \$\endgroup\$ – IVIike May 10 '17 at 9:23
  • \$\begingroup\$ yes. That's right. \$\endgroup\$ – Jack B May 10 '17 at 9:32

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