### Author Topic: Milli-Amp  (Read 1585 times)

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#### soninja8

• Robot Overlord
• Posts: 136
##### Milli-Amp
« on: August 02, 2011, 12:53:29 AM »
Okay, so I have a 8.4v 1600mah battery, and then i just got a 8.4v 3000mah battery in the mail yesterday. My 1600 was suprisely small, and the 3000 is like 1.5 times its size...my question was, do batteries have to be bigger with more milli-amps?

#### Gertlex

• Supreme Robot
• Posts: 763
• Nuclear Engineer · Roboticist
##### Re: Milli-Amp
« Reply #1 on: August 02, 2011, 07:23:43 AM »
Yes.  Also make sure that you get it straight that mAh == milliamp-hour, not milli-amp .  It's yet another parallel between electricity and water... you need a bigger volume to store more water; likewise you need a bigger battery to store more energy (which is what mAh is a convoluted, but useful unit for*).  This is true within a battery type.  Different battery types (LiPo, NiCad, NiMH, PB-acid) will have different energy densities, so size for the same energy capacity will vary between the battery types.

*Actually it's not an energy unit either.  You need to multiply by the battery voltage to get milli-watt-hours.
I

#### Soeren

• Supreme Robot
• Posts: 4,672
##### Re: Milli-Amp
« Reply #2 on: August 02, 2011, 07:50:15 AM »
Hi,

[...] my question was, do batteries have to be bigger with more milli-amps?
Not to belittle Gertlex's answer, which is fully to the point, but more as a general idea of how to decide in such a case.

Take the question (any such question) to an extreme like:
"Is it possible to fit a 1,000,000,000,000 mAh battery into the same space as a 1,600 mAh battery?"
Then the answer should become quite obvious.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Engineering is based on numbers - not adjectives

#### soninja8

• Robot Overlord
• Posts: 136