Measuring mah?

[tom10122]

So I just found out that the batteries I were looking at lied about the mah, so now looking on ebay but don't want to get screwed, any way to test mah?

 

[Mr. Hooker]

I would just quote someone's answer for you, but this might help more.
http://jamesrbass.com/batterylife.htm

 

[hailrazer]

You need to know the exact amps a device draws. Then charge the battery and start the device. Play till the batteries completely discharge.

I use an N64. I measure the amps it pulls with Super Mario running as a demo. Usually around 1.2A with a screen and sound. So if the batter last 4 hours then they are around 4800 mAh batteries. 1.2A x 4 hours.

 

[tom10122]

how would I measure the mah it draws? Sorry amperage confuses me haha

 

[hailrazer]

how would I measure the mah it draws? Sorry amperage confuses me haha

You need a multimeter. Put it in mAh mode. Attach the power wire to the black lead then attach the red lead to the n64/screen/etc. it will read the current draw.

 

[Life of Brian]

You're basically putting the multimeter in series with your power supply while measuring the current (Amps) that's "flowing" through it.

Just to be clear on some terminology: 1Ah = 1 Amp-hour = 1000 mAh = 1000 milliamp-hours, which is a measurement of battery capacity (well, sorta). Amperes (or just "Amps") is a measurement of current. Like hailrazer said, if you know how long your battery lasts (hours) and what your current draw is (Amps) then you can figure out your battery capacity (Amp-hours or milliamp-hours). Similarly, if you know your battery's capacity in (Ah or mAh, typically it's mAh) you can divide that by your system's current draw (A or mA) to calculate about how many hours your system should last in ideal conditions.

I don't mean to be patronizing, just clarifying for anyone else teaching themselves electronics by reading these forums, which a lot of people do.