Milliampere Hours (mAh)

Milliampere Hours (mAh)

Milliampere Hours (mAh) is an important figure because the easiest way to determine the capacity of a battery. It is also a way to compare battery run times on batteries with the same voltage. The higher the mAh, the longer the battery will last. Batteries with same footprint and different mAh ratings are usually interchangeable. If your battery is rechargeable then the mAh rating is how long the battery will last per charge.
Milliampere Hour is 1/1000th of a Amp Hour, therefore 1000mAh = 1.0Ah
It is similar to a car fuel tank. Voltage is how much fuel is being used, and mAh is the size of the tank. The bigger the fuel tank (mAh) rating the longer the device will run. If your battery is rechargeable, then think of the fuel tank as refillable (rechargeable).
 ampere-hour

(Mathematics & Measurements / Units) a practical unit of quantity of electricity; the quantity that flows in one hour through a conductor carrying a current of 1 ampere. 1 ampere-hour is equivalent to 3600 coulombs Abbreviation a.h

 

 am·pere-hour (mpîr-our)

 A.h. or amp hr

The electric charge transferred past a specified circuit point by a current of one ampere in one hour.

 The table below shows the battery volume for cell sizes AAA, AA, C, and D. The volume does not change with the type of battery, but the weight does, as shown here.

Battery Cell Size	Volume ml	Alkaline Weight g	Carbon-Zinc Weight g	NiCad Weight g	NiMH Weight g	Lithium Ion Weight g
AAA	3.9	12	9.7	11	12
AA	8.3	24	19	29	26	24
C	26.5	65	48	85	82
D	55.8	135	98	200	170

Energy storage in AAA batteries

Battery Type	Avg. voltage During discharge	milli-Amp hours (mAh)	Watt-hours Wh	Joules J
Alkaline Long-life	1.225	1150	1.41	5071
Carbon-zinc	1.1	320	0.35	1268
Nickel-Cadmium	1.2	300	0.36	1296
NiMH	1.2	800	0.96	3456

Energy storage in AA batteries

Battery Type	Avg. voltage During discharge	milli-Amp hours (mAh)	Watt-hours Wh	Joules J
Alkaline Long-life	1.225	2122	2.60	9360
Carbon-zinc	1.1	591	0.65	2340
Nickel-Cadmium	1.2	1000	1.20	4320
NiMH	1.2	2100	2.52	9072
Lithium Ion	3.6	853	3.1	11050

Energy storage in C batteries

Battery Type	Avg. voltage During discharge	milli-Amp hours (mAh)	Watt-hours Wh	Joules J
Alkaline Long-life	1.225	7800	9.56	34398
Carbon-zinc	1.1	2172	2.39	8600
Nickel-Cadmium	1.2	2500	3.00	10800
NiMH	1.2	4500	5.40	19440

Energy storage in D batteries

Battery Type	Avg. voltage During discharge	milli-Amp hours (mAh)	Watt-hours Wh	Joules J
Alkaline Long-life	1.225	17000	20.83	74970
Carbon-zinc	1.1	4733	5.21	18743
Nickel-Cadmium	1.2	5000	6.00	21600
NiMH	1.2	9500	11.40	41040

Lithium-Thionyl Chloride -- Special Mention

Although non-rechargeable,Lithium-Thionyl Chloride has the highest energy storage per kilogram of any battery type. Lithium-Thionyl Chloride cells do not supply high discharge currents, typically 1/10 the current of other cell types. However they last for 20 years, and withstand temperature extremes of -55 to +150 degrees C.

Lithium-Thionyl Chloride (non-rechargeable)	Avg. voltage During discharge	milli-Amp hours (mAh)	Watt-hours Wh	Joules J
AA cells	3.6	2400	8.64	31104
C cells	3.6	8500	30.60	110160
D cells	3.6	19000	68.40	246240

Finally, if you would like a D-size battery that can supply 20 amperes of current for a short time (5 seconds), that will last for 10 years, check out the Ultracapacitor at Maxwell Technologies Inc. It is not really a battery at all, it is a 350 farad capacitor rated 2.5 volts. Yes, we said farads, not microfarads. As such it can store 277 Joules at 2.5 volts. This is not a great amount of energy storage, hence the limited discharge time. However, it can deliver more peak current than a lead-acid battery of the same size, and it recharges easily more than 500,000 times. The cost compares favorably with other D-size rechargeable batteries, but the cost per Watt-hour is not too good, $195.