Large Batteries

Large Batteries 101

Batteries store electrical energy. The most common battery energy rating is the AMP-HOUR.

• ‘Ah’ is the symbol for ‘amp-hour’
• ‘mAh’ is the symbol for ‘milli-amp-hour’
• 1 Ah is equal to 1000 mAh

Ah and mAh are units of measurement for battery capacity, and can be found by multiplying the current flow (in amps) by the time it takes to discharge the battery (in hours). For example, if a battery has the capacity to deliver 100 Ah of electricity, it could power a 5 amp device for 20 hours (5A * 20H = 100Ah), or a 1 amp device for 100 hours (1A * 100H = 100Ah).

Some Scenarios
Here are some ideas of things a battery could power and for how long (if fully charged)

A small solar panel setup that has a single 12 volt deep cycle battery with a rating of 55 Ah

• A laptop computer that draws 2.5 amps @ 12 volts (55 Ah / 2.5 amps = 22 hours)
• A 12 volt RV fridge that pulls an average of 4 amps (55 Ah / 4  = 13.75 hours )
• A portable radio that only needs 200 mA @ 12 volts (55 Ah / 0.2 amps =  275 hours)
• A CFL bulb pulls 13watts@120volts = 0.9amps@12volts (55 Ah / 0.9 amps = 50 hours)
• A 100 watt light bulb @ 120volts = 8.3amps @ 12volts (55 Ah / = 8.3 amps = 6.6 hours)

A 12 volt emergency power pack, like the Duracell DPP-600HD Powerpack is rated at 28 Ah

• Power a 32” LCD TV for 2.5 hours
• Power a desktop computer and LCD monitor for 2 hours
• Power a basic kitchen refrigerator or chest freezer for 4 hours
• Power a laptop computer for 10 hours
• Power a small space heater (500 watt) for 1/2 an hour, or less...

* Note: If you are using an inverter, some of your electricity will be consumer in the process of transforming the electricity from DC to AC. This could be as much a 25% loss.

A 12 volt battery rated at 55 amp hours will have 660 watt-hours (12v * 55Ah = 660w)
watt-hours = amp-hours * voltage (a 100 watt light bulb will use 100 watt-hours in 1 hour)

*In general, disposable batteries have higher energy densities than rechargeable batteries.