# battery back up chargers



## trips-man (Apr 26, 2015)

I started looking into battery back-up chargers (power banks). I did a little research on the unit 'mAh', but still a little confused. Does the higher the number before the 'mAh' mean the unit can store more power or does it mean that it charges faster?


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## paraquack (Mar 1, 2013)

mAH = milliamp = 1/1000 of an amp. 1000 mAH = 1 amp. When it comes to a charger, the higher the number the faster the charge but the faster the charge, the more heat is created in the storage device (battery). 
AH or mAH on a battery is how much current the battery can put out from a full charge but usually says a specific number of hours or minutes.
Batteries are usually designed to take a charge at a maximum current (amps). Too much will over heat and and can damage the battery. Chargers frequently will say what the max amperage of the battery should be for the charger.


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## Prepadoodle (May 28, 2013)

Battery banks are rated by total capacity. For bigger batteries, this is usually expressed in Ah, or amp/hours, but smaller systems will use mAh. A mAh is 1/1000 of an aH.

These ratings are for that battery under specific conditions. You will often see battery capacities listed at different rates, for example...

A 20 Ah battery would deliver 1 amp for 20 hours. This is the 20 hour rate.

That same battery might deliver less than 2 amps for 10 hours. This is the 10 hour rate. (battery capacity varies with discharge rate, faster discharge means lower capacity)

These ratings assume a standardized constant load at a specific temperature (usually 25 C or about 77 F)

So the rating you see is how much energy it can store, not how fast it will charge.


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## Kauboy (May 12, 2014)

Your title is a bit confusing. Are we talking about a device that stores a charge within an internal battery AND can deliver that charge to other battery devices? Such a device can be wired up to charge at one rate, and discharge at a much different one.
As has been stated, the mAh is the batteries discharge rate over time, or capacity. The larger the number, the more it can hold and discharge over time. Most of the handheld devices I've seen for this purpose range from 5,000mAh to 10,000mAh, with outliers on either end of the spectrum. Under optimal conditions, they could put out that number of miliamps over the period of 1 hour if the receiving device needed it. Now, most devices are set to output at a *rate* of about 500 miliamps to 1,000 miliamps, or .5 to 1 amp. This would be the rate at which it pushes the electricity out to the receiving battery. A .5 amp output will charge a device at a slower rate than a 1 amp output. Some newer chargers even have special "fast charge" ports that output at 2 or 3 amps. You have to be careful about pushing this much power out to a device because not all batteries can handle this much charge at once. They will get hot and could burst. Be sure your device is rated for these higher amperage chargers. I've got a charging station at home that has one output USB port for 1A charging, and another for 2A charging. We plug the tablet into the 2A, and phones into the 1A.


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## Ralph Rotten (Jun 25, 2014)

UPS devices are actually pretty cool for more than protecting your PC. When the power goes out, they hold enough charge to run small lights, charge laptops and tablets, radios, etc. Some of the bigger units will run a PC. You just leave the things plugged in around the house and they're charged to-go. I've done some crazy testing with the things, including taking one on our last snow camping trip (to run the vaporizers). 

AH=amp/hour


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