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I want to buy some lithium batteries, have a few questions

post #1 of 7
Thread Starter 
Hi , so I have couple devices that I want to power with a lithium battery , both devices are 5v and on the adapter for one it says its 2.6a and the other is 1a , I was checking out the batteries on ebay and I noticed that almost nobody gives an amps rating they only give the voltage and the mah (milliamps per hour).

I know when you buy an adapter its important to match the voltage and the amps to the device, is it the same for batteries or does the voltage only need to be matched and not the amps?

thanks
post #2 of 7
Quote:
Originally Posted by Kawai_man View Post
Hi , so I have couple devices that I want to power with a lithium battery , both devices are 5v and on the adapter for one it says its 2.6a and the other is 1a , I was checking out the batteries on ebay and I noticed that almost nobody gives an amps rating they only give the voltage and the mah (milliamps per hour).

I know when you buy an adapter its important to match the voltage and the amps to the device, is it the same for batteries or does the voltage only need to be matched and not the amps?

thanks
Doesn't matter for batteries. The device will draw the current it needs, and the battery will supply the power as long as it can. MaH is the total capacity of the battery. The more current you draw, the faster the batter runs down. MaH rating are based on a certain discharge rate, which is usually not specified.
post #3 of 7
Try dealextreme for batteries, but like you said you have a adapter to regulate the current, and voltage too(or it runs within a range).
post #4 of 7
Thread Starter 
Quote:
Originally Posted by beerguy0 View Post
Doesn't matter for batteries. The device will draw the current it needs, and the battery will supply the power as long as it can. MaH is the total capacity of the battery. The more current you draw, the faster the batter runs down. MaH rating are based on a certain discharge rate, which is usually not specified.
THanks
post #5 of 7
Some different amperage batteries can have effects on the charging circuit if it is a rechargable device.
post #6 of 7
The mAh rating is just a reference to how much current a battery would give if discharged in one hour - it talks nothing about the peak power handling capability of the battery.

What you need to know is the C rating, eg: a 1000mAh lipoly rated at 30C continuously & 50C peak means that the battery can discharge 30 x 1000mA = 30,000mA or 30A continuous & likewise 50A for a few seconds (before the battery gets damaged)

Similarly a 1000mA battery having a continuous charge rate of 1C & peak charge rate of 5C means it can be charged with 1A continuously on the long run & quick charge occasionally with 5A

Also for RC users power-weight ratio, charge-discharge cycles of the battery mean a lot.

Hope this helped !!
post #7 of 7
When choosing a charger for the battery - the charger output voltage must be higher than the rated voltage of the battery, only then the electrons will flow from the adapter to the battery as electrons (like water) flow from higher potential to a lower potential.

If the voltages are same - then it will be a parallel connection & if the battery voltage is higher, then the battery will try to charge the adapter (you know what I mean right?)

So once the direction of electron flow is established (adapter to battery) - the charge time depends on the battery mAh capacity divided by the charging current of the adapter (time in hours).

However, you have to match the Charge current rating of the battery with that of the adapter - the charger may have less than the necessary charging current but should not be more or the battery will be damaged.
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