need help about this battry question ..!

hi every body

I have the following question .. it seems easy .. but I feel a trick there ..

the question af follows:

- It is written on a car battery 60A , 12v and 100AH this means that:

a- it has internal resistance of 12/60 ohm.
b- it is charged by 12v source.
c- it can store energy sufficient for lighting 12 ohm bulb for 100 hour.
d- it must be charged by current no more than 60 A.


my first answer was "c" but I became doubt after I thought about the meaning of 60 A ...

can any body tell me why 60 A .. and then 100Ah ..

it make some kind of confusion ..


thanks at all ..

i think it is short time duty surge discharge current maximum.
if it is autmotive battery , then it is the current at starting of starter motor.

srizbf
17thmay2010

Hello,

A and B are wrong, D is very likely wrong also. C can be true.

Normally they mention the voltage (12V), capacity (100Ah) and (cold) cranking current (for example 400A).

The 100Ah is the product of time and current before it is empty (your C option), under certain conditions. The actual capacity available depends on the load current during the discharge cycle and temperature. It is advised to avoid full discharge of the battery as this reduces lifetime.

The 60A spec I expect for UPS backup batteries. In that case it means that you may draw 60A from the battery for a certain time (mentioned on the battery).

A 12V battery must be charged with a current limited higher voltage (about 14V) to get current (charge) in it.

Internal impedance of a car starter battery is very low as it must be able to deliver high current during short time. It is in the mOhms range.

I should consult the manufacturer's website to find how they specify their batteries if this is more than just a curiosity.