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how to measure Battery Charge

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ehsanelahimirza

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measure battery charge

hi all

plz tell me how to measure the current stored in the battery

i mean how the capacity and storage of charge can b measured.

i want to measure car battery for its charging capacity and generator automatic cutout function that how does it work
 

leotim

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measuring battery charge

you can measure the internal resistance (Rin) of the battery. then you can one of use these 3 conditions to check that the battery is charged or not:

1) check the absolute value of Rin if it is less than a threshold value (Rth) the battery is charged.

2) check if the change rate of Rin while a constant current is charging the battery, is less that a threshold value (dR/dt)th.

3) charge the battery usign a constatnt current (Ich) and for a constant time (Tch) such that (Ich×Tch = Battery Capacity)

The threshold values may be calculated or found in battery datasheet (if available) or may be estimated by experiment.
 

Sal

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how to measure battery

Hi

There are some "battery testers" in the market which are mainly composed by 2 circuits. 1) The battery current capacity which is applies a load while measuring voltage and amperage. the load should be applied for short time lets say less than 1 min, then release it, wait a few minutes and apply the load again, if the battery can recover its nominal voltage (~12vdc) and during the measuments provided high current (I dont remember how many) then the battery is concluded to be capable of retaining charge. The ph of the acid is also meassured by other simple instrument.

About the charging system, you can use an analog voltmeter and measure at the battery poles while the engine is runing, it usually reaches 14 or 15 vdc. It means the car charging system is working.

cheers

Sal
 

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