How to Test the Battery Power ?

Detect ordinary zinc-manganese dry battery level is sufficient, there are usually two ways.The first method is by measuring the battery instantaneous short-circuit current to estimate the internal resistance of the battery, and then judge the adequacy of battery power; The second method is an appropriate resistance resistor in series with ammeter, calculate the battery by measuring the  Inspiron 1545 battery discharge current resistance, in order to determine whether the battery is sufficient.

The biggest advantage of the first method is simple, with a multimeter the current file can directly determine the dry battery power, the drawback is that the test current, far more than dry batteries to allow the discharge current limit, to a certain extent the impact of dry vgp-bps13 batteries. life expectancy. The second method has the advantage of small test current, security, and generally do not have a negative impact on the life of dry batteries, the drawback is a bit trickier.

I use the MF47 multimeter to a new No. 2 batteries and an old dry cell using the above two methods to test contrast. Assume that ro is a dry  hp g70 battery internal resistance, RO ammeter internal resistance, the second test method, the RF is the additional series resistance, the resistance of 3 ohms, the power of 2W.

The measured results are as follows. New on the 2nd  hp g62 battery E = 1.58V 2.5V DC voltage profile measurements, the voltmeter internal resistance of 50k ohms, is much larger than the ro, it can be approximated to that 1.58V is the emf of the battery, or open-circuit voltage. The first method, the multimeter set 5A DC current file, meter internal resistance RO = 0.06 Ohm, the measured current of 3.3A. Ro + RO = 1.58V ÷ 3.3A ≈ 0.48 Ohm, ro = 0.48-0.06 = 0.42 ohm. The second method, the measured current of 0.395A, the RF + ro, + RO = 1.58V ÷ 0.395A = 4 ohms, current 500mA file internal resistance of 0.6 ohms, so ro = 4-3-0.6 = 0.4 ohms.

Old on the 2nd  latitude e4200 battery when the first method measurements, first measured the open circuit voltage E = 1.2V, the meter internal resistance RO = 6 ohms, a reading of 6.5 mA, a multimeter set to 50mA DC current file, ro + RO = 1.2V ÷ .0065 A ≈ 184.6 ohms, ro = 184.6-6 = 178.6 ohms. The second method, the measured current is 6.3 mA, ro + RO + the RF = 1.2V ÷ 0.0063A = 190.5 ohms, ro = 190.5-6-3 = 181.5 ohms.

Obviously the two results of the test method is basically the same. The final calculation of small differences due to reading error, resistance caused by the RF error and the contact resistance and other factors, this small error would not affect the judgment of the  latitude e5400 battery power. If the measured battery capacity, high voltage, you should adapt to increase the resistance of the RF.