Foxwell BT-705: the meaning of SOH, SOC, and RES MR

Purchased Foxwell BT-705 battery tester, have question what do the letters SOH, SOC, and RES MR stand for on page 2 of the “battery test”, because the manual is vague.


SOH:  the health status of the battery.


SOC:  the state of charge.


RES:  the internal resistance of the battery.


One more question: what are good numbers for RES?

Here is the reply:

  1. The internal resistance of the car battery is milliohm level. The larger the capacity, the smaller the internal resistance of the battery. For example, the internal resistance of 12 volts 100 amps should be around 4.5 milliohms, and the internal resistance of the battery at 12 volts and 38 amps. It is about 8 milliohms.
    2. It is related to the percentage of actual electricity. Generally, the internal resistance over 40% of electricity is not changed much. Below this percentage, there is no reference value. The ion state of the electrolyte is relatively stable after the amount of electricity is higher than 40%.



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