We measure the two voltages V_res on the resistor (R_ch) and V_bat1 on the battery. One easy method is to wire the battery as if we like to charge it via a resistor. If the charger refuses to continue charging the battery though its voltage is nominal then we can conclude that it detects its internal resistance (R_bat) first which usually increases with time. But if dissipation is not a problem (by using a power resistor or many resistors in parallel, series or both, to get R_ch), using 12V for example can let the charging current be rather constant while V_bat is increasing with time.
R_ch = (Vcc - V_bat) / I_ch (worst case is when V_bat=0)įrom the formulas above it is better to choose a low Vcc to decrease dissipation (not higher than 5V). The charging current (I_ch) doesn't have to be high since we are not in a hurry :wink: This can be done via a resistor and a DC supply. If its voltage is too low then we should try charging it with a simple method till it restores its nominal voltage.
Sorry, I couldn't get your point on how to let the charger see the battery as having internal low impedance.īy the way, I supposed that measuring the voltage of the old battery gives a nominal value (for example like 1.2V or a bit less).
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