Precautions for Battery Loading
11. Precautions for Battery Loading
In regard of the blooming EV, the test application for high power battery has become more
and more; and the 63200 Series high power, high voltage electronics loads such as 63204
and 63210 that comply to customer’s the most. However, since it is to test the battery with
high power and voltage, it is necessary to pay more attention to the application safety.
According to the RMA data, the damage part is MOSFET mainly for the high power, voltage
Electronic Load to be repaired in general and the most possible cause is connection over
voltage between MOSFET and UUT. It maybe just a transient, but it could cause the MOSFET
damaged by a little energy if it exceeds the maximum voltage.
Common battery application often forms high voltage by paralleling multiple batteries to avoid
the transmission lost caused by low voltage high current. As the switch is uses directly to
connect the battery and applied object, the study shows it is the main cause of LOAD damage.
Figure 11-1 shows the wire connection of Electronic Load & Battery. When the switch is
shorted same as inputting a pulse signal, the effect caused by the stray element on the circuit
(series inductance and parallel capacitance resonance) will generate a transient high voltage
to damage the MOSFET and cause short circuit explosion as the simulation shows in Figure
11-2. It can see that if the battery voltage is 500Vdc, the equivalent series inductance is
10uH and the equivalent parallel capacitance is 10uF (the Load internal damping uses
capacitance to parallel with the Coss of MOSFET), also when the switch is shorted, up to
911V Spike will appear which is beyond the IC maximum voltage.
Figure 11-1 Wire Connection of Electronic Load & Battery
The figure below shows the simulated circuit diagram of the application that causes damage.
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