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Jump Start a Combustion Engine from an Electric Vehicle? It works! And is the reason why also EVs need load dump protection
Though the main power train of electrical vehicles use a high voltage battery, all these cars have still the traditional 12 V battery on board. Reason is that most electronic and electrical systems in a car - lights, screen-wiper, infotainment etc. - are made for that voltage level. This battery is further used for the switch to connect and disconnect the high voltage system when the car is started or stopped. As such, EVs can jump start cars using a combustion engine - and also vice versa!
At that procedure, load dump protection becomes important. A load dump transient is the voltage surge generated when the battery is disconnected while the alternator is connected. This typically happens if a discharged car battery is powered up by a second one and afterwards jump leads are removed. The peak voltage of this surge may be as high as 120 V and the surge may take up to 400 ms to decay. It is typically clamped to 40 V in 12 V vehicles (cars) and about 60 V in 24 V systems (trucks).
Diotec's new application note "Automotive Load Dump Protection" describes suitable TVS diodes for surges according to "Test A" (elements for centralized suppression) as well as "Test B" (distributed protection of on-board electronics), all described in the standard ISO16750-2.