openinverter forum

so yet another newb question from those of us who don't "identify" as electric engineers, ha ha

Question is: How come I can directly connect a high voltage battery pack such as the one from a 2018 BMW 530e plug in hybrid to a Tesla Model S Gen 2 charger for example and it will not go BOOM, but I can not do the same with my 2010 Lexus GS450h Inverter? [FYI: using some 20 amp fuses between the battery pack and the charger of course]

Same goes for my Chev Volt Gen 1 DC-DC Converter, I can connect a 350 volt battery pack directly to it, but again I can not do the same with that Lexus Inverter, why is that?

Now I know the principals of, and the need for a pre charge circuit, I get it, but it seem like the Inverter is arguably the most important / central component to the entire operation, not to mention most expensive (if comparing used OEM parts to OEM parts), therefor why wouldn't the manufacturers build in some internal protection.

I realize that inside my BMW high voltage battery pack (traction battery as some call it) there is a "Safety Box" aka an OEM pre charge circuit, and that is what protects the inrush of current to the Inverter, I get it. But without that "Safety Box" the charger and or converter are still safe, yet the inverter is not?! So is it that there are no capacitors inside the other components like there are in the Inverter, or are there?, but they are just smaller?

I honestly don't know / understand this dilemma, or are the charger and converter engineers just smarter than the inverter ones, LOL ?

The charger will only have some small output capacity, say 10uF. Connecting that to HV will result in an inrush but it is so short that it won't weld a relay. The DC-DC converter might also have low input capacity, judging from the Prius Gen2 it is also just a couple of uF. The inverter however contains a 500-1000uF capacity. Connecting that to HV uncharged will weld your relays. It's also not favorable for the capacitor to be charged that quickly but the biggest problem is the relay.
Putting "protection" inside the inverter would mean putting the pre-charge and main relay into the inverter. But that's not where these belong. Relays must be located as close to the battery to act as a safety device.

Gregski wrote: ↑Mon Feb 14, 2022 3:10 pm Question is: How come I can directly connect a high voltage battery pack such as the one from a 2018 BMW 530e plug in hybrid to a Tesla Model S Gen 2 charger for example and it will not go BOOM, but I can not do the same with my 2010 Lexus GS450h Inverter? [FYI: using some 20 amp fuses between the battery pack and the charger of course]

When i made my Volt gen2 DCDC converter go BOOM i took it apart and i noticed it has two strange oval things connected inline to DC input legs. It seems those could be inrush protection NTC resistors/limiters. This is how i could explain Volt has only a measly 15A DC relay across DCDC contacts.
Current should never exceed preset limit with normal operation.
I however managed to connect DC link in reverse and sadly there is no protection from stupidity .

thanks, I recon we best study up on those darn farads especially them μF baby ones