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Discussion Starter #1
Precharge of the capacitors on a drive inverter is well understood - and most inverters manage this themselves. But I'm curious about the other accessories that run on ~380 volts DC.

DC/DC converters have a certain amount of capacitance that would potentially weld a contactor. Likewise, high voltage DC-supplied air conditioning compressors have a good 200 uF of capacitance.

So what is the 'best practice' for these parts? Do we just leave them permanently hooked up to the full pack voltage?

Do we switch them with contactors and precharge circuits?

From an isolation perspective it would be good to know that when the car is off - it's thoroughly off. But being able to keep the auxiliary battery topped up from the DC/DC converter, especially when charging is a good idea.

Any thoughts?
 

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You make a good point and i think some provision for pre-charge is necessary.

In the Mits miev they use a "charging" contactor for pre-charging the big cap in the inverter and all other HV devices at the same time.
 

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Discussion Starter #4
Yeah I have worked on stuff with Ian's precharger gear before. But I'm wondering if there is a smarter way to design the high voltage distribution around the vehicle.

The single precharge circuit isn't a bad idea - the DC/DC converter and air conditioning compressor will be permanently charged up, but they are not necessarily using power as they have digital controls to wake them up once charged.
 

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The big "smoothing condenser" is basically holding up the HV buss (+) for all the users even though it is located within the motor inverter. The 20A fuse provides the HV feed for the DCDC converter.
 

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Discussion Starter #6
I just got this note from TC Charger - they supplied the DC/DC converter I'm going to install in a conversion:

"Hi Chris,

There is precharge process in our converter. The external precharge circuit is not necessary.

2018-07-03
Best Regards

Bella Xu"

Well that makes it easy!
 
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