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Inverter Disconnect Switch with Precharge

Inverter Disconnect Switch with Precharge 2022-12-14

To get the paper, click on the orange
1635717748739.png
button at the top of this page.


This circuit is designed as a disconnect switch that allows the user to pre-charge the inverter capacitors before turning the switch completely on.

26 June 2020 update:
  • At request of a forum member I added a circuit design for 48 volts.
    Warning: I have not built/tested the 48 Volt design.
  • Added comments on how to build the circuit without the PTC thermistor.
28 July 2020 update
  • Expanded on building the circuit without the PTC thermistor. (It is not needed in many (Most?) situations)
8 August 2020 update
  • Updated link to PTC in the parts list.
5 October 2020 update
  • Added slide showing the connections in the four different switch states. (this helps explain how the circuit works)
  • Added label and printing instructions for Perco 8511 switch.
6 October 2020 Update
  • Added discussion of Inverter Disconnect vs Battery Disconnect
28 November 2020 Update
  • Added assembly picture for building w/o the PTC resistor.
Author
FilterGuy
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Very good writeup but it appears the Marinco BEP switch referenced for 48v systems is only rated for 48v MAX, not 58v needed for 48v systems.
FilterGuy
FilterGuy
The marinco voltage range has been confusing. I have seen messages from them saying 48V is the Max and others say the spec is for a 48V nominal system (and it can handle 60V)

https://diysolarforum.com/threads/48v-disconnect.62004/post-776166

48V would be an odd max voltage but would make sense for a nominal voltage, so I tend to believe the email from Marinco.
Unfortunately, it is still the closest thing I have found to something that works. I have built it and it works... but the mixed messaging leaves that big question mark. YMMV

Now that the cyber truck uses 48V for their low voltage systems, hopefully we will start seeing more items clearly supporting 48V.
Awesome work
Excellent made mine with a blue sea switch. No more arcing!
I ordered 100w 20 ohm resistor. Will this work with 48v inverter? ?
FilterGuy
FilterGuy
Please post the question to the general discusion board (Flag me with an @FilterGuy)
Thanks for the information! There is some really good stuff in there. One thing that seems to be missing is the timing of the pre-charge. Consider adding information on how to calculate how long the switch should be in the pre-charge before connecting directly.
A simple and elegant "foolproof" solution for someone like me.
The assembled photo was just what I needed to understand how to put this together
Simple solution. Thanks!
Thank you, I built and installed one based on your plans for a 200AH LifePO4 system with 48V and 3KVA inverter. No more sparks :-)
Great design for a vexing problem, thank you very much
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