Anybody have experience with Golf cart solenoids?

[Roswell Bob]

Looks like my cells have left west coast for New England. I'm putting system down on paper.

I am going to do a precharge system for powering up the inverter. I would like to use a golf cart solenoid for the main contactor. Is this a fairly common way to go?

thanks
Bob

 

[chrisski]

I’m getting ready to do upgrade from 12 volts to 24 volts and not sure what you would use the contractor for.

I think the pre-charge you’re referring to on the inverter, is where with one lug already secured on the DC negative side of the inverter, I took my big resistor and shorted the positive cable to the positive lug. This prevents the spark which at 3000 watts could sling molten metal.

 

[Roswell Bob]

Yes. I am talking precharging the inverter.

I have simulated the inrush current on inverter and I believe the Class T 125A input fuse will clear on power-up. I haven't been able to get an answer from Growatt on what the input capacitance is so I assumed 0.1F /100,000uF. The battery array is a 16S 280ah EVE cells. My main concern is if the BMS disconnects the inverter. When it reconnects I think is when the inrush problem will surface.

The solenoid will just short across the 1 ohm charge resistor when the bus is charged. My concern with solenoid might be that is might get welded shut.

Do you have a BMS that switches inverter in and out?

 

[chrisski]

Do you have a BMS that switches inverter in and out?

No. I have the Overkill BMS. I did not realize BMS’s had options for that.

This is the resistor I’m using, just going to short this the first time I connect the 3000 watt inverter:

That resistor came recommended to me And others have used it for 24 volt 3000 watt inverters. I’m not quite sure of the math with Farads to Ohms for resistor size, but 1 ohm seems a bit small.

 

[Bvillebob]

Any relay or solenoid, other than a vacuum relay, will quickly be destroyed by the arc created by the huge surge of current on inrush if you don't use a resistor to slowly charge the input caps. One solution, which is used in lots of equipment, is to use two relays that switch the resistor in and out of the circuit on startup. An appropriate time delay can be added, or you can switch it manually.

 

[Roswell Bob]

No. I have the Overkill BMS. I did not realize BMS’s had options for that.

This is the resistor I’m using, just going to short this the first time I connect the 3000 watt inverter:
View attachment 74417
That resistor came recommended to me And others have used it for 24 volt 3000 watt inverters. I’m not quite sure of the math with Farads to Ohms for resistor size, but 1 ohm seems a bit small.

The math is a little fuzzy. It depends on what the inrush limiter is trying to accomplish. My concern is clearing the Class T fuses and welding the contactor closed. The value of the resistor is not especially important. Without a resistor the current it limited by the source impedance and stray wiring reactance. I am looking at 50v with about 0.005 ohms of cell/wiring impedance with 16 of the 280Ah cells. This puts the peak current near 10,000 amps. If we put a 1 ohm resistor in series we then limit the current to near 50 amps. The 10,000 amp pulse will most likely clear the 150A class T fuse while the 50A pulse will not. The more important specification with the resistor is the Joule rating. The joule rating of the resistor must be greater than 1/2C*V*V or it will blow open when charging the bus.

 

[Roswell Bob]

No. I have the Overkill BMS. I did not realize BMS’s had options for that.

This is the resistor I’m using, just going to short this the first time I connect the 3000 watt inverter:
View attachment 74417
That resistor came recommended to me And others have used it for 24 volt 3000 watt inverters. I’m not quite sure of the math with Farads to Ohms for resistor size, but 1 ohm seems a bit small.

No. I have the Overkill BMS. I did not realize BMS’s had options for that.

This is the resistor I’m using, just going to short this the first time I connect the 3000 watt inverter:
View attachment 74417
That resistor came recommended to me And others have used it for 24 volt 3000 watt inverters. I’m not quite sure of the math with Farads to Ohms for resistor size, but 1 ohm seems a bit small.

Sorry, I wasn't clear when I asked if your BMS switches inverter in and out. (I'm hoping to use the overkill BMS as well.) It does disconnect the inverter(load) when it detects an under-voltage condition. I am concerned with the safety of the BMS when it tries to reconnect when under-voltage condition is removed. I haven't heard much chatter concerning this. Either the BMS is designed to power up into a large bus, or users are integrating some type of automatic inrush limiting.

 

[BentleyJ]

Looks like my cells have left west coast for New England. I'm putting system down on paper.

I am going to do a precharge system for powering up the inverter. I would like to use a golf cart solenoid for the main contactor. Is this a fairly common way to go?

thanks
Bob

Hello, wanted to let you know I just posted something that may be relevant to your inquiry about golf cart contactors.

 

[Roswell Bob]

Hello, wanted to let you know I just posted something that may be relevant to your inquiry about golf cart contactors.

Thank you and welcome to forum.