Prosine 2.0 Remote Shorepower Disconnect Circuit

[RCpilot]

The Prosine 2.0, as long as it's plugged into "Shore Power" will not go into the inverter mode. So, I walk out to the shed, unplug it and then can run off battery power. If I need to go back to Shore power, gotta walk back out to the shed and plug it back in. (I know, I know, exercise right!) So, digging in my junk I found a couple of 25A SPST solid state relays, a really cool project box that seemed like it was made just for this project, a tiny 120VAC to 20VAC reduction transformer, an encapsulated bridge rectifier and a phone jack. The circuit is simple, I am breaking both legs of the Shore power AC line by using two relays, #12 stranded for the current side. The transformer and bridge supply the need of 3-32VDC for the "coil side" and the phone jack is to make it look similar to the Xantrex's phone jack inputs that it uses for the display panel and the remote temperature probe. The way I have it wired is the phone jack comes out with two wires and simply opening and closing them enables or disables the "coil" on the relay. Since I already have a 100' of 8 conductor phone cable running to my computer room from the shed for the Prosine's remote display (It only needs 4 conductors) all I will have to do today is rig up a small switch from my room out to the phone jack of the unit. The Prosine draws no more than 16A from Shore power when charging at 100A so I am hoping the aluminum back of the project box will be enough of a heatsink. I will find out soon if that's the case. Here are some pictures of it. When I get more time I will try to post a small schematic of the unit but I don't think you really need one. If anyone is interested more, let me know.




Kelly

[RP]

Kelly,  A couple thoughts:

1.  Might be a good idea to hook about 10uf of capacitor across the bridge rectifier.  I don't know how fast those solid state relays switch but technically your switching signal is turning off 120 times/second.
   
2.  Also, since those relays usually only need a miniscule current to turn on, I'd suggest putting a load of some kind on the DC side.  An indicator LED or just a 5K resistor shunted across the terminals would  prevent stray electrical noise from switching them on accidentally.
   
   

Looks nice!

[RCpilot]

RP Thanks for the great comments, I had hoped some comments would come in. I had forgot about the "Cool" factor, an indicator light to show It's on or off besides being functional as well. As for the cap, you are right. Even the cheapest wall adapters have some sort of cap in them to buffer the AC. I am adding both components right now.

[RCpilot]

I have a question about my setup. I am using two relays to disconnect the hot and neutral on the AC line going to the inverter. I tested the unit this afternoon connected to the AC input of the inverter and one of the two modules blew as soon as I enabled the unit. I remember leaving the inverter in the charge mode but according to the manual the maximum the inverter draws from the AC line is 15 amps even when it's outputting 100amps while charging. So, I replaced the module, and decided to load test the unit. With a floor heater and the wife's blow dryer I ran 17.5 amps through the unit. It got fairly warm but handled the current no problem. I know now I am going to need a heatsink on the back of it. My question is since the relays are in series with the AC and there's two of them am I getting twice the heat from them and would be better off with just one? The inverter must have some kind of surge current that exceeds the 25amp rating of the relays? It happened so quick I was not able to do any testing while connected to the inverter. Maybe I would just be better off with a mechanical relay that is DPST like one of the standard Dayton kind that fits into a socket that resembles the same socket tubes used to plug into?

Kelly

[RP]

I can't think of anything other than inruh that would hurt it.  Is there any chance you simply had a bad one from the start?

Also, was it the hot leg one or the neutral one?

[RCpilot]

I wondered if I had a weak one. I think it was the hot leg that failed. I have the box fixed up again and will try it again but I need to find a heatsink for it as it gets pretty warm when I had it pulling 17.5A earlier tonight. I guess it's a trip to the salvage yard tomorrow to see if he's got any.

Kelly

[RCpilot]

RP, I decided to hook it up last night and now, it seems to work just fine. Maybe it was just a weak unit and an inrush that killed the other one. I didn't load it beyond about 11 amps so It wouldn't get too hot. If it fails again I will probably just try to locate a mechanical relay or contactor that can handle 20 amps or so. Got the switch in my computer room hooked up and tested it several times. I would say the project is a success unless another relay fails. Now to find a heatsink today at the salvage yard. Thanks for the help!

Kelly

[RCpilot]

The unit is working and got really hot the other evening to the point I couldn't touch it but didn't blow. So, I got my hands on a large heatsink and cut and fitted it to the back, carefully filing the heatsink and back until I had less than .005" clearance all over the mating surfaces and then attached it using heatsink compound. Tonight, ran around 11 amps through it and it got warm but not hot. I think I might have it under control but will have to wait and see when I use the inverter to charge the battery again. Then it will see about 16 or 17 amps through it and I will know if I need a small PC fan on it or not. Gradually making progress and this seems to be a worthwhile project so far.

[RCpilot]

I thought I would post some pictures of the final setup as it's mounted in my shed showing the label I made for it and the heatsink that had to be added. I really figure I will end up with a small fan on it as well.