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Xringer · 03-31-15, 02:09 PM

Using the golf cart relay to disconnect the 800w PV array when the tank hits 70C.

This is the third day of testing. So far it's working.
I'm not sure what the open relay contact gap is.
But golf carts run between 36 and 48 volts.
So, I'm not too confident in contact longevity, with a PV voltage over 100v.

One other problem is the parasitic load of the closed relay is about 800ma.
That's almost 10w wasted. The PSU is on a timer, so it's not on all night.

Oh, one other problem. The 12v relay coil has a lot of back-EMF when disconnected.
While measuring it's current use, the EMF killed the back-EMP protection diode.
The next spike cost me $40.. It killed my little Turnigy DC meter..

http://i46.photobucket.com/albums/f1...testmeters.jpg

Anyways, I'm thinking of going back to the FETs.. Not as a PPT gizmo,
but just as a DC switch, to do relay duty..

03-31-15, 02:09 PM	#27
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 114 Thanked 250 Times in 230 Posts	Golf kart relay Using the golf cart relay to disconnect the 800w PV array when the tank hits 70C. This is the third day of testing. So far it's working. I'm not sure what the open relay contact gap is. But golf carts run between 36 and 48 volts. So, I'm not too confident in contact longevity, with a PV voltage over 100v. One other problem is the parasitic load of the closed relay is about 800ma. That's almost 10w wasted. The PSU is on a timer, so it's not on all night. Oh, one other problem. The 12v relay coil has a lot of back-EMF when disconnected. While measuring it's current use, the EMF killed the back-EMP protection diode. The next spike cost me $40.. It killed my little Turnigy DC meter.. http://i46.photobucket.com/albums/f1...testmeters.jpg Anyways, I'm thinking of going back to the FETs.. Not as a PPT gizmo, but just as a DC switch, to do relay duty.. Attached Images __________________ My hobby is installing & trying to repair mini-splits EPA 608 Type 1 Technician Certification ~ 5 lbs or less..