I was installing Solar a few months ago and found myself, looking at my battery separator solution. Due to cramming more stuff into the same area, the heat of the continuous duty solenoid started give me some concern, or at least a reason for me to try something new. I do like some of the magnetic latch relays, but I did not want any of the Voltage sensing features that come along with the Blue Sea 7620 or 7622. Blue Sea also has the same thing minus automatic voltage monitoring in the 7701. It is really just a remote battery switch.
While this seems like a simple replacement, there are some pitfalls, My current solution was using the 12 Volts from the “Run Circuit” on the van to close the trombeta solenoid that I used from my old SurePower 1315. The problem with the magnetic latch relays is they need a pulse instead of steady on voltage and usually have multiple inputs or polarity changes for on or off. To get around this I turned to a Directed Electronics 452T Door lock Pulse/Double Pulse Generator for the solution
The 7701 wiring is pretty straight forward, it usually comes with a momentary SPTD momentary switch. It has one Red 12 volt wire that is always connected. I fused this with a 7.5 amp fuse to my house battery, A black wire goes to chassis ground, a yellow wire that goes to a LED indicator, orange wire is a 12 volt input to open the relay, and finally the brown wire is a 12 volt input to close the relay. Both of these inputs must be a pulse or momentary. So this is where the 452T comes in, I can use this to turn my 12 volt run signal into a pulse to close the Blue Sea 7701, and likewise when the 12 volt run Signal goes away I get a pulse to open the Blue Sea 7701. The 452T has 9 wires for hook up,
• Red (+) 12 Volts
• Black (-) Chassis Ground
• Orange (-) Activation Input
• Violet (+) Activation Input
• Green (-) 200mA Lock Output
• Blue (-) 200mA Unlock Output
• Green/White (+) 200mA Lock Output
• Blue/White (+) 200mA Lock Output
• Red/white (+) Pulse Duration Input
I used the Red, Black, Orange, Blue/White, and Green/White wires. The Violet, Green, Blue, and Red/White wires will be unused. I put heat shrink on the ends. I hook the Green/White to the Brown wire on the 7701, the Blue/White wire goes the Orange wire on the 7701. The Red and Black go un switched Power and Ground. This leaves us the Orange (-) Activation input. This means the Orange wire needs to go Low (gnd) to activate the Green/White Lock Output. Actually the Orange wire input is edge triggered. It will activate the Lock out put when the leading edge goes from a high level to a low level. Conversely, when the trailing edge goes from a low to a high it will activate the Unlock Output.
This is where I added a feature of a secondary SPDT relay, I added a switched ground connection to pins 86 (coil) and 87 (NO) , I connect the “Run” circuit to pin 85 (coil) on the relay. Pin 30 or output of the relay will go to the Orange input on 453T. Now when the “Run” Circuit has 12 Volts (Van is running) the SPD relay will close and I will get the High to Low edge needed to close the 7701. When I turn off the van, the relay opens and I get a Low to High edge to open the 7701. Having the ground for that relay switched allows me to disable the 7701 from being engaged. I do use a cover switch for this. Now the SPDT relay also has a Normally closed input, this can be used to control the 7701 manually with a separate switch to ground.
Note: If you do not want to use the secondary SPDT, you could run the 12 Volt “Run” Circuit to the Violet input of 452T.
Also if replacing a SurePower 13xx note that the studs of the 7701 are 3/8 vs. the 5/16 that were on the SurePower.
Blue Sea 7701 $155.00 or lower
Blue Sea LED 8172 $6.29
DEI 452T $9.95