latching master relay wiring

oldspark wrote: ....IMO it's the wrong relay for the purpose. You should have a dual-coil latcher....

This was actually my first thought. This is the only one I have found that was made for Automotive purposes that will handle 150 amp switching and is tried and tested. It is just a modified starter solenoid. A dual coil would have made solving the problem easier since you would have a dedicated on side and off side.

After looking at all the information, and the advice offered here, I searched for a while and found a battery disconnect that requires reversing the polarity across the coil to change state. So if i is on, pushing on again will do nothing, and that solves the entire problem. Thanks for all the help guys, back to working on my car....

Idiot: That would work on the new one that works by reversing polarity. But the one I have now would change state no matter which one you hit at any given time. So you could hit on twice and it would go on then off.

Glad you found a new relay, and hopefully it is a latcher. Your info....

seattle_ice wrote: This ... was made for Automotive purposes that will handle 150 amp switching and is tried and tested. It is just a modified starter solenoid.

... had me worried. You don't just modify a starter relay and turn it into a latcher. Modifieds usually don't have zero current. And modifying an intermittent relay for long-term use... But problem solved, so end of story.

oldspark wrote: Glad you found a new relay, and hopefully it is a latcher. Your info.... seattle_ice wrote: ... It is just a modified starter solenoid. ... had me worried. You don't just modify a starter relay and turn it into a latcher. Modifieds usually don't have zero current. And modifying an intermittent relay for long-term use...

I simply meant that the manufacturer used the same casing and parts as a typical starter solenoid. The new one is actually a heavy duty one made for RV use. It is rated for 200 amps continuous. And of course it is a latcher. If it wasn't that would defeat the entire purpose of what I was asking for.

I have a final resolution, and it works very well. So I am posting it here for informational purposes. The original relay I had would not work well, so I found one made for RV's. Specs:

• It is rated for 100 amps continuous (you can get up to 200 if needed)
• Mechanical Latching Function (Magnetic)
• Reverse current to change state

After testing, I determined there was one aberrant behaviour - if it was off, and you applied current to turn it off again, it would be momentarily on while the current was applied. So I routed the power to the "Off" switch relay from the "On" side of the main latching relay, so if it was off and you tried to turn it off again, nothing would happen. I wired it to use a SPDT momentary switch locked in the box with the alarm for testing/working purposes, and also use the alarm outputs.

And here it is installed in the battery box (The right one is the starter solenoid, the left one is the one relevant to this thread):