Battery Cutoff Solenoid Indicator Light

kbuhagiar · Jan 29, 2020

55 Rescue Dog said:
I plan on using a latching solenoid disconnect on my car too and would also want to know with a small light whether it open or closed since it's momentary trigger. I would think just a light on the load side would work for that fine. As far as memory I wouldn't jumper across the relay, but just use a separate feed off the always hot side from the battery that would only be connected to the memory circuit. That would keep it alive with the relay open or closed, and even if you forgot to turn on the disconnect nothing bad would happen.

Agreed!

This is what I may have to do, if all else fails and I can't come up with some sort of indicator solution.

55 Rescue Dog · Jan 29, 2020

To eliminate another hot wire running through the car I was going to hook up the momentary switch using a ground wire from there to the solenoid. But you could also pick up power for the switch from the memory circuit too.

kerrynzl · Jan 29, 2020

kbuhagiar said:
I want some indication when the solenoid is closed. The solenoid is controlled by a momentary contact switch, which toggles it between open and closed states; therefore at the present there is no way to determine, at a glance, whether the solenoid is open or closed. And if I accidentally attempt to start the car while the solenoid is in the open position, I'll pop the breaker and lose my settings. Unfortunately, having the memory saver in the circuit eliminates the very simple option of having a light on the switched (load) side of the circuit, since there will always be a low current present whether the solenoid is open or closed.

Firstly a Solenoid is a Relay [depending on who tells the story]

If the starter button feed is "downstream" from this solenoid it is impossible to Accidentally start it and blow the fuse [The solenoid must be switched on]

What you want to achieve is quite simple. Refer back to the SPDT relay.

#30 post from the battery side of the Solenoid.

#87A post goes to a LED [via resistor] to glow when battery is disconnected
OR
#87 post goes to a LED [via resistor]If you want it to glow when battery is connected

#85 or #86 goes to the switched side of the Solenoid AND the other post is to ground [these can go either way]

You could use 2 LEDs with this method Red disconnected and Green Connected with the above method

Those little LED's are 2.3volt and draw 0.02 amps so you'll need to add a 485 ohm resister inline.
The problem is the LED doesn't draw much current , but the resister continually creates heat
That is why I recommended grounding the LED via the door light switches.

You only need to open the door to see which way the Solenoid is switched [and if you use 2 LEDs it doesn't annoy you while driving, but can warn you if the door is left open]

kbuhagiar · Jan 29, 2020

kerrynzl said:
Firstly a Solenoid is a Relay [depending on who tells the story]

If the starter button feed is "downstream" from this solenoid it is impossible to Accidentally start it and blow the fuse [The solenoid must be switched on]

kerrynzl,

I appreciate your input. I'm not trying to be argumentative, but I need to clarify how my battery cutoff solenoid is wired.

See attached schematic. All of the current from the battery feeds through the cutoff solenoid. The 'memory saver' breaker (the yellow cartridge in the schematic) is wired in parallel with the primary terminals of the solenoid, and allows for a small amount of current, 3 amps, to flow into the electrical system and maintain settings, even when the solenoid is open.

If the solenoid is open, however, and one attempts to start the car (or turn on any other high-current accessory), the high current flow will route through 'memory saver' breaker and pop it...and this is why I was hoping to establish some kind of visual indicator.

As I have mentioned before, if all else fails I will just run a separate fused memory power feed from the unswitched side of the solenoid and eliminate the 'memory saver' breaker.

Thanks again for your interest in my situation! :shakehands:

kerrynzl · Jan 30, 2020

Just get rid of that memory saver.

Or if you must use it , simply wire it direct to the memory circuit [instead of bridging around the solenoid]

The 3 amp rating is enough to drain the battery if a door was left open or key left on.
If the light switch wasn't switched off properly 2 x 27/8 taillight bulbs would only draw 1.34 amps so it defeats the purpose of the solenoid.

Battery Cutoff Solenoid Indicator Light

kbuhagiar

55 Rescue Dog

kerrynzl

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