A fancy battery disconnect

[Tired iron]

So, my wiring harness is pretty bad, but I'm not able to spring for a new spendy harness  for my 1950 Meadowbrook at this time.  I fixed the worst parts...but, still, all those fire stories...

 

So, I thought I'd use those commonly available battery disconnects.  But then I got to thinking!  I know myself, and I'd get lazy about lifting the hood after a ride to discconect the switch.  So, I came up with another plan I thought i'd share here.  I am in NO way suggesting that everyone should do this...it's just  another way to get things done.

 

I decided to leave the starter circuit, and the supply to the horn alone since they are short wires and their condition is readily visable and, instead, focus on the main wire that supplies most everything  else.  I spliced in a herky power relay into the line before it disapears thru the fire wall.  Then a control wire for the relay and a switch hidden under the dash to keep things looking stock.  Hit the switch and the relay basically connects the battery to the car (and mostly fireproofs it when it's off).  But, then I got to thinking (my wife says I think too much) that I'd forget to hit the switch to turn everything off.  Sooo, I schemed up a locking relay (just the power relay and another smaller one) and use a little hidden push-button switch.  Now, when I turn the key on, and then hit the push-button, the power relay locks on and the car is energized and I can start it or whatever AND when I turn the key off, the relay shuts off and disconnects the battery from the car.

 

I know, maybe it's overkill, but I sleep better.

[Oldguy48]

Great idea....

 

[OldPly]

Not all relays ( like a starter or   horn ) will not stand up being engaged for long periods of time 

[Tired iron]

Yep. Good point.  I used a different type that is designed for continuous on time.

[vintage6t]

IMO it adds complexity and therefore additional points of potential failure when you're out on the road. I'd add one more component.

 

Either carry a jumper wire or permanently wire in a switch across the the relay power terminals. Jumper of proper gauge or switch of proper amp rating to carry full amp load for your car. 

 

Then If you have a failure in your new disconnect circuit while on the road just install the jumper or simply close the switch and you'll be able to drive on.

[Sam Buchanan]

12 hours ago, Tired iron said:

So, my wiring harness is pretty bad, but I'm not able to spring for a new spendy harness  for my 1950 Meadowbrook at this time.  I fixed the worst parts...but, still, all those fire stories...

 

So, I thought I'd use those commonly available battery disconnects.  But then I got to thinking!  I know myself, and I'd get lazy about lifting the hood after a ride to discconect the switch.  So, I came up with another plan I thought i'd share here.  I am in NO way suggesting that everyone should do this...it's just  another way to get things done.

 

I decided to leave the starter circuit, and the supply to the horn alone since they are short wires and their condition is readily visable and, instead, focus on the main wire that supplies most everything  else.  I spliced in a herky power relay into the line before it disapears thru the fire wall.  Then a control wire for the relay and a switch hidden under the dash to keep things looking stock.  Hit the switch and the relay basically connects the battery to the car (and mostly fireproofs it when it's off).  But, then I got to thinking (my wife says I think too much) that I'd forget to hit the switch to turn everything off.  Sooo, I schemed up a locking relay (just the power relay and another smaller one) and use a little hidden push-button switch.  Now, when I turn the key on, and then hit the push-button, the power relay locks on and the car is energized and I can start it or whatever AND when I turn the key off, the relay shuts off and disconnects the battery from the car.

 

I know, maybe it's overkill, but I sleep better.

 

Except for the locking relay your system is similar to the master contactor (relay) we use in aviation. Your implementation is pretty clever.

 

However.....it seems to me the greatest risk of electrical fire is when the vehicle is in operation and while the battery cutoff may inhibit a fire once it starts if you turn off the ignition it won't prevent the short from occurring. But if your installation gives you confidence that a fire won't start undetected it has value for you.

[Tired iron]

God suggestion about the jumper wire...I'll make one up and stow it.

 

And good point, Sam...a electrical fire could start whilst on the road.  I worry more, tho, about the night fire that takes my garage as well!  And, by the way, I used to have a '71 TR6--the most fun car I've ever owned and the stupidest thing I've done selling it!

 

Stay warm everyone!

[Sam Buchanan]

1 hour ago, Tired iron said:

God suggestion about the jumper wire...I'll make one up and stow it.

 

And good point, Sam...a electrical fire could start whilst on the road.  I worry more, tho, about the night fire that takes my garage as well!  And, by the way, I used to have a '71 TR6--the most fun car I've ever owned and the stupidest thing I've done selling it!

 

Stay warm everyone!

 

Yep, a garage fire would be much worse than just losing the car.........

 

I've enjoyed the TR6, nearly everything on it has been repaired or replaced......typical for what is needed to keep an old, cheaply-made British car running as it should. But I always have a grin after a drive over the backroads. 

 

The '48 Plymouth is light years ahead of the TR6 in materials, engineering and build quality!

[SteveR]

I remember when I was 16 and looking for my first car. I desperately wanted a Fiat 850 sport spider or British MG. My Dad always had a good head on his shoulder and said, "Do you want a car to drive or to work on"? I ended up with a great driver, a 65 Plymouth Barracuda. The best car I have ever owned next to my 1990 Dodge Dakota.

Now I have the best of both worlds, a 1937 Plymouth. Fun to work on, most times, and the smiles while driving are priceless. Here in England it it's not your normal car and gets many looks and admiration.

Edited January 14 by SteveR