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Posted by: dgraves Oct 23 2017, 04:58 PM

I've got a slow drain in my battery. My guess is that it's from the 911 dash installed by a previous owner. After about a week, the car may or may not start. Is anyone out there using a battery cut off switch? There are a lot for sale, but many look similar and several have some bad reviews.
Thanks

Posted by: mobymutt Oct 23 2017, 06:33 PM

I got this for my car:

https://www.princessauto.com/en/detail/top-post-battery-master-cut-off-switch/A-p4210962e

As simple as it gets, but you do have to open the engine cover every time.

Posted by: Mark Henry Oct 23 2017, 06:43 PM

I've had a Moroso switch on my bug for years, never a problem.

Posted by: thelogo Oct 23 2017, 07:45 PM

I also ha e the moroso on my 914 , mark knows his stuff

I also use a trickle or float charger too when the batt gets disconnected
The trickle chager go's on

I assume this will make the bat last longest as possible

Posted by: SKL1 Oct 23 2017, 08:09 PM

I have the one shown by mutt above on both cars. Don't have the bypass wire as neither car has anything with "memory" - they're 45+ years old!!!

Works fine- easy twist and power is off.

Posted by: Dave_Darling Oct 23 2017, 09:20 PM

You should still figure out where the problem is.

--DD

Posted by: Rand Oct 23 2017, 09:43 PM

For sure. There's a parasite on board. I like cutoff switches, but, don't allow one to hide while you shut it off.

Posted by: thelogo Oct 23 2017, 10:27 PM

Sorry i should started with i use the cutoff because

My modernish sony radio clock supposedly drain the batt

Or

Or i had ! an optima and let it drain down , left on the lights


And so im paranoid


Aggreed dave , find the source of drain isnt a bad idea

Posted by: ThreeV8s Oct 23 2017, 11:12 PM

We just pulled a battery out of my father's car after 16 years because we wanted to switch to agm for corrosion prevention. The battery was still cranking strong with the same style cut-off switch as post 2 (without the wire and never charged it). I'll be adding the same switch when I replace the battery that's in my 914 if there's room. The only downside of that style is the fact that it can still leave a slight connection to the battery if it's sticking at all. A blade style is probably best but finding the clearance with a rain tray would be a challenge.

Posted by: Mark Henry Oct 24 2017, 07:29 AM

Pull all your fuses, replace one at a time, tap the ground cable on the - battery and look for sparky.
Doing this will hopefully narrow your search to one circuit.

MSD is on all the time, as in it will charge the capacitors, so if you have an MSD disconnect it for this test.

Posted by: drem914 Oct 24 2017, 10:05 AM

Mark, Thanks for the sequence, as I too, like many here, have got a parasite power drain. I was not sure how to go about narrowing down the offending circuit. If I don't leave a trickle charger on it I will have a dead battery w/in 2 weeks.

Posted by: Keith914 Oct 24 2017, 11:34 AM

I also had a battery drain issue. I conducted testing by removing the negative battery lead, then carefully moving it towards the battery terminal looking for a spark which occurs about 1/16" distance (low surrounding light helps to see the spark) from the terminal. After researching this issue, I removed two in line fuses installed with a modern radio plus self powered woofer. This almost removed the significant spark at the battery There is still a very small spark remaining which I assume is a discharge of capacitors in the MSD system. So far so good.

Posted by: GregAmy Oct 24 2017, 11:39 AM

Leverage Mark's "hot start relay" idea: Ford starter solenoid in the battery line with a SPST switch hidden under the dash. Switch off, battery solenoid open. Switch on, battery solenoid closed.

That's what I do on one of my race cars. And a replacement is easy peasy to find, should I need it.

Posted by: Mark Henry Oct 24 2017, 12:18 PM

Yes I meant to add the radio too should be disconnected as it will give a tiny spark as well. Old school radios without a clock should be OK.
Once you narrow it down to one circuit you can start by disconcerting wires from things on that circuit.

I'd disconnect the MSD just to rule it out.

Posted by: forrestkhaag Oct 24 2017, 02:14 PM

Check with Keith914 for possible clues / he just recently chased down the same problem / and solved it.

Posted by: dgraves Oct 26 2017, 05:49 PM

All replies were helpful, guys. Thank you. I've been away for a few days. I may have it narrowed down to a "modern" radio install. I always thought it looked funky.

As always, the help in this forum is great...even for people not as mechanical as most of you.

Best regards,
Dan

Posted by: plays with cars Oct 26 2017, 11:57 PM

I've always used a lever type battery terminal clamp to be able to quickly disconnect the battery. I usually only use it on one lead to break the circuit. I've used the lead style ones over the years but on the most recent installation use this steel style. I was skeptical but ffor 3+ years its been working fine.

http://www.autozone.com/batteries-starting-and-charging/battery-terminal-quick-clamp/lynx-battery-terminal-quick-clamp/95965_0_0

I don't like the disconnects shown in post #2 because they are too tall and frequently cause clearance issues.