Battery Isolator installation. - Alfa Romeo Bulletin Board & Forums
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post #1 of 3 (permalink) Old 06-12-2019, 01:57 PM Thread Starter
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Battery Isolator installation.

My car, a 1987 Spider came with a new battery. The battery has both the Positive and Negative poles in the back.
I'm in the process of cleaning electrical connectors, refreshing grounds and troubleshooting interior lights and such.
I'm doing this little by little, since I want to also use the car. Hence I was tired of constantly removing the battery to disconnect the Negative cable and then reconnecting again to use the car.
I had to lift the carpet, remove the battery retainer, move the battery out and then disconnect the cable from the post. Aggravating!!!

The common Green Button Battery isolator or disconnect could not be used as intended since if fitted to the Neg. pole of the battery and was unreachable.

By the way, maybe my battery should just have the posts in the front, I don't know. But I'm not going to buy another battery, thank you.
I owned, back in the day, two Spiders (86 and 89), but I don't remember at all if the batteries had the posts in the front.

Anyhow, this is what I did:

1) Remove the battery, clean the two post and put aside.
2) Remove the Negative cable from the car by unscrewing it's grounding bolt. Perfectly clean the ground screw hole and surrounding area until it's bright and shiny.
3) Clean both battery clamps and the ground end of the black cable until shiny.
4) Get a set of threaded conversion posts from NAPA # 728199. You'll need the smaller diameter only (Negative). About $6.00.
5) Get a common Big Green Button Battery Isolator from NAPA or Amazon or EBay, about $5.00.
6) You need two new bolts. I got them from ACE. They had Allen heads because is a tight fit in there!. One is 40 mm long and the second is 25 mm long. Both are 8 X 1.25 thread. I also got two washers for the bolts.
7) Drill an 8 mm hole through and through the Negative post in #4 above.
8) At one end, the Big Green button Battery Isolator has a post with a hole. Thread this hole with a 8 x 1.25 tap.

Now the installation:

1) Attach the Negative NAPA post to the car ground hole using a washer and the 40 mm bolt.
2) Install the battery pole clamp side of the Big Button Isolator to the new pole above.
3) Attach the Negative Battery cable to the other end of the Big Green Button isolator (the end that was threaded to 8mm) using a washer and the 25 mm bolt.
4) Attach the Battery cable to the negative in the Battery. Finish re-installing the battery in it's proper position.
We are done.

Now whenever I need to disconnect the Battery is just a matter of reaching on the right side of the Battery and unscrewing the Big Green button a little!
I hope this helps someone out there.
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post #2 of 3 (permalink) Old 06-12-2019, 02:02 PM
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Join Date: Jan 2005
Location: San Juan Capistrano
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Note that those $5 cut-off switches don't have a sterling reliability record. If your car ever fails to crank, the cut-off will probably be the cause.

Not that they are any better made, but the style of cut-off pictured below is designed to be body-mounted, with an intermediate cable between it and the battery. The benefits of this model are that 1) it isn't mounted via its the electrical connection and 2) you can remove the key as an anti-theft measure.

Jay Mackro
San Juan Capistrano, CA

'65 Guilia Sprint GT
'67 Duetto
'91 164L

Last edited by Alfajay; 06-12-2019 at 02:07 PM.
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post #3 of 3 (permalink) Old 06-12-2019, 02:18 PM Thread Starter
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Yes I know, That's why they are $5. There are others but many require anchor holes, are bulky and can fail with corrosion too. Probably you are familiar with the switches used in boats. I had those very expensive (and big) ones fail me before.

With this set up, you need to be vigilant and periodically inspect and maintain it. Just as with battery terminals, corrosion, deposits and tightness of connections must be watch for. Also the more connections the more to fail. But the connect/reconnect the battery routine had me climbing walls.

A 5mm Allen wrench has been added to the car tool kit. In case of problems, you just remove the whole thing and reattach the negative cable again to the car ground using the short bolt and washer.
This is not a Do and Forget Forever thing.

Thanks for your advise!
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