Battery Update
 

I have a predatory battery draw that is hard to figure out on my ‘86 Carrera. No rhyme or reason to it, I thought electric window switches, sunroof switch, even the glovebox light switch.

I still haven’t nailed it down.

It got me thinking I would buy a new smaller battery (Odyssey style) and a Rennline cage for it with a cut-off switch. My idea is to guard the battery from the car drain.

Anybody have battery (make and model #) suggestions for me? The new ones I’ve looked at don’t have near the CCA that the car manufacturer says is needed and this has me questioning.

I had an Odyssey PC925(?) in my Targa, but what is the ”latest” opinion on lightweight batteries?

Thanks in advance and pictures would be clutch!

Happy New Year!

They make battery terminals that are also cutoff switches if you want something simple.

You can take a test light and put it between the negative battery terminal and the negative cable. If you have a drain the light will come on, maybe just barely. Then start pulling fuses to try and isolate the circuit the parasitic drain is coming from. Simple quick test.

I would highly recommend you follow emac911's advice. Spend a little time to get it properly sorted. It really is simple to isolate, then a bit harder to nail down. I had a few drains on my '86, now it sleeps well for 6 weeks or longer with still 12.8V to crank.
My battery is a LifePo4 drop in Group 48 OEM Anti-Gravity lithium battery. Pricey but light !
Happy New Year and good luck!

I had a drain on the SC.

I checked each fuse wit the multimeter and found the guilty one. A bit weird (fuse for air con or something I didn't even have) so I pulled that fuse out and it's been fine ever since.

Dome light switches in the A pillar can fail to ground when the door opens and leave the window relay activated. If the window goes up/ down with the key off and door open, that's a draw. It's a carrera thing.

My windows do work with the key off and when open.

Hmmmmm?

I went to buy a PC925 battery and the Batteries+ store showed me a superseded model they stock.
It’s about half their size of the stock (boat anchor) battery.

Any comments on these?

They don’t have the cold cranking amps Porsche specs 650.

http://forums.pelicanparts.com/uploa...1672601628.jpg

330a -- https://www.odysseybattery.com/products/ods-agm28l-battery-pc925/ --

Personally, I'd go with a Group 48 AGM -- smaller/lighter than the stock Group 49 battery, but will fit w/o modification (there's a second screw down on the battery tray that will accommodate the shorter group 48) -- doing so will give you a lot more reserve power to deal with unexpected drain issues (i.e. it can easily start your car after powering an accidentally-left-on glove box light overnight, something a smaller battery might not be able to do)

Sounds like you found the source of your drain -- presume that your dome lights don't turn on/off automatically when you open/close your doors. If that's the case, your door pin switch has failed/is dirty and is causing the power window relay to remain energized (and drawing power) whenever your car's turned off.

Thanks! I have had a slow drain and this is probably my problem. I have been keeping the old SC on my battery tender to combat the draw, but I might be able to actually fix it now.

I’ll dig into the door switches tomorrow.

Thanks, and will report back.

Hi Lawrence - Hope all is well with you. Happy New Year.
Michael :)

Trust in John to 'off the cuff' immediately point to the hidden issue.
Always amazing!

Hey buddy!

It took me a while to trace the current draw on my car. You need a good wiring diagram. I started by measuring current across the pulled fuse terminals. When I found it and it was milliamps, I used the wiring diagram to eliminate the various branches from the fuse. I found a harness passing through the body with no grommet on the body. The shiner was very small but it was there.

I added a Moroso battery lug disconnect. Alas I am not thrilled with it. Twice it has unscrewed while driving. You really have to crank the sucker down. I will replace with a contactor sometime.