Mongo

I am 90% sure my drain is related to the alarm, but I prefer to keep it on just in case, but is disarmed when the car is resting in the garage.

WallyP

The major difference between a battery charger and a battery tender is that the tender should cut off/go to float level when the battery is charged, while the charger just keeps charging...

A properly functioning battery tender can be left hooked up all the time.

jpitman2

My charge socket is under the rear license plate - positive connecting plug as used in 4x4 offroad trucks, with a cover to seal it. Connected direct to battery poles via a fuse. No need to open hatch or hood, and I can isolate battery from car body for work, but leave the charger connected.
Mine is similar to the surface mount unit here:- http://www.mudstuff.co.uk/12v-sockets.shtml
jp 83 Euro S AT 53k

dr bob

Andy--

I have the Schumacher maintainer attached to the car for days and often weeks at a time between my visits home. My car will start OK with a month between runs, but it's pretty obvious that the battery isn't spinning things as fast as when it's fully charged. With the maintainer attached I don't even think about the car missing a beat. Even for folks that drive their 928 as a weekend-only car, a maintainer makes the alternator's job a lot easier. IMHO, it's an inexpensive way to extend the lives of both the battery and the alternator.

Bill Ball

My concern is that if you have a significant parasitic drain, the battery tender may never get into tender mode. Even at 1.5 amps it could eventually vaporize enough fluid to expose the plates (well, not likely with car battery, but I've seen it with motorcycle batteries). I have several of these WalMart Schumackers. Watch if the green fully charged LED comes on and STAYS on. If it does, great.

It's usually pretty easy to locate the culprit circuit responsible for the draw, although fixing it may be another thing. I had an epic battle with a 90 S4's window controller circuit. https://rennlist.com/forums/928-foru...dow+controller

jeff spahn

James, your connection looks a little frayed

Mongo

I had my maintainer on all night and have left it on for the day. If the car won't start when I get back I may just yank the battery and hook the maintainer up directly to it. If it is still unreponsive I may just buy another one. I have about 4 years on this Interstate one.

Mongo

Wow the maintainer works like a charm! I came home to a green light indicating a full charge! It looks like it is maintaining the charge now. Sweet little toy.

928mac

I had the same proble as you guys, a large drain.
I connected my multi meter between the bat and the cable with a long wire so I could set in on the passenger seat.
The drain dissapeared when I removed the rear defog relay.
I have also replaced the battery with a deep cycle style bat. 800 amps.
I can now let the car sit for 2 months and it will still crank over like it never sat.

Install a deep cycle battery
and
locate your drain by pulling fuses or relays with a amp meter hooked up.

Here is some info on them
http://www.islandbatteries.com/pages...automotive.php

WallyP

A true deep-cycle battery is not very good as a starting battery.

Deep cycle batteries are optimized for deep draw-down with light to moderate current draw.

Starting batteries are optimized for brief periods of heavy current draw.

dr bob

Plus I'm not sure I've ever seen a deep-cycle in Group-48 size for the 928. I see 24/74 and 27/77 regularly. The 24/74 can be wedged into the box but doesn't clamp down. Plus the posts extend up to where there's a risk of shorting on the lid unless you add insulation.