Battery master switch? S818A

[Derek K]

Just looking at the Data for vehicle identification number: WBAGB4316NDB70111 for my 92 735i and under Optional Equipment is: S818A - Batteriehauptschalter - Battery master switch. Is there a switch (anti theft) to turn off the battery somehwere that I don't know about?

[dancerst]

Those switches were installed at BMW factory in Germany before shipping vehicles over sea, to safe battery life due to long travel.

When car arrives, dealer removes the switch and sell car without it.

I've installed that switch separately on my car...

[shogun]

The complete unit looks like this http://www.bimmerboard.com/members/q...y%20Switch.jpg http://www.idon-industries.com/bimmer/various/89.jpg
The dealer ships it usually back to the factory.

[Avec]

Do they just leave it lay in the trunk and leave the key there, but in the off position? Or do they tuck it in behind the trunk's panels?

[dancerst]

They just leave it in the trunk

[cdnalpina]

Is that the OEM switch or an aftermarket one you have in there? I have been wanting to do something like this on my cars as they go into hibernation for the winter. Saves having to pull batteries or have a fleet of trickel chargers. If you could kindly share some detail on how you installed that and what you used I would greatly appreciate it. Or if there are instructions somewhere I could follow.

cheers,

Rob

[dancerst]

This is a Hella Battery main switch.
They were used by BMW.
It's about 8 feet long.

I don't remember if I have pic of installation process, but I'll look.

[E32FAN]

My E32s are fitted with simple switches like: NOCO ID220S 6V-24V 125 Amp Battery Disconnect Switch

They work great! You do have to lift the rear seat to get at it, of course. It's a good theft deterrent as well.

[gregeast]

I have one in my car, it's on the right side of the trunk. Pretty flimsy looking piece of black painted plywood and a red handle. Makes it easy to disconnect the battery if I'm working with the airbags or around the starter. I'd take a picture but it's dark and raining out...

[Derek K]

It doesn't list it on the data sheet for my 1990. Looks like the ones used as emergency shut offs on race cars. You can get them after market, I just thought mine was already equiped with one.

[gregeast]

Finally remembered to take a picture of mine:

[cdnalpina]

Thanks for posting that - nice clean install!

[Avec]

Does that completely shut down everything, including clock and radio? It might be worth it to run a power line to them to bypass the master switch.

[gregeast]

It shuts down everything

[Auzeras]

Out of interest - Why would you want one? If you just wanted a theft deterrent it would be much easier to have a switch for the starter or something? I guess in the USA winterising your vehicles would be a good reason.

[gregeast]

For the record, my car lists "S818A Battery master switch" on the VIN decoder, so I'm assuming it came from the factory with it installed, maybe they forgot to remove it prior to delivery?

[cdnalpina]

For me it is for the winter hibernation. I store most of my cars in the winter and it would be easiest to be able to just turn a switch like this rather than having to lift up the rear seat to disconnect the battery each time.

[whiteghost1]

For me it is for the winter hibernation. I store most of my cars in the winter and it would be easiest to be able to just turn a switch like this rather than having to lift up the rear seat to disconnect the battery each time.

Why don't you just disconnect the negative cable rather than remove the rear seat? This is a pain on the iL models.......
This can be easily done by popping open the access panel and undoing the 13mm nut, at least you could do this on your e32's.

[Avec]

Why don't you just disconnect the negative cable rather than remove the rear seat? This is a pain on the iL models.......
This can be easily done by popping open the access panel and undoing the 13mm nut, at least you could do this on your e32's.

^^^^
Very easy to do. Plus, that is exactly what that is designed for.

Also, Every BMW shipped from Germany has a battery master switch listed on its build sheet. It us supposed to be removed by the dealership and returned to the factory.

[shogun]

the negative cable in front of rear seat
http://www.ow.no/index.php?option=co...&g2_itemId=132
http://www.ow.no/index.php?option=co...&g2_itemId=136
http://www.ow.no/index.php?option=co...&g2_itemId=140
Just in front of the battery http://www.ow.no/index.php?option=co...&g2_itemId=122
and on the other side are the relays and fuses, modules http://www.ow.no/index.php?option=co...&g2_itemId=158

[cdnalpina]

I always wondered what that plastic part there was for! Thanks so much guys, that makes life a whole lot easier!!

[shogun]

The battery main switch for transportation from factory to verseas is shown here again, the factory options sheet list "Battery Master Switch", option code S818A
http://www.bimmerforums.com/forum/sh...-Master-Switch

[Mmrmm]

the negative cable in front of rear seat
http://www.ow.no/index.php?option=co...&g2_itemId=132
http://www.ow.no/index.php?option=co...&g2_itemId=136
http://www.ow.no/index.php?option=co...&g2_itemId=140
Just in front of the battery http://www.ow.no/index.php?option=co...&g2_itemId=122
and on the other side are the relays and fuses, modules http://www.ow.no/index.php?option=co...&g2_itemId=158

Sorry, is that cover + ground wire inside the cabin on the 8 series?

[shogun]

It is the cover and ground wire inside 7 series E32. On the E31 8 series the 2 batteries are not under the seat, they are in the trunk, so completely different arrangment, better ask in the E31 forum for details.

[Sansouci]

Related to this thread is the question " How best to store the battery over the winter in a cold climate?" I previously removed the rear seat cushion, discon the positive cable and put on a ctek charger on it, inspecting every 2-4 weeks. Then I got a little smarter and used the hot post in the engine compartment so that the charger would stay out of the weather. This way, all electronics were normally energized. But beware: crappy chargers will boil your battery dry. CTEK's are pretty good, I top it off when I put the White Whale to sleep, but I check fluid level every month. Sure wish I had a heated garage for it, but that precious spot is taken by my E24.....