E38 740il Dead Battery

kjones · 02-19-2003, 05:54 PM

I think I have a draw that is killing my battery. It goes dead if I let it sit for more than 18 hrs. I checked for the obvious: glove box light, trunk light, etc... Please ////HELP!!!
p.s. the car sat for the last two years.

KC Ron Carter · KC Ron Carter's Garage

You will need an AMP meter to locate.

Is it drivable?

Any Auto Zones around?

They have a VAT tester to check cutomers batteries.

Dozen donuts may get you 30 minutes with a meter.

Later,

Bear · 02-20-2003, 10:45 AM

Disconnect the negative battery cable.
Make sure all electrical accesories are turned off.
Connect ammeter between battery negative post and negative battery cable.
A range of 0 to 100 miiliamps is normal but a current draw of 500 milliamps or more is excessive.
To locate the device that is drawing too much current, remove one fuse at a time until the current drops to a normal range.

rmorin · 03-08-2003, 10:09 AM

If it sat for two years I am not surprised that the battery is dead. You should use a float charger that maintains your battery at the right voltage.

prairieman · 03-08-2003, 03:52 PM

rmorin is correct.

if a battery is allowed to sit for a long period of time without a full charge it will sulfate - which means it will never take a charge.

it is likely a boat anchor.

take the battery out, have it charged and a load test applied to it.

I believe your battery will flunk the load test. Buy a new battery and you'll be set.

Jared at Pelican Parts · 03-10-2003, 09:31 AM

I agree, this sounds like a flat battery.

Bear · 03-10-2003, 10:25 AM

If indeed your battery is Kaputen, you nedd not buy an expensive battery. Basically two companies make most of the batteries, Johnson Controls (Sears, Exide, Walmart, COSCO,Auto Zone, etc) and Interstate( Advance). I just bought a Advance Silver for my 1988 750, it has mega cranking amps, is a clone of the Interstate platinum, and cost me $65.00 for a 72 month, two year free replacement battery.

Jared at Pelican Parts · 03-11-2003, 04:07 PM

You may even want to upgrade to an Optima battery. I have one that I have used in two cars, and it has NEVER gone dead. I work on my car alot, and thus i need car workin music playing at all times. I have a 1000 watt custom sound system with a 18 inch sub in the trunk. I can play this for hours on end without the enigne running and have the engine start up on the first turn every time. Im convinced that the Optima is the best battery on the market.

rul70 · 09-29-2003, 07:29 AM

Did you end up buying a new battery?

I am looking for a new battery for my 1995 740iL and was hoping to buy one from Advance Auto Parts, Auto Zone or similar but they don’t appear to carry a battery for my car. Will I have to go to the dealer and pay big bucks or is there another solution?

Bear · 09-29-2003, 08:46 AM

I have a 1988 750 and both Advance and Auto Zone have a battery for my car ($65.00), I can not believe they do not have one for your car. Cll them and ask or go tonline to their websites for a battery.

rul70 · 09-29-2003, 09:04 AM

I both checked out their websites and called, but they don’t have a battery listed for the 1995 E38. I found one of your comments earlier in a thread and wanted to see if Advanced Auto Parts had a battery listed for your –88 750, and they do. They guy at Advance Auto Parts told me I could bring my old battery in and he could try to match it…I guess I could try that but wanted to do some research first.

Bear · 09-29-2003, 09:43 AM

Auto Zone lists a 49D battery for the 1994 740, this is the same battery I use in my 1988 750( 850 CCA at $59.99). I would pull the seat cushion (PITA) and drive to a Auto Zone, I have to believe the '94 and'95 batteries are very similar.

rul70 · 10-01-2003, 11:15 AM

I ended up getting an Interstate MTP-93 for $110. This battery is shorter than the original but fits fine when using the second clamp position. Interstate confirmed that this battery is used in many E38s.

E38 has the battery mounted in the trunk instead of under the seat, as E32. This may or may not make a difference but apparently the 49D is being used in the E38s as well.

MaxBoost · 10-06-2003, 05:58 PM

Check the electrolyte level the [this is done through a tester you can purchase at major or Wal-Mart or any auto part store for just a few bucks the specific gravity should be above 1.225 and with a volt meter check to see that that your battery is reading above 9.6 volts also check to see if your alternator is charging the battery.
PS looks like this person originally posted was about 8-9 months ago why are people still replaying????

publicx2001 · 07-14-2005, 01:11 PM

i too have the dead battery problem if i dont drive my 2001 740i for more than a day. im in the middle of doing a current draw test. i have it down to .45ma with everything off. with the gps connected it was drawing .75ma.....i found the gps getting rather warm.....so i disconnected it. kinda sucks with it removed now because the screen does not light so i cant see what radio station im listening to. im still thinking even .45ma may be a bit excessive. any thoughts?
thanks
erik

Bear · 07-14-2005, 03:20 PM

.75 amp does not sound excessive. Next question, how good are battery and alternator? With engine off connect a volt meter (DC volts) between + and- battery posts or if your battery is under the seat between the jumper post under the hood and ground (a strut nut workks) and you should read 12.0 volts. Next, start her up and do the same test and you should read between 13.5 and 14.1 VDC ,. If either test fails there is your problem. Now, if battery is bad, do not rush to the dealer, go to Advance or Auto Zone and buy a battery they are made by Interstate and Johnson Controls respectively. I had a Advance battery in my 1988 750 and she could sit for three weeks and fire right up at a cost of about $60.00 and 950 CCA.

publicx2001 · 07-15-2005, 05:41 AM

bear-
did the volt test and the alternator output test and both have good values- 12.03volts and 14 volts respectively. the only thing left is to have the battery VAT tested......i will let you know.
thanks
erik

publicx2001 · 07-15-2005, 05:42 AM

bear-
did the volt test and the alternator output test and both have good values- 12.03volts and 14 volts respectively. the only thing left is to have the battery VAT tested......i will let you know.
thanks
erik