For the better part of two years I have had this problem. If I don't drive my 2005 at least once every two days, on the third day the battery is dead. I have put a meter on and get a .4 milliamp reading, pretty normal. Had the car into the dealer several times, they could not find the fault (one symptom is that the spoiler deploys when you boost the battery). On my most recent attempt I have been told that the "Body Control Module" is responding. It seems that it wakes up periodically and drains the battery. The replacement cost is just under $3,000. Not planning to do this put will install a trickle charger instead. Any thoughts , comments ?

 

 

Not the battery, that was replaced a year ago (only drive the car 6 months a year). This is some internal electrical fault for which I have seen no reasonable
explanation yet.

 

I had a similar problem. My excessive battery drain was caused by a faulty alarm module (up under the windscreen wiper grill). These cars are getting old now and the rechargeable batteries in the alarm module had deteriorated so much that they had leaked out all over the circuit board and destroyed it, it was beyond repair. So I unplugged the module and my excessive battery drain is gone. Have a look at your module, or just unplug it, as its worth a try.

 

You said 0.4 Ma which is good, did you check the charging voltage to ensure that the battery is being charged. Should be at least one volt above resting battery voltage. Somewhere between 13 and 14 volts temp dependent.... Enjoy Woody

 

 

Trust me, its not the battery.. First test in the series was a load test, no issues. I do agree stuff happens.

 

 

Or a used car salesman.

 

400 milliamps is normal for the first 30 seconds or so, but then it should drop to under 55 milliamps.

.4 amp is 400 milliamps. Anything over 55ma (.055 amp) is too much. With .4 amp I'd expect the battery to last MAYBE 36 hours.

• Disconnect the battery ground cable, insert an ammeter, and start pulling fuses until you find where the current is going.
• Start in the little box next to battery. Pull each 50 amp fuse, if the current is still there, pull 200 amp fuse.
  • If 200A makes it go away, put the fuse back and go to the main fuse boxes and start pulling fuses (box next to brake controller, then go to fuses on the Relay Control Board, then go to fuses in the ICM, driver's end of instrument panel.)
  • If the 200A being out does not make it go away, it's the alternator or starter (which means it's the alternator).
    • Disconnect the big fat red cable at the alternator - if the current goes away, replace alternator

REMEMBER that the current will be high when you first connect the meter or insert the 200A fuse. Stand there, wait at least 90 seconds each time for all the modules to "hibernate". After 90 seconds, you should see .055amp or less.

REMEMBER, doors must be closed, trunk must be closed and key NOT in the ignition.

REMEMBER that taking the car to almost any garage/dealer for a battery drain issue is a waste of time because NO ONE is teaching electrical troubleshooting these days. I once worked for a Motorola radio shop, we got cars from dealers often with battery drain issues. I usually could find the problem in 1/2 hour. I either fixed it or, if it was an OEM module, I'd just inform the garage/dealer which module to replace.

 

Really good write up Mark ! Thanks.

 

I'll agree , that goes into memory. Not mine , I'm losing that!...

 

Do you have OEM radio or other? Offten new radio if is not correct installed can kill battery quickly.
If you have roadster please check if your trunk is close totaly.

 

That sounds more like .4A or 400ma. Spec is under 50 ma. Normal after it settles is about 20-30ma (.020-.030A). Over 200 will kill a battery in a few days. Something is pulling a lot of current. I usually connect a trouble light and pull fuses until it goes away. Find a new shop.

 

I have a confusing question. I have read about certain security or alarm modules that contain rechargeable batteries. What are they and where are they located?

 

The siren module has the rechargeable batteries, it is located in the center under the wiper cowl.

 

I have always been curious on how and when the rechargeble batteries in the alarm/siren are recharged. Is the car battery continuously charging the alarm/siren even when the car is off or does it only occur when the car is running? If it's the later, then what happens when the car is in winter storage, or the car has a dead battery. How do these factors effect the longevity of the rechargable alarm/siren batteries? It is assumed that cars in hotter climates will have their batteries degrade faster.

 

The siren module is connected thru Fuse 9 to battery at all times. It seems to me that someone reported a car battery going dead that was caused by the siren module.

Personally, I did not know those batteries were rechargeable. Of course, I know of no diagram of the siren, so I do'nt know for sure what the case is.

 

Hmm! The siren module contains two 3.6v 140mAh NI-MH batteries. I just assumed that because they were NI-MH batteries that they were rechargeable. Which begs the question if those batteries are rechargeable and near the end of their lifespan and take longer to charge will that cause excessive drain on the car battery?

 

It depends on how the charging circuit in the Siren Module is designed. A charge current of a few (5 or 10) mA is no big deal. But if the circuit is poorly designed, (not current limited) then sure, it can be a cause of trouble.
Of course, there is certainly a current limiting resistor (at the least) involved,

A battery rated at 140mA (I assume that's 140mAH) should have a charge limiting circuit on it of less than ten mA.