Battery going dead - No Draw Found

[SHO-NUF93]

Been through 3 batteries in the 8 months I've owned my SHO. The one that came with the car was a cheapie Autocraft, figured that was the problem, since it would go dead after about a day and a half of not being driven. Replaced it with a Napa Orbital(similar to Optima). Was fine until I parked the car when the clutch went out. The car sat for 3 days, before I went out to crank it, just to run it for a bit...it was dead. Jumped it, disconnected the battery, and let it sit til I fixed the clutch. After that, it gradually got worse, it would last for less and less time until one day I drove it to work and it sat for 5 hours and was dead again. Exchanged it, that was February or March. Since then, I have noticed the same problem. Took it to a trustworthy auto electric shop near my own shop(I am a mechanic, but I am no electrician). They detected a draw no more than 60 milliamps, and then stated 50 was normal. Any thoughts on this? Anyone with a similar experience?

The car is not my daily driver, but it is nice to be able to jump in it after work and go for a ride, without having to crank it every 10 hours or so, or jump it.

 

[hawkeye18]

have the charging system tested at an Advance auto parts. Make sure they put the ammeter on the positive cable. This should tell you if the diode pattern in the alternator is good. If you have a bad diode (or two), the alt will still put out voltage... but it will only put out 50-60 amps. This is not enough to charge the battery with any sort of load on it, and it will slowly, but surely, drain the battery.

Of course, if the diodes are good, then I don't know what to tell you. There is an incredibly slow, but incredibly accurate, method of figuring it out. Start pulling fuses. Pull 3 or 4. If the battery continues to draw down, the problem isn't in those fuses. if the problem goes away, the problem is in that group! Plug them in one by one and go from there. It could take months, but it will work. Of course, some things (radio, EEC that I know of), will always draw power. This would be the 50 mA that is normal. Most batteries have about 100-200 AH of capacity, so divide that by 60 mA... 2500 hours. That's how long a battery with 150AH should last with 60 mA of draw. that's 104 days, or almost 15 weeks. Something else is wrong...

Another option is to install a battery disconnect switch. Once you're done with the car, simply flip the switch. No more current draw. Of course, you will have to do the idle reset procedure every time you started it up again, as the KAMRFs will be set back to 1.0.

Either that, or get a multimeter and start a'huntin'...

 

[SHO-NUF93]

Had it checked. So I guess 13.5 v and 16 amps is bad? Wow...

I am still unsure of how this can make the battery go dead after a day or two...or most recently a half a day of sitting...or is that exactly the case?

 

[SHOZ123]

13.5V is too low. Should be above 14V.

Check the voltage after the car has been running at highway speeds for 20 minutes (to recharge the battery) and at 1500 rpm at least.