ELECT-26, Excessive Battery Discharge Rate
All 924s, 944s, and 968s use a BCI Group 41 size battery. That means that the dimensions of the battery are 11- 3/16" L x 6 - 7/8" W x 6 - 7/8" H. For a full list of BCI Battery sizes click here. Most 944 batteries now days are rated for 50 to 70 amp-hours (AH). That's means if you have a 50 AH battery, it should be able to discharge 1 A for 50 hours without falling below 10.5 VDC terminal voltage. That's considered about the minimum cranking voltage for a battery.
The normal battery discharge rate for a 924, 944, or 968 with the ignition turned off and the key removed from the ignition should be less than 60mA. If you current draw is more than 65 mA, you should start looking for a problem.
So, working the math, if you have a 50 AH battery and your battery discharge rate is 60 mA, the battery should last for about 30 days and still be able to crank the car. Realize that this will change as the battery gets older and it will also be different under varying weather conditions to which the car (and battery) may be subjected.
Checking Battery Discharge Rate and Identifying Causes of High Battery Discharge Rate
Clark's Garage © 1998