4th dead battery within a year. 94 RX7
 

Hi, I have been having issues with my cars batteries. They are dying prematurely. About every 3 - 5 months. If I don't drive my car for more than a week. Most likely my battery will be dead. Any ideas what causing this?

you should do a Parasitic draw test on your electrical system,by putting an Ammeter in series with the battery and the Positive wire of the harness and seeing what it is drawing while the car is off.
If it is sucking juice from the battery while off (excessively) then you have found your problem.
Then you start hunting down what is making the system draw that current..like aftermarket gauges,stereo,bad door switch,hatch switch not being closed..etc,etc.
You can get your alternator checked free at most auto parts stores too.they are "just dying" to sell you one..(you don't have to BUY it though..lol!)

If you have a multimeter, you can check the voltage when it's running to see if the alternator is working. Should be somewhere around 14 V.

I've got a turbo timer that shows the volts. It fluctuates from 14.22 to 13.50. Just got a new alternator, before the volts would drop to 12.20 and stall!

Why would you go longer than a week without driving such an awesome ride anyway? lol!

I use a CTEK 3300 battery tender to keep my battery charged when RX is not driven for a while.

Good suggestion, but beware that u use ur multimater properly, so u dont blow any fuses on ur mulitmeter. Most of them are at max 10amp.

When the car is shut down(timer on interior light etc, are off), it should not exceed more than 0.07-0.1 Ampere per hour. Remove fuses from ur car, and check if it makes any difference.