Hi, I have a 97 [US] Miata and I only drive it about 2-3 miles a day on average. About ever 2-3 weeks, the battery will slowly die until there's not enough left to crank and then I have to put it on the charger.
The car also has an [unchecked] LoJack unit, which is due for a checkup. I'm not sure if the LoJack is draining the battery or not but I'm mainly thinking it's the low mileage [time] that keeps the battery from charging fully (i.e., I don't drive it enough to recharge the power lost from starting it up in the first place.)
Does this sound plausible, or do you think it's a hardware problem?
(The battery is the original 1997 Panasonic unit.)
Even just 2 to 3 miles should be enough to replace the charge used to start the car, but if you've got an ongoing parasitic load when the car is off, it may not be enough to recharge the battery....
A "parasitic load is something which is on all the time, even when the motor is off, such as a....
It MUST use some current to operate. Chances are it uses more than your
2 to 3 miles a day replaces. Have you considered buying the milk and bread further afield?
Well, yes, if you do enough daily distance, you can tolerate a higher parasitic load. Otherwise you need to either reduce the load or apply an external charger. Like I said, drive more!
It doesn't sound like a fault, per se, so much as a combination of unusually low mileage and unusually high parasitic load.
Thats also a fairly old battery if it's a conventional battery. I gather the original glassmat batteries have spectacular lifespans.
Check (or have someone else check) the current being drawn with the motor off. Check the alternator is in fact delivering 13.8V or more after a few minutes running.
If the parasitic load is over about 100mA, thats probably excessive.
If the parasitic load is under about 100mA and the alternator is charging properly, either drive more or charge regularly.
Cool, thanks for the quick and thorough response. I had that LoJack/alarm unit. Hate with a capital H. quickly followed by some other big letters, namely A., T., and an E.
If I could find the thing, I'd rip it out thusly. (It's hidden somewhere over the engine, methinks - like up against the firewall as far as I can tell by the alarm's incessant cries for attention when I poke it with sticks and violate its territory by actually trying to use it.)
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