I guess that this comes under the category of things I've never really thought about, much, before.
Thanks for the previous answers to my battery questions. Thought I'd start a new thread, though, for this.
a. If one gets a brand new battery, how long, typically, is it "safe" not to use the car (and thus re-charge the battery) and not cause any permanent battery damage (such as sulfate buildups on the electrodes that had been mentioned) ?
b. How long of non-use befor a brand new battery becomes so depleted the car won't start. Realize this depends probably on a zillion factors, but "generally" ?
To keep a battery in good shape, the car should be started once a week and the engine run at speeds higher than idle. While the engine is idling, the alternator barely puts out enough amperage to charge the battery.
A brand new battery that is not connected will last several months and still be good. If it is hooked up to a car, parasitic draw from the radio, clock, and computer will probably drain the battery enough that a car won't start in two or three weeks.
If the car is kept in a garage, think about installing an automatic trickle charger in the car. The charger is installed in the car and all you have to do is plug it in when the vehicle is parked for a long time. The charger starts and stops as needed to keep the battery fully charged.
If it was me, I would disconnect the battery when I need to leave the car for a long time. Given the history of the vehicle tends to drain a good battery when not in use.
If the battery is installed in the car and hooked up (running the clock, the ECU memory circuits and a possible burglar alarm system) you should let it sit no more than two weeks.
And every week to two weeks you need to take the car out for a half-hour to 1-hour drive to recharge the battery.
You might get a car without an alarm or any other added loads to start after sitting unused for a month or more, but the small draws from the clock and the memory will be deep discharging the battery over that extended period and causing cumulative battery damage. That
6-year battery might only last you two or three years.
If the car is regularly sitting for a week or more, get either a solar cell trickle charger or mains-powered trickle charger. If you use a 120V charger, be sure to drape the extension cord over the drivers door or the windshield, so you don't forget to disconnect it before driving off.
If you park in a garage, a solar cell is obviously a bad choice...
If the battery is sitting on the shelf at the parts store, or in your garage, or in the car but the cables are disconnected, you need to put it on a trickle charger to top it off every three to six months.
Unless you have a very unusual size battery they don't sell many of (example the VW Beetle with the special cover tab over the positive post and the remote drain/vent hose) I wouldn't buy a "new" battery with a manufacturing date code over six months old, because I can guarantee you stores do not recharge the batteries in stock.
A battery maintainer is what you need. It will not boil the battery dry like a trickle charger. Google battery maintainer and you will find what you need to know and buy and use.
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