Toothbar installation with cordless drill

[Ozarker]

<font color=blue>What really shortens the life of lead acid batteries is deep cycling them. A shallow drain has little effect. (researched a bunch of this when I was looking at setting up my new house "off-the-grid" using wind and solar power to charge a bank of batteries).</font color=blue>

Bingo!!!!!!!

It isn't the shallow drain that gets you. It is the combination of shallow drain and then cranking the engine that gets you. Deep cycling is precisely what you are doing when you drain 6amps from your cranking battery for an hour and then hit it with a big amp drain when you start your engine. It is a drain/recharge cycle that your cranking battery isn't designed to handle. That is why campers use auxiliary batteries isolated from the cranking system to run 12v electrical accessories.

I went through 2 Die Hards in 2 years before I figured out it was the drain my radar detector was placing on the battery that was killing them. It was pluged into an auxiliary plug that powered it all night. Every morning I was cranking with a battery that was not fully charged, ie, I was deep cycling the battery more than it was designed to.

The two worse things you can do to a battery is undercharge and overcharge. A shallow drain before you crank the starter is the same thing as undercharge.

 

[John_Mc]

I don't know what my car battery is rated for, but I've gotta believe that 6 amp-hours is on the order of a couple of percent of the total capacity. I can't beleive that such a small percentage has a significant effect. If it did, more people would be having problems with the drain caused by their clock, alarm, and other "always on" accessories if they let the car sit for a couple of weeks.

John Mc

 

[Ozarker]

Well your're talking about milliamps with radio memories and clocks but yes, if it was someone's habit to let a car set unused for a couple of weeks and then drive it for a day and they always did that, it would reduce the usable life of the battery. Just about any battery manufacturer will tell you that if you leave a car sit for long periods to hook a trickle charger up to it to keep it charged up. If you are going to store a car, you take the battery out or at least disconnect it.

What I am telling you about battery is not speculation. It is from experience. I ate up two die hards in two years before I figured out it was from putting a load on it just like the one you describe. That is why I use a second battery now. One designed for deep discharge.