Most battery manufacturers are using recycled lead, and there is really no reason not to. Once it's been properly recycled, it is "100% pure lead," as some companies advertise. A few years ago, Deka developed some reputational problems because of their admitted use of recycled lead. Whatever issues they may have with their batteries, the lead is probably not the cause. A few months ago when I was shopping for batteries, I half-heartedly tried to order a Deka 31M from my usual vendor, and he talked me out of it. His view (and he moves a lot of batteries) is that the Deka is fine when new, but that I would be replacing it sooner than I would one of its better competitors.
I have done a fair amount of research and kicking things around with manufacturers and mechanics, because of the battery issues I have had over the last few years. The consensus seems to be that it is not a self-discharge problem as much as it is a parasitic drain problem. All the electronic crap on newer vehicles has increased the parasitic drain to the point that even a daily driver sees a significant drain that is not always replenished during a short commute. Do that over a long enough time and you get a degree of sulfation, and most drivers can't even spell sulfation. The sulfation can be cumulative in some situations and can lead to premature battery failure. The obvious culprits would be clocks and alarms and USB cell phone chargers that are left plugged in all the time. Nobody in the general public seems to realize that things like proximity starters (in some cars) are always looking for a ping from a local "key," and the car's computer is almost always awake to some extent. Even on vehicles in which the computer is ostensibly designed to completely shut down, there is often a much longer delay than in the past. When you lock the car and walk away, it might take the computer ten minutes to power down. I have been told that some alarm systems will keep the body module awake, even when the alarm is not activated, because the body module is programmed to look for a ping from the alarm sensors. I recently learned that some power programmers (like the Edge Evolution in my Dodge) add a tiny bit of parasitic drain when they are left plugged in to the OBD-II port, and I generally leave mine plugged in because it is also an eight-parameter programmable gauge pod. It shuts off about thirty seconds after I remove the key, but even with the display off, there is a drain. The National Luna battery monitors that I just got seem to add a bit of parasitic drain, even when turned off. All this little electronic crap adds up.
I also read up on some the the emergency vehicle upfitter websites (fire, police, ambulance, etc.), and they seem to have similar concerns, but even greater than ours because of the huge amount of electronic gear in those vehicles. When in service, a typical police car spends the whole day and often the night with all the electronics on, but the engine at or near idle, so less than full replenishment from the alternator. One AGM battery manufacturer told me that transit buses in Los Angeles get put on conditioning chargers periodically to offset their constant low-speed use in L.A. traffic. A mechanic told me that one reason Chrysler is now offering dual alternators on Hemis is that so many police departments are now buying Hemi sedans that they realized the single alternator could not reliably keep up with the load from the electronics in crowded urban service at low speeds. The single biggest issue they face is sloppy installation and programming, even by professionals. Electronic gremlins are even more insidious than electrical gremlins, and often cannot be tracked by mere mortals.
