|
|
Posted by D Sherman [72.47.9.228] on Monday, May 23, 2011 at 12:13:06 :
In Reply to: give your batteries a second chance posted by clueless [196.40.10.231] on Monday, May 23, 2011 at 00:29:14 :
It looks like he's selling some version of the "resonant pulse" battery charger that's been around for quite a few years. The idea, the way it's generally described is that by zapping the battery with narrow spikes of electricity at much more than the normal charging voltage, it allegedly "breaks up" sulfate deposits and rejuvenates old batteries. Some versions claim to apply a burst of RF in the low megahertz range which supposedly matches the resonant frequency of sulfate molecules and helps break them up. I highly doubt that there's anything to the "breaking up" of sulfate other than the fact that they apply a higher voltage (albeit in pulses) than most battery chargers do. They also must surely create a heck of a lot of radio interference.
I have had good luck getting another year or two of life out of badly sulfated batteries by simply cranking up the charging voltage until they will start to accept a charge (which might take 20-30 volts on a 12 volt battery), and then once it's charging, turning the voltage down to where it draws 3-5 amps and leaving it at that charge rate for a week or so.
My charger uses a variac to let you dial in any voltage from 0-72, and has meters to monitor the volts and the amps. There's nothing "automatic" about it. If these pulse gimmicks work, it's because most people only have "automatic" battery chargers that only put out a little over 12 volts, which means if the battery has been left in a discharged condition for a long time, it won't accept a charge.
Lead sulfate is insoluble and most of it falls to the bottoms of the cells in a flooded battery (which is part of why flooded batteries will take more abuse than gel-type batteries). As long as there is still some lead left on the plates, however, you can eke some more life out of the battery if you can force it to charge and convert whatever sulfate is still on the plates back into sulfuric acid. I doubt that the pulse gizmo does any better job of that than simply hooking up a higher-voltage DC battery charger and watching the meters until things stabilize, but it probably does work if left attached for a long time.
Another way to get more life from an old battery is to add acid. I know all the books say "never add acid", but they're wrong. Assuming you're careful not to burn yourself, and assuming you have a hydrometer and can be sure that you don't get the gravity of any cell above a "full charge" reading, it's safe to add acid. When a battery gets old, a lot of the acid is locked up in lead sulfate sitting on the bottoms of the cells where it will never get broken down or do any good again. So long as there is still some metallic lead on the plates, however, you can add enough acid to make use of that remaining lead. You don't even have to buy sulfuric acid, which can be hard to find in a good grade. Sodium bisulfate will do the job. There used to be some sort of magic battery-rejuvenation powder that was actually just sodium bisulfate, but you can buy it cheaply as "pH down" in the pool supply department.
If I really want to get the maximum life from a battery, I'll charge it at 5 amps or less for a week, check the cells with a hydrometer, and add acid to any that are still low in order to bring it up to spec.
Follow Ups: