RE: [Chrysler300] Group 27 Batteries

There is a big difference between a battery charger and a battery maintainer. All lead acid batteries lose some of their charge over time. The rate is about 1/4 to 1% per day depending on what makes up the plate alloy, and the temperature in which it is stored. Old style lead /antimony alloys are around 1%. New calcium and other proprietary alloy mixes are less. If a battery enters winter storage fully charged, and the car is stored in cold temperatures the rate is slowed by the cold temps. Stored at a high temp will increase local action within the cells and will self discharge faster. A good battery maintainer, with circuitry designed for the type of battery design; sealed AGM/ gel vs. flooded, will only MAINTAIN the state of charge to full. It only puts in what is needed to offset the internal loss.

The trick with VRLA (valve regulated lead acid) sealed batteries is to limit the charge voltage to just enough to charge the plate but not cause too much pressure buildup within the cell. When that happens the valve releases and the battery gasses, losing water in the process, drying the battery out and killing it. This is why flooded cell batteries are more durable, if they get overcharged and boil off water, it can be easily replaced. VRLA batteries are also called recombinant cells. That is, the hydrogen and oxygen recombine within the cell to form water again, that is why they don't need additional water as long as the recombinant design requirements are met. Proper float voltage is an important part of that process.

I have personally inspected dozens of stationary battery installations of lead acid storage batteries that are kept on charge 24/7 for 20 to 30 years. These are the same battery banks that back up large computer and telephone infrastructures to provide backup power should the AC fail. Proper float voltage is critical to keep each cell at full charge while minimizing water consumption. The float voltage (maintenance voltage) is critical in these installations, and determined by the alloy type and content of the plate, as well as the specific gravity of the acid put in the cell when manufactured.

Bob J

Past San Francisco Exide District Manager