Trickle Chargers, Float Chargers, Self Discharge Rates and How it Works Together
Batteries are not inherently stable, they are holding onto power, electrons, that desperately want to move. As they are held in check, a bit of power is lost, perpetually. We call this loss self discharge, or the self discharge rate for a battery. Generally a battery starts to self discharge in the first seconds it is removed from the charger. In the first 24 hours the battery will lose between 2% (Premium AGM batteries) and 10% of it's original charge. Again this process will repeat itself over the next 30 days to leave an AGM battery at 90% (100% - 5% day 1 - 5% over 30 days = 90%) full. For a flooded battery one should expect to return to an 70% charged battery in 30 days due to self discharge, (100% - 15% day 1 - 15% over 30 days = 70%). Click here for a graph for Lifeline Batteries Self Discharge Graphs The moral of the story, if you want to leave a battery unattended, you need to replace that lost current, or your well will run dry all by itself.
Some like the water tank analogy; your battery is a power tank, like a water tank, but it has a leak.
If you don't charge it with a small trickle, the hole in the bottom will drain your tank.
Trickle chargers are designed to compensate for the self discharge loss involved with the sustained storage of lead acid batteries. When using large banks of batteries and installed chargers, the trickle function is usually inherent, but referred to as the float cycle. A float cycle is a charge at the same voltage as the full battery. If the battery is full at 13.1 volts, 13.2 or 13.1 volts would be the proper trickle charge for the longest life. Should you want to keep the batteries a little fresher (more charged), but not as long (months between replacements), you tune that trickle or float voltage up a bit to say 13.5 volts. Here are several types of chargers that have a trickle/float function.
Battery Charger Warnings:
Always read and follow the manufacturer's battery charging instructions prior to
connecting your battery, or trying to charge a battery bank. Do not attempt to charge batteries
in a confined environment. Explosive and hazardous gases are an inherent byproduct of
battery charging, do think ahead. Batteries contain sulphuric acid, and lead, both of which are hazardous material if removed from the battery, or disposed of improperly, do take care to be
environmentally responsible. Batteries are useful, just be safe.