Discharging
Discharging batteries is a function of your application. Below is list of helpful items;
* Shallow Depth of Discharges (DOD) will result in a longer battery life. <50% DOD is recommended.
* 75-80% DOD is the maximum safe discharge for flooded and AGM batteries.
* Do not discharge flooded batteries >80%. This will damage (or kill) the battery. Recommend operating DOD for flooded batteries is 50% to 75% of capacity.
* A periodic equalization charge for flooded batteries is a must.
* Do not leave batteries deeply discharged for any length of time.
* Lead acid batteries do not develop a memory and need not be fully discharged before recharging.
* Batteries should be charged after each period of use.
* Batteries that charge up but cannot support a load are most likely bad and should be tested.
Charging Information Recap for AGM and Gel batteries
1. Only charge gel cells using a confirmed and reliable, temperature sensing, voltage regulated charger. Never use a constant current charger!
2. Charging Current or Amps is the flow of electricity. Every battery can only store, deliver or receive a certain amount of electricity. Voltage is electrical pressure. The amount of voltage dictates the rate at which the amps will be forced into the battery during the re-charge process. The temperature at which this process is taking place also effects charging. When the right pressure is used – at the right temperature – the battery will be charged at its optimal rate. If to much pressure is used, current or charge will be forced through the battery faster than it can be stored. This will cause the battery to give off hydrogen and oxygen faster than it can be recombined leading to the destruction of the battery. A warmer battery accepts re-charge easier.
3. At 25˚C/77˚F keep charging current in the range of 2.38 volts to 2.42 volts per cell for Gel cell batteries.
4. At 25˚C/77˚F keep charging voltage in the range of 2.4 volts to 2.45 volts per cell for AGM batteries.
5. Compensation for battery temperature above or below 25˚C/77˚F can be made by subtracting 0.005 volts per cell for each 1˚C above 25˚C or by adding 0.005 volts per cell for each 1˚C below 25˚C. Add .028 volt per cell for every 10˚ below 77˚F and subtract .028 volt per cell for every 10˚ above 77˚F.
6. When re-charging - consider that to replenish the ampere hours removed in the discharge process - you will need to replace 110% to 120% of the charge removed. Also, the time it will take to re-charge will depend on certain variables such as the depth of the discharge, the ambient and battery temperature, the age/condition of the battery and the chargers overall features. Typically you should expect that it will take 60% of the charge time to return the battery to within 90% of its original capacity. It will take the remaining 40% of the charge time to completely recharge the battery.
7. As an alternative to continuous constant voltage charging - to speed the charge process - it is acceptable to charge both Gel and Absorbed Electrolyte Cells by first bulk charging them at up to 30amps per 100AH of 20hr capacity (.3CA) to an end voltage of 2.45 volts per cell at 25˚C. This bulk charge must be followed by a finishing stage where the terminal voltage is maintained between 2.38 to 2.42 volts per cell for Gel cells and 2.4 to 2.45 volts per cell for absorbed electrolyte cells – both at 25˚C/77˚F. This final stage will see the current fall off as the voltage rises. If the battery is to be maintained and the charger left in a float mode, the current should be managed to maintain a float voltage of between 2.25 and 2.30 volts per cell at 25˚C/77˚F.
8. The process of re-charging a battery should be considered completed when the charge rate drops below or equal to the batteries self-discharge rate. For example a 100AH battery with a 3% self discharge rate should be considered to be re-charged when the charge rate reaches and remains stable at 3 amps.