Thursday, Aug 28, 2008 at 19:30
Pippy,
I agree with Robin.
If you have a 3 stage controller, the factory preset on good quality controllers for bulk voltage is 14.3, float voltage 13.5. The adjustable range for bulk voltage is normally 12 -16.5, the same applies to float voltage.
If your controller is a 3 stage one on bulk charge a preset maximum constant amount of current is fed into the battery, the voltage of the battery increases gradually. After the preset voltage is reached it is then held constant, absorption charge, and as the battery continues to be charged at constant voltage, the charging current decreases.
The charging voltage is held at bulk voltage setting for 1 full hour with various rapid on-off pulses and then switches to Float Charge Mode.
The controller will maintain battery voltage at the float voltage by giving shorter on-pulse charge to make up for any detected self discharge.
When the battery voltage drops below the Float Voltage setting for a total of 10 minutes, a new charging cycle is activated in Bulk or Absorption charge.
So you can expect to see varying voltage during a charging cycle even when the sun is at it's optimum angle.
I understand that AGM and Gel batteries can tolerate a bit more charge than your normal lead acid but I agree that 15.5 is too high. Check the manual for your controller and hopefully you should be able to adjust.
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