Ask PYS: Power

Rudy, on Jul 09, 2012 asked:

We seem to run the generator on our boat for in order to charge the batteries to an acceptable level. I checked the monitor and with the generator running, we charged at about 115 amps but it still seemed to take a long time. If the batteries were at 50% it would take almost 2 hours to get to 70%. Could it have anything to do with the set-up of the charger? I see you can change the absorption time and it does not seem to be on bulk charge for very long. We were not using a lot of power other than for the fridges and freezer. Despite running the generator for 3-4 hours per day, the batteries never got charged much past 80%. Do you have any ideas about what the problem could be?

Let's first remember that lead acid batteries take about 50 cycles to reach their optimal capacity. This is a process called surface etching and provides you with more surface plate area which in turn gives more capacity. This surface etching not only affects capacity but also the ability for your batteries to charge and discharge as fast as they can. Your current battery setup is two L16s, which translates to approximately 400 AHrs of capacity. Ideally, you should cycle between 50% and 85%, which provides you with 133 Amp hours of useable capacity. The charge rate should be at approximately 115 Amps for the whole duration between 50% and 70%, this can be measured at the battery via the battery monitor mode on remote display. Also, the charger output should be higher, perhaps 140 to 150 amps. Once your batteries are completely broken in, your absorption charge mode should only come into effect when you reach 80% to 85%.