Getting to "Full" with Not Enough Solar
More on camping tactics etc to try to get batts full while off-grid and not enough solar per PT's "rules" (PT says you need at least 60w solar per 100AH of battery to "equalize" that day sometime b...
Forum Discussion
Hi BFL13,
Solar system sizing for BATTERY charging.
60 watts per 100 amp-hours minimum to allow equalization--but NOT necessarily all in one day. My Blue Sky counts the hours at equalization voltage--and if not enough hours happen it continues on the next day. If that next day is cloudy then it will attempt to continue on the following day (and etc.).
The other number I quote is not 100 watts but rather 150 watts as a maximum per 100 amp-hours for "best bang for the buck". It is based on the fact that at 85% state of charge a lead acid cell will not accept more than 12.5 amps (which happens to be 150 watts @ 12 volts). Since the whole idea of solar is to get to 100% state of charge so there is not much point in having more wattage.
Solar system sizing for USE.
Is a different kettle of fish entirely. That would require an energy audit, or careful monitoring using an amp-hour counter or watt meter. Minimum size would be average daily use plus 60 watts per 100 amp-hours of storage. Sufficient room on the roof may not exist, so solar "wings" that deploy when standing still almost certainly would be required.
Solar system sizing for BATTERY charging.
60 watts per 100 amp-hours minimum to allow equalization--but NOT necessarily all in one day. My Blue Sky counts the hours at equalization voltage--and if not enough hours happen it continues on the next day. If that next day is cloudy then it will attempt to continue on the following day (and etc.).
The other number I quote is not 100 watts but rather 150 watts as a maximum per 100 amp-hours for "best bang for the buck". It is based on the fact that at 85% state of charge a lead acid cell will not accept more than 12.5 amps (which happens to be 150 watts @ 12 volts). Since the whole idea of solar is to get to 100% state of charge so there is not much point in having more wattage.
Solar system sizing for USE.
Is a different kettle of fish entirely. That would require an energy audit, or careful monitoring using an amp-hour counter or watt meter. Minimum size would be average daily use plus 60 watts per 100 amp-hours of storage. Sufficient room on the roof may not exist, so solar "wings" that deploy when standing still almost certainly would be required.
