Solar Power Question? Any Body?

A Question looking for an answer? Any body? 35AH 12V DC DEEPCYCLE SLA.. how long to charge on 100 watt solar system?


3 thoughts on “Solar Power Question? Any Body?

  1. Quote:
    Quote Originally Posted by raymondalmeda View Post
    how about a norman PWM charge controller? what is it’s normal efficiency? it is close to 66% too?
    At very best is 50%

    Quote Originally Posted by raymondalmeda View Post
    and also, can you explain to me (please) why I would need another 8 batteries in my bank?
    Battery capacity are deigned to have a number of days reserve capacity with 5 being the lowest number which actually is only 2.5 days of usable as you never want to go below 50%. Si if your winter or minimum production is 1320 wh as you have, Then the proper battery capacity = 5 days x 1320 wh = 6600 watt hours. So with a 12 volt battery would be 6600 wh / 12 volts = 550 AH @ 12 volts.

    Don’t get the wrong idea that you have to buy more batteries, because you do not, it is just your system is a bit out of normal design parameters. Having a larger panel wattage than needed is not bad thing providing the charge current does not exceed C/8 for flooded lead acid batteries, or C/4 for AGM. Th ereal problem is having too small of a panel wattage whereby the charge current is to low to agitate the battery acid (bubble).

  2. Quote:

    If you are using a MPPT controller the maximum efficiency you can achieve is 66%. So with 200 watt of solar panels and 5 sun hours the most energy you can generate = Watts x Hours x .66 = 400 watts x 5 hours x .66 = 1320 watt hours so you were way off with 2000 watt hours because you did not account for efficiency.

    For the batteries to get a rough idea take the battery Voltage x Amp Hours = Watt Hours. So 12 volts x 100 AH = 1200 watt hours, and you have 2 batteries so 2400 watt hours of reserve capacity.

    By now you have all you need to know. All you have to do os factor out the watts to be left with time in hours.

    So if your batteries have 50% charge you need to replace 1200 watt hours. Your panels can generate 1320 wh with a 5 sun hour day or 1320 wh / 5 hours = 264 watts. So factor out the Sun Hours 1200 wh / 264 watts = 4.55 hours. The formula is w = wh/h, which means h = wh/ w, and wh = w x h.

    FWIW this tells me you do not have enough battery capacity for your system, you need another 8 batteries.

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