# Advantages of chaining another battery to 130Ah AGM deep cycle 12V battery

I have a 130Ah AGM deep cycle 12V battery for camping connected to 2 x 100W solar panels. I have been testing the system out to see whether it will sustain what I require. I think I’ll require around 100Ah of charge per day which would approximately discharge the battery to 25% SOC.

How much charge can my solar panels theoretically replenish if I can access say 6 quality sun hours in a day?

Does the wattage of the solar panels represent the amount of charge that can be supplied to the battery per hour? If so, I imagine I could generate 1200 Watt Hours or 100 Amp Hours in a day which would be enough to replenish the amount of charge that I wish to consume. Is my math correct?

If I didn’t use more than 100Ah of charge per day, would there still be an advantage in terms of battery longevity by chaining another identical battery to my existing one to double the capacity?

If I wanted to use more than 100Ah of charge then I would require a second battery so as not to discharge the first battery to less than 25% SOC. However, would my solar panels be capable of regenerating enough charge to make adding the second battery viable? Or would there be other advantages to add the second battery in terms of operating on average at a higher SOC even if I were unable to regenerate all of the charge that I had consumed in a day?

• It is close, but not quite enough. For a 12V battery, 100 Ah is around 100 * 12 = 1200 Watt-hours (Wh). Your panels, rated nominally at 100 W, will probably produce around 80 W each under real world conditions, assuming a high quality MPPT charge controller. So 80 W * 2 panels * 6 hours = 960 Wh per day. You could add a third panel, or find a way to reduce your energy consumption a bit. Adding a battery won't really help. Dec 24, 2017 at 0:30