AGM batteries?
Is it imperative to have AGM batteries with a solar set-up? Why? Could you not just use 2 6v batteries (not AGM's)? Do they last longer? How much and are they really worth the price difference?
Forum Discussion
Flooded cells are cheap and can be abused some without much damage, require periodic maintenance.
AGM are more expensive but must be fully recharged periodically, no maintenance.
Lithium cost more initially and must be charged with proper equipment, but are the cheapest in amp -hrs delivered over their life. They are also tolerant of operating for long periods at a partial state of charge, which lead acids are not.
In the example given above, discharging the AGMs to 50%, 1000 cycles will give you 100,000 AH by end of life, or $0.0065/AH delivered. The lithiums discharged to 80% for 2500 cycles will give you 400,000 AH by end of life, or $0.0045/AH delivered. In practice you would replace a 200 AH lead acid battery with a 120 AH lithium making the initial cost difference less, while keeping the life cycle cost advantage.
AGM are more expensive but must be fully recharged periodically, no maintenance.
Lithium cost more initially and must be charged with proper equipment, but are the cheapest in amp -hrs delivered over their life. They are also tolerant of operating for long periods at a partial state of charge, which lead acids are not.
In the example given above, discharging the AGMs to 50%, 1000 cycles will give you 100,000 AH by end of life, or $0.0065/AH delivered. The lithiums discharged to 80% for 2500 cycles will give you 400,000 AH by end of life, or $0.0045/AH delivered. In practice you would replace a 200 AH lead acid battery with a 120 AH lithium making the initial cost difference less, while keeping the life cycle cost advantage.
