Marine Battery DOD life cycles, it's your pocket...
If you could determine whether your batteries lasted 1500 charge and discharge cycles or 300, which would you prefer?
Basically I am asking you whether you want your batteries to last up to five times longer.
The Depth of Discharge, or DOD for short, determines the number of times your batteries can be cycled, based on the rules of chemistry. Basically, a battery is a electro-chemical device, storing power by chemically changing something. In nature, nothing we know how to do is perfect, so a little bit of the chemicals are degraded each time you cycle your marine battery. The level to which you discharge, or depth, determines the amount of the chemicals lost. Generally, DOD numbers for deep cycle marine batteries are directly connected to the cycle life of the battery as well. Some really smart engineers figured out that there was a direct correlation, and the rest is history.
To save your pocket, you must buy more than 2x the amount of power you think you might use, or you will end up paying 4x for it. Simply put, if you need 100 ah, buy 200 - 400, or plan to buy batteries routinely. When you look back, you will find that you will have purchased 2-4 times the batteries because you undersized the battery bank. To get normal usage, use 2x the power, and shoot for 50% DOD, resulting in roughly 1000 cycles with premium AGM batteries.
When you want them to last even longer, be sparing with your usage, and frequently charge those batteries. By using less power, or buying 4x the power you use, you only discharge the top 25% of your batteries, resulting in 1500, 2000 life cycles of the battery.
If you click here for Johnny's Battery Story you can see the particulars
Using 2 cycles a day at 80% DOD expect 300 cycles; 300 cycles is eaten in 150 days, or 5 months.
Using 2 cycles a day at 50% DOD expect 1000 cycles; 1000 cycles is eaten in 500 days, or 18 months or a year and a half.
Using 2 cycles a day at 25% DOD expect 1500+ cycles; 1500+ cycles is eaten in 750 days, or 25 months or 2 years.
When Johnny cut his consumption, his cycles went down to 1 a day, and he just sends customers now:
Using 2 cycles a day at 80% DOD expect 300 cycles; 300 cycles is eaten in 10 months.
Using 2 cycles a day at 50% DOD expect 1000 cycles; 1000 cycles is eaten in 33 months or almost 3 years.
Using 2 cycles a day at 25% DOD expect 1500+ cycles; 1500+ cycles takes nearly 5 years to eschew.