Marine Battery Sizing Calculator
Marine Battery Sizing
Size your marine battery bank based on electrical loads, usage hours, and desired reserve capacity to ensure reliable power on the water.
Formula
Daily Amp-Hours = Total Load (amps) x Usage Hours; With Reserve = Daily Ah x (1 + Reserve %); Battery Bank Size = With Reserve / Max Depth of Discharge
Frequently Asked Questions
How do I size a marine battery bank?
Calculate your total amp-hour consumption per day, add a reserve margin of 25 to 50 percent, then divide by the maximum depth of discharge for your battery type. Lead acid batteries should not be discharged below 50 percent, while lithium can safely go to 80 to 90 percent.
What type of marine battery is best?
Lithium iron phosphate batteries offer the longest lifespan, lightest weight, and deepest discharge, but cost more upfront. AGM batteries are a good mid-range choice. Flooded lead acid batteries are the most affordable but require maintenance.
How long do marine batteries last?
Flooded lead acid batteries last 2 to 4 years, AGM batteries 4 to 7 years, and lithium batteries 8 to 15 years depending on charge cycles and maintenance.
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