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lithium batteries

Posted by on June 19, 2012


600 amp hours of LiFePO4 batteries

It’s official! The boat is now modern electric.

Over a few days, Wil spent time wiring our new LiFePO4 battery cells together. Each cell has an individual float of 3.2 volts per cell. Using 12 200 amp hour CALB cells, we have 3 parallel banks each consisting of 4 cells that are wired in series. This gives us a 13.8 volt system with a total of about 600 amp hours (420 available amp hours). A distributed miniBMS battery management system is attached to each cell in order to monitor and regulate the individual cells, as well as maintain a balanced system.

The upfront cost of lithium batteries is quite high, but over the long-term it seemed like a win-win situation. With a 600 amp hour system, in reality that means we have 420 amp hours available to us. With lead acid batteries, close to 1000 amp hours would be needed to give the same result. Lithium batteries are also smaller and much lighter. We now have about 180 pounds of batteries, compared to the normal 800 to 1000 pounds. Talk about the perfect system for a catamaran! Finally, the life cycle of lithium batteries is considerably higher than wet, gel, or AGM batteries. Lithium batteries can cycle 3000 to 5000 times, compared to 300 to 1000 times for the other batteries. Lithium batteries just seem like the way to go.

Soon it was time to disconnect the old lead acid batteries and wire in the new lithium batteries. One the first day, the solar panels dumped 250 amp hours into the batteries before the bulk charging quit, and the BMS system alarm sounded. Wil disconnected the solar panels, and proceeded to let the boat run off the new batteries. The battery cells needed to be top balanced. Balancing the cells takes several hours, and the process is nearly complete.

In the meantime, Wil has done some polishing of the hulls. I have not returned to the boat yet, but the photo speaks wonders. I can’t wait to see it in person!

what a shine!

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