Choosing a Charger for Carbon Foam Batteries

Question:

Hello Jeff, I am at the end of my knowledge and in need of a pro here and so far you're the only one I know to trust. Currently, we have a C-Charger 40amp 500 series battery charger in the boat (age unknown). We are hoping to go from old batteries and charger to a new and more efficient system. We are looking at the firefly batteries and upgrading the charger as this one is not adjustable and I believe after watching your videos it needs to be for the new battery chemistry. The boat came with two Victron solar regulators and they are nice and I like the interface. Also, upgraded to a battery monitor which again Jeff recommended and so it was done!  With the new batteries should we upgrade to a similar charger or go from 40-50amps? We have 4awg wire coming from the existing charger travelling to the main bank about 12-15 feet away. I am not sure moving to 50 is even a good thing or even possible. I don't want over taxing on the system :) Meaning more work for me at some point... I am sure you know how that goes.... Thank you for your time and help with this. - Robert

Answer:

Hi Robert, for Firefly batteries, charging should be ideally 20% of battery capacity. For instance, if you have 2 Group 31s at 116 amp-hour each, or total capacity of 232 amp-hours, you should have a 50 amp battery charge. Your wire gauge of #4 is plenty to handle 50 amps of charging. - Jeff

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