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Thursday, May 03, 2012

Transplanted Power

As the 24volt electrical system is built out, there is a need, of course, for a 24volt power source. I had a couple old flooded cell batteries of different sizes kicking around, but those ultimately died (I mean dried-up, exposed plate, dead). I tried wiring in a small 24volt DC power supply, similar to the type you might find in a desktop computer or similar electronic device. This was good for testing lights and gauges but it did not supply enough 'umph' for running multiple high-load devices like pumps. I need a real 24volt battery bank.
As the boat is in the midst of construction, I did not want to spend money on new batteries that will sit for a few years before they get used "in production".

Small-boat to the rescue 

Our little 28 footer has four 6volt "golf cart" style batteries wired as a 12volt house bank. Despite being eight years old, the battery testers (hydrometer and electronic) have always tested  these as "good". Which, for us, is almost unheard of. Seems we always hear of boaters having to replace bad batteries every couple years, due to, if anything... age. We experienced the same until we upgraded to a more modern charging system (Balmar alternator & three stage regulator) ten years ago. Side note: I am convinced that with modern three-stage charging systems and proper maintenance (keeping electrolyte levels up and never discharging more than 50%), deep-cycle flooded cell batteries can last almost indefinitely. Anyway, I figured if I had to buy new batteries, it would be for the small boat, which would reap most benefit, and the old ones would be transplanted into the Westsail.
Tailgate party: top-up and test of batteries.
So, I am up early and down at the marina, taking advantage of the high tide and minimal gang-plank angle on the dock, hauling up-and-down new and used 6volt batteries weighing 65lbs each. Having hauled the old ones home, I top up electrolyte, put them on the charger, and do a final test before installing into the Westsail. The battery tester still says 'good'.
Batteries installed and wired in series to form a 24volt bank, 245 amp-hour capacity (125 useable).
In the Westsail, the batteries are fitted into the house bank battery box and tied together with insulated copper buss bars (custom, easy to make). The house battery box is located under the floor, in the forward end, center section of the main salon.

To give an idea of how many more batteries we can fit, this last picture shows the remaining space in the box. We can fit at least eight more of these golf-cart type batteries, which would give a total capacity of 735 amp-hours (367 amp-hours useable) and 780 lbs of more ballast!. For 24volts that is a LOT of reserve capacity. Should we ever fit out with more modern, higher power density batteries (like lithium), add the inverters, and wind and solar generation, I figure the boat could power a small third-world country. Just need a long extension cord.

Room for more.
In the next few weeks, before these batteries get used too much,  comes the battery charger installation. Stay tuned...
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