And we're back.....
27 April 2016 | Nanny Cay, Tortola BVI
Captain
On a schedule that is. In just under two weeks we set off for a 1,000 mile nonstop trip back to Fort Le De Da Florida. These last 6 months in the Caribbean have seemed to just slip under our keel. Not unnoticed or without our enjoyment however.
April arrived and with it a lack of wind. We had a week last week where there was not a breath stirring for 4 days straight. It made getting around in the dinghy easy and less wet but provided no wind power from our Silentwind generator while we sat behind a reef in Dakity in Culebra PR. Our generator is currently awaiting a new water pump from Fischer Panda from Germany, then to FL, then to USVI, then to BVI to us, hopefully in the next week or so it it’s back up and running for our trip to FL.
The lack of energy production did allow us a small experiment with our Lithium Ion batteries. We have a ridiculously large 1200 amp hours in our house bank. We had room so when we replaced our AGMs we put in 4 8Ds at 300 AH a piece. Normally any lead battery you use the top 50% of the capacity so as to not crash your battery bank. LIon’s though are like your cell phone battery which we all regularly run down to 0% and see the dreaded red battery on your Apple device indicating not enough charge yet to even run the operating system. So practically we run twice the amp hours out of our bank than lead, AGMs or otherwise.
An amp hour is a unit of measurement that expressing the output of a battery. 300 AH puts out 150 hours if lead, 300 hours if LIon. The best way to track how much you need is to track how much you use. We have a battery monitor that converts current charge into remaining hours left in your bank. Its real time so if you run an energy hog like a water maker it assumes your current charge is used the remaining time and your remaining hours may read 12 hours. Water maker was not needed as we had planned to be out a week. When we arrived it settled in a just under 8 days worth of energy.
Then the wind died. And it got hot so our freezer and fridge were running overtime. Slowly the hours ticked down and it got to be Thursday and and it dropped to below 30%. I ran the main engine with our 100 Amp alternator that once up to temperature and at 1800 rpms put about 40 amps into the system and about 5% of the capacity in 2 hours on running. We could run 4 hours a day and hold steady if needed. Then I stopped doing that and when we left on saturday morning we were in the mid teens for percentage left of charge. The hours remaining stopped calculating at 25% remaining capacity so i just watched the percentage and total expended AHs and knew that if it did run down all the way we still had out engine starting battery that would get the alternator running again.
We bashed 6 hours into the wind coming back from PR, motoring and we got back maybe 30% of the capacity. It wasn’t until we got hooked up to shore power and we were able to dump 80 amps in on a steady basis that the full charge came back over another 15 hours or so.
I talked to Fischer Panda today and no water pump yet. Fingers crossed for tomorrow.