Many people have posted questions about power consumption.
On Eight we have 860 Watts of solar, a 600-Watt Hydro generator, an 11kW generator, two chargers of 80 amp and two engines with an alternator which typically will do about 60 to 70 amps each. Don’t believe the brochure……
I have made a spreadsheet with all energy users (as we have it). Of course, the challenge is to use not more than the available energy. Click here to download the spreadsheet. Power consumption spreadsheet
I have analyzed two logical scenarios:
Because of the hydro-generator that we have, there is a big difference for us when we are underway or at anchor.
As you can see o the spreadsheet, we are short of energy at anchor, but this may depend on the time of year. We are now (March) at anchor near St. Maarten for instance. Trade winds are east so our additional solar panels, which are installed on the port side, are facing north. The sun is still in the south. End of April it will get better as the sun will be north of us during the day.
We use about 400 Ah in a day when we are at anchor and refrain from switching on unnecessary lights. That is without making water. Making water is another 100 Ah or so. Our solar panels generate about 350 Ah. So, we are 150 Ah short each day.
The conclusion is that we would need 400 extra watts of solar or a wind generator to be energy neutral. For now, we have to run the generator for one hour per day.
I don’t like the look of the wind generators, nor solar panels above the dinghy or panels extending out from the overhang. So, for us, it is generator time for one hour a day. Best is to run the generator in the morning when the batteries are at about 75%. They can be charged much faster when they are empty. I switch the generator off when we reach 85%-90% SOC. From there the sun can do its work and top up the batteries during the day. If you do it the other way around and decide to top up the batteries with the generator at the end of the day, it will take two or three times as long. While charging the batteries we can use the excess power of the generator to run the washing machine, scuba compressor and some A/C’s. It is best to run the generator above 50% load. With an 11kW Generator that is not easy.
Standard the boat comes with one Victron 80/2000 charger/inverter. The default charging setting is 60 Amps. When you run the water-maker (30 Amps) there will be 30 amps left. The boat uses 18 Amps which leaves you just 12 Amps to charge the batteries while making water. After making water (3 hrs) this goes up to 42 Amps. Without additional solar it will take 8-10 hours to charge to batteries every day. So if you want to live on board, you need to add other means of charging.
With a computer interface, the default charge rate of the Victron can be set to 80 Amp. I added a second charger (set at 60 Amp) so I can now charge at 140 amps. Please also have a look at my post: Balancing water and energy
While underway at a decent speed (7-8) knots, our Watt and Sea generates 25 amps easily, 24 hours a day. In that case, we have energy left over. As soon as the State of Charge of the batteries reaches 95%, I switch on the 12 volt water maker. Trying to add the last 5% of charge in a battery takes a long time. Make water first.
Feel free to modify the spreadsheet in accordance with your own set up on board.