So now that we have all of the major boat systems - we need to power them - which means generating and storing electricity. Lets start with estimates of what we will use:
Usage At Sea
Refrigeration 48
Lights 18
Navigation 6
Radar 24
Autopilot 48
water pumps 4.5
Communications 15
Fans 24
Other 15
Water maker 26
Total 254 Ah
The biggest variable at sea is wind and sea state, if elevated or foggy for example both autopilot demands and radar demands could easily double.
At Anchor
Refrigeration 48
Lights 18
Navigation 0
Radar 0
Autopilot 0
water pumps 4.5
Communications 15
Fans 24
Other 15
Water maker 26
Total 176 Ah
At anchor our usage decreases because we will not be using the radar and the autopilot.
For the rest of the analysis we will use the At Sea usage as this represents the largest requirement. Next we need to size the battery bank, rule of thumb is that only 40% of your battery bank is usable, because you cannot discharge regularly below 50% of the bank without damage and charging the last 10% is very inefficient. Assuming allowance for 1 day of use the minimum capacity of the bank is 635Ah (254 / 40%).
Our house battery bank is 705 Ah thus sized with a small safety margin.
Next we need to look at how we will generate electricity noting that there are three options; 1) from the main engine 2) from a dedicated generator 3) from renewable sources (wind, water, solar).
We have decided not to put on a dedicated generator because of expense and ongoing maintenance, additionally our estimated load requirements are a little light to make efficient use of a generator.
On our main engine we will install a high put alternator, generating 120 Ah, assuming 2 hours of operation a day (1 in the morning and 1 in the evening) this will provide 240 Ah.
We will also install alternative charging, most likely a water/wind generator that you tow while at sea and use as a wind generator at anchor. Estimated output in water mode is 144 Ah and in wind is 96 Ah.
In total our At Sea generating capacity is thus 384 Ah with 2 hours of engine and towing the water/wind generator. While at At Anchor we will have 336 Ah. This can be adjusted based upon needs with the default to charge as much from our alternative sources as possible.
If we left the boat for a period of time the 96 Ah from the wind generator should be sufficient to support minimum systems (refrigeration, anchor light and fans).
Further we expect to balance the load by running the water maker and engine at the same time to manage that peak draw.
So in total our system will be well balanced - if we assume that we are off by 25% on our actual usage then we see that we would really need 320 Ah At Sea and batter bank of 800 Ah. This is probably more realistic thus minimizing the impact of the water maker will be critical.
Finally, to keep all this system working we will need to monitor and maintain the batteries. We will use a Mastervolt combination inverter/charger with a MICC for battery monitoring and have installed the Tudor Battery filling system to keep water levels at optimum level in the batteries.
Equipment List
62 amp start battery 245 amp house battery
Shore connection, 117V, islolator, breaker, land cable, 4 outlets
Marinco-inlet for 110 V
Additional Batteries, Flat Plate, 12V 235 Ah -order 2 additional for a total of 705Ah
Tudor BFS water filling system for batteries, 12v/225/210ah
12V/120 Amp Alternator and emergency start (Yanmar)
Lopolight LED Tricolor light and Anchor Light
Combi Mastervolt 12/2000-100A (120V), MICC remote
Red night light over galley and navigation table
Extra 110 V outlet: galley
Hella Turbo Fans (8)
DuoGen
Electric Gas Switch
The only thing that will not be installed at the Yard is the DuoGen, which do to ease in installation and rapidly improving technologies we will wait to install ourselves in 2008. At the moment though this seems to be the best wind/water generator on the market.
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