Battery Charging Plans
Electric auxilliary propulsion will require a large 48 volt battery bank and sufficient charging capacity. Renewable energy charging sources are strongly preferred. Two 58V home solar panels in parallel would be adequate. A small wind generator mounted on the mizzen mast would also help. A small shore power charger will also be provided.
The price of both solar panels and wind generation are dropping substantially each year. Home solar panels are by far less expensive than marine solar panels and generally also deliver higher power per panel surface area.
There are two major sections here. The first describes the selection of the three types of charge sources. The second is focused on charge control.
Charging Sources
At this point a decision has been made on which solar panels to use, the Panasonic. A Air Breeze Marine 48v with carbon fiber blade upgrade and mizzen mast mounting kit has been ordered but not yet shipped. The shipping hold up is the mounting kit. A shore power charger has been purchased and returned to a distributor for reprogramming for the 48V battery bank. This subsection provides options considered.
The Solar Panel Mounting and Solar Mount Metalwork web pages provide details on installing the solar panels. The Wind Generator Mounting page provides details on installing the wind generator.
Solar Panel Options
It makes sense to select panels at the time of purchase. At the moment two contenders are:
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REC Solar 315 Watt N-Peak Monocrystalline Solar Panel is a nominal 315 W panel delivering 18.9 W/sqft. This panel is 65.9" x 39.25" x 1.1" and weighs 40 lbs. It is rated at 315 W, with 33.9 V and 9.31 A at MPP. It costs $195. This panel is nominal 36V and so under voltage for this application and would need two in series.
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Panasonic VBHN330SA17 330 Watt Mono Solar Panel is a nominal 330 W panel delivering 17.8 W/sqft. This panel is 62.6" x 41.5" x 1.57" and weighs 41 lbs. It is rated at 330 W, with 58.0 V and 5.70 A at MPP. It costs $368.
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The newer Panasonic HIT High Efficiency Solar Panels at 335W and 340W are also nominal 58V. These sell for $320 and $338. Both are 62.6" x 41.5" x 1.6" and weigh 42 lbs.
The Rec Solar panel provides 15W less but at just over half the cost. Right now 300W panels are older technology, 310-315W provides the lowest cost per power, 330W incurs a big jump in price. Panels up to 360-400W are available but at very high cost. If prices continue to fall the 330W panels will be among the price leaders and command the bulk of the market. Two 330W panels would provide 660W or 2.6 to 3.3 kWh of power per day.
The Panasonic HIT panels or Panasonic HIT+ panels seem the best choice. The Panasonic panels are 96 cell, nominal 58V panels. Most panels are about nominal 32-36V are require two in series. Panels in series on opposites sides of the mast will have severe shading problems since one or the other is likely to be shaded.
Most panels are about 66x44 inches. With 11'2" beam, two panels can easily be fit forward of the mizzen mast, on either side of the center line with a wide gap for the main boom. Another possibility is to mount two panels on each side with the long side athwartship and tilted at an angle of 20 degrees to each side. This would require about 5'2" width per panel, leaving a gap of about 11" between panels with no overhang beyond the beam of the boat.
Using four lower cost nominal 36V panels would not cost much more than two nominal 58V panels. Bringing the panels closer to the centerline will increase shading problem. The larger area will also add a lot of windage. The benefit is over 1200W of total solar panel capacity, even if shading may cut that in half. There also needs to be 80" (6'8") between the mizzen mast and aft of the main mast enough to not interfere with sheeting (the traveller or aft or the traveller). Carefull measurement would be needed before considering this option.
Wind Generation Options
While wind generator prices have dropped, the rate of drop is nowhere near that of solar panels. Two contendors are:
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Primus Windpower Air X Marine 48v 1-ARXM-15-48 is rated at 400W, with a startup speed of 8 mph. The 400W peak power is generated at a specific wind speed with most conditions producing under 200W. The Air X normally sells for about $1,200.
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Primus Windpower Air Breeze Marine 48v 1-ARBM-15-48 is a nominal 200W generator with 7 mph start up speed. The Air Breeze normally sells for about $1,200.
The Air Breeze produces slightly more power at under 23mph and twice the power over 32mph. The Air X produces a sharp power peak of over 400W at about 28mph, then drops quickly to 100W. The Air Breeze peaks at only about 250W but sustains 200W of power at higher wind speeds.
An AIR Breeze 48V Wind Generator can produce 1-1.25 amp at 48V with 12-15 knot winds or roughly 50-60 watt. Over 24 hours this could add up to 1.2 to 1.4 kWh per day. Output drops to near zero at 7 knots or under. Rotor diameter is 46".
Shore Power Charger
Very few 48V AC chargers are available. Fewer are suitable for marine use. A 48V charger is offerred by the battery supplier, Lithium Battery Power, but inaccuracies on the web page and warnings on the web page and the use of aligator connections did not inspire confidence. The auxilliary motor supplier, Electric Yacht, offerred two lines of charger, QuickCharge and Delta-Q IC1200. The QuickCharge line is based on a large transformer and has very limited programability with no mention of changing voltage threshholds. The Delta-Q line is programmable but only by a distributor and for a $150 fee. It is not custom programmed but rather one of a set of existing programs is selected.
A 48V Delta-Q charger was purchased. This is their IC-1200 charger. Unfortunately charger setup for Delta-Q chargers is highly proprietary. If buying in the US, after purchase the charger must be programmed for a fee of $150 by Delta-Q's US distributor who in turn requires information beyond what is available from manufacturers spec sheets. None of this information is actually required to program the charger and if Delta-Q was not so secretive could be handled by many end-users, particularly ones with degrees in electrical engineering and over 30 years experience, like me.
After over a month of back and forth email some of the limitations of the programming service and the charger itself was revealed. Custom charging profiles are only created for OEMs (those purchasing at least hundreds of chargers). For consumers, a review of the charging requirements is done, actually a computer search of existing profiles, and an existing profile is selected. Then the charger can be shipped to the distributor to have that charge profile added to the charger and selected.
The 48V Delta-Q IC series chargers can only reach 58.8V. There are a limited number of charge profile numbers, apparently limited three decimal digits. Delta-Q wants a single mapping of charge profile number to actual charge profile hence the reluctance to create new profiles for end users. The charger itself can only hold a small number of profiles, about a dozen, creating the reason to return the charger to get "programmed". This is a bad design that has created a bad situation for users. Reserving a single charge profile number for "custom" might solve it but Delta-Q appears to see no reason to solve the problem.
The charge profile selected was one that set the absorbtion voltage to 58.8V, the highest voltage the Delta-Q IC series charger can support. Until 58.8V is reached the charger will provide 25A (6.25A per string) at whatever voltage it can reach. After reaching 58.8V, the charger will cease charging if less than 3A (0.75A per string) charge is being absorbed. It will also stop charging after 12 hours. After the charger stops charging it has to be power cycled to start charging again.
Eventually I figured out how the charge program on the Delta-Q chargers gets set. The charger has to be shipped to a location on the west coast where they will pick an existing charge profile which is closest to the parameters you are asking for and install it and charge you $150 plus shipping for this service. Only for an OEM who would be buying at least hundreds of chargers would they create a new charge profile. The chargers themselves can only hold a limited number of profiles so the factory only loads a few common ones that cover some AGM batteries. This is a major drawback of the Delta-Q chargers.
Charge Control
Two configurations of solar charge controllers were initially considered to charge the 24V and 12V batteries. A decision was made to charge the 12V battery from the 24V battery and the 24V battery from the 48V battery using Morningstar ProStar charge controllers. The other configuration considered would not charge the 24V and 12V batteries when wind or shore power charging.
Solar Charging Configurations
The 48V battery bank will charge directly from one or two TriStar solar controllers that are powered by the two solar panels. TriStar has to be used since the panels are 58V nominal and the battery is 48V, both exceeding ProStar ratings. Two controllers may be used, one for each panel, so that if shading of one panel occurs then each panel can be held at its maximum power point (MPP).
The 24V and 12V batteries could also be connected to separate TriStar solar controllers. Alternately, and it seems better is to have the 24V and 12V batteries connected to ProStar solar controllers which draw power from the 48V battery rather than directly from the panels.
Direct Connect to Solar Panels (not used)
Coonecting each of the three battery banks to solar controllers that are driven directly by the solar panels would require that TriStar solar controllers be used. ProStar could not be used in this configuration due to the nominal 58V panels with Voc well above 60V. The minimum would be three TriStar solar controllers, but six is likely to be needed.
Shading on a sailboat can be a severe problem. If one solar panel is mounted on each side of the centerline, much of the time one or the other solar panel will be shaded by either one of the masts or the main boom, or a mast and the boom. If the sun is on the port side of the boat, the port solar panel would be in the clear, other than stays which cast very little shadow (having an affect, but minimal).
When shading is an issue MPPT controllers make even more sense. To be effective one MPPT controller is needed per string (set of panels connected in series). It would be foolish to put the two panels in series since one panel would be shaded much of the time and degrade the performance of the string (of two). If the two panels are in parallel, this is two strings of one panel each. With three battery banks, a total of six MPPT controllers would be needed. These are costly and therefore this design is not cost effective.
The 12V battery and 24V battery are together only 3 kWh. Each solar 330W panel on a sunny day and if not shaded should be able to deliver 1.3-1.6 kWh of power per day. With some contribution from the partially shaded panel, 1.5-2 kWh per day. Other than by installing and abusing a AC/heat system, this amount of power is unlikely to be used by these two house banks. Some of the power delivered by the panels would go toward recharging the 48V bank though if discharged that could take days.
Charging can be prioritized using RD-1 relay controllers and solenoids. For example, the 12V battery can be prioritized over the others due to its role in running systems needed for navigation. If charge on the 12V battery falls below some levels, then the other two batteries would not be charged. The 24V battery could be given a secondary priority. If the 24V battery level falls below some threshhold, then the 48V bank would not be charged. RD-1 relay controllers and solenoids can also be used to disable non-essential loads such as AC/heat, any entertainment systems, some galley appliances, inverters, and if necessary all but minimal cabin lighting.
Connect to 48V side of Solar Controllers (configuration used)
There are many advantages to using the 48V battery bank to power the charge controllers for the 24V battery and the 12V battery. Charging the 48V battery bank can use one TriStar controller for each solar panel. The charge controllers for the 24V battery and the 12V battery can be ProStar controllers and can be the less expensive ProStar PWM controllers.
If there are consecutive days with very little sun, then the 24V battery and the 12V battery can draw power from the much larger 48V battery bank. For example, if the largest load in port is refrigeration instead of having 1.8 kWh of 24V battery available, some portion of the 10.8 kWh 48V bank would also be available. If underway and the refrigeration autopilot and radar were the largest power draws, then some portion of the 10.8 kWh 48V bank would also be available.
Prioritization of battery charging and disabling loads can be accomplished using RD-1 relay controllers and solenoids. For example, the 24V and 12V charging can be disabled if the 48V bank is drawn down below some threshhold of auxilliary power needed to travel a short distance and for manuevering into a slip or picking up a mooring. If either the 24V battery or 12V battery falls below some threshhold, then charging of that one battery could resume until a lower 48V battery threshhold is reached. RD-1 relay controllers and solenoids can also be used to disable non-essential loads.
Charge Controller Selection and Wiring
The Charge Controllers web page describes how DC-DC converters and PWM and MPPT charge controllers work and the charge controllers considered.
The charge controllers themselves are the tip of the iceberg. The Battery Monitoring and Protection web page describes the electronics used to monitor battery health and protect the batteries. The charger wiring and the load wiring connected to the three battery banks is described in the Battery Charge and Load Wiring section of the Battery and Electrical Wiring web page.