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Monitoring your Boat’s Energy / Trimetric

The least expensive way to keep track of what’s happening in your boat’s electrical system is with a voltmeter.  The best way is with a system monitor.  A voltmeter tells you the battery voltage, which gives a general idea of the state of charge (SOC) and charging and discharge.  However, in order for the voltmeter to give you an accurate measure of SOC, the batteries have to sit for at least several hours (some manufacturers recommend 24 hours), before you can read the “at rest voltage”.   This is hard to do when you are living aboard and the battery is constantly being charged or discharged.   Your electrical panel probably includes a voltmeter.  However, if it has a needle and scale (called analog), then it only gives a rough estimate.  A fully charged battery at-rest voltage is about 12.8 volts.  A battery at 50% discharge is about 12 volts.   It is unlikely that you can see the voltage to an accuracy of 0.1 volts, unless you have a digital voltmeter, and even a digital voltmeter only gives you an approximation.

If you have an ammeter, it shows current flow in your system but cannot keep track of the total energy used from the battery bank(s).

The best way to keep track of your boat’s electrical system is with a system monitor.  This has a display will tell you the battery voltage, amps, and battery state of charge (as well as a number of other things that are not as important, like maximum voltage, days since equalization, etc).   We sell the TriMetric system monitor that has proven to be very reliable, as well as being the least expensive monitor.

We’ve also come up with a couple of tricks that can be used with the TriMetric (or other system monitors) so that you can monitor the wind and solar output.  Call for more info.

TriMetric    2030  $190          BUY NOW

TriMetric 2030 Battery System

What the Trimetric 2030 can tell you:

  • “Percent Full” (“State of charge”) of your batteries, so you can see if you need to charge them more, or check that overall usage is less than your charging resources.
  • Volts of the batteries, for example to check that they are being charged at proper voltage.
  • Energy going in, or out of your batteries, measured in amps or watts, so you can see that your charging sources are charging properly, or how much current your loads are using.
  • How many days since the batteries were fully charged: to remind you to not wait too long between fully charging your batteries to maximize their life.

The TM2030 is easier for you to program the necessary system parameters.

  • The TM2030 has some minimal data logging, which can be useful for a technician to diagnose some common setup or operational problems with battery systems.
  • The TM-2030 will operate with (nominal) battery systems from 12 to 48V. The TM-2020 will operate with 12 or 24 V systems, but requires the addition of the “TM-48VA” Adapter and lightning protection board when using it with 48V battery systems. This also provides lightning protection for the TM-2020.
  • The TM-2030 can also monitor the voltage only of a second battery, such as a starting battery, or possibly also the input voltage of a solar array (if less than 100 volts.)
  • The TM-2030 has a “simplified” level of operation suitable for most users, but can be configured for more flexibility (and complexity) where occasionally required.
  • (For the technically knowledgeable only) The TM-2030 has a serial data output of all the “real time” data—which could be used to access data for other control or output in, for example OEM applications.
  • The newer TM-2030 includes better lightning protection compared with the TM-2020.
  • It is easier to view and enter programmed parameters..
  • It is about typically about $15 more than the TM-2020. For 48V systems it is less expensive than the TM-2020 because it does not require an extra 48 volt adapter.



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Solar Incentives

There is a 30% federal tax rebate available.  It covers 30% of the installed cost of the solar system.  You must have a tax liability (you must owe taxes in that year) to take advantage of the tax rebate, but it does “rollover” (you can take the rebate in the following year).

Solar panel prices have fallen by more than 50% in the last three years.  The Florida Public Service Commision has influenced the state’s invester owned utilities into offering rebates for solar installations, typically $2 per watt.  With the utility company’s rebate and the federal rebate, there is a “window of oportunity” to get a solar system for very little cost.    For example: a 2000 watt system might cost $9,000 up front.  The Utility rebate = $4,000.  The federal incentive would be $3,000.  Your cost = $2,000.  If it saves you $1 per day, $365 year, that’s 5.5 years to recover the investment, for a system that should last over  25 years.  Depending on how you calculate your return on investments, this should be better than the stock market, even if you know how to invest there.

If you have equity in your home, you can borrow the money.  There are federal loan programs that can help.  Most bankers are not familiar with these, so you will need to do your homework.    Most solar distributors have loan programs (though not at very good rates).  There are lease-back programs, where you do not pay for or own the system, but get some of the benefits.  There may be available PACE (Property Assisted Clean Energy) where the loan is tied to your property, and the payments are through your property taxes.

Under Florida (pending, but in effect) statutes, the county cannot raise your property taxes because of the solar installation.  There is no sales tax on solar products.  Our insurance went up less than $100 per year when we included the solar system in our home owners.  Deed-restricted communities cannot prevent you from installing a solar system.

For more information about federal and Florida  incentives, see: 

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Solar for your Boat – the Basics

The Technology    Skip to “Bottom Line”  if you really don’t care how they work.  There are two basic kinds of solar panels (more properly called modules); crystaline and thin-film.  The crystaline fall into two catagories; mono-crystal and poly-crystal.  Thin-film modules look monolithic, with no noticeable individual cells.  Polycrystal cells have a crystal look to them, sort of like broken ice, when viewed at the right angle.  Mono-crystal cells are gray to dark blue, with no crystal structure visible.

 The cells in a monocrystal module are more efficient – they produce more power per square inch, but the way they are made requires that they start off round.  Trimming some of the edges, so that they can fit more closely together, helps them fit together more tightly, but the cell material is very expensive.  Polycrystal cells start off square or rectangular, meaning they can be packed in more tightly, covering the area more completely.  So, the overall efficiency of mono vs poly-crystal modules is very close, with there being a slight advantage in price to the less expensive poly-crystal modules, and slightly more power per square inch for monocrystal.  What it usually comes down to is what fits better.  Poly-crystal modules tend to be shorter and fatter, while mono-crystal modules tend to be longer and narrower.

Thin film modules use a lot less of the expensive pure silicon than crystaline modules.  Unfortunately, the very low cost modules that this promises have only recently started to come to market, and in forms that are not well adapted to boats.  The down side to thin film is that it is less than 1/2 as efficient as crystaline, meaning that at least twice as much area is needed to produce the same amount of power.  The up side is that they are not nearly as effected by shading.  Shading one cell of a crystaline module can reduce the output by 50%.  Completely shading one row of crystaline cells can bring the output to near zero.  Shading a portion of a thin film module only reduces the output by the amount shaded.  Shade it 10% and lose 10% of the power.

Bottom Line    You’ll want to use crystaline modules if they are going to be fully exposed to the sun all the time (like over davits), and thin film if they will be significantly shaded (like under the boom).

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Solar vs High-output Alternator or Generator

Whether you are keeping the batteries from going dead or running your alternative lifestyle, solar panels on a boat make a lot of sense.  Most of us are not willing to live without the comfort and safety afforded by electrical power.  Creating that power from fossil fuels can be expensive, smelly, loud, and inconvenient.  Solar power is silent, reliable, environmentally correct, and in most cases cost effective.

Solar vs Fossil Fuels    Making all of your electrical power from a generator or high-output alternator on the auxilary engine will be much more expensive than getting it from the grid.  A typical cuising sailboat uses about 150 a amp-hours per day (Ah/d).  If you were getting this power from the grid (like at your house), this would cost about $0.20 per day.  If you make this amount of power with fossil fuels, just the fuel alone is likely to cost over $1.00 per day (and require that you carry additional fuel or top off the tanks more often).  If you add maintenance, depreciation, and repairs that could easily go to over $2.00 per day, and that doesn’t consider the noise, smell, etc.  With solar there is virtually no maintenance (maybe cleaning the bird pooh off occationally).  Solar modules will last a long time, probably more than 40 years.  The warranty is typically 20 – 25 years.  Figure the cost of the solar at $6 watt (including the controller and installation equipment), and the break-even point compared to fossil fuels is about 3.5 years.

Other Advantages     But wait, there’s more; solar does not polute.  Solar is much more cool (it doesn’t heat up the boat).  Batteries prefer to be charged at a low rate over a long time, compared to the high rate for short time from a high-output alternator or generator, which can overheat and shorten their life or even damage them.  Your batteries are more likely to get fully charged with solar, because when charging in a short time from fossil fuels, they typically do not accept the last 10% or so of the charge, and they are likely to not get cycled as deeply with solar, making them last longer. 

The Down Side     Cost.  At $6 per watt, a typical system for an offshore cruising boat would cost about $2700.  But, unless you have a catamaran or have a generous sized arch, you probably do not have room for the all the solar modules needed.  Also,if your boat already has a high-output alternator or gen-set, then you will have little in the way of avoided cost, at least for the initial investment.

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105 Amp Alternator

New 105 amp alternator for Yanmar and most Japanese engines with 3 1/8 spacing between mounting ears.   Dual cooling fans, solid 2 1/2 inch pulley for quick charge at low engine speeds.  Adaptors plug into original wire harness.  They come with a built-in voltage regulator or set up ready to use a “smart” (external) voltage regulator.  Please specify which you want when ordering.   Note; the case is slightly larger than most original equipment alternators, and may require you use our optional adjusting arm.

$199 BUY NOW

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80 Amp Alternator

New, not rebuilt.  80 amps is the largest capacity that can be used while  maintaining your warranty on a Yanmar engine.  The wire connections are “plug and play”.  The case is slightly larger, and may require that you use our optional adjusting arm, especially on engines smaller than 20 HP.  On engines smaller than 18 HP, I recommend using an external regulator with a feature that allows you to reduce the output by 1/2, so that full power is available when you need it.  These regulators also have a “soft start” feature, where the engine is not loaded with the full electrical load until the engine has warmed up a bit.

Includes a 2 1/2 inch solid pulley for good low engine speed output and low heat transfer to the front bearing.   3 1/8 inch spacing between mounting ears, standard on all Yanmars and most other japanese engines.

$135  BUY NOW

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High Output Alternators

Eventually, even with wind and solar power, you will need to charge the batteries with fossil fuel.  If you do not have a generator, the engine driven alternator is your last choice.  The largest alternator that can be used with a single belt is about 100 amps.  Even then, you will have increased belt wear and will need to be careful about maintenance.  Yanmar says the warranty is void if you use larger than 80 amps, due to increased strain on the front main crankshaft bearing.  You will also be putting more load on the waterpump bearings as well.  I hope I haven’t talked you out of a high output alternator, because I do believe they are worthwhile. (“Compromises must be made.”)

We have in stock new, 90 amp ($135) or 105 amp ($199) alternators that are a bolt-on replacement for the original alternator on most diesel engines.   No core charge.  These are not marinized, where a screen is placed over the cooling vents, meaning that they cannot be used with gasoline engines.

GO TO 90 AMP “Perkins” ALTERNATOR  (two inch foot)


If you add a “smart” voltage regulator, the batteries can be charged more rapidly and the charging regimen can be taylored to fit your battery type, helping the batteries to last longer.  The smart regulator also allows you to add a battery temperature sensor or an alternator temperature sensor.  If you have a large battery bank of flooded batteries or gel or AGM batteries, you should consider an alternator temperature sensor, because the alternator will be working very hard and might overheat or have its life shortened by operating at high temperature.  If you have a small battery bank, or if the batteries are in the engine compartment, you should consider a battery temperature sensor, so that the charging voltage can be optimized for the relatively high temperature that the batteries might encounter.

Your high output alternator will be working really hard.  If you have a smart voltage regulator, you can add a temperature sensor to the alternator that will cause it to reduce output to prevent overheating.  If you have gel or AGM batteries, they will accept more amps and add even more to the overheating potential.  The advantage the smart voltage regulator offers with gel and AGM batteries is being able to taylor the voltages to the batteries.  Your expensive batteries will last longer if you charge them at the correct voltage.  The advantage with flooded batteries (the kind you have to add water to) is that they can be forced to take more charge when the process first starts, reducing charging time with a smart regulator.

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Solar System “Packages”

Nearly everything is included in these packages or “kits”.   Many more combinations of solar modules (panels), inverters and mounting packages are available.  Info from the vendors:    and

Some typical packages:

Kyocera MyGen MG-2    2160  WATTS,     KYOCERA 180 MODULES

Sunwize 999GTS033-Z     2112 WATTS,     SHARP MODULES