Posted on

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.



Posted on

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).

Posted on

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.

Posted on

Battery Testing FAQ

Q: My batteries don’t seem to be holding a charge.  How can I determine if they need to be replaced?
Yes, it could be one or more bad batteries.  If they are more than 5 years old, then that’s the most likely issue.
There are a couple of ways to test batteries.  The best is with a capacitance tester (an expensive tool, and not likely to be available). A capacitance tester does not require that the batteries be fully charged to test.  All other tests require that the battery be fully charged before testing.  Only a professional will have the capacitance tester, so it’s unlikely you can find one, although a store that sells batteries might have one.
Next best is a load tester, basically coils of heating wire (like a toaster) enclosed in a metal box (with lots of holes for the heat to escape) that you attach to the battery with what looks like short jumper cables.  This thing loads the battery heavily and has a volt meter that (on a good battery) will drop from about 12.8 volts to 11.7 and then stay close to that for at least 15 seconds.   On every bad battery I have tested, the voltage falls quickly and steadily.  Most auto repair shops have one of these, and many discount auto parts stores will do this test for free.  You can do something similar with the starter motor of your engine.  With the “engine kill” cable pulled, or with the engine stop button pressed, crank the engine for 15 seconds or so.  Do this with only one battery hooked up.  A bad battery will run out of juice quickly.  Unfortunately, this is not very scientific, and I don’t know the amps your starter will draw, nor exactly what the “normal” battery voltage will be.  If you have several batteries and only one is bad, this test will dramatically identify the defective one.
The easiest way to test a battery is to measure the voltage “at rest”.  To do this test, fully charge the battery, then let it sit for 24 hours.  The measured voltage after 24 hours is the “at rest” voltage.  It should be 12.7 – 12.8 volts.  However, this test is not definitive.  You can have a battery that has very little capacity, and it could still pass this test.  This test will find a battery with a bad cell, which is sometimes indicated by single cell using more water that the other cells (in a flooded battery).
Posted on

Kaneka Solar Modules


KanekaThe least expensive solar panels available, dollars per watt.  60 watts, thin film, 25 year 80% power output warranty, UL listed, made in Japan.  Rated 91 volts open circuit.  Great for water pumping or residential array, where there is plenty of space.  These panels produce about 1/2 the power per unit area, compared to crystaline type solar panels.

Manufacturer’s Data Sheet

$75 (yes they are that inexpensive!)

Posted on

Divert Load FAQ

Frequently Asked Questions

How does the divert load work?

A divert load accepts excess power that a wind generator can produce beyond what the batteries are capable of safely accepting and disperses that extra power as heat. With a charge controller but no diversion load, the excess power would flow to the controller and have nowhere else to go, damaging the controller. The divert load helps to maintain system safety.

Hotwire makes a Resistive Load Bank of ceramic resistors to be used as a diversion load, but the preferred option by far is a dual voltage water heater element. It has two loops in one unit.  One loop (element of heating wire) is made to work on 12 volts at 300 watts, and the other operates on 120 volts at 500 watts.

You can make hot water from the 120 volt side using shore power or a gen set.  Because the 120 volt side is smaller than the original heater element, it will take longer to reheat the water in the tank when all of the hot water has been used, typically 2 to 3 times longer.

The 12 volt side is used to dissipate the excess power from a wind generator or solar panels, and the amount of current going to it is controlled by a diversion type charge controller.  The controller senses battery voltage and diverts current into the water heater when the battery reaches the voltage set point.

One of our customers, who has a lot of solar panels on his boat, uses a switch and turns the 12 volt side on every day after his batteries are full.  In the past, diversion type controllers sent the excess energy to heating coils that turned the power into hot air, a bit the way Hotwire’s Resistive Load Bank works.  With the dual water heater element, you get something useful and don’t heat up the inside of the boat. A distinct advantage in the tropics!

Posted on

Solar Modules

Photovoltaics give you a silent, reliable, maintenance-free source of electricity to charge your batteries. You can start with a small system and easily add more modules as your needs grow.

Hotwire Enterprises offers solar products from Aurinco, Solar World, Kyocera, SolarTech, and Battery Solutions Plus. Evergreen, BP, Yingli, GE, Power Up, Iowa Thin Film, Sopray, Uni-Solar, Kaneka, Mitsubishi, Sanyo, SunWize, Sharp and other brands also are available. The solar modules most popular and useful to boaters are listed below.

The photovoltaic market is changing. We are following developments closely and will update this page as we learn about additional options opening up.

How to Select Solar Modules

How do you know which one(s) to get? The first question you should ask yourself is “Where will I mount it on my boat?” Refer to the Solar FAQ page and read #3. Look at your chosen site. How often does that area get shadowed? Choose high output technology for sites that get a lot of full sun; choose shade tolerant technology for sites that are often or always shadowed. Go back to the Solar FAQ page and read #8. Then measure the dimensions of your chosen location, and find a module that will fit within that area.

Please contact us if you need details on solar modules not shown here or need help on deciding what’s right for you.

Note; as of spring 2012 the supply and pricing is changing rapidly.  Please call for the latest information.

Shade Tolerant/Heat Tolerant
(Amorphous, Thin Film)

Model Output Size Price
FlexPower 20 1.2A 12″x73″, 1.9 lb. $349
Ennergy IP10F 0.58A 13.0″x25.0″x7/32″, 2.0 lb. $150.00
Kaneka 60 Watt 0.9A (at 67 Volts) 39.0″x 37.8″, 62 lb. $75.00**

** Pallet quantities, or pick up in Tarpon Spring only

High Output
(Monocrystal and Polycrystal)

Model Output Size Price
Sopray 5 0.3 TBD $25.00
Sopray 20 – 60 1.8 – 3.5 TBD $2/watt
Sopray 70 (POLY) 4.1 TBD (will be shorter and fatter) $149.00
Sopray 70 (MONO) 4.1 47.6″ X 21.25″ X 1.1″ $149.00
Kyocera 85 4.8A 38.4″x 25.7″x 1.4″, 21.2 lb. $398.00
Kyocera 135 7.39A 56.1″x 25.7″x 1.4″, 26.8 lb. $349.00
Aurinco 12 – 100 watts semi-flexable
Kaneka 60 open circuit voltage 67 volts 40″ X 40″ $75.00*
Kyocera 135 7.63A 59.1″x 26.3″x 1.4″, 28.7 lb. $349.00
Kyocera 140 8.2

* Pallet Quantities available


More Solar Modules

We have access to many other solar modules. Please call for pricing on Mitsubishi, BP, Sharp,  and others.

Choosing a Solar Module

Which module you choose will depend partly on your available space and its size and partly on how much and how often that space is shadowed. If you plan to put a module across your dodger where it will be shadowed by the boom, then choose one of the shade-tolerant modules. You’ll get more power from it in the long run. If you can put one (or more) above your davits (or on your arch) where it isn’t likely to be shadowed, then go with a high output technology. And we’re available to assist you with your choice.

Solar Panel FAQ

Still have questions about solar panels? See our Solar Panel Frequently Asked Questions (FAQ) page.