Archive for the ‘FAQs’ Category

The least expensive way to keep track of what’s happening in your boat’s electrical system is with a voltmeter.  It 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 manufactuers 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.  

If your panel has an ammeter, it probably just shows the amperage going out of the battery.  Upgrading to a digital ammeter and sensing the current flowing into or out of the battery will give you a better indication of what is going on. 

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. 

TriMetric 2020

We use to recommend the model 2020, which can only monitor one battery (bank), because the house bank is the one that gets cycled up and down.  The engine start battery typically gets completely recharged each time the engine is started, and so closely monitoring it is not as critical.  If you have a system monitor that has failed, you can probably use the shunt that you have, saving $25 on your new TriMetric.  The new TriMetric 2025 will do all the 2020 does, but also gives you the volatge of a second (typically the engine start) battery.  Slightly smaller in size, the 2025 comes with a box for surface mounting.   It also has more resistance to damage from lightning and is easier to program, all for $10 more (I think it looks better too).

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

TriMetric    2020   $175     MORE INFO      BUY NOW

2025

TriMetric    2025   $185      MORE INFO       BUY NOW 

The 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!)

Got questions? Here are the most common ones and their answers: Read the rest of this entry »

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!

Got questions about solar? These are the most commonly asked along with our answers: Read the rest of this entry »

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 Solar World, Kyocera, SolarTech, and Battery Solutions Plus. Evergreen, BP, Yingli, GE, Power Up, Iowa Thin Film, 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.

Shade Tolerant/Heat Tolerant
(Amorphous, Thin Film)

High Output
(Monocrystal and Polycrystal)

* LSS = laminated stainless steel

** 67.5 volts open circuit, for use with MPPT controller that drops the voltage to charge batteries

More Solar Modules

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