Here are some common questions and answers.

What does SharksHead do?

SharksHead monitors different sensors on a boat or some other environment that can provide the 12V DC power, like a motorhome (aka RV) but also in a building.

One type of sensor module can measure temperature, air pressure and the relative humidity level. By deploying several such sensors, many different areas can be monitored simultaneously.

Another type of module measures the level of explosive gases. This is most important to detect a gas leak before it can be harmful to the occupants or even cause an explosion.

The data is stored in an on-board database so you can check various graphs about the past, up to the last few years. Pretty neat if you're trying to see long term trends.

It also constantly compares these measurements against various thresholds and will then alert you, via several means, that something has breached a threshold.


How does it work?

The headquarter module (HQ) is the heart of the system and should be installed in a central area of the boat. This could be at the chart table on a sailing boat or on or behind the dashboard of a motor cruiser.

It communicates to the individual modules via a 2.4GHz wireless link, which is the same frequency band as your household WiFi or WLAN.

The modules send their sensor data data to the HQ. That can be voltages, currents, power and energy, equipment temperatures, atmospheric temperature, pressure and humidity, as well as the state of its hardware components, such as a relay being closed.

The HQ in turn can control the modules, e.g. remotely disconnect a battery from the bus if the battery voltage is too low.

All this functionality can be accessed from anywhere on the boat via a web browser, even by multiple devices simultaneously.

Can I install it myself?


The Headquarters (HQ) and most modules need a 12V connection to the bus. If you've connected other devices before, you should be good to go.

The plastic enclosures can be mounted in a dashboard or behind a bulkhead using small screws or bolts and nuts. These are not provided in the package as everyone prefers a different style.

Hook and loop tape, double-sided tape or cable ties would work fine, too, especially if you haven't decided yet where to finally attach a module.

Some modules, like the battery controller, have external sensors to measure the battery temperature. They can also be bolted, taped or glued in place.

Is it safe?

We would answer that with a resounding "yes"! However, no prudent boater or sailor would take someone else's word for it.

So how can we prove it? We have a track record of our system running for more than 2 years continuously on our test vessel. Ultimately, it's "your boat, your decision". As with many other electric and electronic devices, the liability of the manufacturer extends only to the replacement of a faulty product and not to other direct or indirect damages or losses.

Over time, there will be more and more reviews and feedback from other users, of course. We encourage you to check the relevant websites like the Cruisers Forum, which is also where we hang out.

Suffice to say that a lot of the functionality and usefulness of SharksHead is based on the monitoring of sensor data, which does not interfere with any actions you take.

The more you "allow" the system to proactively turn devices on or off, the safer it can get, especially when you're not on board. For example, if the solar panels are charging your batteries at full power and the battery temperature gets too high, SharksHead can remove those batteries from the bus for you, possibly preventing damage, fire or off-gassing.

How much of my precious power does it consume?

The Headquarters (HQ) should be running at all times in order to store sensor data and be able to react to thresholds. It uses about 60mA (at 12V).

Each module consumes between 1 and 20 mA, depending on its function. A battery controller (BC) sits at the high end of that range. A device controller (DC) uses around 10mA, and the TPH around 1mA.

So, say, an average system consists of an HQ, 4 BC's, 3 DC's and a TPH. These devices together would consume about 60 + 80 + 30 + 1 = 171 mA from your 12V bus. That's 0.171 A * 24 h = 4.1 Ah per day. If you prefer Watt-hours, that's just shy of 50 Wh.

The average boat today consumes 100Ah or more per day without blinking twice. SharksHead adds at most a 4% increase in the overall power consumption.

Can it be updated?


Upgrading HQ and any modules is explained in the HowTo Upgrade module firmware page.

What if I have more than one battery bank?

Not a problem: whether you have one big house bank today or four different locations for your batteries (like on our test vessel), SharksHead can handle every single battery as a bank!

Instead of remembering to turn this bank on for charging or that bank off over night, you can now turn every single battery on and off at will as shown below:

Does it interfere with my WiFi or WLAN?

No, it peacefully co-exists with them. Even though we are using the same frequency band (of 2.4GHz), SharksHead dynamically selects a channel within that range that is not in use by your or any other network nearby.

Does it interfere with my existing battery monitor?

Possibly. One design goal behind SharksHead is to be able to identify weak batteries. It shows you short and long-term statistics about how many Amp-hours (Ah), or Watt-hours, if you prefer that, are going into and coming out of each battery. To help identify a weak battery you can then remove it from the bus by clicking one button. This will then affect the overall combined capacity of your batteries. It's as if you would physically disconnected that battery, only easier and much quicker.

Any other battery monitoring system is prone to draw the wrong conclusion from such a change.

How can I tell if a battery is weak?

On our test vessel, we left some very dated AGM batteries on board to test the system.

The graph shows the last four days of energy (and temperature) in and out of this particular specimen living in the (dry) bilge. If your solar charger is pumping in 11.3Ah but you're only getting 0.6Ah out something is clearly not right.

Over that same period, our "work horse" battery graph looks like this:

We're putting in 25.4Ah and getting 17.8Ah back. That might not be a stellar efficiency either but orders of magnitude better than the previous one. And, yes, both batteries came from the same batch and were installed on the same day.

A decision as to which battery you should replace next cannot be made without monitoring them individually. What do boat owners nowadays do if their battery bank is as weak as ours? They have to replace them all in one go.

Does it work on all types of boats and even RVs?

Whether you run a 27 foot fibreglass sail boat or the RMS Queen Mary II this system will work! Now you might want to read the fine print:

The big advantage of deploying a wireless system does not come without its own limitations.

On your average 27 to 50 foot fibreglass sail or power boat the radio modules should be able to reach the HQ from every nook and cranny, stem to stern, so to speak. If they don't, you can add a radio relay module in between the far flung place and the HQ. It will automatically pass on all the data from this and any other module that's on "the far side". So you certainly don't need a relay for every module tucked away in your chain locker. The same goes for wooden boats.

Our test vessel is a 45 foot steel sloop. We do have a battery in the forward chain locker to power the windlass. This locker has a steel bulkhead which doesn't allow the windlass battery controller to talk directly to the HQ located in the pilot house. Hence a relay module has been installed next to the door to the forward head. This relay also happens to measure the air temperature, pressure and humidity in the salon so no milliAmps will get wasted there, either.

The same applies to aluminium (or aluminum) boats as well as ferro-cement vessels.

Coming back to the QM II: Even though the Cunard line hasn't fitted SharksHead yet, it would work on the refurbished grand lady as well since we can string more than 200 relays in a very long line to cover a cruise ship or a container ship.

Can someone hijack this wireless system and snoop on me?

Even though our encryption system has not been approved by GCHQ or NSA or some other intelligence agency it is less than trivial to snoop on our network.

Every module uses a different encryption key which is randomly chosen on first power-on and never gets exchanged in the clear over the air. Even we don't know the key, and we wouldn't want to, anyway.

The maximum transmit power of the nRF24L01+ radio module (by Nordic Semiconductor) is very low at 4dBm (or 2.5 mW). Someone would have to be on your boat or the pier to even receive the signal.

Is it OK for world-wide use?

Yes, thanks to this Wikipedia page we are only scanning those channels within the WiFi range that are allowed to be used world-wide.

Does it replace my existing battery charger?


What will it cost me?

We strive to keep the cost for an average boaty to less than 1 "boat unit". One boat unit is generally considered $1000. May those be USD or AUD.

What is in these modules?

The HQ is based on a Raspberry Pi Zero Wifi mounted on a custom-designed board that supports an nRF24L01+ radio, RGB LED, switch, small buzzer, battery-backed real-time clock and a serial interface.

The other modules are based on a 3.3V Arduino ProMini mounted on a custom-designed board containing an nRF24L01+ radio plus whatever other components are required to implement that module's functionality.

The HQ and module software is written in C++. The web interface is written in PHP and Javascript, with a little C++ thrown in for good measure, and is HTML5 compliant. All of which is back-ended by a MySQL database.