Engage the Silent Drive

I’ve been busy electrocuting my boat – here are our first impressions of the Torqueedo Cruise 2.0T on the water.

About 2 years ago I decided to try sailing, so I bought a second hand Hartley TS16; a popular small “trailer sailor” here in Australia. Since then I have been getting out once every week, having some very pleasant days with friends and family, and even at times by myself. Sailing really takes you away from everything else in the world. It keeps you busy as you are always pulling a rope or adjusting this and that, and is physically very active as you are clambering all over the boat. Mentally there is a lot to learn, and I started as a complete nautical noob.

Sailing is so quiet and peaceful, you get propelled by the wind using aerodynamics and it feels like like magic. However this is marred by the noise of outboard motors, which are typically used at the start and end of the day to get the boat to the point where it can sail. They are also useful to get you out of trouble in high seas/wind, or when the wind dies. I often use the motor to “un hit” Australia when I accidentally lodge myself on a sand bar (I have a lot of accidents like that).

The boat came with an ancient 2 stroke which belched smoke and noise. After about 12 months this motor suffered a terminal melt down (impeller failure and over heated) so it was replaced with a modern 5HP Honda 4-stroke, which is much quieter and very fuel efficient.

My long term goal was to “electrocute” the boat and replace the infernal combustion outboard engine with an electric motor and battery pack. I recently bit the bullet and obtained a Torqeedo Cruise 2kW outboard from Eco Boats Australia.

My friend Matt and I tested the motor today and are really thrilled. Matt is an experienced Electrical Engineer and sailor so was an ideal companion for the first run of the Torqueedo.

Torqueedo Cruise 2.0 First Impressions

It’s silent – incredibly so. Just a slight whine conducted from the motor/gearbox pod beneath the water. The sound of water flowing around the boat is louder!

The acceleration is impressive, better than the 4-stroke. Make sure you sit down. That huge, low RPM prop and loads of torque. We settled on 1000W, experimenting with other power levels.

The throttle control is excellent, you can dial up any speed you want. This made parking (mooring) very easy compared to the 4-stroke which is more of a “single speed” motor (idles at 3 knots, 4-5 knots top speed) and is unwieldy for parking.

It’s fit for purpose. This is not a low power “trolling” motor, it is every bit as powerful as the modern Honda 5HP 4-stroke. We did a A/B test and obtained the same top speed (5 knots) in the same conditions (wind/tide/stretch of water). We used it with 15 knot winds and 1m seas and it was the real deal – pushing the boat exactly where we wanted to go with authority. This is not a compromise solution. The Torqueedo shows internal combustion who’s house it is.

We had some fun sneaking up on kayaks at low power, getting to within a few metres before they heard us. Other boaties saw us gliding past with the sails down and couldn’t work out how we were moving!

A hidden feature is Azipod steering – it steers through more than 270 degrees. You can reverse without reverse gear, and we did “donuts” spinning on the keel!

Some minor issues: Unlike the Honda the the Torqueedo doesn’t tilt complete out of the water when sailing, leaving some residual drag from the motor/propeller pod. It also has to be removed from the boat for trailering, due to insufficient road clearance.

Walk Through

Here are the two motors with the boat out of the water:

It’s quite a bit longer than the Honda, mainly due to the enormous prop. The centres of the two props are actually only 7cm apart in height above ground. I had some concerns about ground clearance, both when trailering and also in the water. I have enough problems hitting Australia and like the way my boat can float in just 30cm of water. I discussed this with my very helpful Torqueedo dealer, Chris. He said tests with short and long version suggested this wasn’t a problem and in fact the “long” version provided better directional control. More water on top of the prop is a good thing. They recommend 50mm minimum, I have about 100mm.

To get started I made up a 24V battery pack using a plastic tub and 8 x 3.2V 100AH Lithium cells, left over from my recent EV battery upgrade. The cells are in varying conditions; I doubt any of them have 100AH capacity after 8 years of being hammered in my EV. On the day we ran for nearly 2 hours before one of the weaker cells dipped beneath 2.5V. I’ll sort through my stock of second hand cells some time to optimise the pack.

The pack plus motor weighs 41kg, the 5HP Honda plus 5l petrol 32kg. At low power (600W, 3.5 knots), this 2.5kWHr pack will give us a range of 14 nm or 28km. Plenty – on a huge days sailing we cover 40km, of which just 5km would be on motor.

All that power on board is handy too, for example the load of a fridge would be trivial compared to the motor, and a 100W HF radio no problem. So now I can quaff ice-cold sparkling shiraz or a nice beer, while having an actual conversation and not choking on exhaust fumes!

Here’s Matt taking us for a test drive, not much to the Torqueedo above the water:

For a bit of fun we ran both motors (maybe 10HP equivalent) and hit 7 knots, almost getting the Hartley up on the plane. Does this make it a Hybrid boat?


We are in love. This is the future of boating. For sale – one 5HP Honda 4-stroke.

New Lithium Battery Pack for my EV

Eight years ago I installed a pack of 36 Lithium cells in my EV. After about 50,000km and several near-death battery pack experiences (over discharge) the range decreased beneath a useful level so I have just purchased a new pack.

Same sort of cells, CALB 100AH, 3.2V per cell (80km range). The pack was about AUD$6,000 delivered and took an afternoon to install. I’ve adjusted my Zivan NG3 to cut out at an average of 3.6 v/cell (129.6V), and still have the BMS system that will drop out the charger if any one cell exceeds 4.1V.

The original pack was rated at 10 years (3000 cycles) and given the abuse we subjected it to I’m quite pleased it lasted 8 years. I don’t have a fail-safe battery management system like a modern factory EV so we occasionally drove the car when dead flat. While I could normally pick this problem quickly from the instrumentation my teenage children tended to just blissfully drive on. Oh well, this is an experimental hobby, and mistakes will be made. The Wright brothers broke a few wings……

I just took the car with it’s new battery pack for a 25km test drive and all seems well. The battery voltage is about 118V at rest, and 114V when cruising at 60 km/hr. It’s not dropping beneath 110V during acceleration, much better than the old pack which would sag beneath 100V. I guess the internal resistance of the new cells is much lower.

I plan to keep driving my little home-brew EV until I can by a commercial EV with a > 200km range here in Australia for about $30k, which I estimate will happen around 2020.

It’s nice to have my little EV back on the road.

8 Mega Watts in your bare hands

I recently went on a nice road trip to Gippstech, an interstate Ham radio conference, with Andrew, VK5XFG. On the way, we were chatting about Electric Cars, and how much of infernal combustion technology is really just a nasty hack. Andrew made the point that if petrol cars had been developed now, we would have all sorts of Hazmat rules around using them.

Take refueling. Gasoline contains 42MJ of energy in every litre. On one of our stops we took 3 minutes to refuel 36 litres. That’s 42*36/180 or 8.4MJ/s. Now one watt is 1J/s, so that’s a “power” (the rate energy is moving) of 8.4MW. Would anyone be allowed to hold an electrical cable carrying 8.4MW? That’s like 8000V at 1000A. Based on an average household electricity consumption of 2kW, that’s like hanging onto the HT line supplying 4200 homes.

But it’s OK, as long as your don’t smoke or hold a mobile phone!

The irony is that while I was sitting on 60 litres of high explosive, spraying fumes along the Princes Highway and bitching about petrol cars I was enjoying the use of one. Oh well, bring on the Tesla charge stations and low cost EVs. Infrastructure, the forces of mass production and renewable power will defeat the evils of fossil fuels.

Reading Further

Energy Equivalents of a Krispy Kreme Factory.

Fuel Consumption of a Pedestrian Crossing

WTF Internal Combustion?

At the moment I’m teaching my son to drive in my Electric Car. Like my daughter before him it’s his first driving experience. Recently, he has started to drive his grandfathers pollution generator, which has a manual transmission. So I was trying to explain why the clutch is needed, and it occurred to me just how stupid internal combustion engines are.

Dad: So if you dump the clutch too early the engine stops.
Son: Why?
Dad: Well, a petrol engine needs a certain amount of energy to keep it running, for like compression for the next cycle. If you put too big a load on the engine, it doesn’t have enough power to move the car and keep the engine running.
Dad: Oh yeah and that involves a complex clutch that can be burnt out if you don’t use it right. Or an automatic transmission that requires a complex cooling system and means you use even more (irreplaceable) fossil fuel as it’s less efficient.
Dad: Oh, and petrol motors only work well in a very narrow range of RPM so we need complex gearboxes.
Dad thinks to himself: WTF internal combustion?

Electric motors aren’t like that. Mine works better at 0 RPM (more torque), not worse. When the car stops my electric motor stops. It’s got one moving part and one gear ratio. Why on earth would you keep using irreplaceable fossil fuels when stopped at the traffic lights? It just doesn’t make sense.

The reason of course is energy density. We need to store a couple of hundred km worth of energy in a reasonable amount of weight. Petrol has about 44 MJ/kg. Let see, one of my Lithium cells weighs 3.3kg, and is rated at 100AH at 3.2V. So thats (100AH)(3600 seconds/H)(3.2V)/(3kg)=0.386MJ/kg or about 100 times worse than petrol. However that’s not the whole story, an EV is about 85% efficient in converting that energy into movement while a dinosaur juice combuster is only about 15% efficient.

Anyhoo it’s now possible to make EVs with 500 km range (hello Tesla) so energy density has been nailed. The rest is a business problem, like establishing a market for smart phones. We’re quite good at solving business problems, as someone tends to get rich.

I mean, if we can make billions of internal combustion engines with 1000’s of moving parts, cooling systems, gearboxes, anti-pollution, fuel injection, engine management, controlled detonation of an explosive (they also make napalm out of petrol) and countless other ancillary systems I am sure human kind can make a usable battery!

Internal combustion is just a bad hack.

History is going to judge us as very stupid. We are chewing through every last drop of fossil fuel to keep driving to and from homes in the suburbs that we can’t afford, to buy stuff we don’t need, making plastic for gadgets we throw away, and flying 1000’s of km to exotic locations for holidays, and overheating the planet using our grandchildren’s legacy of hydrocarbons that took 75 million years to form.

Oh that’s right. It’s for the economy.

Degrowth Economy

Just read this article: Life in a de-growth economy and why you might actually enjoy it.

I like the idea of a steady state economy. Simple maths shows how stupid endless growth is. And yet our politicians cling to it. We will get a steady state, energy neutral economy one day. It’s just a question of if we are forced, or if it’s managed.

Some thoughts on the article above:

  • I don’t agree that steady state implies localisation. Trade and specialisation and wonderful inventions. It’s more efficient if I write your speech coding software than you working it out. It’s for more efficient for a farmer to grow food than me messing about in my back yard. What is missing is a fossil fuel free means of transport to sustain trade and transportation of goods from where they are efficiently produced to where they are consumed.
  • Likewise local food production like they do in Cuba. Better to grow lots of food on a Cuban farm, they just lack an efficient way to transport it.
  • I have some problems with “organic” food production in the backyard, or my neighbours backyard. To me it’s paying more for chemically identical food to what I buy in the supermarket. Modern, scientific, food production has it’s issues, but these can be solved by science. On a small scale, sure, gardening is fun, and it would be great to meet people in communal gardens. However it’s no way to feed a hungry world.
  • Likewise this articles vision of us repairing/recycling clothing. New is still fine, as long as it’s resource-neutral, e.g. cotton manufactured into jeans using solar powered factories, and transported to my shopping mall in an electric vehicle. Or synthetic fibres from bio-fuels or GM bacteria.
  • Software costs zero to upgrade but can improve our standard of living. So there can be “growth” in some sense at no expense in resources. You can use my speech codec and conserve resources (energy for transmission and radio spectrum). I can send you that software over the Internet, so we don’t need an aircraft to ship you a black box or even a CD.

I live by some anti-growth, anti-consumer principles. I drive an electric car that is a based on a 25 year old recycled petrol car chassis. I don’t have a fossil fuel intensive commute. I use my bike more than my car.

I work part time from home mainly on volunteer work. My work is developing software that I can give away to help people. This software (for telecommunications) will in turn remove the need for expensive radio hardware, save power, and yet improve telecommunications.

I live inexpensively compared to my peers who are paying large mortgages due to the arbitrarily high price of land here, and other costs I have managed to avoid or simply say no to. No great luck or financial acumen at work here, although my parents taught me the useful habit of spending less than I earn. I’m not a very good consumer!

I don’t aspire to a larger home in a nice area or more gadgets. That would just mean more house work and maintenance and expense and less time on helping people with my work. In fact I aspire to a smaller home, and less gadgets (I keep throwing stuff out). I am renting at the moment as the real estate prices here are spiralling upwards and I don’t want to play that game. Renting will allow me to down-shift even further when my children are a little older. I have no debt, and no real desire to make more money, a living wage is fine. Although I do have investments and savings which I like tracking on spreadsheets.

I am typing this on a laptop made in 2008. I bought a second, identical one a few years later for $300 and swap parts between them so I always have a back up.

I do however burn a lot of fossil fuel in air travel. My home uses 11 kWhr/day of electricity, which, considering this includes my electric car and hence all my “fuel” costs, is not bad.


In the past I have written about why I think economic growth is evil. There is a lot of great information on this topic such as this physics based argument on why we will cook (literally!) in a few hundred years if we keep increasing energy use. The Albert Bartlett lectures on exponential growth are also awesome.

Energy Equivalents of a Krispy Kreme Factory

My 15 year old son is rather excited at the prospect of Adelaide’s first Krispy Kreme factory. This factory will be pumping out 5,000 donuts an hour.

Now a donut contains about 1000 kJ of energy. This is chemical energy, in the form of fat and sugars and carbohydrates. Our bodies are designed to run by “burning” this chemical energy. If we don’t need more energy when we consume the donut then some of the excess will be stored as fat.

Now energy comes in different forms, for example as electricity, mechanical, solar, thermal, or potential energy. It’s possible to convert between one form and another using a machine, for example a petrol motor converts chemical into kinetic energy. A solar panel converts the energy in the suns radiation to electricity.

Energy is measured in Joules (J), lots of energy in kilojoules (kJ), or megajoules (MJ). Power is the rate we use (or produce) energy. If I use 1 J/s in my LED torch, that is 1 Watt (W). My electric car uses 5 kW when I cruise along at 60 km/hr. So 5,000 J/s is moving from my batteries to the electric motor of the car.

The average human uses 8700 kJ per day. That means we need to injest roughly 8700 kJ of energy, and our body uses about the same amount of energy. This energy runs our body, and gives us some energy for moving about. There are 24(60)(60) seconds in a day. So the power consumption of the average human (energy/second) is 8,700,000J/(24(60)(60))=100W. About the same as a large incandescent light bulb.

So as we know the energy in a donut, and the rate at which the donuts are produced, we can measure the Power Output of the Krispy Creme factory. Then compare that to all sorts of other power producers and users in our lives.

Here are a few energy equivalents (spreadsheet):


A related analysis is Fuel Consumption of a Pedestrian Crossing.

Aspitech E-waste Recycling Tour

Yesterday Robert Hart was kind enough to take a group of local hackerspace members on a tour through Aspitech, and Adelaide e-waste recycler. The Australian government has mandated that all importers must pay to recycle 33% of their products (by weight), which has created a new, high growth industry. The South Australian government is unique is requiring zero landfill from old TVs and PCs which I think is pretty cool.

Aspitech currently processes 200 tons per month. The TVs and PCs are disassembled into broad categories, such as plastic, copper wire, circuit boards, metalwork. These are then bagged up and shipped off to other companies that can use them as raw materials, for example melting down the copper, or using glass from CRTs as road base. Aspitech is a social enterprise that employs a number of disabled people.

Robert is looking for entrepreneurs who have ideas and most importantly the passion to create spin off businesses from e-waste resources.

Busting Teenage Partying with a Fluksometer

On New Years Eve 2011 I was in Geelong at a restaurant, 800km from my home in Adelaide. This year I happened to be away from my children, who were staying elsewhere in Adelaide while I was interstate. My home was supposedly vacant. However I knew it was very hot in Adelaide that day (40C) and I wondered if this would affect my power consumption, for example an increased duty cycle on the fridge. I am just that sort of power-geek.

So I checked my Fluksometer via my 3G android phone. I was surprised to see 1000W being used since 1pm – about what my Air-con uses. I also noticed that around 7pm the power jumped by a few 100W, just like the lights had gone on, or perhaps the TV.

Looked like some one was in my home. On New Years Eve. Hmmmmmm.

The 24 hour plot below just was captured on (1 Jan) at 5:30pm, so it actually shows the tail end of the Dec 31 festivities. You can see the 1000W consumption until it shoots up around 1900 hours, then the rapid, parentally-induced decline at around 2030 hours as explained below…..

I was fortunate to be at the restaurant with a couple of people expert in these situations. Teenagers. They suspected “Party”. I was unsure. I called my beloved 16 year old daughter Amy to see if she “knew” anything about this phantom power problem. My gut feel was to call my mother (Amy’s grandmother) and ask her to visit my home but I thought I’d give Amy the benefit of the doubt. Amy said that she was at a friends house but would go around and check my house. She was not keen on using her grandmother to resolve the issue. Exactly 30 minutes later I received a text from her saying the air con and TV was on but she had switched them off.

By this stage half the restaurant (I was with a friend’s extended family) were crowded around my phone, watching the next development with excitement. My teenage brains-trust were calling “Party” but there was no way to know for sure. Sure enough the power drops, down to about 180W. About what the fridge motor uses. However curiously, there was none of the regular fridge cycling on and off. It was as if all the lights were off in the house but the fridge motor was running all the time to cool or freeze something.

I returned to Adelaide the next day (1 Jan). My home was very clean but I found a few tell-tale signs: disposable cups with sticky red liquid in them in one of the bins, a trace of the same red sticky stuff on my sink, and post it notes accidentally left on my fridge saying things like “Molly, you may have to open up another bottle”.

What happened to Amy? Well to be honest I wasn’t very mad, just curious about the mystery. I actually enjoyed the detective work side of guessing what was going on and finding supporting evidence. Bart, the inventer of the Fluksometer, was rolling on the floor laughing when I told him the tale.

All my friends knew about the incident so when Amy joined me in Geelong for the next week she was teased relentlessly. Eventually she came clean, and said:

“All my friends who didnt know Dad said ‘How could he do that? Who measures power from across the country’? Those that did know Dad said ‘He knows. Dont worry!'”

“When I realised we were busted there was a mass exodus. I was the last one out and could see a continuous line of teenagers stretched up the street over three blocks.”

One of Amys friends put it well: “You gotta get dumber parents Amy.”


Flukso Web Site
Flukso – Wifi Household Power Logging
Buying a Fluksometer in Australia

Prescription for The Planet – Tom Blees

My friend Bill Kerr gave me a copy of this book to read, which provides several ideas for solving energy and climate problems.

The book has some interesting ideas, for example using boron as a fuel. Apparently any solid metal will burn under the right conditions, so you can use iron or boron as a fuel, in the same sense as hydrogen is a “fuel”. Hydrogen is a way to store energy, like a battery. You can’t dig it up naturally in a form and volume sufficient to drive a car on. So it’s generated using fossil fuels or electricity.

Metals can be used in the same way, you burn the boron, capture the oxide, then recycle it back to boron using an external energy source. The fascinating thing about the proposed Boron engines are the exhaust products are liquid at combustion temperatures. A nice twist on traditional engines which have liquid fuels and gaseous exhausts.

One problem is that Boron engines, let alone cars, don’t exist yet. In contrast I drive a practical, low cost, Electric Car that is solar powered. I am doing this today, no R&D required.

The book recommends breeder reactors as our energy future, nuclear reactors that can generate their own fuel. I don’t understand the nuclear technology, however a system that makes it’s own fuel is pretty cool. The social problems in selling such technology to the general public are daunting. Although given the risks of dam failure I would rather live 1km away from a reactor than 1km down stream from a hydro dam. Unfortunately emotion around nuclear technology has clouded the issues. I do think nuclear deserves more of a “fair go” in public debate.

Using some numerical models the book makes the point that large scale renewable anything (wind, solar, hydro) is a big problem right now. I tend to agree. I figure coal fired electricity will be the base for a long time to come.

However I’m more bullish about Solar PV than Mr. Blees, at least for home use. His models assume the US average of 10c/kWh but thats low by world standards (we pay around 20c/kWh). Solar is about AUD$5/Watt retail here at the moment. Payback period of < 10 years and falling. There are other benefits over central generation - no transmission lines, peaks during summer, lower gird loading, and insulation from rising energy costs. It's possible to halve most peoples electricity use (I did it) – his figure of 888kWh/month average US usage is 30 kW/hr day. Easy to get this down to sub 10-15kWhr/day for most people, at least in Australia.

One key message is that there are plenty of options for a energy rich, non fossil fuel future. It’s not the science or technology that is the barrier – it’s political will and public education.

The core issue for me is that any big changes in our energy systems will take 20 years. The central argument of Peak Oil is that we have much less time than that. Governments are blissfully charging ahead with growth oriented economies aimed at consuming more and more scarce resources. They are planning exponential growth against a finite resource base. So we will be entering an “energy decent” over the next decade, very little can now be done to stop that and the economic problems it implies.

Low Energy Pool

Backyard science is cool. For the last few months I have been working on a theory to reduce the energy consumption of my pool. I started with a theory, and tested it with an experiment. It failed a few times, so I re-worked my theory and have now reduced my pool energy consumption by 75%. That’s a saving of around 7.5 kWh/day in summer. Now I can write it up and share my results with others. I think it’s just great that the Internet enables all of us to do real science on this scale.

Pools suck from an energy point of view, as I explained a few years ago in this popular blog post on the Floatron. The Floatron allowed us to reduce our filter run time from 10 hours day in summer to 4 hours. In addition every few weeks we would add solid chlorine tablets to boost the chlorine level a bit. However I wanted to go a step further, 4 hours is still around 4kWh/day, a big chunk of our household power consumption.

With the Floatron system some residual chlorine is required to keep the pool clear, about 0.5ppm. When this chlorine levels drops, the pools becomes cloudy, and slightly off color. However the cloudy appearance is not a full blown “green pool event”, as the copper ions keep the algae at bay. It can be simply corrected by raising chlorine level to 0.5ppm for a few days (you don’t need a legion of chemicals).

Maintaining or raising the chlorine level often means running the pool pump, which is connected to the salt cell. The pump pushes water through the salt cell,which injects the actual chlorine via a current passed through the cell. So to raise the chlorine level, you need to run the 1kW pump. A salt cell connected to the pool pump looks this this:

The actual power required to run the salt cell is much lower that the pump. Mine had a power input of 150W, and I measured 7.1V at 9.4A or 67W at the cell.

So I decided to try running the salt cell outside of the pump system. Under normal usage salt cells die every few years, so I had an old one lying around. They don’t usually die completely, they just become less effective and need to be replaced. So I took an old cell, waterproofed the electrical connections with some tubing and silicon, and threw it in the pool:

The idea is that with both ends of the cell open, natural convection currents would spread the chlorine around. The pump would still run a few hours a day and occasional pool use would also stir up the water.

I connected the wires to a 20W solar panel, via a Maximum Power Point Tracker (MPP) developed by Elektra. The MPP enables the solar panel to operate at it’s maximum power point (e.g. 17V) while allowing the load (in my case the cell) to find it’s own operating voltage, about 6V for my salt cell. A MPP is like a switch mode power supply in reverse. It allows the output voltage to vary, which keeping the input voltage fixed. They can double the efficiency of your solar panel.

Using the MPP I managed to get a maximum of 6.8V at 2.3A (15.6W) into the salt cell in the middle of the day. Plenty of tiny bubbles coming out of the cell. So I backed off the filter run time to 2.5 hours, then waited a few days to see what would happen to my chlorine levels.

The pool went cloudy and a little green. My good wife was not happy, and muttered something about “Honey, I shrunk the kids” experiments. I reasoned that the panel was too small, not enough current (or power, whatever makes the bubbles) was being supplied. It could probably only supply current for an average of 8 hours/day, or (125Wh/day).

So I connected a lab type power supply to the cell, and put 3.2A at 8V through it for 24 hours a day. After a few days the pool was clear and the measured chlorine was 0.5ppm and rising each day. Backing it off to about 15W kept the chlorine level constant and pool nice and clear.

OK, so that gave me a ball park figure of around 15W for 24 hours/day, or 45W if solar powered for 8 hours/day. Adding a bit of overhead for losses lets say a 60W panel. They cost around $500 here which was vetoed by the financial controller.

For a permanent power supply I bought a cheap 12V, 2.5A car charger. I chose a cheap charger as I wanted a simple unregulated transformer type design. Buying a charger and hacking it was cheaper and more fun that buying all the parts, drilling a box etc and building my own power supply. Looking inside I could see it was a simple fullwave rectifier using two diodes and two 12V windings configured as a center-tapped transformer. My first attempt was simply to remove one of the diodes to make a half wave rectifier. This would give an average DC voltage of half of 12V which is 6V. This worked, but the transformer ran hot and consumed 44W of AC for a power output to the cell of about 13W.

So I partially unwound one of the 12V windings until the unloaded AC voltage was 7V. I then built a bridge rectifier for just this winding and obtained around 5.4V and 1.9A at the cell (10.3W). This is a bit low, but I’ll see how it goes in the pool for a few weeks. I have the other winding spare so I can try unwinding again, this time leaving a few more turns on. The power input is about 23W so it’s not as efficient as I would like. A switch mode power supply configured as a current source would be ideal.

My filter run time is now 2 hours day. This filters the pool water, and injects extra chlorine from the conventional in-line salt cell. Total power consumption is 2kWh/day for the pool plus 600Wh/day for the continuous chlorination gadget. Thats a total of 2.6 kWh/day, down from 4 kWh/day with just the Floatron, or 10 kWh/day pre-Floatron. The 1.4kWh/day saved is enough to run my fridge. In addition we no longer seem to need supplementary chlorine in the form of tablets (saving maybe $60/year). The pool is crystal clear, best we have ever seen it:

Curiously, the measured chlorine level is quite low. I measure it every few days and it’s hovering around 0.2ppm. With the pool looking this good I had figured the chlorine should be higher. Maybe its concentrated in pockets that I am not measuring, as with my “outboard” salt cell chlorine distribution is likely to be less uniform.

Is it safe?

My understanding of how the copper ions (from the Floatron) and the chlorine remove algae and bacteria is weak. I am not even sure what all those bubbles are coming out of the cell. Are they chlorine gas, or some other by-product? I am pretty sure the Floatron takes care of algea, as we haven’t had a runaway green pool event in years. The Floatron site claims that it can also kill bacteria, and has a test report you can read. However the sample size is small (one pool). Other sources maintain that a high chlorine level is required to kill bacteria.

I had some interesting comments on my Floatron post from Nick work works for a state Water board (here and here). He makes safe water for a living, and also posted some interesting links on pool sanitisation.

So I am not sure if my system is taking care of bacteria. Bacteria are invisible so there are no obvious signs like water clarity. Swallowing pool water with bacteria can make you ill, in particular if you are sick already, or very old or very young. People are the main source of bacteria in pools. Like many pools, ours spends 355 days a year people free. Of course I don’t want anyone to get ill in our pool, but to be honest my main motivation is to make sure the damn thing doesn’t go green, while wasting minimal energy (both electrical and human).

From my previous pre-Floatron days, I know that pool chlorine levels vary wildly as most people (like me) aren’t likely to closely monitor the pool every day. This usually means multiple “green pool events” a year, and many hundreds of dollars in chemicals. These chemicals and high chlorine levels also have nasty side effects, like itchiness and sore eyes. So with a crystal clear pool that requires hardly any maintenance I do feel I am ahead of the pack in safety. To double check I will get a professional bacteria test done on my pool water, to see if my system is taking care of bacteria.