Compact DIY generator (Honda)

[Paul H (admin)]

How much was the Honda engine Jeremy? - it might suit MilliBee.

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[Jeremy]

I bought it secondhand for £30, but they are just under £100 new from here: http://www.seddondirect.co.uk/productDetails.asp?productID=371

I've modified mine by removing the centrifugal clutch and making up an adapter for the flywheel nut so that it now has one half of a flexible coupling on it (the other hald is on the alternator shaft.  The casting that the strimmer arm fitted to was machined down to allow a small brushless DC model aircraft motor to be fitted, working as a three phase alternator.  I still need to make up a case for the whole unit, with an extra silencer and some insulation to reduce the noise level still further, but with luck I should end up with a low voltage DC generator capable of delivering around 1kW maximum for a total cost of maybe £70 or so.

[Jeremy]

Here's a picture of my part completed mini-generator:



Ignore the carburettor hanging off the side, I'm still working on it!  The black thing is a spare brushless DC motor that I've fitted for testing.  It's a standard model aircraft type that costs around $40 or so.  The whole generator, including (empty) fuel tank is sitting on the palm of my outstretched left hand, whilst I took the photo.

A cargo electric bike seems a good starting point for a hybrid, Brian.

The motorised bike is illegal here, although legal in the USA.  I know of one person that has bought a motorised bike kit here and made it legal as a moped, but it was a lengthy and costly process to get it through motorcycle single vehicle approval and it needed a number plate, insurance, licence etc.  These kits are readily available from China and commonly sold on ebay - search ebay for "motorised bicycle" and you'll find hordes of them.

I'm thinking along the lines of a wind/electric hybrid for the duck punt.  Maybe add some decking to make a sleeping compartment, sit on the sole in a semi-reclined position and use a wind generator to drive the electric propulsion system, perhaps with some solar cells on the deck and the backup of the mini-generator (which might also be useful when camping if it's not too noisy).

[Paul H (admin)]

Jeremy,

That would be excellent for MilliBee and could fit under the bridge deck that Ancient has recommended - a box at the front of the cockpit with a hinged lid that provides a 12in deep seat in front of the companionway.

With the seat lifted the engine can be started, flexible exhaust pipe leading to the rear. The box will provide additional sound proofing. Is it quieter than a small 2 stroke outboard?

I'm very tempted to buy one - if so can you provide assistance with coupling a generator/pulley?


People have used solar regulators with DC generators, a capacitor for smoothing and the PWM efficiently and safely charges the battery. With the genny off PV panels can be switched into the regulator.

cheers
Paul

[Jeremy]

Paul, I'd be happy to do the same mods as I've done to mine for you, but bear in mind this is relatively unproven!  There is evidence that it will work, from this German chap who's done the same thing (more or less): http://www.torcman.de/faszination/praxis/jochen/honda-gx35_430-30.htm

My coupling is pretty much exactly like the one on the German site, except that I simply threaded the inside of an off-the-shelf Lovejoy L050 type coupling (http://www.lovejoy-inc.com/products/jaw-type-couplings/l-type.aspx).  As my motor came from a strimmer I machined the big strimmer pole mount down to give a flat surface to bolt the motor too, rather than use the flat plate that the German chap used.

The output from the motor as an alternator will be three phase AC so can easily be rectified to DC with 6 diodes.  I'm working on getting better throttle control, by seeing if I can't sense the voltage and use it to drive a small model aircraft servo, but the German chap just uses a simple screw throttle, so maybe this isn't needed.

Noise level is a bit higher than a small generator, but I've worked out a way to fit an extra silencer and plan on fitting the whole thing in an insulated box, with filters on the air inlet/outlet to reduce the noise still further.

[Paul H (admin)]

Jeremy,

For charging a battery any current will do if using a charge controller - so I think setting a comfortable noise level with an auto-shutdown at the end of charging is ideal.

On YouTube some people have used belt driven car alternators which easily produce 50A (720 Watts, 1HP-ish) for a fast charge.

cheers
Paul

[Jeremy]

Paul,

Car alternators are OK, but very big, heavy and inefficient when compared to the small BLDC motors used as alternators.  That little black motor in the photo is rated at 2800 watts, so more than double the maximum that a car alternator would deliver, plus it doesn't need energising in order to work, so is far more efficient.

The challenge is finding a motor with the right Kv (the rpm per volt ratio) to provide the voltage needed at a reasonable engine rpm.  These little engines run at around 7500 rpm for maximum power, but will be noisy at that speed.  Running them at 4000 to 5000 rpm makes them a lot quieter, but with the loss of a bit of power.  If we need around 15V out at 4000 rpm then a motor with a Kv of about 266 is needed.  The choice then seems to be from one of these:

http://www.hobbyking.com/hobbyking/store/__18175__Turnigy_Aerodrive_SK3_5055_280kv_Brushless_Outrunner_Motor.html  about $50, 60 A and Kv = 280, but with a small shaft of only 6mm

http://www.hobbyking.com/hobbyking/store/__13973__C6364_230kv_Brushless_Outrunner_Motor.html about $50, 90 A and Kv = 230 with a 10mm shaft

http://www.hobbyking.com/hobbyking/store/__13974__C6364_270kv_Brushless_Outrunner_Motor.html about $50, 2700 W, 90 A and Kv = 270 with a 8mm shaft

http://www.hobbyking.com/hobbyking/store/__4651__KD_63_34S_Brushless_Outrunner_206Kv.html about $43, 43 A and Kv = 206 with an 8mm shaft

http://www.hobbyking.com/hobbyking/store/__2130__KD_63_28S_Brushless_Outrunner_248Kv.html about $43, 48 A and Kv = 248 with an 8mm shaft

http://www.hobbyking.com/hobbyking/store/__5204__TURNIGY_50_65D_270kv_Outrunner_eq_4030AXi_.html about $30, 70 A and Kv = 270 with an 8mm shaft

The current ratings for these motors are the maximum they will tolerate, usually not for extended periods of time.  Derating them to around 1/4 to 1/3rd of the maximum is usually a good idea for cool running, so that last cheap $30 motor should really be rated at around 20 A or so for continuous use as a generator.  Still, 20 A is probably a fairly good charge rate for most purposes.  

These motors are current limited, rather than power limited, so running at a higher voltage will give more power from a given size of motor, albeit at a higher rpm.  If you can switch to a 24 V, rather than 12 V, system (and change to a different Kv motor) then more power could be delivered.  I'm looking at generating at around 48V and powering a high efficiency DC DC converter to deliver a regulated and current limited lower voltage, but this needs a low Kv motor, which in turn has meant rewinding one to get what I want.

[Paul H (admin)]

Jeremy,

Ideally 40A at 12V as that would drive an electric outboard at 2/3rd HP (500W) with a run-down battery. Useful for the "drifting towards sharp rocks moments" in a pocket cruiser.

That's why I suggested a car alternator, rugged and built for high temperature use at sustained speeds.

20A at 24V would be same power with 2 batteries in series, and 2 batteries would improve the range. But the outboard could only connect across one battery, so full power will only be available after the batteries are charged and returned to parallel connection.

-Paul

[Paul H (admin)]

For a DC-DC converter the Victron Orion 24/12-30 looks suitable.

20-35V input, 30A max, 13.8V output and it can be used as a battery charger. Just over £100.
http://www.victronenergy.com/dc-dc-converters/orion-dc-dc-converters-12v-24v-48v-96v/

-Paul

[Jeremy]

The easy (and cheap) way to get the outboard to run more efficiently from 24V is to bin the built in speed control and run it on a cheap Ebike brushed motor controller.  You can just use a throttle limiter (dead easy to set up) to restrict the motor to 12V or so, and the nice efficient PWM controller will do the rest.  Overall losses will drop, as long as you keep the high current wires from the controller to the motor as short as possible.  If the motor is one of those with resistive speed control (the ones with switchable speeds, rather than a continuously variable speed control) then you'll also see a useful gain in motor efficiency.  Here's an example of a cheap 500 W brushed motor speed controller that would probably do the job: http://www.ebay.com/itm/24V-500W-Brush-Motor-Controller-Electric-Bike-Scooter-/320764798230?pt=Other_Vehicle_Parts&vxp=mtr&hash=item4aaf126516

Alternatively, just use a bigger BLDC motor, which would still be a lot lighter and smaller than a car alternator and have much better efficiency.  If you want 40 A at 12V (say 15V from the alternator) then something like this would do the job: http://www.hobbyking.com/hobbyking/store/__5140__HXT_80_85_A_250Kv_Brushless_Outrunner_eq_70_40_.html

If it were me then I think I'd opt for the higher voltage solution, as that would give you more potential range from the better efficiency.  A chap over on the Boat Design forum did some mods to a cheap electric outboard that significantly increased the power and efficiency, one of which was to fit an electronic speed controller.

[Paul H (admin)]

(To prevent further hijacking of Brian's thread I've moved the Honda generator stuff here.)


I disassembled my El Cheapo electric outboard and it could well have resistors controlling the speed.
Here are the resistance readings (Ohms +/- 0.1) at each speed:

   Forward    Reverse
1   3.4            2.6
2   3.0            2.2
3   2.7
4   2.5
5   2.3

There are 4 wires going to the motor housing - which must contain multiple windings or more likely resistors.

[Jeremy]

Yes, you have one of the resistive speed control motors.  Denny Wolfe (over on the Boat Design forum) made some interesting posts on improving a motor very like yours.  He fitted a PWM speed control and gained 16% efficiency straight away, so worth doing.  This post: http://www.boatdesign.net/forums/boat-design/efficient-electric-boat-27996-17.html#post305142 summarises all the mods he did and the performance impact of each.  Denny used a model car speed controller (as they have reverse), but the electric bike ones are cheaper and can be made to reverse with a two pole changeover switch or relay.  The electric bike controllers are rated for input current, so a 24V 30A controller would output 12V at up to 60A if set to half throttle maximum as a voltage limiter for a 12V motor.  They have active current limiting to help protect things from going up in smoke.

Denny posted a follow up to the one linked to above that has some photos of his final installation: http://www.boatdesign.net/forums/boat-design/efficient-electric-boat-27996-28.html#post381261

The 20 A 12V DC DC converters I have came via ebay and were around $15 each (they are these: http://www.astrodyne.com/ecatalog/usa/high-reliability/UV48-12 ).  They accept 36 to 72V at the input and give out a regulated (and adjustable) voltage from 10.8V to 13.2V (12V +/- 10%, adjustable with a trim resistor).  The new price is in the hundreds of $, but they appear on ebay as surplus from time to time (as do many other types of DC DC converter modules).

Jeremy

[Jeremy]

I've just had another thought about regulating the output of the mini generator.  The cheap ebike brushed motor controllers are simple PWM switched mode converters.  They have a fairly wide input voltage range (and are easily available for up to 48V input).  This opens up the possibility of having a cheap BLDC model aircraft motor running as an alternator and putting out around 36V or so, via a rectifier and smoothing capacitor.  This could then feed the brushed ebike controller and give whatever voltage output was needed, from 0 to the input voltage, adjustable via the controller "throttle" control.  Fitting a simple voltmeter and maybe an ammeter on to the unit would allow it to be adjusted to meet a range of output requirements.  Better still, adding one of these: http://www.hobbyking.com/hobbyking/store/__10080__Turnigy_130A_Watt_Meter_and_Power_Analyzer.html would provide a display showing voltage, current, power etc all in one small unit.  The output of the ebike controller would need smoothing, ideally with a small high current inductor and capacitor, but it may well be OK fed directly to a battery.

[Anders]

So how much noise will this thing make and will it be legal use?

I have to admit that I´m really against the use of generators in the nature. Its soooooooo annoying.

[Paul H (admin)]

I totally agree with you Anders. However consider the limitations of my 14ft x6ft pocket cruiser on the River Thames:

Really, really hard to row due to massive drag compared to a rowing boat/canoe

Wind is intermittent and sheltered by trees, sailing is impossible 75% of the time

Electric outboard used for the first day of the 2009 Raid, then battery flat

   - first campsite had electric, but only a partial charge due to small 4A charger, needed 20A+ charge

Electric outboard worked for few hours next day, battery flat, then switched to 2-stroke outboard

Remaining campsites had no power, could not charge battery, so forced to use 2-stroke outboard

  - but 2-strokes create oil pollution in the water (50:1 petrol:oil mix)

Better to use a 4 stroke (no oil pollution)

Used electric outboard in locks, so silent and zero pollution for my rowing/paddling HBBR buddies

  all squashed into a small space

If I could charge battery every 10 miles on the Thames the whole trip could be silent electric

  - "Environment Agency" that look after rivers are in the Dark Ages

  - The cater for the huge diesel boats who pay huge licence fees, some with

      10L engines that create huge pollution far, far greater than a small boat

      Ratio of big motor boats to small boats is literally 50:1

  - because they cater for huge diesels electric charging facilities are a joke.

  - so where does the electricity come from?

A 4-stroke generator can be used discreetly....when my paddling/rowing buddies are close by

   I can turn it off and run from the (charged) battery 

   At a campsite the moored boats will be some distance from tents, so an evening

   charge with the genny might not be heard above the revelry of HBBR chaps on the beer/whiskey

   One campsite was near a weir - I guarantee you would not hear a quite genny above the

    24/7 noise of the weir

In terms of pollution - similar CO2 to driving a car. So using a car at start/end of raid creates

  more CO2 than a small boat could. 

I-Paul

On 21 December 2011 09:16, Anders [via UK HBBR Forum] <[hidden email]> wrote:

So how much noise will this thing make and will it be legal use?

I have to admit that I´m really against the use of generators in the nature. Its soooooooo annoying.

http://news-from-the-workshop.blogspot.com/

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[Jeremy]

If we go for a DC DC converter solution then I've just found a box of Acon DH50S24033 DC DC modules that I bought a while ago for a cell level charger.  Unfortunately I couldn't get them to trim up to 3.65V, so they were no use for my project (they were only a couple of dollars each via ebay).  I think I have around 20 of them altogether.  Anyway, they are fully isolated, so their outputs can be connected in series and their inputs in parallel.  The input voltage is 18 to 36V, the output voltage is 3.3V nominal, but will trim from 3.2 to 3.4V via a trim pin according to the data sheet.  However, I've just tested a couple and they trim to 3.44V when the trim pin is connected to the negative output, so you can get a little bit more from them.  Four connected in series would give 13.76V, probably OK for 12V battery charging.  Their rated output current is 16A each, a bit less than you might have wished for, but possibly OK.  I think it might well be feasible to run them in parallel pairs, so eight could probably be wired to give 13.76V at 32A.  They have full over current, over voltage and over temperature protection.  You're welcome to a bunch of them if you decide to go down this route, Paul.

[Anders]

Admin
I totally understand what you say..... But I´ve so many places now where stupids have used their generators in nature to charge cellphones, to use refigerators, laptops, dvd players etc , that it really is one of the thing that I think should not be allowed to be used. There must be some limits somewhere. I have a feeling that you´ll be a discreet user but you´re just one.
Actually I dont like the use of electric engines if it mean that one has to use a generator. Then I prefer a 2,5hp fourstroke, which´ll be turned of when not in use. My experience is that the generator will just mean more of the above mentioned use, more noise. etc. Cant you charge with a wind generator???

[BrianP]

Early on in the Duck Punt thread, Jeremy explained he was planning solar and wind power to charge batteries and use the micro genset as a backup. If running this micro set can be achieved with good soundproofing then that will be good.

I know my similar engined hedge cutter is very noisy indeed, so feel sure Jeremy and Paul will work to reduce sound effects to a minimum. I was driven crazy one lovely summers evening on a campsite by a generator running next door all evening. When I queried next day what they were charging for so long, it turned out to be the son's I-Phone!

Brian

[Paul H (admin)]

Anders,

Small wind turbines (the ones you have seen on yachts) have a minimum wind speed to turn, usually 5 knots, and then they only generate about 25-100 Watts in a strong blow which is not enough power.

For 1HP you need 750 Watts so it would take a tremendous amount of time to charge the batteries....and if the wind is blowing enough to spin the turbine I'll be sailing! (as nature intended).

A generator can be made quieter than a 4-stroke outboard by fitting it into a sound insulated box, also additional expansion boxes can be added to further reduce noise.

The generator only needs to run when the boat is moving by making sure it produces enough power for the desired boat speed - e.g. just enough power to stop the battery running flat. It also means the generator can be switched off and the battery provides power - by locks, busy areas, at night etc.

One day the "Environment Agency" will provide easy electric charging along rivers powered by offshore wind turbines......then fossil fuel engines and generators can be scrapped.

-Paul

[tony waller]

I really like the idea of this tiny generator. All of us on the Thames raids will remember the problems of flat phone and motor  batteries.  Regarding noise, at one time I worked for an air compressor manufacturer and, as a project, they designed and a made a box to go round a large ( ca. 20hp) compressor and it was so quiet that it could be quite difficult to tell whether it was running. The box had to allow for a lot of airflow for cooling and the air inlet itself. The sound proofing of the airflow channels was achieved with felt baffles although these days one would probably use the special sound absorbing foam which is also fire-resistant. I think that it would be quite easy to make it so quiet that the main problem would be forgetting to turn it off.Tony

 

From: adminHBBR [via UK HBBR Forum] [mailto:[hidden email]]
Sent: 22 December 2011 12:04
To: tony waller
Subject: Re: Compact DIY generator (Honda)

 

Anders,

Small wind turbines (the ones you have seen on yachts) have a minimum wind speed to turn, usually 5 knots, and then they only generate about 25-100 Watts in a strong blow which is not enough power.

For 1HP you need 750 Watts so it would take a tremendous amount of time to charge the batteries....and if the wind is blowing enough to spin the turbine I'll be sailing! (as nature intended).

A generator can be made quieter than a 4-stroke outboard by fitting it into a sound insulated box, also additional expansion boxes can be added to further reduce noise.

The generator only needs to run when the boat is moving by making sure it produces enough power for the desired boat speed - e.g. just enough power to stop the battery running flat. It also means the generator can be switched off and the battery provides power - by locks, busy areas, at night etc.

One day the "Environment Agency" will provide easy electric charging along rivers powered by offshore wind turbines......then fossil fuel engines and generators can be scrapped.

-Paul

http://www.millibee.com

 

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