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Hey folks,

I think it would be a good topic if we all shared what electrical charging and management systems works well for you and your needs aboard. Obviously it is all down to replacing the amperage juice we like to consume on a daily basis. On Cookie, we have mainly shunned electrical technology over the years but during last years adventure I wanted to keep in touch with family and any followers of the Jester Challenge. Here's what worked really well for us:

An 80Ahr AGM battery that feeds a 10watt masthead light, cabin lights, 12V outlet sockets and a NASA AIS radar display. I worked out that running the AIS display, 2x handheld GPS and charging satphone, VHF periodically we used approx. 0.5Amps - so about 12 Amps per day.

To charge up again we used an Aquair 100 water towed generator. It worked really well and as long as we were doing about 5kts plus it would top up the battery in about 4 hours after every 3 day period. Of course if I used cabin lights a lot or the masthead light I would be charging much more. The Aquair from Ampair did slow us down about 1kt when towing, but hey Cookie is only a 500kg lightweight - I expected some sort of performance loss when towing. In fact one or two of the other monohull Jester sailors towed their water chargers 100% of the time to keep on top of radar set demands, autopilots etc. So for larger Wharrams, I doubt there would be any hull speed loss. Ampair state a load of pull from the towed propeller of around 40lbs at 6kts and that seems about right from what I observed on Cookie.

So although it was some manual work to deploy and retrieve the tow to charge each time, It meant that as long as we were not becalmed I had control of my green charging ability. For North Atlantic I think it was the perfect solution for us rather than solar panel and the lack of sun we had.

If I had a larger Wharram and wanted to go cruising without fossil fuels, I would probably have a combo of solar, wind charger and water towed charger.

What feedback do others have that works well for them? Equipment specific would be helpful.

Cheers, Rory & Cookie


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There were the sun is shining......We started in the Med, the boat is at the moment in Grenada.

in order to save weight, and efficiency , i am looking around the lithium battery because i am thinking electric motor also .

this is the better proposition i got :

on the right is  the last TORQEEDO battery  wich is  a must : lithium manganese, but still expensive !

on the left  is a good quality  pack lithium iron with same data  BMS included, almost half price and more cycles ?


                                             LINICoMnO2                            LiFePO4 (24V100Ah)
- Capacité :                               2.685 Wh                                          2640 wh 
- Tension nominale :                   25.9 V                                              26.4 V
- Tension finale de charge :         29.05 V                                            31.2
- Tension finale de décharge :     21.0 V                                               21.6  
- Régime de décharge (A) :         160 A                                               300 A 
- Régime de décharge maxi :        4.500 W                                          8000 W
- Poids :                                     20 kg                                               27,2 kg
- Dimensions :                        577 x 218 x 253.5                                290 x 220 x 272

Prix :                                      2399€ TTC                                        1300€ TTC (BMS compris)

- Cycle :                                 1000 cycles                                        3000 cycles

When making electrical connections I use vaseline (petroleum jelly) on the bare wires. I push the end of the  wire into the jelly and make sure it is worked well into the wirs and up to the insulation.  I have been using this technique for about 10 years on domestic quality wire and have not had any significant corrosion problems.



Rory McDougall said:

Hey Robert - will be interested to hear how the Forgen works and what output you get. It seems a much safer way to go for small boats than to have a high tubular frame with deadly windmill blades ready to take an arm or head off. The Air breeze I fitted gave me a good cut on one finger just by spinning the blades by hand in no wind!!!

I did just find a supplier of 80watt panels on ebay selling now for 155 pounds!! I wonder what the catch is??

Obviously the achilles heel of all electrical systems is resistance - and that mainly comes from connections and terminals as long as wire size is rated correctly. I advise using heat shrink connectors if you can afford them, otherwise I use sikaflex or 5200 forced into the open ends of the connectors once crimped to keep them as watertight as poss. A good spray with corrosion inhibitor afterwards works well to give your electrics a waterproof barrier. Cookie is a pretty good electrical test bed!!!

Cheers, Rory.

Hi all,


I need some help, I don't understand noting about eletric chargers.


My boat will have : Mast ligth, cabin ligths (2 each side), VHF with AIS built in 2100 Standart Horizon, GPS Garmin 421, Raymarine autopilot ST1000, litle fishfinder, bomb for pressure water (two ends), 2 bomb for water out(I don't know the exat name) one each hull.


I will think about 2x 75 amp batery, is too much?


And one 40 w painel solar ? is ok? rigid or flex?


I will sailing in Brazil and tropics,


please some help.


P.S. I like that Aquair from Ampair but the price? Here we hare a lot off sun...maybe solar panels is better.


Thanks Roger


I will use one mercury 8hp four stroke (without eletric start)

Bombs are bad on boats!!!   I think you mean pump

Hello Roger,

     A 40W panel will give you about 12 amphours per sunny day.  It will match to a 36 amphour battery.  Many panels have a maximum power point at about 17.5 volts.  The wattage of the panel is calculated at the maximum power point voltage.  If you are operating at 13.5 volts you will realize less wattage because the panels are constant current.  If you are using a MMP solar charge controller, it will give the rated wattage, but it will cost almost as much as an additional panel.  The charger I am using is made by Sunsei and it equalizes the batteries, but is not an MMP charge controller. 

     If you calculate your daily amphour use and divide by 5, it will give you the amp rate necessary from your panels.  Multiply that number by 17.5 to get the total wattage required.  Battery capacity should be about 3 times the daily amphour use.


     I hope this helps.


Andy, thanks I understand and calculate aft.


Boatsmith...kkk...here in Brazil, the pump we call "bomba" and very similar "bomb" ... hehehe in Rio de janeiro we don't use bombs only machine guns...

I'm a long time from the water, but am working in theory for when I complete a tiki 30 or 38. Anyway I have an idea that I wonder what you more experienced folk think of it.

I'm designing a Hydrokinetic wave energy converter. think of a stainless box with sealed shaft protruding to which you attach a carbon pole that extends down from say the forward beam to a float resting on water just north of, or between the outboards.

The shaft is attached to a ratcheting mechanism that drives a gear that in turn spins a flywheel. The flywheel is coupled to an alternator to charge batteries. The action is when any wave pushes up on the float force is sent to the flywheel, when the wave troughs the paddle drops to repeat on next wave.

This charging could be used at anchor or underway, in clouds or dark of night. Not being a trailing prop, water current not required, and very little drag on the boat. the energy to lift a boat should provide ample drive energy to offer more or less continual dc energy. I suppose you could rig an off switch for the field current, you could automate something from charge controller for when you had totally full can in the lead acid array.

if the flywheel was well engineered and boxed it should have very little noise associated with it's use, be sealed from corrosive effects etc...

What say you? would a wave powered generator be something the cruising community might be interested in?



If I was building or sailing a bigger boat than a Tiki 21, I would certainly go for this:

It comes down to one simple thing, solar panels are now the result of 30 years of accreted development. They are solid state, reliable and efficient. Whatever you build will (sadly) break and be inefficient. I've a small 10W flexible solar panel one my 21 it cost £35. I now have charged lights, phone, VHF and pad computer. 

Respect the simple KISS principle.

Hi Robin,

would the rising wave not lift the boat as well, thereby negating most of the movement you plan to use to power your generator?


Hi Robert,

Since wave height, distance between tops and troughs, and direction is constantly variable, a bit of variability would have to be built in to optimize the result.

In my theory, I imagine being able to mount Wave Energy Converter, from any water craft. by lengthening the carbon rod (removable sections?) you could say position the paddle/float aft of the rudders while mounted to the front beam. I envisioned this thing between canoes on a cat to provide a bit of collision protection, but it could be mounted for, aft, or midship and hung over the side. As long as the paddle was lifted prior to the hull it was mounted to, the rise and fall of the wave should be energy harvestable.

Robert said:

Hi Robin,

would the rising wave not lift the boat as well, thereby negating most of the movement you plan to use to power your generator?


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