the perennial battery charging problem

[DaveS]

A fridge can certainly run down batteries, however it is a handy thing to have. My solution is to have the fridge (and a small dehumidifier) supplied via a VSR * such that it only takes power when I'm motoring or the boat is plugged in to shore power. Given reasonable insulation and a good thermal mass (cool blocks or, in my case, a double tier of draught Guinness cans) the fridge is quite happy being run intermittently.

* This is not quite as straightforward as it seems. With a charged battery on float it is possible for the voltage to stay below the VSR switch on level. To get round this I now have a relay in parallel with the VSR which is made when 230V is present. My original plan was to drive a relay from an "independent" output from the battery charger, but an attempt at this showed the output to be rather less independent than the manufacturer claimed...

 

[James Marinero]

Are you tidal?

If so a towed gen at anchor would supplement your power, I believe.

Wind - tick that
Water - tick that
Fire (fuel cell) - tick that (well, sort of)
Earth - now there's one to ponder on. Anchor chain with linear induction generator (is there such a thing)?

 

[Solent sailer]

I did think about an EFOY unit but decided against it because:

I finally went with:
1) Reduce usage a bit (LEDs & move to sl. warmer climate so no heating needed)
2) Fit some solar (65W)
3) Fit Wind gen (Rutlan 913)
4) Better batteries (golf cart type) well better than original leisure ones
5) Backup Honda petrol gen. (Hardly ever used now)

i have been very disappointed with the last few leisure batteries i have bought, i think our charger may be over charging them (14.8v all the time the engine is running!) and i cannot top up the batteries. a decent traction battery with caps to fill then seems the way to go, but has anyone found a decent suppler?

 

[Iliade]

... And then these windmills are noisy, have 4 foot diameter fans on them and are as ugly as h*ll.

If you plan on being anchored for long enough how about a cheap big domestic turbine, on a stick, on the end of a long wire, on the (hill above the) beach?

What could possibly go wro.
`~

 

[lw395]

It seems to me the cheapest solution might be a generator that is fuel efficient when producing 30A or so.
Bring back the YAPP micro-generator!
Plus it could give a useful amount of hot water or heating....

 

[wotayottie]

Thanks for the suggestions both practical and downright off the wall.

Given that my boat is a 35 footer, sufficient area for a full set of solar panels just isnt there. Friends real life experience of windmills suggest that they arent the answer either, leaving alone the issue of all the ironmongery they involve. My boat has a beautiful bum - putting a stainless steel gantry on her would be like putting Kylie's nether regions in a boiler suit.

So I guess the practical answer is a portable genny and a decent battery charger. With maybe as many solar panels as can be fitted to deck and sprayhood.

 

[Richard10002]

Thanks for the suggestions both practical and downright off the wall.

Given that my boat is a 35 footer, sufficient area for a full set of solar panels just isnt there. Friends real life experience of windmills suggest that they arent the answer either, leaving alone the issue of all the ironmongery they involve. My boat has a beautiful bum - putting a stainless steel gantry on her would be like putting Kylie's nether regions in a boiler suit.

So I guess the practical answer is a portable genny and a decent battery charger. With maybe as many solar panels as can be fitted to deck and sprayhood.

Kylies nether regions in a boiler suit would look just fine!

I have fitted a 100W solar panel, which seems to provide between 1 & 3 Amps over the course of a sunny day - which is pretty much neither use nor ornament if I am on board with the fridge running, amongst other stuff. It comes into its own when I'm not aboard for 3 or 4 days, when it can top up with 30 or 40Ah.

I say this when comparing the solar with the generator which can put 40Ah in in less than an hour, if the batteries are at a low enough SoC. I think I've said before that, at about 50% SoC my 70A charger runs at its full 70A for almost an hour.

Getting the genny out every day, or every other day, is a faff, as is buying the petrol and topping it up.

Given that you can buy a diesel built in genny for a few thousand quid, this may be worth considering if you live aboard, and can't see yourself selling the boat for many years.

 

[BruceDanforth]

On my mooring I use about 70aH per 24 hours, mainly on the fridge but with some for lighting. I suspect that my figure is reasonably typical for the majority who do not want to do the hair shirt camping on the water bit. Civilised sailing if you like with ice for the G&T.

Problem is how to keep up with it and do away with the hour or more per day of engine running.

According to the PBO test only the biggest of the windmills will generate that sort of output in typical UK breezes, and that ignores the losses in charging ( to get 70 aH in you need to generate more than 70aH) and the issue that we moor or anchor in sheltered spots where the wind is hopefully less than average. And then these windmills are noisy, have 4 foot diameter fans on them and are as ugly as h*ll.

But a 100 watt solar panel can only be expected to deliver 30aH during the 24 hours of a normal UK summer day so that means I would need something like 230 watts of panels to match the windmill which we already know isnt sufficient. At 100watts per square meter ( Solara smk220 type) that is 2.3 square meters of panel at a cost of about £1900. And where do I have that amount of spare space?

So has anyone found a solution to this conundrum other than running the engine or festooning the boat with ugly tube structures on the stern? Honest answers please and I am not interested in reducing consumption and standard of living on board.

Your solar panel costs look a bit whacky compared to Chinese panels from ebay.

 

[wotayottie]

I say this when comparing the solar with the generator which can put 40Ah in in less than an hour, if the batteries are at a low enough SoC. I think I've said before that, at about 50% SoC my 70A charger runs at its full 70A for almost an hour.

That comment puzzles me TBH. I used a friends clamp on ammeter on the battery leads to monitor my charging from the alternator with its sterling regulator. I cant remember the precise figures now, but the 60amp alternator never got quiteas far as 60amps and fairly rapidly fell back to 10 /15 amps or so once the voltage at the battery terminals reached 14.8 that is set. This is much what Sterling told me to expect.

How confident are you in your measurements? How are you measuring the amps? And what generator are you using - I have a Yanmar one in the garage but it is a heavy lump and only good for about 800 watts from memory.

 

[Richard10002]

That comment puzzles me TBH. I used a friends clamp on ammeter on the battery leads to monitor my charging from the alternator with its sterling regulator. I cant remember the precise figures now, but the 60amp alternator never got quiteas far as 60amps and fairly rapidly fell back to 10 /15 amps or so once the voltage at the battery terminals reached 14.8 that is set. This is much what Sterling told me to expect.

How confident are you in your measurements? How are you measuring the amps? And what generator are you using - I have a Yanmar one in the garage but it is a heavy lump and only good for about 800 watts from memory.

The figures were a bit of a guess but see below for a real time example

I have a clamp ammeter, (UNI-T), and a NASA BM-2 monitor. The NASA measures at the shunt, and the clamp at the charger, so there is a slight difference if things are running. Pretty confident re the measurements.

Generator is a Honda Eu20i. Charger is a Sterling Pro Combi S 2500W which has a 70A charger, (but see below).

As a real time example, I set the charger at open lead acid, so its Absorbtion charging mode is at 14.8A. Started at 10.55am with a SoC around 60%. 35 minutes later it's put in 41Ah, and is charging at 35A.

I usually start at 50% SoC, with Absorbtion mode set at 15.1V, so I would usually expect to get the full 70A for longer.

To complicate things a bit, my charger failed a couple of months ago, and Sterling supplied a new electronics unit for me to fit. After fitting, the charger starts at 80A, rather than the previous 70A. So I think I've actually got an 80A charger, rather than a 70A.

Update: Now after 53 mins of charging, it's at 20A, and has put 46Ah into the batteries. This doesn't allow for the 3 or 4 amps I might have used in the time, so maybe I've had almost 50 Ah in 53 mins.

 

[wotayottie]

That sounds much like my experience of charge rates tailing off albeit starting and finishing with bigger numbers.

What do you think of the Honda generator? Looks like quite a neat package and fairly practical to store and use on board.

 

[Richard10002]

That sounds much like my experience of charge rates tailing off albeit starting and finishing with bigger numbers.

What do you think of the Honda generator? Looks like quite a neat package and fairly practical to store and use on board.

I've no experience of any other generator. Had it since December or so. It's one of those areas where I decided to buy "the best", albeit second hand, and, so far, it's lived up to expectations.

It's quite heavy, (21kg), and SWMBO can't manoeuvre it up and down steps, or in and out of lockers. The Eu10i is only about 13kg, so much more manoeuvrable. It would probably run a 50A charger, but not the 80A charger or the Hoover, (50A x 15V = 750W)

If it wasn't for the charger, I might consider researching the smaller one.

 

[Greenheart]

Ultimate accessory for under-used mizzen masts...

View attachment 20936

How about one of these, spinning at the top of the mizzen mast? The Rutland 1803. Cranks out nearly half a kilowatt. And self-furls automatically, if the wind gets too strong. I'd agree it's an attractive idea to reduce reliance on electricity...

...but equally it'd be pleasant to know there's always a nice quiet quarter-tonne of 90%-charged batteries under the floor, easily enough to take care of your modest requirements, without ever having to run generator or auxilliary.

How long till somebody fixes dozens of long narrow strips of solar-panel into a furling boom, so they can unspool with the mainsail, or just whenever the amps are needed?

 

[AngusMcDoon]

On my mooring I use about 70aH per 24 hours, mainly on the fridge

Could you cope with less fridge volume? The Waeco compressor coolboxes uses a miserly amount of power compared to built in fridges, the smallest using 10Ah per day in UK conditions when run as a fridge.

Perhaps you could use the main fridge for when power is plentiful, and a coolbox when it isn't. This may solve your problem for not too many £€$¥.

 

[Greenheart]

Assuming nobody needs to be told that front-opening fridges are bad news for power-consumption, does anyone have a top-opening fridge with a sliding door, rather than one that sucks the coolness up and out, when the door is raised?

Tenting in the 'nineties, I used to wrap a champagne bottle in one of those 10mm foam sleeping mats, wound tightly round, with a T-shirt stuffed in the bottom to keep coolness and drips inside, and about a litre of ice cubes above the wine, then another T-shirt on top...

...and depite it being high summer (back when summer meant heat), the ice was still ice, at breakfast time next morning!

The champagne was nicely chilly too, and the lesson was learnt; insulate and don't disturb, and it isn't half easy to keep things cold.

 

[Iliade]

How about a top-loading three-way (gas (!!eeek!!), mains and 12v) fridge sat on deck somewhere or in a vented cabin you don't occupy?

You could even opt for installing a proper flue if you insist on having one in the galley, but not the best idea IMHO.

We have used one for years (now on second one) and never connected the 12v circuit to the boat (though I have had to jump start the car after forgetting to disconnect it when stopping overnight on the autoroute...)

Ours have always been in the saloon so we use gas when sailing and switch the thing off when 'indoors'. We usually switch to marina mains, but we just spent three weeks without power and nothing went off overnight.

 

[DaveS]

How about a top-loading three-way (gas (!!eeek!!), mains and 12v) fridge sat on deck somewhere or in a vented cabin you don't occupy?

You could even opt for installing a proper flue if you insist on having one in the galley, but not the best idea IMHO.

We have used one for years (now on second one) and never connected the 12v circuit to the boat (though I have had to jump start the car after forgetting to disconnect it when stopping overnight on the autoroute...)

Ours have always been in the saloon so we use gas when sailing and switch the thing off when 'indoors'. We usually switch to marina mains, but we just spent three weeks without power and nothing went off overnight.

These, however, are absorption cycle fridges. They have the advantage of silent running, but they are much less efficient than a compressor type.

 

[Pleiades]

Bootifull Batteries

I agree with Paul's criticism of the leisure batteries commonly found in chandleries and marketed as "heavy duty", "suitable for caravans, boats and engine starting" - complete twaddle. Proper batteries are either cranking batteries or service batteries - they are different things. Wasted 160 squid on a pair of these items as they were the only ones in stock at the swindlery. My last set of these "MaxRubbishPower" wonders lasted less than 20 months - after a few deep cycles they were scrap.
Decent batteries - Electric Vehicle AGM or Gel deep cycle batteries are far superior as service batteries and well worth the price - maybe three times as much per battery - a price differential which will be happily ignored when they don't suddenly collapse down to 10 volts half way across Lyme Bay as my PowerRubbishMax ones did on Friday night. Happily a call to Cornwalll Batteries - 01872 270011 prompted a white van attending upon my vessel at Falmouth Yacht Haven within 2 hours bearing two wonderfully heavy proper deep cycling Haze batteries. Hazebattery.com is the manufacturers web site - defintely worth a call if after real batteries.
And the answer to Wottayotty's question is to buy some nice oil lamps - one only needs a lecky light for reading - drink whisky with room temperature water rather than ice and buy the lamp oil in bulk to be cost effective, although re-equipping with a boat more in keeping with the oil lamps will be perhaps a tadge more expensive - but worth it of course

Robin
Pleiades of Birdham
MXWQ5

 

[Greenheart]

Are there any clever persons who can calculate how large an aqua turbine-screw would have to be, to spin a wind gen (through gearing), at a pace which would usefully charge batteries using just the tide passing the moorings?

All that vast weight of water pouring in and out of harbours every six hours, ought to represent an opportunity to gain amps.

I realise that Aquair-type towed chargers weren't designed to be used behind a stationary vessel, but...why not? How about a big frame-mounted collapsible fan, four/five/more feet across, with a pitch that a two-knot tide will turn...

...even if the amount of amps which such a system creates is small, the fact the tide is running 23 hours per day must make a difference. No breeze, no sun, no daylight required at all. Enough amps to run a very small beer-cooler, perhaps? Must be worth considering.

 

[DaveS]

I realise that Aquair-type towed chargers weren't designed to be used behind a stationary vessel, but...why not? How about a big frame-mounted collapsible fan, four/five/more feet across, with a pitch that a two-knot tide will turn...

I think you'll find that a tidal turbine big enough to generate significant power will also impose significant drag forces which will require to be met if it is to stay put. There is also the inconvenient fact that tidal turbine output varies with the cube of water velocity, so while some water movement might well take place 23/24, turbine output will follow a much more restricted profile. The turbine, if rated for Springs maximum, will on average produce a small fraction of this.