12v hot water heater?

[Seagreen]

Refit time! And I'm looking for a small and efficient 12v instant hot water maker, for basin washing only, not to power a shower.
Are there any new-ish devices which will do this, without being attached to a generator? This only has to heat perhaps 2l at a go and run straight off a 125Ah battery, so charging requirements aside.
Size and cost are the most important considerations.
TIA

 

[macd]

I think there are such things as 12V kettles in the US, but I've never seen one in Europe. All I know of over here are a sort of 12V immersion-heater type element with a handle, which you dangle in your water. Not massively convenient, I'd have thought.

Raising your 2 litres by just 30C would also take a bit of power: around 40A at 12V to do the job in 8 minutes, although that's only a little over 5Ah in total.

So my question, prompted by yours, is does anyone make a neat solar water heater of a size suitable for boats?

 

[Mistroma]

I was about to say the same thing. Approx. 2 litres from 10 - 50C in 5 mins. would draw approx. 93A (rough estimate) when heating.

I imagine the market will be quite small and any product difficult to find and expensive. The plug in car versions are only suitable for a small mug and take ages to warm the water enough for tea.

 

[Hydrozoan]

I bought a 12V kettle (in the UK) for emergency if we run out of gas, and it takes what seems like an age (but probably <10mins) to heat perhaps ~400ml of water. The current draw is ~10A or slightly more - which fits roughly with Mac's 40A for 2litres in 8mins. I have 2x110Ah domestic batteries, which is fine, but I fear that you may be disappointed in the speed and efficiency for frequent use.

 

[Trundlebug]

Roadpro are a good source for such things, they also sell a 12v sandwich toaster if ever you should want one. Edit: well they used to, I can't see one now

https://www.roadpro.co.uk/retail/12...ter-heaters/12v-kettles/12v-jug-kettle-76.htm

 

[pvb]

There are small instantaneous water heaters which fit over sinks - we have a Triton Handwash heater in a changing room at home. However, they run on mains and the smallest power rating is around 3kW. This is achievable with an inverter, but you'd need a big battery bank.

There are also small oversink heaters which store around 5 litres of heated water. You can get these with 2kW heater elements, allowing a smaller inverter and fewer batteries.

Perhaps your best bet would be to make your own oversink heater, using a 12v element. As it stores a volume of heated water, which is immediately available, it doesn't really matter if it takes a relatively long time to heat up (and to reduce battery drain you could heat it up when the engine's running).

 

[jwilson]

I think there are such things as 12V kettles in the US, but I've never seen one in Europe. All I know of over here are a sort of 12V immersion-heater type element with a handle, which you dangle in your water. Not massively convenient, I'd have thought.

Raising your 2 litres by just 30C would also take a bit of power: around 40A at 12V to do the job in 8 minutes, although that's only a little over 5Ah in total.

So my question, prompted by yours, is does anyone make a neat solar water heater of a size suitable for boats?

For actual "instant" hot water from 12v you'd probably be looking at 200-300 amp draw, much like a starter motor. Very heavy cabling would be needed, leaving a tap on for long would kill a battery: no-one makes one as a standard product.

 

[Mistroma]

Roadpro are a good source for such things, they also sell a 12v sandwich toaster if ever you should want one. Edit: well they used to, I can't see one now

https://www.roadpro.co.uk/retail/12...ter-heaters/12v-kettles/12v-jug-kettle-76.htm

Doesn't alter the laws of physics I'm afraid. They claim 15 minutes to boil mugs using 10A. Must be small mugs as 2*200mls would draw about 13.5A for 15 minutes. So heating 2 litres from 10-45C would take about 30 minutes if directly wired to a battery. Probably more like 40 minutes, so not that instant.

 

[jakeroyd]

An interesting question.
The inefficiency here is obvious.
Got me thinking these devices may be ok if the engine , hence alternator is charging.

However there is more energy available from waste heat from combustion than from driving the alternator so this best explains why we have a heat exchanger and calorifier ?

 

[PotatoNavigator]

Quicker and easier to stick a pot on the gas stove than to use a 12v kettle IMHO. I've got a solar heater, but can't comment on it's effectiveness, never used it! Always forget to hang it up in time to do the washing up.

 

[Hydrozoan]

… Perhaps your best bet would be to make your own oversink heater, using a 12v element. As it stores a volume of heated water, which is immediately available, it doesn't really matter if it takes a relatively long time to heat up (and to reduce battery drain you could heat it up when the engine's running).

I see the logic – but even then you’d have to think about just how long you might want to wait and the cable size necessary, especially if it was a long run from the battery. You’d presumably also need a thermostat (or mixer valve) for safety. A calorifier (is the smallest 10 litres?) would be much more efficient - and whilst it would of course introduce other issues, 2 litres doesn’t go far either.

 

[Iliade]

I used to have a gas geyser for this. Almost in keeping with your boat and it actually worked

 

[prv]

Perhaps your best bet would be to make your own oversink heater, using a 12v element. As it stores a volume of heated water, which is immediately available, it doesn't really matter if it takes a relatively long time to heat up (and to reduce battery drain you could heat it up when the engine's running).

If it's only going to heat up while the engine is running (and I agree any decent sized unit is rapidly going to knacker the batteries otherwise) then it might as well just be a conventional calorifier and save the inefficient conversion to electricity and back.

Pete

 

[pvb]

If it's only going to heat up while the engine is running (and I agree any decent sized unit is rapidly going to knacker the batteries otherwise) then it might as well just be a conventional calorifier and save the inefficient conversion to electricity and back.

No, it could heat up anytime. Heating up a few litres with a 12v kettle element would draw about 15A for maybe 45-60 minutes. The OP mentioned a single 125Ah battery, which would take a big hit with this sort of load (taking about 25% of its charge), hence suggesting heating when the engine's running. With thermostatic control, the storage heater would keep the water at the desired temperature. It's not a great solution, but might work for the OP who apparently doesn't have a calorifier.

 

[Alpha22]

There are a number of 12 volt water heaters for washer jets.... not sure how much and how continuous the flow would be..

http://www.laserlinedirect.com/prod...stem/heatshot-heated-washer-fluid-system.html

http://www.autoanything.com/driving-accessories/69A5007A0A0.aspx

 

[Mistroma]

There are a number of 12 volt water heaters for washer jets.... not sure how much and how continuous the flow would be..

http://www.laserlinedirect.com/prod...stem/heatshot-heated-washer-fluid-system.html

http://www.autoanything.com/driving-accessories/69A5007A0A0.aspx

No matter what you buy you will still hit a problem with the properties of water. These products will heat a dribble of water a bit. They won't get 2 litres of water up to 45C in any reasonable time (even if perfect insulation is assumed).

 

[Plum]

Refit time! And I'm looking for a small and efficient 12v instant hot water maker, for basin washing only, not to power a shower.
Are there any new-ish devices which will do this, without being attached to a generator? This only has to heat perhaps 2l at a go and run straight off a 125Ah battery, so charging requirements aside.
Size and cost are the most important considerations.
TIA

The only 12v water heater i have see is this http://www.piratescave.co.uk/whale-12v-water-heater.ir not instantaneous but at that price and the big battery you would need i am not sure why anyone would buy one.

Www.solocoastalsailing.co.uk

 

[Mistroma]

The only 12v water heater i have see is this http://www.piratescave.co.uk/whale-12v-water-heater.ir not instantaneous but at that price and the big battery you would need i am not sure why anyone would buy one.

I did say in post #5 that "the market will be quite small and any product difficult to find and expensive". Wow, hadn't thought it would have RRP £500.

Their figures look a bit dodgy. Current 30A @12V and 300W (??) to heat 12 litres to 60 °C in an hour.

Well heating 12 litres of water from 10 - 60 °C 2.512MJ and over an hour you'd need about 700W. But they claim 300W and 30A @ 12V is still only 360W.

So it is going to take closer to 2 hours to get from cold to max. temp.
You'd only get from 15 - 45 °C in an hour. So start with water that isn't very cold and heat it a bit.

But it is keenly priced wit a discount bringing down to only £450 and you don't need an expensive inverter or charging source Just a big battery and ideal for use with an outboard. Better rush out now before they are sold out.

Actually, they must be aiming at dive boats. I suppose a RIB with a 100HP outboard would have a big enough alternator to run this device. Hope nobody leaves it on a few miles offshore and gets a flat battery.

 

[AngusMcDoon]

I've got a solar heater, but can't comment on it's effectiveness, never used it! Always forget to hang it up in time to do the washing up.

You don't hang them up, you lay them down to heat. They take half a day of good sun, but you get 10 litres of pretty hot water.

 

[pcatterall]

My little gas water heater would heat water for the heads and galley sinks but now we are in warmer climes it overheats the galley so is redundant.
There is the gas issue of course and also the need to vent the unit if there is more than one sink plumbed in. I think the units new were only about £200 Saunier Duval enters my head (but so do lots of things)!!