Brewing Up with an Inverter on a small boat

freddyuk

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You need the same amount of "power" to heat a kettle of identical amounts of water using 900w or 3000w it just happens quicker with 3000w.
A starter battery is not the same as a leisure battery. Starter battery is used for a few seconds at high amperage to turn the engine over which once fired up is then recharging the battery instantly. A kettle via an inverter is dragging out high amperage over a much longer period ie. minutes, so will damage a starter battery by taking it down to a deeper discharge which can damage the cells permanently so it will fail sooner. There are losses via the inverter too. (about 20%)
Having a large inverter just to make a cup of tea makes little sense. Very little else requires 3000w on a boat. A correctly installed gas hob is safe. A table top camping burner less so.
I used to install offgrid solar and imported several versions of cheap Ebay inverters and have a video somewhere of my tests before I would ever sell them and many went up in smoke which meant they were scrapped. Not worth the risk on a boat. Buy Coteck as one of the best providing it has a hardwired option but they cost money of course.
Just my tuppenceworth.
 

limecc

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I think I have roughly worked up that for a 6 - 7 Min on the little kettle will pull about 12 - 15 amp hours out of the Battery so no issue I recon. Will test it on the battery at home first

Hi Dennis,
Can you share your calculation?
Mine's different.

A 900w appliance draws 3.75a at 240v but this equates to a continuous 75a load on a 12v battery.

What size and type battery were you thinking?
Lead acid suffer degrees of shortened life or permanent damage below 50% (12v) charge so if you've got a large 100ah battery there's only 50ah theoretically available.. at low draws. Higher ones and Peukert's Law applies reducing it to as little as 15 to 30ah true capacity depending on the C rating and age of the battery and if the ambient temperature's not too cold (can reduce further 10-50%).

From the spec your inverter only supplies 650w continuous so you would be overloading of it worked at all. With a low voltage trip of 9v it has the potential to destroy a SLA battery on first use.

Better go lithium, get a bigger inverter, or better stick with the flask or gas camping stove. Maybe you can find some folding sheet metal box to put the stove in?
 

Bigplumbs

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Hi Dennis,
Can you share your calculation?
Mine's different.

A 900w appliance draws 3.75a at 240v but this equates to a continuous 75a load on a 12v battery.

What size and type battery were you thinking?
Lead acid suffer degrees of shortened life or permanent damage below 50% (12v) charge so if you've got a large 100ah battery there's only 50ah theoretically available.. at low draws. Higher ones and Peukert's Law applies reducing it to as little as 15 to 30ah true capacity depending on the C rating and age of the battery and if the ambient temperature's not too cold (can reduce further 10-50%).

From the spec your inverter only supplies 650w continuous so you would be overloading of it worked at all. With a low voltage trip of 9v it has the potential to destroy a SLA battery on first use.

Better go lithium, get a bigger inverter, or better stick with the flask or gas camping stove. Maybe you can find some folding sheet metal box to put the stove in?



I have been brewing up using that inverter for about a year and a half now and all is working very well in my camper van. In which I have a 100 amp hour leisure battery connected to the alternator via a charge harness via a 'non return' device. It also has a wire that you earth to use the leisure battery as an emergency starter battery.

I hear so much theory about batteries having flown RC Turbine, Glow, Petrol and loads of Lipo stuff that to be honest it all leaves me rather cold. What I do know is that my set up in the Camper van works very well and at the end of the 6 - 7 min cycle the battery is still way over 12.7 volts. It boils such a small amount of water that it all works very well. I will soon test it on my smaller 80 Amp hour battery in the Rib which will have been charged to the hilt on my journey to the brew up location.

As for the gas stove If you read my posts you will see that the danger involved in that in my small rib is considerable. Yes on my sealine S24 and my 19 foot Bow Rider the gas is the way to go but not on the small 4.5m rib which can at times get quite cluttered.

Also worth remembering that some people just use these

12V In Car Water Soup Tea Coffee Baby Bottle Immersion Heater Boiler Element NEW | eBay

Regards

Dennis
 
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Bigplumbs

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You need the same amount of "power" to heat a kettle of identical amounts of water using 900w or 3000w it just happens quicker with 3000w.
A starter battery is not the same as a leisure battery. Starter battery is used for a few seconds at high amperage to turn the engine over which once fired up is then recharging the battery instantly. A kettle via an inverter is dragging out high amperage over a much longer period ie. minutes, so will damage a starter battery by taking it down to a deeper discharge which can damage the cells permanently so it will fail sooner. There are losses via the inverter too. (about 20%)
Having a large inverter just to make a cup of tea makes little sense. Very little else requires 3000w on a boat. A correctly installed gas hob is safe. A table top camping burner less so.
I used to install offgrid solar and imported several versions of cheap Ebay inverters and have a video somewhere of my tests before I would ever sell them and many went up in smoke which meant they were scrapped. Not worth the risk on a boat. Buy Coteck as one of the best providing it has a hardwired option but they cost money of course.
Just my tuppenceworth.

Not Sure
 
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DrSpock

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You need the same amount of "power" to heat a kettle of identical amounts of water using 900w or 3000w it just happens quicker with 3000w.

I think you mean energy as opposed to power however either way it's incorrect. In practicality heat loss from a boiling kettle is substantial and the longer it takes to heat it the greater the heat loss that occurs. Other things to add into the equation are inverter efficiency at different loads but I think we all agree (apart for the OP) boiling a kettle with an inverter is daft.
 

Bigplumbs

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I think you mean energy as opposed to power however either way it's incorrect. In practicality heat loss from a boiling kettle is substantial and the longer it takes to heat it the greater the heat loss that occurs. Other things to add into the equation are inverter efficiency at different loads but I think we all agree (apart for the OP) boiling a kettle with an inverter is daft.

Apart from the fact that the OP has done it many many times and it is safe and works very well. Do tell Mr Spock do you actually own an inverter and if so have you tried it ?
 

limecc

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Although nice, unless there are nearby toilet stops on the Deben, having a drink on a SIB presents other problems. What goes in must come out and in full public view! :coffee::oops: Worse for Mrs Plumbs to find somewhere of course..
 

Bigplumbs

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Although nice, unless there are nearby toilet stops on the Deben, having a drink on a SIB presents other problems. What goes in must come out and in full public view! :coffee::oops: Worse for Mrs Plumbs to find somewhere of course..

Well that is never a problem
 

freddyuk

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I think you mean energy as opposed to power however either way it's incorrect. In practicality heat loss from a boiling kettle is substantial and the longer it takes to heat it the greater the heat loss that occurs. Other things to add into the equation are inverter efficiency at different loads but I think we all agree (apart for the OP) boiling a kettle with an inverter is daft.

Thanks for clarifying but I was generalising to make the point easy to understand rather then lecturing the science. You will note "power" was in inverted commas? The inverter would be labelled with power output thus the relationship could be made between power output and loads used. However you are correct in fact. The point is a whopping great inverter to make tea is not efficient or safe using a generic Chinese inverter.
 

Bigplumbs

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Thanks for clarifying but I was generalising to make the point easy to understand rather then lecturing the science. You will note "power" was in inverted commas? The inverter would be labelled with power output thus the relationship could be made between power output and loads used. However you are correct in fact. The point is a whopping great inverter to make tea is not efficient or safe using a generic Chinese inverter.
Perfectly safe been doing it for 2 years. Practical real use V theory from people who have not tried it wins every time in my book
 

limecc

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So you obviously haven't tried it with SIB or RIB yet then? Just the camper van, and that's got at least one battery, probably 100ah for the starter and same again if there's a leisure battery fitted. Are you planning to carry a bigger battery in either inflatable?
 
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DrSpock

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Apart from the fact that the OP has done it many many times and it is safe and works very well. Do tell Mr Spock do you actually own an inverter and if so have you tried it ?

I've had inverters from 300w to 3kw on boats - I think they all went in the bin at some point.

I'm not saying it doesn't work - it's just a massively inefficient process which makes it daft.
 

limecc

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I've got 400w of solar, 240ah storage in two leisure batteries and a 2kw (3kw peak) sine wave inverter. Even with this setup, for high draw items like the 900w microwave, it makes sense to use a generator for a few minutes. Am using a kettle on the gas cooker, else would run the genny and use an electric one. Larger size inverters are fan cooled and not very waterproof for smaller craft. Wouldn't mix very well, but if it proves to work for you Dennis when you try it then fine. Let us know. Prefer a latte ourselves lol.

Incidentally, for anyone who this applies to, I found Chinese circuit breakers are absolutely dreadful when used with large currents because of the voltage drop they induce. Fusible links of the same value are far better and allow you to get more power out of your battery before the load (eg inverter or caravan motor mover) trips because of low voltage. Also I learned that correctly wiring two batteries as one is important, you can't just wire them in parallel even if using 35 or 50mm/sq cable.
 
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Bigplumbs

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I've had inverters from 300w to 3kw on boats - I think they all went in the bin at some point.

I'm not saying it doesn't work - it's just a massively inefficient process which makes it daft.


I've had inverters from 300w to 3kw on boats - I think they all went in the bin at some point.

I'm not saying it doesn't work - it's just a massively inefficient process which makes it daft.

Did you bother to read my reasons for doing it with an inverter or did you simply not bother. Many people buy things like this and struggle to use them correctly and they end up binning them. I suspect it all boils down to lack of Knowledge and or lack of ability
 

Bigplumbs

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So you obviously haven't tried it with SIB or RIB yet then? Just the camper van, and that's got at least one battery, probably 100ah for the starter and same again if there's a leisure battery fitted. Are you planning to carry a bigger battery in either inflatable?

Oh dear you do seem to struggle to understand..... Would the real Limecc Please stand up
 

limecc

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Oh dear you do seem to struggle to understand..... Would the real Limecc Please stand up
Yep. Re-read your responses and don't understand. Please give me more to go on and tell if it works on the rib? 80ah simply not going to work imho, you're asking 75a continuous and your battery's rated 80a over 20 hours (when new). 'Charged to the hilt' isn't going to help. I wish I could be more positive, not meaning to be critical, just set your expectations.
 
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limecc

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Many people buy things like this and struggle to use them correctly and they end up binning them. I suspect it all boils down to lack of Knowledge and or lack of ability
You speak the truth! Using them correctly requires knowledge. Accurate knowledge not helped when mis-sold as 3kw when the continuous rating is only 0.65kw. Not sure I would feel safe using it, the earthing arrangement is non-existent.

Not sure ability comes in, anyone can connect croc clips and throw a switch.
 
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