12v versus 240v/inverter

[Paul Naylor]

Some of you were kind enough recently to help me with advice about ropes
for my co-owned barge in France.

There is now a debate over the advantages or otherwise of using 12v
small appliances (eg TV/Music Centre etc) as against buying (cheaper)
240 v appliances and running them through an inverter. The barge has a
battery charging system built in and the use of shore lines at overnight
moorings is commonplace. There is an inverter in place (although
apparently rather old and inefficient and requiring plugging in when
required) and there is a suggestion that this be replaced by an
automatic 800 watt device.

Some members believe that the use of 240v appliances would be more
likely to run down the batteries and, for example, knock out the fridge.

Any advice or comments would be welcome.

Many thanks

Paul

[David Long]

Post by Paul Naylor
There is now a debate over the advantages or otherwise of using 12v
small appliances (eg TV/Music Centre etc) as against buying (cheaper)
240 v appliances and running them through an inverter. The barge has a
battery charging system built in and the use of shore lines at
overnight moorings is commonplace. There is an inverter in place
(although apparently rather old and inefficient and requiring plugging
in when required) and there is a suggestion that this be replaced by an
automatic 800 watt device.
Some members believe that the use of 240v appliances would be more
likely to run down the batteries and, for example, knock out the fridge.

It's far more convenient to have a 240v (or 230v in France) system - all
the everyday household appliances are then available to you - cleaners,
hairdryers, fans etc..

I fitted a 230v fridge to my nb in France last year, and beefed up the
inverter to an 800 watt one. It's been great - but the inverter is at
the end of its range when the fridge kicks in - a bigger one would be
better. It should be wired in, but you need reliable battery capacity if
you're to have an automatic system - mine has a switch.

As you say, electricity on moorings is commonplace - but on a barge you
may find that you can't get near enough to the plugs - many moorings,
especially on rivers, are a single, small pontoon. In a narrow boat I
can swing half-on and half-off if a cruiser has got there before me - a
barge would have more difficulty. You will need a generator as well for
when you can't get to electricity. Many towns have wharves, but no other
facilities, so having independence is useful.

The length of time it takes an inverter to run down your domestic
batteries depends both on use and their capacity. It's surprising, in
the warmth of France, how often the fridge kicks in, drawing maximum
output.

[b***@reading-college.ac.uk]

I am fairly concvinced that a mains A rated fridge plus inverter is
probably just as efficient as a 12v fridge or possibley a little more
so, however one must look at the efficiency of the inverter.

A 2000 watt inverter that is 95% efficeient would waste about 3 amps
doing its inverting at 12v input, however if it was only producing say
4 amps running a radio it would be very inefficient because it would
still be using that 3amps within itself (or so says my electronic
collegues) - I await correction if I have been misinformed!

So perhaps it is best not to purchase too large an inverter.

Tony Brooks

PS Hope thsi post gets through better than my last one.

[Allan Jones]

Post by b***@reading-college.ac.uk
I am fairly concvinced that a mains A rated fridge plus inverter is
probably just as efficient as a 12v fridge or possibley a little more
so, however one must look at the efficiency of the inverter.
A 2000 watt inverter that is 95% efficeient would waste about 3 amps
doing its inverting at 12v input, however if it was only producing say
4 amps running a radio it would be very inefficient because it would
still be using that 3amps within itself (or so says my electronic
collegues) - I await correction if I have been misinformed!
So perhaps it is best not to purchase too large an inverter.
Tony Brooks
PS Hope thsi post gets through better than my last one.

I looked up a few fridge specs and did some quick calculations recently.
This was the result (unless anyone knows better?):

Shoreline's latest 12 volt fridge, the RR47, is quoted as having an average
consumption of 0.95 Amps/Hr. Assuming they actually mean that the average
consumption is 0.95 Amps, this equates to about 100 Kilowatt-hours per year.
A quick look at the specification of similar-sized mains fridges shows that
even the best A-rated models consume between 150 and 230 KWh/yr. The cheaper
models are generally B-rated, and take even more power. Thus IF the test
conditions are similar, it is still better to use a 12v fridge.

[Richard Edwards]

On Thu, 7 Apr 2005 08:53:52 +0000 (UTC), "Allan Jones"

Post by Allan Jones

Post by b***@reading-college.ac.uk
I am fairly concvinced that a mains A rated fridge plus inverter is
probably just as efficient as a 12v fridge or possibley a little more
so, however one must look at the efficiency of the inverter.
A 2000 watt inverter that is 95% efficeient would waste about 3 amps
doing its inverting at 12v input, however if it was only producing say
4 amps running a radio it would be very inefficient because it would
still be using that 3amps within itself (or so says my electronic
collegues) - I await correction if I have been misinformed!
So perhaps it is best not to purchase too large an inverter.
Tony Brooks
PS Hope thsi post gets through better than my last one.

I looked up a few fridge specs and did some quick calculations recently.
Shoreline's latest 12 volt fridge, the RR47, is quoted as having an average
consumption of 0.95 Amps/Hr. Assuming they actually mean that the average
consumption is 0.95 Amps, this equates to about 100 Kilowatt-hours per year.
A quick look at the specification of similar-sized mains fridges shows that
even the best A-rated models consume between 150 and 230 KWh/yr. The cheaper
models are generally B-rated, and take even more power. Thus IF the test
conditions are similar, it is still better to use a 12v fridge.

Now that is a really sensible post!!!!
Obviously the statement "IF the test conditions are similar" is the
biggest question.
Personally I would always go for a DC fridge.

Richard

Nb "Pound Eater" Parkend G+S

[David Long]

Post by Richard Edwards
On Thu, 7 Apr 2005 08:53:52 +0000 (UTC), "Allan Jones"

Post by Allan Jones
Thus IF the test
conditions are similar, it is still better to use a 12v fridge.

Now that is a really sensible post!!!!
Obviously the statement "IF the test conditions are similar" is the
biggest question.
Personally I would always go for a DC fridge.

But in France 230v shore supply is commonplace - and often paid for as
part of your mooring fee (and often free) - so, since you're tied up for
longer than you're cruising each 24 hours, going for 230v makes better
sense.

[martin]

Post by David Long

Post by Richard Edwards
On Thu, 7 Apr 2005 08:53:52 +0000 (UTC), "Allan Jones"

Post by Allan Jones
Thus IF the test
conditions are similar, it is still better to use a 12v fridge.

Now that is a really sensible post!!!!
Obviously the statement "IF the test conditions are similar" is the
biggest question.
Personally I would always go for a DC fridge.

But in France 230v shore supply is commonplace - and often paid for as
part of your mooring fee (and often free) - so, since you're tied up for
longer than you're cruising each 24 hours, going for 230v makes better
sense.

The standard EU mains voltage is 230 volts +/-10 volts both UK and
France are compliant with this.

[Richard Edwards]

Post by David Long

Post by Richard Edwards
On Thu, 7 Apr 2005 08:53:52 +0000 (UTC), "Allan Jones"

Post by Allan Jones
Thus IF the test
conditions are similar, it is still better to use a 12v fridge.

Now that is a really sensible post!!!!
Obviously the statement "IF the test conditions are similar" is the
biggest question.
Personally I would always go for a DC fridge.

But in France 230v shore supply is commonplace - and often paid for as
part of your mooring fee (and often free) - so, since you're tied up for
longer than you're cruising each 24 hours, going for 230v makes better
sense.

Hang on David IMHO that somewhat contradicts your first reply to the
poster, where you discussed your experiences with access to landings.
Given a good 3 stage charger on board, the 12v or 24v option covers
all eventualities.

Richard

Nb "Pound Eater" Parkend G+S

[David Long]

Post by Richard Edwards

Post by David Long

Post by Richard Edwards
On Thu, 7 Apr 2005 08:53:52 +0000 (UTC), "Allan Jones"

Post by Allan Jones
Thus IF the test
conditions are similar, it is still better to use a 12v fridge.

Now that is a really sensible post!!!!
Obviously the statement "IF the test conditions are similar" is the
biggest question.
Personally I would always go for a DC fridge.

But in France 230v shore supply is commonplace - and often paid for as
part of your mooring fee (and often free) - so, since you're tied up for
longer than you're cruising each 24 hours, going for 230v makes better
sense.

Hang on David IMHO that somewhat contradicts your first reply to the
poster, where you discussed your experiences with access to landings.
Given a good 3 stage charger on board, the 12v or 24v option covers
all eventualities.

I still think, on balance, that the ready accessibility of shore-based
electricity makes the 230v option best, with the gennie and inverter
completing the kit. If you want to stop anywhere for any length of time,
relying on your batteries becomes a problem - bigger boats have to do a
bit more planning about stops to try to get to electricity as often as
possible.

[brianH]

Post by b***@reading-college.ac.uk
I am fairly concvinced that a mains A rated fridge plus inverter is
probably just as efficient as a 12v fridge or possibley a little more
so, however one must look at the efficiency of the inverter.
A 2000 watt inverter that is 95% efficeient would waste about 3 amps
doing its inverting at 12v input, however if it was only producing say
4 amps running a radio it would be very inefficient because it would
still be using that 3amps within itself (or so says my electronic
collegues) - I await correction if I have been misinformed!

I have an A rated mains lec fridge, I think its the same one they fit the
12/24 compressor in. I also have a 24/230 volt true sinewave 1500W
(Mastervolt I think) inverter which is surprisingly efficient if the
Stirling battery monitor is anywhere near right. With no load it draws 0.3 A
at 24V DC with the fridge running it goes up to about 3A .

[Adrian Stott]

On Thu, 7 Apr 2005 07:27:57 +0100, Paul Naylor

Post by Paul Naylor
Some of you were kind enough recently to help me with advice about ropes
for my co-owned barge in France.
There is now a debate over the advantages or otherwise of using 12v
small appliances (eg TV/Music Centre etc) as against buying (cheaper)
240 v appliances and running them through an inverter. The barge has a
battery charging system built in and the use of shore lines at overnight
moorings is commonplace. There is an inverter in place (although
apparently rather old and inefficient and requiring plugging in when
required) and there is a suggestion that this be replaced by an
automatic 800 watt device.
Some members believe that the use of 240v appliances would be more
likely to run down the batteries and, for example, knock out the fridge.
Any advice or comments would be welcome.
Many thanks
Paul

First comment - if you are installing DC, use 24 V not 12 V. Allows
smaller wiring, and/or fewer losses, due to smaller current.

I now always try to use AC equipment. Much easier to find, usually
much cheaper. In particular, it is readily possible to buy *used*
domestic appliances, often for next to nothing. That is usually not
feasible for DC equipment.

Also, many DC fridges are under-the-counter size (and maybe purchase,
if you buy in a street market <g>). House-sized ones, which is really
what you probably want in a a barge. can be hard to find and/or
expensive.

Post by Paul Naylor
I am fairly concvinced that a mains A rated fridge plus inverter is
probably just as efficient as a 12v fridge or possibley a little more
so, however one must look at the efficiency of the inverter.
A 2000 watt inverter that is 95% efficeient would waste about 3 amps
doing its inverting at 12v input, however if it was only producing say
4 amps running a radio it would be very inefficient because it would
still be using that 3amps within itself (or so says my electronic
collegues) - I await correction if I have been misinformed!
So perhaps it is best not to purchase too large an inverter.

I think that isn't how the efficiency of inverters works.

A typical inverter relaxes on "sleep" mode if there is no AC load on
it. In this mode, it uses very little power.

When an AC load is turned on, the inverter comes to life. In this
most, it will comsume a higher, substantially fixed, amount of power.
As a result, the bigger the load on it (up to its rated maximum,
obviously!), the *more* efficient it becomes.

On Thu, 7 Apr 2005 08:53:52 +0000 (UTC), "Allan Jones"

Post by Paul Naylor
I looked up a few fridge specs and did some quick calculations recently.
Shoreline's latest 12 volt fridge, the RR47, is quoted as having an average
consumption of 0.95 Amps/Hr. Assuming they actually mean that the average
consumption is 0.95 Amps, this equates to about 100 Kilowatt-hours per year.
A quick look at the specification of similar-sized mains fridges shows that
even the best A-rated models consume between 150 and 230 KWh/yr. The cheaper
models are generally B-rated, and take even more power. Thus IF the test
conditions are similar, it is still better to use a 12v fridge.

Be careful to compare like with like. Most DC fridges are small, many
AC ones are large. The losses very with the surface area of the
cooled volume.

Go for AC. You can get them anywhere, get a better selection, and it
is easy to get them fixed. You will surely have an inverter on board
anyway, and probably a generator, so why not use them?

Adrian

[Will Chapman]

Post by Adrian Stott
I think that isn't how the efficiency of inverters works.
A typical inverter relaxes on "sleep" mode if there is no AC load on
it. In this mode, it uses very little power.
When an AC load is turned on, the inverter comes to life. In this
most, it will comsume a higher, substantially fixed, amount of power.

We have a Mastervolt 2500 invertor and Mastervolt Charger equipped
with an electronic display that shows current consumption. When the
invertor is on it draws a steady 3.9amps. I have never seen a 'sleep'
mode in evidence. We use a 240v TV and when that is switched on
current increases to around 5amps (including the invertor draw). When
the TV and other 240v equip (computer/battery chargers/microwave etc)
are not in use we switch off the invertor to conserve batteries.

Provided batteries are fully charged during the day, we have no problem
running TV all night (and morning when I fall asleep on the couch!) even
though
our batteries (4x110ah) are now over 4 years old.

[Julian]

Post by Will Chapman
We have a Mastervolt 2500 invertor and Mastervolt Charger equipped
with an electronic display that shows current consumption. When the
invertor is on it draws a steady 3.9amps. I have never seen a 'sleep'
mode in evidence.

If you switch the TV off at the remote or on the front panel and leave it on
at the socket you will never see a "sleep mode" as most TVs etc draw enough
current when they are off to keep an inverter switched on.

As an aside consider the following approximate consumption figures when
items are switched "off"

Washing machine 10w
TV 5w
Video 5w
Stereo 5w

As you will see that is a total of 25watts
So if you leave them on overnight that is the same as leaving a 100watt lamp
on for two hours.

As you can see this is an awful lot of wasted energy that has to be
generated........

I could go on


J

[Will Chapman]

Post by Julian

Post by Will Chapman
We have a Mastervolt 2500 invertor and Mastervolt Charger equipped
with an electronic display that shows current consumption. When the
invertor is on it draws a steady 3.9amps. I have never seen a 'sleep'
mode in evidence.

If you switch the TV off at the remote or on the front panel and leave it on
at the socket you will never see a "sleep mode" as most TVs etc draw enough
current when they are off to keep an inverter switched on.

Ah, thats a good point...I hadn't thought of that. I must try that when I go
on the
boat in the next couple of days.

Post by Julian
As an aside consider the following approximate consumption figures when
items are switched "off"
Washing machine 10w
TV 5w
Video 5w
Stereo 5w

Gosh, as high as that!

That's a good lesson to learn for future use;; many thanks for pointing it
out.

[Brian]

Post by Will Chapman

Post by Adrian Stott
I think that isn't how the efficiency of inverters works.
A typical inverter relaxes on "sleep" mode if there is no AC load on
it. In this mode, it uses very little power.
When an AC load is turned on, the inverter comes to life. In this
most, it will comsume a higher, substantially fixed, amount of power.

We have a Mastervolt 2500 invertor and Mastervolt Charger equipped
with an electronic display that shows current consumption. When the
invertor is on it draws a steady 3.9amps.

I have just checked and mine is the Mastervolt Mass Sine 24/1500
You can set a jumper plug so that it switches off at no load and is on
standby, it then draws 25ma when idle.
Set to low energy mode it draws 180ma when idle
and the way I run mine high power, i.e.. 230 volt on all the time it draws
200ma when idle
These are from the manufacturers data sheet and my current meter indicates
0.3 A

[Will Chapman]

Post by Brian
I have just checked and mine is the Mastervolt Mass Sine 24/1500
You can set a jumper plug so that it switches off at no load and is on
standby, it then draws 25ma when idle.
Set to low energy mode it draws 180ma when idle
and the way I run mine high power, i.e.. 230 volt on all the time it draws
200ma when idle
These are from the manufacturers data sheet and my current meter indicates
0.3 A

Thanks Brian, I check my setting over the next couple of days. I must say
the
only disappointment I've had with the MasterVolt is the virtually
impenetrable
manuals; they seem to be more suited for an installer rather than user.

[Richard Edwards]

On Tue, 12 Apr 2005 15:26:23 +0100, "Will Chapman"
<***@dsl.pipex.com> wrote:
Snip

Post by Will Chapman
Thanks Brian, I check my setting over the next couple of days. I must say
the
only disappointment I've had with the MasterVolt is the virtually
impenetrable
manuals; they seem to be more suited for an installer rather than user.

They do not even suit installers! Certain info is missing from the
manual! when you call and ask you are given the wrong info!!
Richard (who needs to modify the wiring to an MICC on Friday)

[Will Chapman]

Post by Richard Edwards

Post by Will Chapman
only disappointment I've had with the MasterVolt is the virtually
impenetrable
manuals; they seem to be more suited for an installer rather than user.

They do not even suit installers! Certain info is missing from the
manual! when you call and ask you are given the wrong info!!
Richard (who needs to modify the wiring to an MICC on Friday)

I just downlownloaded the latest PDF manuals in the hope that
they have been updated. I haven't had a chance to compare them
with the originals yet.