First attempt at Power Audit - missed anything?

[BEngo]

Good ventilation us essential for any fridge to be efficient.

If you buy a12v one with a danfoss compressor the electronic unit has a special terminal for switching a fan or fans ( up to 0.8 A ) to cool the compressor and condenser.  Two  40 mm (0.08 A each) fans on mine make quite a difference, at the expense of a little extra noise. The difference is between running 50 % and running 30%

N

 

[robtheplod]

14 minutes ago, Keeping Up said:

On it's own the hole would not do much, but with a small computer fan in the hole it is very effective.

that makes sense... presume extracting air from the bilge rather than other way?

[Keeping Up]

37 minutes ago, robtheplod said:

that makes sense... presume extracting air from the bilge rather than other way?

Correct. If a 12v fridge, as stated above there will probably be a pair of terminals on the back for a fan, so that it runs only when the compressor is running. Since I changed to a 240v fridge I instead run it from the 12v supply via an old room-thermostat set to about 25 degrees C

[ditchcrawler]

3 hours ago, robtheplod said:

I'll double check the wattage when next on the boat - its a 12v shoreline - I've guessed its on 12hrs in 24hrs....

In that case unless you measure it you can only go by their published estimate. there is no standard for the numbers they give unlike a domestic fridge that is tested to a standard 

[Detling]

Remember Solar works wonderfully well for 4 months of the year, fine for 6 months and does nowt of use for 2 months.  Charging batteries if Lead requires a full charge at least once a week, and the last 15% is controlled by the battery and takes a long time with gradually diminishing current whatever the charging source.  Topping up a bit 'as and when' is a recipe for a short life of the batteries.

[robtheplod]

3 hours ago, Keeping Up said:

Correct. If a 12v fridge, as stated above there will probably be a pair of terminals on the back for a fan, so that it runs only when the compressor is running. Since I changed to a 240v fridge I instead run it from the 12v supply via an old room-thermostat set to about 25 degrees C

ok, so if i look on the back of the fridge there may be terminals to take a 12v fan already?  thats good!

[Keeping Up]

28 minutes ago, robtheplod said:

ok, so if i look on the back of the fridge there may be terminals to take a 12v fan already?  thats good!

Almost certainly yes, if it is a Shoreline.

[BEngo]

15 minutes ago, Keeping Up said:

Almost certainly yes, if it is a Shoreline.

Or any other fridge where the 12/24  V compressor is a Danfoss BD35.  It is the 'F' terminal on the electronic unit and it switches the negative, at up to a nominal12 V, so you need to provide the 12 V fans with a (switched and fused)   positive supply even on a 24 v boat..

 

N

Edited October 26, 2020 by BEngo

[IanD]

2 hours ago, Detling said:

Remember Solar works wonderfully well for 4 months of the year, fine for 6 months and does nowt of use for 2 months.  Charging batteries if Lead requires a full charge at least once a week, and the last 15% is controlled by the battery and takes a long time with gradually diminishing current whatever the charging source.  Topping up a bit 'as and when' is a recipe for a short life of the batteries.

If lead-acid charging is properly controlled using tail current to go from absorption to float even solar would probably just about cope (if you have enough panels) except in winter. The problem is that most (all?) MPPT controllers which claim to have "smart multi-stage charging" are actually pretty dumb, they use a fixed timer after hitting absorption voltage and almost always drop to float too soon (assuming they ever get that far) before the batteries reach full charge. Or they just don't have enough current for enough hours to ever reach this point except on a really sunny day. Cue dead batteries...

 

This is probably the biggest drive towards using LiFePO4 cells, even with all their other issues and the high cost today. Hopefully the cost will keep dropping with widespread adoption in BEV, and in a few years nobody would even consider installing those horrible old-fashioned lead-acid batteries any more...

[Tony Brooks]

2 hours ago, BEngo said:

Or any other fridge where the 12/24  V compressor is a Danfoss BD35.  It is the 'F' terminal on the electronic unit and it switches the negative, at up to a nominal12 V, so you need to provide the 12 V fans with a (switched and fused)   positive supply even on a 24 v boat..

 

N

Except the Waeco ones use it to power a fan behind their silly small, folded radiator. no to say you could not piggy back onto the F terminal but the wires are stupidly tig ht - or they were on my fridge.

[robtheplod]

On 25/10/2020 at 08:59, Alan de Enfield said:

You cannot mix 230v and 12v in the same table.

 

The 230 volt appliances will be running using an inverter, to estimate the 'amps' at 12 volts you need to divide the watts by 10.

So, for example your washing machine is 1550 watts ao that equates to 155 amps from the batteries, running for 2 hours means 310Ah.

 

BUT

 

Your washing machine will not be using that much for the whole 2 hours, some time will be with the heater, some just spinning, etc etc so your calculation cannot be 2x max current.

For a couple of £'s you can but a plug in 'watt' meter, plug it in, plug your washing machine into it and run a full cycle and it will tell you how many Wh it uses. Divide this by 10 and you will have the Ah taken from the batteries.

 

Do the same with the lap-top - your laptop will be using something like 4.5 amps so 5 hours will be 22Ah

 

Edit to add picture of 'watt counter' (about £12 on Amazon, less on Ebay)

 

 

Got one of these Alan, been playing around with it - quite an eye opener, thanks for the recommendation!

 

[Alan de Enfield]

16 minutes ago, robtheplod said:

 

Got one of these Alan, been playing around with it - quite an eye opener, thanks for the recommendation!

 

 

Yes, its a bit like getting a DC clamp meter, you can measure all sorts of things you never knew needed measuring.

 

The 'wattometer' is a useful tool for working out your exact consumption for each appliance over (say) a couple of days so it smoothes out the ups & downs,

 

Alternatively just plug it in the ouput of your inverter and everything is then fed thru it, after (say) a week you will have a very good indication of your ACTUAL weekly total Wh used on 230v. No more estimates, guessing how many hours something runs, or forgetting to include something in your calculations.

 

Well worth "a couple of quid" for the entertainment value alone.

 

Maybe I'm just 'odd' (replies not required)

[noone]

On 25/10/2020 at 11:37, Alan de Enfield said:

You can save a 'lot of leccy' by using 12v to charge it.

 

My laptop is 19v and I have a 12v to 19v adapter that plugd onto the cigarette lighter sockets.

Comes with a host of 'adapters' to suit all (?) laptops.

 

Seems daft to take 12v DC take it up to 230v AC then back down to 19v DC with all the losses at each stage.

If you don;'t need to have the inverter on just use the adapter and gp 12v Dc directly to 19v DC

 

On its way from Bimble Solar.....

See how long it takes me to break this one!

[Alan de Enfield]

27 minutes ago, Leggers do it lying down said:

On its way from Bimble Solar.....

See how long it takes me to break this one!

 

I had one very similar and it didn't last long - I don't know if it the fact it is 'multi voltage' or they just cannot take the 4 amps, thats why I went for the more expensive 'single voltage' 19v adapter.

Hopefully you'll be OK.

[ditchcrawler]

5 minutes ago, Alan de Enfield said:

 

I had one very similar and it didn't last long - I don't know if it the fact it is 'multi voltage' or they just cannot take the 4 amps, thats why I went for the more expensive 'single voltage' 19v adapter.

Hopefully you'll be OK.

I wonder how efficient they are?

 

[noone]

16 minutes ago, Alan de Enfield said:

 

I had one very similar and it didn't last long - I don't know if it the fact it is 'multi voltage' or they just cannot take the 4 amps, thats why I went for the more expensive 'single voltage' 19v adapter.

Hopefully you'll be OK.

No ebay or amazon here,went with Bimble so I can get a refund when it blows!!

[philjw]

I got one of these from Bimble. Used it for the first time last weekend and I was impressed by how fast it brought the laptop battery up from about 15% to full in about an hour.

Time will tell how long it lasts.

[cuthound]

22 hours ago, philjw said:

I got one of these from Bimble. Used it for the first time last weekend and I was impressed by how fast it brought the laptop battery up from about 15% to full in about an hour.

Time will tell how long it lasts.

 

I find with dc-dc chargers they charge very quickly and then the battery on the charged device discharges quickly too. 

[robtheplod]

At the boat briefly this weekend and had a rummage at the back of the fridge. Looks like I do have an 'F' terminal, so this is a switched negative reading earlier posts and it needs a fused positive in addition?

 

 

[noone]

On 31/10/2020 at 15:15, Alan de Enfield said:

 

I had one very similar and it didn't last long - I don't know if it the fact it is 'multi voltage' or they just cannot take the 4 amps, thats why I went for the more expensive 'single voltage' 19v adapter.

Hopefully you'll be OK.

 

Lasted a month before it melted!?  Full refund received!!.?

[Alan de Enfield]

12 minutes ago, Leggers do it lying down said:

 

Lasted a month before it melted!?  Full refund received!!.?

You must be jinxed - are you sure you are buying one with a high enough watt / amp rating ?

[BEngo]

On 02/11/2020 at 11:29, robtheplod said:

At the boat briefly this weekend and had a rummage at the back of the fridge. Looks like I do have an 'F' terminal, so this is a switched negative reading earlier posts and it needs a fused positive in addition?

 

 

That is similar to our fridge except ours is a different refrigerant: C-Pentane.   Yes, it is a switched negative. It will not sink more than 0.8 A.

The fan needs a switched and fused positive to it  then the fan negative connects to F terminal.  The compressor and electronic unit manual is on line.  I have a pdf copy somewhere.  If you want it it is on the Danfoss site, or PM me and I will excavate it.

With ours the main  positive and negative cables take up so much room at the terminal block that there is no room to piggy back a positive lead for the fan supply, so I took it from where the fridge positive is connected to the boat cable,  with an in line fuse.

 

It takes a few seconds from the motor starting to the fan coming on.

 

N

[noone]

1 hour ago, Alan de Enfield said:

You must be jinxed - are you sure you are buying one with a high enough watt / amp rating ?

Input voltage 11-14v @ 8A max. Output 19v @ 4A...Think I'll look for something with a greater capability.?

[Alan de Enfield]

12 minutes ago, Leggers do it lying down said:

Input voltage 11-14v @ 8A max. Output 19v @ 4A...Think I'll look for something with a greater capability.?

 

The problem I found with the multi-voltage ones is that they quote the current rating at lower voltages making it look 'better' than it really is.

 

Watts are 'fixed' so if it is (say)  a 40watt unit, then it may be 4 amps at 10v, but is only 2 amps at 20 volts.

 

Try and find a unit that quotes current at your required voltage (that matches your mains unit)

[Alan de Enfield]

39 minutes ago, Leggers do it lying down said:

Input voltage 11-14v @ 8A max. Output 19v @ 4A...Think I'll look for something with a greater capability.?

How about this ?
Extend the leads, add a plug and away-u-go !!

 

 

EBILUN DC 12V To 19V Step Up Converter, 8A 152W Power Supply Voltage Changer Adapter Regulator: Amazon.co.uk: Car & Motorbike

 

 

Or the one I use is 4.7A @ 19  volts