Fridges

[Jokar]

I had removed my original 12v ENGLE fridge as it was grubby and smallish, I fitted a 240v fridge but now need to go back to 12v so I don't need hook up, I'm going to refurbish the Engle one for now, but would rather get a newer version,  if anyone is selling a waeco 12v or similar please message me privately 

[Robbo]

If your 240v is quite efficient, why not go down the inverter route?

[Jokar]

We use the inverter while the engines are running, but the fridge takes too much from the batteries. I am fitting another two batteries but it would be simpler  with a newer 12v fridge

I would experiment with the 240v fridge and the 4 x 110ah batteries  with 200w of solar to top them up after we berth, but to be honest I may want to berth a couple of days at a time,  so it's a big ask from the batteries

[Dr Bob]

A good inverter will take say 30Ahrs per day to keep on continually. You need to work out how many AHrs more the 12v fridge will take compared to the 240V one in 24 hrs.. Our 240V fridge is very efficient- some 12V ones may not be.

Moving to 24/7 for the inverter gives you many other benefits.

[Robbo]

31 minutes ago, Dr Bob said:

A good inverter will take say 30Ahrs per day to keep on continually. You need to work out how many AHrs more the 12v fridge will take compared to the 240V one in 24 hrs.. Our 240V fridge is very efficient- some 12V ones may not be.

Moving to 24/7 for the inverter gives you many other benefits.

I would say 30ah per day is a bad inverter, mine is around 20ah (15yr+ Victron multiplus) and that’s not brilliant compared with some of Victron’s Inverters.

[Jen-in-Wellies]

1 hour ago, Jokar said:

We use the inverter while the engines are running, but the fridge takes too much from the batteries. I am fitting another two batteries but it would be simpler  with a newer 12v fridge

I would experiment with the 240v fridge and the 4 x 110ah batteries  with 200w of solar to top them up after we berth, but to be honest I may want to berth a couple of days at a time,  so it's a big ask from the batteries

I have a similar set up. 240V fridge, 4x110Ahr batteries and 240W of solar. The 240V fridge is inverter driven when away from the shore line (victron). This works well when cruising in the summer. Can stay moored for several days without running the engine before needing to move on, or charge from the engine as long as the sky isn't too overcast. I would say that these days, with a good quality, high efficiency inverter, there is little in it between a 12V and 240V fridge. A good mains fridge + inverter may well beat a cheaper, or older 12V fridge for overall consumption.

Installation of the fridge is important. I've seen 12V fridges installed under counters with no ventilation to the coils at the rear that run the compressor all the time and can't get down to temperature. On mine, there is a slot in the worktop over the rear of the fridge and vents in the floor to allow cooler air from the bilges to flow up through the coils and out the top. No idea what the duty cycle is, but when cruising you can tell when the compressor kicks in as there is a momentary drop in engine speed as the inverter draws on the alternator to make the inrush current. This doesn't happen too often in a days travel.

Jen

[Dr Bob]

1 minute ago, Robbo said:

I would say 30ah per day is a bad inverter, mine is around 20ah (15yr+ Victron multiplus) and that’s not brilliant compared with some of Victron’s Inverters.

Yes I agree, but I was sort of rounding up the other stuff on the 240v that gets left on like chargers or the BT youview box. With no compressor running I get 1.7A draw from the inverter  plus the other 'hangers on'. Sorry, should have been more specific. If I didnt run the inverter then these hangers on would not be running ...hence the 30Ahrs.

[Jokar]

Just now with 2 batteries the 68w 240v fridge can deplete the batteries during the night, my 1500w inverter is pure sinewave  which wastes more battery power but it gets used for  straighteners  when needed, I do have another inverter I thought about putting in but it's overkill at 4kw. Fitting the 2 additional batteries a d the 200w panels I recon would work but the 12v fridge draws 5amp at 12v and cools very fast, in comparison  to the 240v

[Jen-in-Wellies]

17 minutes ago, Jokar said:

Just now with 2 batteries the 68w 240v fridge can deplete the batteries during the night, my 1500w inverter is pure sinewave  which wastes more battery power but it gets used for  straighteners  when needed, I do have another inverter I thought about putting in but it's overkill at 4kw. Fitting the 2 additional batteries a d the 200w panels I recon would work but the 12v fridge draws 5amp at 12v and cools very fast, in comparison  to the 240v

68W is just under 5A at 12V, similar to what mine draws with the compressor running. Add on maybe another amp for the inverter, then 12Hrs overnight is around 72Ahrs, or a significant chunk of your 50% max safe battery discharge from two batteries. This suggest that the fridge compressor is on almost continuously. See my post above. How is the fridge installed? What through ventilation is there to the rear side? Would be worth putting one of those cheap energy meters on the fridge plug to find the real energy consumption over twelve hours. If this does show that the compressor is on most of the time, then a 12V fridge is likely to be the same. Similalry, what level on the thermostat inside is it running? Too high a value will waste power. Stick a fridge thermometer inside and see if the thermostat can be turned to a lower value safely. Is the door seal in good condition? A leak will waste power. Can a piece of paper trapped between be easily pulled out at any part of the perimeter. I get the impression that you are fixated on 12V vs 240V, but there are many more things that could cause the excess power drain.

Jen

[Alan de Enfield]

Just now, Jen-in-Wellies said:

8W is just under 5A at 12V, similar to what mine draws with the compressor running. Add on maybe another amp for the inverter, then 12Hrs overnight is around 72Ahrs, or a significant chunk of your 50% max safe battery discharge from two batteries.

You are using the figures based on 100% running - in reality the fridge will 'cycle' approximately 1/3 on - 2/3 off (probably less 'on' time during the night as the door is not opened)

In reality it will be much, much less than 72Ah per night - probably nearer 15Ah

My 240v FREEZER (which uses more than a fridge) uses 34Ah per day. + Inverter 'losses'

My 12v Fridge uses 30Ah per day

There is very little difference between the usage of a12v Fridge, and a 230v Fridge (except the inverter 'losses)

If the @Jokar is flattening his batteries overnight with the fridge, then either

1) His batteries are knackered and are sulphated by undercharging, or

2) The fridge installation (or fridge itself) is faulty

There is no reason why you should not be able to run a fridge (230v or 12v) from a twin-110ah battery bank

 

@Jokar - how are you deciding that your batteries are 'depleted' ? 

Do the lights go dim or do you have battery monitoring equipment ?

How do you determine when your batteries are fully charged ?

 

[Jen-in-Wellies]

That is what I am saying. Power consumption depends on duty cycle. We don't know what that is without either a battery monitor, or a power meter on the 240V fridge itself. Worse case of 100% dep!etes the batteries significantly overnight, which is what the OP thinks he is seeing. This could happen with a poor location, or fridge seal etc. So he needs to find what the real compressor duty cycle is and mitigate that if it is high, rather than just buy a 12V fridge.

Jen

Edited April 2, 2018 by Jen-in-Wellies

[Jokar]

Batteries are charged to 13.8v with charger, deleted at 11.5v when inverter switches off to save batteries draining right down, but existing  batteries are now about 6 yrs old so good chance they are knackered, I'll be replacing with 4 new ones I have sitting. I seldom run the fridge without hook up, but on the few occasions  the inverter switches off the load during the night,  best I've had is about 8 am

Meant to add, I will need to pull fridge out, I think it's turned up full, but it adjusts on the rear

[Boater Sam]

13.8v is not fully charged, you need to go to 14,4v with sealed batteries or 14.8v with open lead acid. If you have only being charging to 13.8v for 6 years, your batteries are done, sulfated to hell.

Anyone tried my idea of a dedicated inverter, say 1000w, and using the fridge thermostat to switch the inverter on and off by wiring it across the usual rocker switch? ( which is left switched off )

That way you have no standby losses on the inverter at all.

[Alan de Enfield]

12 minutes ago, Jokar said:

Batteries are charged to 13.8v with charger, deleted at 11.5v when inverter switches off to save batteries draining right down,

11.5v is 'right down' and knackers the batteries in very short order - do not install new batteries until you can resolve your charging and discharging regime.

How do you know you are charging to 13.8v ?

What is the tail current when you think the batteries are charged ?

[Jokar]

Although I'm saying over night, the engines could be off from 2pm till 11am next morning with no solar at the moment, so it is a big ask to recharge the batteries fully while running the fridge and inverter  at the same time, running both engines for 2 to 4 hrs while transiting, then switched off again till next day. Also using led lights and tv  with freesat box or amplifier. For couple of hours at night, water pump etc. 

5 minutes ago, Alan de Enfield said:

11.5v is 'right down' and knackers the batteries in very short order - do not install new batteries until you can resolve your charging and discharging regime.

How do you know you are charging to 13.8v ?

What is the tail current when you think the batteries are charged ?

Never been checked, one night last season I was without hookup and put a 100w solar panel on the deck, I was getting 5amp through the panel at best. I've never been overly concerned  but this season we will be using berths without electric  as we will be visiting the Caledonian  canal.

[Alan de Enfield]

2 minutes ago, Jokar said:

Although I'm saying over night, the engines could be off from 2pm till 11am next morning with no solar at the moment, so it is a big ask to recharge the batteries fully while running the fridge and inverter  at the same time, running both engines for 2 to 4 hrs while transiting, then switched off again till next day. Also using led lights and tv  with freesat box or amplifier. For couple of hours at night, water pump etc. 

You will never charge you batteries correctly running the engine(s) for a couple of hours per day.

What battery monitoring (charging / discharging) system do you have ?
have you ever undertaken an electrical audit ?

[Jokar]

I bought a second 100w panel yesterday, and I've dug out the old 12v fridge to try out / test  run, during the winter I also up rated  my starboard alternator to 90 amp from a 60 amp,  port one is 60amp

[Jokar]

I only have a volt meter, and now the solar charge contoller  which shows current in voltage etc, but I've not connected the load side due to the inverter  current. Until now we have relied on the shore power and battery charging from the mains

[Alan de Enfield]

10 minutes ago, Jokar said:

I only have a volt meter, and now the solar charge contoller  which shows current in voltage etc, but I've not connected the load side due to the inverter  current. Until now we have relied on the shore power and battery charging from the mains

Ok - as a minimum you need a DC Ammeter and you need to charge the batteries (either by running the engine, via a generator, or on a landline) until the current going into the batteries is 2% of the battery capacity (1% is better). So, with 220Ah battery bank you should not stop charging until the current gets below 4 amps.

The size of your alternators is not relevant as it is the batteries that control the rate of charge NOT THE ALTERNATOR.

As the battery becomes charged it demands a higher voltage and a lower current so towards the end of the charge you should be seeing 14.4 volts + and 4 amps.

What voltage is the regulator on your alternators ?

Look the back of your alternator. See the picture of mine showing 14.6 volts (just below the word 'Cargo')

 

Edited April 2, 2018 by Alan de Enfield

[Jokar]

14.4v on the new one, I'm not positive about the older one

[Jokar]

14.4v is pretty standard, I can and do set the charge controller  for solar panels at 14.4v, I use solar on my caravan 400w for twin batteries,  in good sun I can get 20amp from the panels

[Alan de Enfield]

1 minute ago, Jokar said:

14.4v on the new one, I'm not positive about the older one

Great.

Now you need to get a DC Ammeter and charge the batteries EVERY DAY for several hours until you reach the correct tail current. This may involve continuing to run the engines for a couple of hours after finishing cruising.

What engines do you have ?

I have twin 6-Cylinder Ford's.

 

[Jokar]

5.7amp is the best the 100w panels  will do, but depending  on the sun it could be far less

Twin 6cyl Pentas

[Alan de Enfield]

2 minutes ago, Jokar said:

14.4v is pretty standard, I can and do set the charge controller  for solar panels at 14.4v, I use solar on my caravan 400w for twin batteries,  in good sun I can get 20amp from the panels

Can you set the solar controller to around 15.6v.?

If you can an equalisation charge MAY remove some of the sulphation in the batteries and extend their life a little.

[WotEver]

The two important points are:

1. to keep charging (at the very least twice a week) until the current drops to around 1% and

2. To never discharge the batteries below around 12.2V. 

2 minutes ago, Jokar said:

5.7amp is the best the 100w panels  will do, but depending  on the sun it could be far less

Then on those poor days you’ll need to run the engine.