12v versus 230v fridge

[Alan de Enfield]

11 minutes ago, Goliath said:

in theory then ;

allowing 120ah per day for a fridge and a freezer,

and with 3 batteries giving 330ah,

I should never go below 2 thirds of my power, or 60-70%

IF I fully charge my batteries everyday.

 

Assuming you do not have an electric water pump, electric lights, and electrically powered TV, never charge your phone or run you computer.

 

I worked out that my daily (non-fridge and freezer) consumption is around 80Ah, add in the Fridge and freezer and it comes to 150ah-180Ah depending on the weather and the number of hours of daylight.

 

I think you will use your 50% of batteries per day and have to recharge for many hours to replace it,

My 70 amp alternator averages about 30Ah across the duration of charging so to replace 180 Ah would need at least 6 hours engine running per day.

 

I'm fortunate to have 1200Ah of battery bank and 2x 70 amp alternators and generally cruise most days, or alternate days at worst so its not a great problem for me.

 

Do a full electrical audit and then review  your storage and charging capabilities.

[Tony Brooks]

I don't think an alternator charging lead acid batteries will average anything like 50% of rated output except over the first three to four hours. After that the average gets lower and lower because of the charging current is dropping to such low levels. I would not like to try to quantify the average charge from an alternator unless I had the output of a data logger to read. Even a 100amp alternator will send hours at sub 20 and the sub 10 amps as the batteries approach fully charged.

[beerbeerbeerbeerbeer]

7 minutes ago, Alan de Enfield said:

 

Assuming you do not have an electric water pump, electric lights, and electrically powered TV, never charge your phone or run you computer.

 

I worked out that my daily (non-fridge and freezer) consumption is around 80Ah, add in the Fridge and freezer and it comes to 150ah-180Ah depending on the weather and the number of hours of daylight.

 

I think you will use your 50% of batteries per day and have to recharge for many hours to replace it,

My 70 amp alternator averages about 30Ah across the duration of charging so to replace 180 Ah would need at least 6 hours engine running per day.

 

I'm fortunate to have 1200Ah of battery bank and 2x 70 amp alternators and generally cruise most days, or alternate days at worst so its not a great problem for me.

 

Do a full electrical audit and then review  your storage and charging capabilities.

Yes I’ve considered my other electric use and it very very low. 
LED lights a water pump and then there is charging the gadgets (phone, ipad etc) which I tend do mostly when on the move. 
 

I’ve considered a 4th 110ah battery but space is limited, and I’d still have to replace any power I’ve took from that. 
 

I think my alternator is 72A

 

[Alan de Enfield]

1 minute ago, Goliath said:

I think my alternator is 72A

 

But - do not think that you will get 72 amps for the duration of the charge cycle.

As both Tony and I have said, you will get considerably less. I reckon I get about 40%, Tony suggests less.

[beerbeerbeerbeerbeer]

5 minutes ago, Tony Brooks said:

I don't think an alternator charging lead acid batteries will average anything like 50% of rated output except over the first three to four hours. After that the average gets lower and lower because of the charging current is dropping to such low levels. I would not like to try to quantify the average charge from an alternator unless I had the output of a data logger to read. Even a 100amp alternator will send hours at sub 20 and the sub 10 amps as the batteries approach fully charged.

Is it not ok to charge as much as possible from the alternator and then leave the solar to do the rest ?

[Alan de Enfield]

Just now, Goliath said:

Is it not ok to charge as much as possible from the alternator and then leave the solar to do the rest ?

 

 

That is the perfect and most economical way to do it. Charge the battery by running the engine 1st thing in the morning - get it to 85% (ish) and let the solar put the other 15% in durung the rest of the day,

 

(Only works when the Sun shines)

[Tony Brooks]

2 minutes ago, Goliath said:

Is it not ok to charge as much as possible from the alternator and then leave the solar to do the rest ?

 

Yes, that is ideal. Charge from the alternator early in the day, but what you then get from solar will vary by the hour AND solar is likely to go into float early and further limit the charge. How do you know when the batteries are fully charged without monitoring them. I you don't know how much solar charge you will get, when do you know that the alternator has charged the batteries enough?

[beerbeerbeerbeerbeer]

2 minutes ago, Alan de Enfield said:

 

 

That is the perfect and most economical way to do it. Charge the battery by running the engine 1st thing in the morning - get it to 85% (ish) and let the solar put the other 15% in durung the rest of the day,

 

(Only works when the Sun shines)

Yes of course the sunshine!

at least I’m thinking in the right direction.  
 

so far I have only monitored my batteries with an the LED volt meter I wired up years back. 
and the smiley face on my solar controller, 

 

what would the next step be for a dull wit like me to enable better monitoring?

something simple without going down the Victron monitor way. Or is that the next step?

[Alan de Enfield]

I'll let other answer with their thoughts on 'best monitoring devices' as whatever someone has tends to be the 'best' in their mind.

 

I'm a simple chap - the smiley on the solar gives me a clue but I monitor battery state by volts and amps.

 

A battery is (in effect) fully charged when the voltage is ~14.4-14.6volts & the charging current is 1% of the battery bank size, so for your bank it is charged when the charging current is about 3.5 amps. Most people will accept a 2% of bank-size as being near enough full.

 

Batteries are consumables - If you have to replace then every 3 years, so-what.

I'm having too much fun to stress about batteries, I know the theory, I know what happens in practice I just do the best I can without going 'overboard'

[beerbeerbeerbeerbeer]

8 minutes ago, Tony Brooks said:

 

Yes, that is ideal. Charge from the alternator early in the day, but what you then get from solar will vary by the hour AND solar is likely to go into float early and further limit the charge. How do you know when the batteries are fully charged without monitoring them. I you don't know how much solar charge you will get, when do you know that the alternator has charged the batteries enough?

At the moment I am on hard standing so have my batteries on charge with a victron charger and have learned a little more about charging by looking at the data and diagrams.
And understanding bulk, absorption, float and storage. 
 
But normally when cruising it has involved best guess/estimation with the volt reader and diagrams on my solar controller. 
 

My last set of batteries lasted me 8 years ( or more, they were on the bait when I bought it). I am sure they lasted becuase I am such a low user of electricity, tend to drive the boat and some luck. 
 

But if I move up a notch with my electricity usage then I’d like to be a bit better prepared. Although my usage is still going to be very low compared to others. 

1 minute ago, Alan de Enfield said:

I'll let other answer with their thoughts on 'best monitoring devices' as whatever someone has tends to be the 'best' in their mind.

 

I'm a simple chap - the smiley on the solar gives me a clue but I monitor battery state by volts and amps.

 

A battery is (in effect) fully charged when the voltage is ~14.4-14.6volts & the charging current is 1% of the battery bank size, so for your bank it is charged when the charging current is about 3.5 amps. Most people will accept a 2% of bank-size as being near enough full.

 

Batteries are consumables - If you have to replace then every 3 years, so-what.

I'm having too much fun to stress about batteries, I know the theory, I know what happens in practice I just do the best I can without going 'overboard'

Ok 

tjats settled

i can do just fine with volt meter and smiley faces

 

like you, I prefer to get me jollies elsewhere. 
 

when I next meet Dmr he can explain more about reading my solar controller 

 

thanks for the help 👍

[Alan de Enfield]

5 minutes ago, Goliath said:

At the moment I am on hard standing so have my batteries on charge with a victron charger and have learned a little more about charging by looking at the data and diagrams.
And understanding bulk, absorption, float and storage. 
 
But normally when cruising it has involved best guess/estimation with the volt reader and diagrams on my solar controller. 
 

My last set of batteries lasted me 8 years ( or more, they were on the bait when I bought it). I am sure they lasted becuase I am such a low user of electricity, tend to drive the boat and some luck. 
 

But if I move up a notch with my electricity usage then I’d like to be a bit better prepared. Although my usage is still going to be very low compared to others. 

Ok 

tjats settled

i can do just fine with volt meter and smiley faces

 

like you, I prefer to get me jollies elsewhere. 
 

when I next meet Dmr he can explain more about reading my solar controller 

 

thanks for the help 👍

 

Get an ammeter and read that in conjuction with the volts.

Amps are more imprtant that volts.

[Tony Brooks]

12 minutes ago, Goliath said:

hat would the next step be for a dull wit like me to enable better monitoring?

something simple without going down the Victron monitor way. Or is that the next step?

 

In my view a digital voltmeter and ammeter. Alan has told you how to use the ammeter to determine when the batteries are as fully charged as makes little difference. Once you grasp rested voltage the voltmeter will allow you d make a good inference about state of charge during times charging is not taking place. However you need to choose a "no load" moment to take the reading.

 

Unless you put time in to understanding the monitor instructions, setting up and periodically ensure it re-calibrates it is very good a lying and overstating the state of charge. f you just use the ammeter and voltmeter functions you can ignore the lying.

 

The problem with Alan's method is that it requires a charging voltage of more than about 14. 2 volts and if the charge source drops into float (about 13.6V) it will cause you to stop charging too soon. So to get over that spin the engine u

hat would the next step be for a dull wit like me to enable better monitoring?

 

 

[beerbeerbeerbeerbeer]

Just now, Alan de Enfield said:

 

Get an ammeter and read that in conjuction with the volts.

Amps are more imprtant that volts.

If I knew what I was looking at: the screen for my solar controller should give me that?

[beerbeerbeerbeerbeer]

now I understand some of the numbers here 

and I can see it’s good but that’s all I really know. 
 

how do I use this gadget as an ammeter?

 

am I right thinking the solar is trickling in 0.4A while I’m drawing 0.4A

 

🤷‍♀️

 

I can see the figures on the right show I’m not drawing any load from that port. 

 

And I see the batteries are well charged because they’re at 13.2v

Edited March 8, 2022 by Goliath

[Tony Brooks]

18 minutes ago, Goliath said:

now I understand some of the numbers here 

and I can see it’s good but that’s all I really know. 
 

how do I use this gadget as an ammeter?

 

am I right thinking the solar is trickling in 0.4A while I’m drawing 0.4A

 

🤷‍♀️

 

I can see the figures on the right show I’m not drawing any load from that port. 

 

And I see the batteries are well charged because they’re at 13.2v

 

 

You can't use a solar controller like a conventional ammeter.

 

Smiley faces and degree of charge displays tend to be even bigger lies than what battery monitors tell. Ignore them.

 

The 13.2 volts is a CHARGING voltage and indicative of not a lot. Shut down the solar and let the batteries stand for a couple of hours or run your water pump fr 10 minutes and then you would have the rested volage and be able to infer the state of charge.

 

It says the solar input is 0.4 volts and so is the output to the batteries.

 

Solar controllers can have no idea about how much current is being used from the batteries. That is  why you need a decent ammeter, the you can see what s gong in or out.

Edited March 8, 2022 by Tony Brooks

[beerbeerbeerbeerbeer]

4 minutes ago, Tony Brooks said:

It says the solar input is 0.4 volts and so is the output to the batteries.

Right 

let’s assume for a moment it’s telling the truth:

would it mean the batteries are now at that stage where they can only take a small floating charge?

for the solar panel is saying a potential 14.2v but the batteries can only take on 0.4V

 

?

 

thanks for your patience 

I know I’m being a dullard. 
 

I will look into an ammeter. 
If you could recommend one for a simpleton I’d be grateful. 
👍

[Tony Brooks]

No, it means either the controller has gone into float voltage but more likely when you took the photo the panels did not have enough light to produce more current. 13.2V is a bit low for float so most likely lack of light.

 

[beerbeerbeerbeerbeer]

Just now, Tony Brooks said:

No, it means either the controller has gone into float voltage but more likely when you took the photo the panels did not have enough light to produce more current. 13.2V is a bit low for float so most likely lack of light.

 

👍

thanks

there’s a lot to this malarkey 

 

I will just have to keep getting on with it and see. 
 

as others say (and I agree) batteries are consumables but I’d like to get me moneys worth out of them 

 

 

[Alan de Enfield]

1 hour ago, Goliath said:

am I right thinking the solar is trickling in 0.4A while I’m drawing 0.4A

 

 

NO NO NO.

The figures on the bottom left are the voltage and current that the solar panel is producing at the time.

 

The controller takes whatever voltage the panel produces (above whatever the battery voltage is) and 'transforms' it to the voltage the battery needs. The volts and amps going into the battery are the middle figures

 

The figures on the right (0 / 0) are the usage by whatever you have connected into the right hand side set of terminals  - I have previously used those terminals as a 'supply' for my VHF radio.

 

For example if the solar panel is producing 28 volts and 1 amp, the controller, (just as an example) would 'transform' that to 14 volts and 2 amps to charge the battery.

 

If the solar panel is putting out a lower voltage (because it is overcast / raining / dark) then nothing goes into the battery.

 

Look at mine :

 

The solar panel is producing 103.1 volts at 0.8 amps.

The MPPT Controller is taking that voltage and current and 'jiggling around' to make a voltage that is usable by the batteries.

 

It converts that 103v / 0.8 a  to 14.7volts and 5.9 amps.

 

Remember that the wattage of the panel is fixed, and that watts = amps x volts

 

You could have a (say) 100 watt panel that produces 100 volts at 1 amp, or 100 amps at 1 volt, 50 volts at 2 amps, 66 amps at 1.5 volts or any other permutation that totals 100.

 

Once you understanding of the theory the practice becomes much easier.

 

Edited March 8, 2022 by Alan de Enfield

[Withywindle]

With a heavy heart I just removed our ageing 12v fridge and replaced it with a 240v model. I did this because I couldn’t get a 12v model which would fit the rather odd sized fridge gap in the galley. 

 

I have been pleasantly surprised, having expected problems. The 12v fridge was worn out, I suspect it had lost most of its refrigerant and consequently the compressor was running far more than it needed to so it had clearly been putting a high drain on my batteries. They are in much better shape each morning than they ever were with the old 12v fridge. My beer is also much cooler. 👍
 

The best is that I sold the old 12v fridge on eBay as ‘parts or not working’ and got more for it than the new 240v fridge cost! The chap who bought it was a non boater who was intending to run it off a single solar panel in his garden shed and keep cold drinks in it. I tried to subtly point out some of the flaws in this rather hair brained idea but he was having none of it!

[mrsmelly]

1 hour ago, Withywindle said:

With a heavy heart I just removed our ageing 12v fridge and replaced it with a 240v model. I did this because I couldn’t get a 12v model which would fit the rather odd sized fridge gap in the galley. 

 

I have been pleasantly surprised, having expected problems. The 12v fridge was worn out, I suspect it had lost most of its refrigerant and consequently the compressor was running far more than it needed to so it had clearly been putting a high drain on my batteries. They are in much better shape each morning than they ever were with the old 12v fridge. My beer is also much cooler. 👍
 

The best is that I sold the old 12v fridge on eBay as ‘parts or not working’ and got more for it than the new 240v fridge cost! The chap who bought it was a non boater who was intending to run it off a single solar panel in his garden shed and keep cold drinks in it. I tried to subtly point out some of the flaws in this rather hair brained idea but he was having none of it!

I am not suprised. the pendulem swung the other way quite a few years ago now. My first all mains kitted boat with quality gear i bought in 2007 I said then I would not be having 12 volt fridges ever again. My next two boats I removed 12 volt fridges and upgraded to mains, each time with the correct results both in item costs and performance costs. Todays mains fridges through a top notch inverter, realy is a no brainer. I wouldnt have done it twenty five years ago but equipment has changed greatly since then.

[MtB]

16 minutes ago, mrsmelly said:

Todays mains fridges through a top notch inverter, realy is a no brainer.

 

Is it? Really? 

 

The flaw in your assertion is identifying the 'top notch' inverter. They either cost more than the 12v fridge they help you avoid fitting or they are made in a Chinese sweatshop for sale on Ali-express and where the commercial culture is "Get the order, then reduce the quality to wring some profit out of it and test how long it takes for the customer to notice".

[GUMPY]

My 1600va Victron uses 2-3watts in standby, that and a cheap LEC fridge easily outperform the 12v fridge  that was in there, but then the 12v fridge was 20+ years old.

[MtB]

59 minutes ago, Loddon said:

My 1600va Victron uses 2-3watts in standby, that and a cheap LEC fridge easily outperform the 12v fridge  that was in there, but then the 12v fridge was 20+ years old.

 

How much does the Victron cost?

 

 

[Lily Rose]

33 minutes ago, MtB said:

 

How much does the Victron cost?

 

 

 

 

Bloody hell!