What's going on with my battery/ fridge?

[DannyC]

Hi all,

 

So the other day I left the boat for almost a week. Before leaving, I turned everything off at the switch box and turned of fthe isolator switches too. The battery was fairly well charged when leaving (well over 50%). However, when I returned we found that the fridge was still on! So somehow, even thought I had cut out all the power, the fridge was still managing to draw from the batteries - everything in the freezer was still frozen! I checked the battery using the volt meter and it had dropped down to 11.4 (eek!).

 

Ever since I have been cruising I have been so so careful not to let the batteries drop below 12.2v. We use a fairly limited amount of power, but I am starting to wonder about the fridge. Something seems to eat all the electricity, and I can't believe it is having one 12v light on of an evening and the pumps + the occasional laptop charge.

 

Do you think my fridge may not be 12v? It is a Lec brand fridge, but there is no model number on it, so i am not sure the best way to check, and how can it be wired so it is not controlled by the fuse box/ isolator switches.

 

What do you guys think? I am well aware that I may be being a moron!

Edited May 7, 2019 by DannyC

[ditchcrawler]

Some people wire fridges straight to the batteries via a fuse so as not to suffer volt drop through the distribution system. If your fridge is 230 volt it will only work with the inverter switched on.

 

[DannyC]

Ah ok, def not 230 then. That clears that up then  Thanks.

 

I feel like it still seems to eat a lot of power. Is there a way I can check how much is being used just by the fridge? I don't have a manual...

[ditchcrawler]

10 minutes ago, DannyC said:

Ah ok, def not 230 then. That clears that up then  Thanks.

 

I feel like it still seems to eat a lot of power. Is there a way I can check how much is being used just by the fridge? I don't have a manual...

Do you have an ammeter on the boat

 

[Alan de Enfield]

By leaving the fridge at less than 100% (ie 50%) you have reduced the capacity from ??? to ???.

Further discharging to 11.4 volts means that the battery is (probably) now knackered and will hold little charge - if it was (say) 100Ah battery it may well now be less than 50Ah.

 

Your fridge will probably use 40Ah per 24 hours (total guess and depends on model) so you fridge is pretty much taking the whole battery capacity.

 

Do you have any form of battery monitoring ? (how do you know your battery was 50% charged)

Your fridge will probably run for 15-20 minutes per hour so you cannot just take a 'spot' consumption.

 

If you have an amp counter you could monitor (say) 4 hours consumption by the fridge and multiply by 6 to get the daily consumption.

 

At 11.4 volts the battery is pretty much 'dead'.

 

 

Edited May 7, 2019 by Alan de Enfield

[DannyC]

Excuse my ignorance, but is that the same as a volt meter? 

[ditchcrawler]

1 minute ago, Alan de Enfield said:

By leaving the fridge at less than 100% (ie 50%) you have reduced the capacity from ??? to ???.

Further discharging to 11.4 volts means that the battery is (probably) now knackered and will hold little charge - if it was (say) 100Ah battery it may well now be less than 50Ah.

 

Your fridge will probably use 40Ah per 24 hours (total guess and depends on model) so you fridge is pretty much taking the whole battery capacity.

 

Do you have any form of battery monitoring ? (how do you know your battery was 50% charged)

Your fridge will probably run for 15-20 minutes per hour so you cannot just take a 'spot' consumption.

 

If you have an amp counter you could monitor (say) 4 hours consumption by the fridge and multiply by 6 to get the daily consumption.

I would say your numbers are about right. A voltmeter measures the volts and an Ammeter measures the amps, in water terms think volts= pressure and amps  = flow

[DannyC]

Alan - I am pretty sure that is the only time my batteries have gone below 12.2 - I am very careful and am always down there checking with the volt meter. Do you think that one instance knackered my battery?

[Alan de Enfield]

1 minute ago, DannyC said:

Excuse my ignorance, but is that the same as a volt meter? 

No.

 

Amps are very different to volts, and it is Ah that batteries and things like fridges are 'measured in'

[DannyC]

Ok, so I don't have an ammeter.

[ditchcrawler]

If your batteries were in good nick before then damage may not be too great but it will have damaged to some extent. You also need to ensure you charge them fully, so on charge they want to be around 14.4 volts and the an hour after charging with no load they still need to be up at 12.7 volts

[Alan de Enfield]

8 minutes ago, DannyC said:

Alan - I am pretty sure that is the only time my batteries have gone below 12.2 - I am very careful and am always down there checking with the volt meter. Do you think that one instance knackered my battery?

In the perfect world a battery should be recharged to 100% immediately after use, in the real world that is not really possible, but we should try to recharge to 100% every day, or every couple of days.

 

Anything less than 100% results in your battery becoming sulphated.

The fact that it was at 50% when you left it shows that it was well below fully charged, even before taking it down to 11.4 volts during the following week.

 

Think of a 5 litre bucket of water.

When new it holds 5 litres.

If we drop some 'mud' (sulphation) into the bottom of the bucket it is still a 5 litre bucket but now it only holds 4 litres of water.

Repeat with more 'mud' and it now holds 3 litres of water

Repeat ……. now only holds 2 litre

Repeat …………...It is still a 5 litre bucket but now holds 1 litre of water.

 

Your 12 volt battery is still 12 volts but it 'capacity' has been reduced by sulphation for every day it has been left.

 

You need to get it on charge for 12-24 hours to get it as fully charged as it will. Only then will you find out how severe the damage is.

Edited May 7, 2019 by Alan de Enfield

[Dr Bob]

44 minutes ago, DannyC said:

. The battery was fairly well charged when leaving (well over 50%).

Danny, lets start with your first post. Lead acids MUST be charged back up to 100% 'soon' after they have been 'used'. I get mine back to 100% at least every other day. Some people may take this to mean back to 100% every week.....but their batteries wont last as long as mine. If you dont get them back to 100% then they will sulphate and loose capacity.

Your statement could be interpreted to say 60% SoC is well charged. IT IS NOT! Well charged is 100%.

If your batteries were at 60% and you went off for a week, you are asking for problems with your batteries. Get them fully charged before you leave them or at least fairly well charged.

 

 

eta ......crossed with Alan's post

Edited May 7, 2019 by Dr Bob

[DannyC]

OK thanks for the info.

 

I tested the battery when charging yesterday and it was running at 13.9

 

I am charging at the moment, so I will take a look and see what the situation is.

 

My batteries are fairly new (Dec,18), and I have been careful with them, so hopefully the damage isn't too great.

 

We will see.

 

Thanks

Sorry, another question.

 

If you leave batteries and are not using them at all, do they naturally lose charge anyway?

[Alan de Enfield]

4 minutes ago, DannyC said:

If you leave batteries and are not using them at all, do they naturally lose charge anyway?

Slightly - yes (it is called self-discharge) but it is a very small number.

 

Folk have totally killed their battery bank within 1 week of purchase, so you are by no means the 'worst battery baby sitter'.

 

How are you charging (mains power battery charger, solar, engine alternator) ?

 

13.9 charging voltage is very low unless the battery is very flat.

You need to charge until the charging voltage is 14.4 (or more) and the charging current is 2 amps or less (if you have one battery)

 

How many batteries do you have ?

Edited May 7, 2019 by Alan de Enfield

[DannyC]

haha! 

[Alan de Enfield]

Just now, DannyC said:

haha! 

????????????????/

[DannyC]

2 minutes ago, Alan de Enfield said:

????????????????/

 

at the babysitter comment....

 

OK so I have four 100amp hour leisure batteries.

 

I charge by running in tick over/ when i'm cruising (getting solar in a couple of weeks), so I know that isn't kind on the batteries.

 

Oh damn I thought that 13.9 was ok - let me go check what it's at now.

[Dr Bob]

11 minutes ago, DannyC said:

If you leave batteries and are not using them at all, do they naturally lose charge anyway?

That's not the problem though.

Leaving them 60% for a few weeks will wreck them if you keep doing it.

At least get them to 100% every week.

How are you measuring if they are 100%?

[DannyC]

Dr.Bob - volt meter 

 

I charge them with the aim of getting to (or as close to 100%) regularly.

 

Alan - Ok, so I just checked using the volt meter. Reading at 13.95 after running in tick over for 2.5 hours...

 

 

 

 

 

[Alan de Enfield]

9 minutes ago, DannyC said:

OK so I have four 100amp hour leisure batteries.

Ok - you need to get an ammeter.

Charge with everything switched off (yes - including the fridge) until the voltage reaches 14.4v + and the charging current gets below 6 amps (measured with your new ammeter).

 

After a minimum of one hour when you have stopped charging measure the battery voltage, you are looking for (ideally) about 12.9v.

 

You are unlikely to be able to run the engine long enough to get the batteries charged to 100%

have you got a mains battery charger ?

Can you get into a marina (or access to mains) and use the battery charger for a couple of days ?

2 minutes ago, DannyC said:

Dr.Bob - volt meter 

 

I charge them with the aim of getting to (or as close to 100%) regularly.

 

Alan - Ok, so I just checked using the volt meter. Reading at 13.95 after running in tick over for 2.5 hours...

Another 12 hours then !!!

 

How are you measuring 100% ? (serious question)

Edited May 7, 2019 by Alan de Enfield

[DannyC]

Just now, Alan de Enfield said:

Ok - you need to get an ammeter.

Charge with everything switched off (yes - including the fridge) until the voltage reaches 14.4v + and the charging current gets below 6 amps (measured with your new ammeter).

 

After a minimum of one hour when you have stopped charging measure the battery voltage, you are looking for (ideally) about 12.9v.

 

You are unlikely to be able to run the engine long enough to get the batteries charged to 100%

have you got a mains battery charger ?

Can you get into a marina (or access to mains) and use the battery charger for a couple of days ?

 

Yeah I've got a mains charger. Doubt I will be able to do the marina suggestion unfortunately.

 

I will get hold of an ammeter.

 

Thanks.

[Alan de Enfield]

1 minute ago, DannyC said:

 

Yeah I've got a mains charger. Doubt I will be able to do the marina suggestion unfortunately.

 

I will get hold of an ammeter.

 

Thanks.

Make sure it measures DC amps NOT AC amps.

[MtB]

How are you measuring the state of charge?

 

You stated "well over 50%" in your first post. How do you know this? 

 

Depending on how you are determining state of charge, you could be miles out. In fact with no ammeter, you probably ARE!

 

 

 

 

[DannyC]

1 minute ago, Mike the Boilerman said:

How are you measuring the state of charge?

 

You stated "well over 50%" in your first post. How do you know this? 

 

Depending on how you are determining state of charge, you could be miles out. In fact with no ammeter, you probably ARE!

 

 

 

 

Using a volt meter...