Excessive mains electricity use.

[Northener]

As I am about to start using the boat soon I connected to mains power. I don’t usually leave the boat plugged in but plug in to keep the batteries charged up every now and then. Before I plugged in last week I didn’t think the batteries were low but thought they might need topping up. I have found that after 4 days on charge I have used 2 kWh of mains electricity. This seems rather a lot. Nothing was turned on in the boat, and the inverter was switched to charge only mode. 
Can somebody tell me if this seems excessive? I have a starter battery of 80 ah and 2 leisure batteries of 110 ah and (I think) 200ah. 

 

[Francis Herne]

300Ah at 12V is about 3kWh so that's not an impossible amount of energy, especially with the low charging efficiency of lead-acids.

 

It does suggest your batteries were quite low to begin with, which may not be a good thing.

Edited April 21, 2023 by Francis Herne

[Tony Brooks]

7 minutes ago, Northener said:

As I am about to start using the boat soon I connected to mains power. I don’t usually leave the boat plugged in but plug in to keep the batteries charged up every now and then. Before I plugged in last week I didn’t think the batteries were low but thought they might need topping up. I have found that after 4 days on charge I have used 2 kWh of mains electricity. This seems rather a lot. Nothing was turned on in the boat, and the inverter was switched to charge only mode. 
Can somebody tell me if this seems excessive? I have a starter battery of 80 ah and 2 leisure batteries of 110 ah and (I think) 200ah. 

 

 

You may have a shorting cell or cells, that would tend to keep the charger running at higher output than usual. Look for local hot spots on the cell lids, single cells gassing more than the rest when on charge, or individual dry cells.

 

However the more likely cause is someone else has been using your electricity.

[Alan de Enfield]

1 minute ago, Francis Herne said:

300Ah at 12V is about 3kWh so that's not an impossible amount of energy, especially with the low charging efficiency of lead-acids.

 

It does suggest your batteries were quite low to begin with, which may not be a good thing.

 

 

Or that they are sulphated and taking far more charge than they should.

 

 

10 minutes ago, Northener said:

I have found that after 4 days on charge I have used 2 kWh of mains electricity

 

Are the batteries (or a single battery) getting hot when on charge?

Are they (or a single battery) a 'bit out of shape ? (ends blown out and 'rounded') ?

[David Mack]

11 minutes ago, Northener said:

As I am about to start using the boat soon I connected to mains power. I don’t usually leave the boat plugged in but plug in to keep the batteries charged up every now and then. Before I plugged in last week I didn’t think the batteries were low but thought they might need topping up. I have found that after 4 days on charge I have used 2 kWh of mains electricity. This seems rather a lot. Nothing was turned on in the boat, and the inverter was switched to charge only mode. 
Can somebody tell me if this seems excessive? I have a starter battery of 80 ah and 2 leisure batteries of 110 ah and (I think) 200ah. 

 

2 kWh over 4 days equates to an average consumption of about 21W or 0.1A drawn from the mains. If your charger is 100% efficient (and it will not be) that would represent an average charge current into the batteries of 2A. So sounds entirely plausible.

[nicknorman]

2kwh over 4 days is an average consumption of 20 watts. Quite likely that most of this is going to run the charger. It is probably slightly warm. And even if the charger were 100% efficient that only equates to about 1.5A continuous current into the battery.

 

edit: I’m too slow!

Edited April 21, 2023 by nicknorman

[Tony Brooks]

1 hour ago, Alan de Enfield said:

Or that they are sulphated and taking far more charge than they should

 

How does that work then? Unless the sulphation has pushed its way through the separators, so the cell is now shorting. Sulphation produces a loss of capacity so fast discharged and, what is important in this case, fast charging, thus less Ah taken and less current taken from the mains.

[matty40s]

Are you 100% sure that your immersion(if you have one), is switched off. This isnt usually wired through the inverter so it can't be on when you are out cruising, and will.have a separate switch somewhere.

[MtB]

Given a kWh usually costs less than about 50p, I'm amazed the OP even noticed 2kWh being used over four days!

[Northener]

Thanks for all help. It seems that I may or may not have a problem. I’ve left the boat unplugged and will return next week and see if the batteries get warm when I put on charge again. 

[LadyG]

1 minute ago, Northener said:

Thanks for all help. It seems that I may or may not have a problem. I’ve left the boat unplugged and will return next week and see if the batteries get warm when I put on charge again. 

Maybe take your multimeter there are YouTube demos

[mrsmelly]

23 minutes ago, MtB said:

Given a kWh usually costs less than about 50p, I'm amazed the OP even noticed 2kWh being used over four days!

Hes one of them northerners with deep pockets and short arms 😃

[Momac]

If my batteries are fully charged my batter charger used a bit under 0.1kWh per day (about 2 pence worth).

But obviously it uses more if the batteries needed to be charged .

I would check the batteries to see if there is  a fault like batteries gassing or getting hot 

PS

2kwh is probably 60p in electricity so hardly excessive

[Alan de Enfield]

57 minutes ago, Tony Brooks said:

 

How does that work then? Unless the sulphation has pushed its way through the separators, so the cell is now shorting. Sulphation produces a loss of capacity so fast discharged and, what is important in this case, fast charging, thus less Ah taken and less current taken from the mains.

 

Yes - I meant that it could be an internal short, but didn't finish what I wanted to write. Hence my question about them being hot or mishapen.

.

[blackrose]

4 hours ago, MartynG said:

 

2kwh is probably 60p in electricity so hardly excessive

 

At my mooring it's £1.60 (80p/kWh). For those paying less you're fortunate but I doubt you'll stay on a low rate for very long.

[Momac]

28 minutes ago, blackrose said:

 

 I doubt you'll stay on a low rate for very long.

Luckily the marina entered into a 3 year deal for electricity which started on 1st December 2021 (I just checked the date) . So our marina rate for electricity  is fixed until December 2024.

With admin charges added  the present rate come to about 32p per kWh which was  a big increase in price at the time in December 2021  but seems very reasonable right now. In terms of energy costs we save money by spending the weekend on the boat. It's not big money but every little helps.

 

I guess most of us hope energy costs will come down but there seems no sign of that happening .

 

[Lily Rose]

2 hours ago, MartynG said:

 

 

I guess most of us hope energy costs will come down but there seems no sign of that happening .

 

 

As far as I'm aware energy costs are coming down but it's not noticeable (yet) due to the fact that, although reduced, they are still higher than the rate subsidised by the government. That may change later this year if recent trends continue.

 

https://moneyweek.com/personal-finance/605440/will-energy-prices-go-down

[ditchcrawler]

20 minutes ago, Lily Rose said:

 

As far as I'm aware energy costs are coming down but it's not noticeable (yet) due to the fact that, although reduced, they are still higher than the rate subsidised by the government. That may change later this year if recent trends continue.

 

https://moneyweek.com/personal-finance/605440/will-energy-prices-go-down

Electricity Prices

 

Gas Prices 

[Momac]

Perhaps there is hope for some price competition but I expect the energy suppliers will keep prices high as long as they can. 

 

 

 

[Lily Rose]

Well hopefully they won't be able to for too long as Ofgem review the price cap every 3 months now. The next, or next but one, time should see it go below the current government cap.

 

At home I was fortunate (very!) to fix for 2 years when the cap was under £1400 for typical use so I'm hoping prices will have come down a bit by mid-September when that deal ends. Obviously there will be a big hike for me then but not as bad as it seemed it might be a year ago.

 

The marina rate is a lot higher at 32p per kwh vs under 20p at home but even that doesn't seem too bad compared to some marinas, from what I've heard.

Edited April 22, 2023 by Lily Rose