Battery charger - how much shore power to keep charged

Irish Rover

Irish Rover

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For those of you who don't know already I'm not very tech savvy so apologies in advance. I've volunteered to keep an eye on a boat in the marina here for another Paddy who won't be back again until the spring. My duties are simple enough to run the engines every few weeks and top up the shore power credit if needed. The shore power is connected 24/7 to keep the batteries charged but everything else is switched off at the breakers. Checking the shore power meter it appears to be using 1.5Kw per day. Is that excessive just for battery charging with no draw on the batteries?
 
That is huge - over 110 Amp hours.

I can put in a maximum of about 12 amp hours a day via a small solar panel and it’s much more than adequate and has the battery charged by mid morning.

Something is seriously awry - either there is a huge load using power on the boat, the meter is very wrong or you are reading the meter wrongly.
 
Irish Rover said:
For those of you who don't know already I'm not very tech savvy so apologies in advance. I've volunteered to keep an eye on a boat in the marina here for another Paddy who won't be back again until the spring. My duties are simple enough to run the engines every few weeks and top up the shore power credit if needed. The shore power is connected 24/7 to keep the batteries charged but everything else is switched off at the breakers. Checking the shore power meter it appears to be using 1.5Kw per day. Is that excessive just for battery charging with no draw on the batteries?
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I never leave a charger on when away from the boat, if its switched off if cant go duff & boil the batteries or kill its self
 
Irish Rover said:
Checking the shore power meter it appears to be using 1.5Kw per day. Is that excessive just for battery charging with no draw on the batteries?
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I'm assuming you mean 1.5kW-hour, which is what utility meters usually tell you. Sure it's not 0.15kWh? 1.5kWh is high for simply maintaining float charge. It implies a constant 5A at 12V (which would be somewhat less at the batteries because of inefficiencies). I'd expect less for a healthy, fully charged battery bank of typical size. How big is the battery bank? If there are there any battery instruments it would be useful to know the amps actually being delivered. And how long had the batteries been on charge when you got the 1.5kWh figure? If the batteries were still being brought up to full charge, it wouldn't be so surprising.
 
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macd said:
I'm assuming you mean 1.5kW-hour, which is what utility meters usually tell you. Sure it's not 0.15kWh? 1.5kWh is high for simply maintaining float charge. It implies a constant 5A at 12V (which would be somewhat less at the batteries because of inefficiencies). I'd expect less for a healthy, fully charged battery bank of typical size. How big is the battery bank? If there are there any battery instruments it would be useful to know the amps actually being delivered. And how long had the batteries been on charge when you got the 1.5kWh figure? If the batteries were still being brought up to full charge, it wouldn't be so surprising.
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The batteries should have been fully charged when I started measuring. The owner was here for 2 weeks getting work done on the boat. He had it out for a couple of runs and the shore power was connected all the time he was here. I took a reading the morning after he left and again each of the two following mornings. It had used 15 of the meter units each day and I asked the Marina Office this morning what the units represented. They told me divide by 10 for Kw. I don't know the battery details but I'll try to have a look when I'm back in the marina. I'm not really familiar with the layout of the boat which is an old 1972 Grand Banks Classic with wooden hull.
 
Irish Rover said:
For those of you who don't know already I'm not very tech savvy so apologies in advance. I've volunteered to keep an eye on a boat in the marina here for another Paddy who won't be back again until the spring. My duties are simple enough to run the engines every few weeks and top up the shore power credit if needed. The shore power is connected 24/7 to keep the batteries charged but everything else is switched off at the breakers. Checking the shore power meter it appears to be using 1.5Kw per day. Is that excessive just for battery charging with no draw on the batteries?
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Seems very high. How big is the battery bank?

If there's no typo/data-misreading here, and if this isn't a huge battery bank, then there may be a problem; potentially a serious one, or perhaps something has been inadvertently left switched on, perhaps directly connected to the batts?
 
dom said:
Seems very high. How big is the battery bank?

If there's no typo/data-misreading here, and if this isn't a huge battery bank, then there may be a problem; potentially a serious one, or perhaps something has been inadvertently left switched on, perhaps directly connected to the batts?
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Yes, not impossible to have a 60W continuous load somewhere.
 
dom said:
If there's no typo/data-misreading here, and if this isn't a huge battery bank, then there may be a problem; potentially a serious one, or perhaps something has been inadvertently left switched on, perhaps directly connected to the batts?
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What he said, Rover.
I'm also still a little suspicious about the meter readings. There surely must be some units marked on the meter. Could you take a photo for us?
 
Irish Rover,
Does the 240V mains charger have an integral ammeter? Or do you have any other way of verifying what 12V is going into the batts, or potentially elsewhere? And you’re sure there is nothing else running off the mains a/c, dehumidifier, engine heater, etc.?
 
macd said:
What he said, Rover.
I'm also still a little suspicious about the meter readings. There surely must be some units marked on the meter. Could you take a photo for us?
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+1, a scaling error of 10 or even 100 crossed my mind too.
 
OK so I've had a look. 3 batteries present - 2 x 225ah Varta and 1 x much smaller battery which I can't get a good look at but from the size is probably a 90 or 100ah engine start battery. All look fine and not hot to the touch when the charger is on. I took a photo of the charger but can't seem to post from my phone but this is it from google
VL-169.jpg
I'm going to the marina office to ask about the meter units and will report later.
 
Further to my post above I called the marina electrician to the boat. He confirmed the units on the meter are a tenth of a Kw so the 15 per day it's using = 1.5Kw. He didn't seem to think the usage was unusual but he wouldn't, would he. I've disconnected the shore power at the meter and taken a reading so will check again tomorrow. If the reading is still the same then I guess the problem is most likely on the boat and I'll advise my pal to get a proper electrician to check it out.
 
I do leave my battery charger on and can safely say it should consume hardly anything.
1.5 units is about 25pence per day or thereabouts . Not huge but perhaps fridge has been left on?
Has a frost protection heater not been put in the engine bay ? if so it might have cut in in recent nights if on a thermostat? Perhaps frost in your area is not a risk?

Starting the engine every few weeks also seems to me unnecessary and possibly detrimental …………but each to his own,.
 
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