Inverter question

[Dave_P]

For the last few weeks I've been having electrical supply problems. My batteries just haven't been holding up well and my thoughts were that they were on their way out.

 

This reached crisis point on thursday night. I left my mooring on hook-up and went off an moored on the towpath elsewhere. I settled in for the evening and put a film on, using my 2000w psw inverter to a 22" 240v tv. I've had both for years.

 

A couple of hours later my battery voltage had dropped below 12v which was obviously concerning to me. 11.6v I think it read. bad! I turned off the inverter and the voltage picked up to about 12.4 which was ok. The fridge stayed on all night. In the morning the the voltage was reading 12.3 which was ok-ish. I turned on the inverter and tv to watch the breakfast news and the voltage dropped down to 10.8 and the inverter began howling at me. Worrying. My thought was that the batteries were now properly knackered and needed replacing.

 

Then I had to go to work. I left the fridge off. There wasn't much in it anyway.

 

When I got home I checked the electrolyte levels of my three leisure batteries in case I could eek out some more life by topping them up a bit. They were all fine.

 

So I tried charging the batteries off the engine. The voltage immediately jumped to around 14v as expected so I stuck the tv back on. Even with the engine running, the voltage dropped down to 11.6. Enough to run the inverter but clearly not right. I turned the inverter off and let the engine run for an hour and a half then tried to watch tv again. All was fine with the engine running, fridge on, inverter on. I began to wonder if my charge had been abnormally low when leaving my mooring, meaning my mains charger was the issue? I hadn't checked the voltage when leaving.

 

At 8.00pm I turned the engine and everything else off after about 3.5 hours of engine charging. The voltage settled to around 12.9v which I was happy with.

 

I left everything off over night so the only draw was an led bulb and the occasional use of the water pump.

 

In the morning the voltage was still at 12.8v. Nice! I told myself that the problem was leaving my mooring with a low charge and everything was fine now. I tried the inverter + tv. Voltage drop to 11.5v. Tried inverter on it own, nothing else on. Voltage drop to 11.6v??? This seemed odd to me. The batteries had held charge fine all night but couldn't cope with the inverter on it's own? This was highly unusual. So then I tried turning all my 12v stuff on at once, all my lights (including incandescent), my water pump, 12v laptop charger, fridge. The voltage was barely affected. Dropped to 12.7v. Then I turned everything off and put the inverter on again. Voltage drop to 11.5v and I noticed that the inverter fan kicked in immediately like it was overheating.

 

I've had to go out again now and I'm not back until tomorrow night. When I get back, I'll have the inverter off the wall to have a look at it. I guess it's full of dust and fluff? But my question is: Can an inverter really draw that much current? I'm sure the inverter didn't used to draw this much current, I'd have noticed.

 

All my voltage readings have been taken from the digital display for my solar system. I realise that this isn't perfect but when I've tested it against a proper voltmeter on the battery terminals it seems pretty accurate.

 

All help is appreciated.

[Richard10002]

Sounds like a problem with the inverter, or it's running something powerful that you don't know about.

[Alan de Enfield]

I was just wondering if the immersion heater switch had been 'knocked' to the 'on' position ?

[Martin Megson]

An inverter shouldn't be drawing much current when there is no 240v load. At the risk of stating the obvious are you sure there is nothing connected you've forgotten, like a battery charger for instance. If not then I would suspect a fault in the inverter.

[rusty69]

Are the cables supplying the inverter in good condition, of appropriate size and making good connection?

 

Can you measure the voltage on the inverter terminals?

 

 

I cleaned a load of dust out of our inverter and solar controller earlier in the year. I was amazed at the build up, but doubt that would cause the problem you describe.

[Dave_P]

I was just wondering if the immersion heater switch had been 'knocked' to the 'on' position ?

Ooh! Possibly. This would make me very happy!

An inverter shouldn't be drawing much current when there is no 240v load. At the risk of stating the obvious are you sure there is nothing connected you've forgotten, like a battery charger for instance. If not then I would suspect a fault in the inverter.

Everything is off but I am now wondering about the immersion...

[Naughty Cal]

I would check nothing is switched on that shouldn't be first.

 

We have been known to forget to switch our battery charger off!

[Dave_P]

Are the cables supplying the inverter in good condition, of appropriate size and making good connection?

 

Can you measure the voltage on the inverter terminals?

 

 

I cleaned a load of dust out of our inverter and solar controller earlier in the year. I was amazed at the build up, but doubt that would cause the problem you describe.

The cables are are good and thick and given the thumbs up the last time I had a proper electrician on my boat.

 

I'm thinking of cycling back to my boat now to check the immersion switch.

 

I've currently got my head down in the University library - supposed to be working hard, I think I can afford a 30 minute trip back to check, don't you?

[Alan de Enfield]

The cables are are good and thick and given the thumbs up the last time I had a proper electrician on my boat.

 

I'm thinking of cycling back to my boat now to check the immersion switch.

 

I've currently got my head down in the University library - supposed to be working hard, I think I can afford a 30 minute trip back to check, don't you?

 

It'll just 'eat away at you' until you find out - GO !!

[Dave_P]

 

It'll just 'eat away at you' until you find out - GO !!

I did. You were right. I feel very silly now, but happy too.

 

Seems kinda obvious now

[Bloomsberry]

I'm assuming there's a breaker in the 240v supply from the inverter so I would knock this off to make sure nothing is being supplied.

[Alan de Enfield]

I did. You were right. I feel very silly now, but happy too.

 

Seems kinda obvious now

 

Easily done and sometimes things are so obvious it takes a 'simple mind' to suggest it.

 

Good that the problem is 'solved'.

[Dave_P]

In a way I'm extra pleased, it means that my immersion ran for 2 hours on thursday night while I watched tv and my fridge was running. My batteries can't be as bad as I'd thought. Probably will need changing soon now though!

[Alan de Enfield]

In a way I'm extra pleased, it means that my immersion ran for 2 hours on thursday night while I watched tv and my fridge was running. My batteries can't be as bad as I'd thought. Probably will need changing soon now though!

 

Assuming the 'standard' 1kw immersion heater element, that's roughly 200Ah taken out of the batteries over the 2 hours - shows the batteries 'were' fine - try it again now you know what's what and see if they will do it again.

[Naughty Cal]

 

Assuming the 'standard' 1kw immersion heater element, that's roughly 200Ah taken out of the batteries over the 2 hours - shows the batteries 'were' fine - try it again now you know what's what and see if they will do it again.

Surely the immersion would kick out once the water was to temperature though?

[Dave_P]

 

Assuming the 'standard' 1kw immersion heater element, that's roughly 200Ah taken out of the batteries over the 2 hours - shows the batteries 'were' fine - try it again now you know what's what and see if they will do it again.

Er, no. I know when to quit when I'm ahead. Also, I doubt the immersion was actually on that long, seeing as the water should have been hot already. So, the more I think about it, I suspect my batteries are still on their way out. The better indicator was last night when the water was cold, I was running the engine and turning the inverter on pulled the voltage down from 14.2 to 11.6!!!

[Dave Payne]

The better indicator was last night when the water was cold, I was running the engine and turning the inverter on pulled the voltage down from 14.2 to 11.6!!!

 

Wouldn't this just be down to the draw, 1kw is a lot, even with the engine running.

 

I have this also when running the iron or toaster, even when the batteries were brand new.

[by'eck]

For the last few weeks I've been having electrical supply problems. My batteries just haven't been holding up well and my thoughts were that they were on their way out.

 

This reached crisis point on thursday night. I left my mooring on hook-up and went off an moored on the towpath elsewhere. I settled in for the evening and put a film on, using my 2000w psw inverter to a 22" 240v tv. I've had both for years.

 

A couple of hours later my battery voltage had dropped below 12v which was obviously concerning to me. 11.6v I think it read. bad! I turned off the inverter and the voltage picked up to about 12.4 which was ok. The fridge stayed on all night. In the morning the the voltage was reading 12.3 which was ok-ish. I turned on the inverter and tv to watch the breakfast news and the voltage dropped down to 10.8 and the inverter began howling at me. Worrying. My thought was that the batteries were now properly knackered and needed replacing.

 

Then I had to go to work. I left the fridge off. There wasn't much in it anyway.

 

When I got home I checked the electrolyte levels of my three leisure batteries in case I could eek out some more life by topping them up a bit. They were all fine.

 

So I tried charging the batteries off the engine. The voltage immediately jumped to around 14v as expected so I stuck the tv back on. Even with the engine running, the voltage dropped down to 11.6. Enough to run the inverter but clearly not right. I turned the inverter off and let the engine run for an hour and a half then tried to watch tv again. All was fine with the engine running, fridge on, inverter on. I began to wonder if my charge had been abnormally low when leaving my mooring, meaning my mains charger was the issue? I hadn't checked the voltage when leaving.

 

At 8.00pm I turned the engine and everything else off after about 3.5 hours of engine charging. The voltage settled to around 12.9v which I was happy with.

 

I left everything off over night so the only draw was an led bulb and the occasional use of the water pump.

 

In the morning the voltage was still at 12.8v. Nice! I told myself that the problem was leaving my mooring with a low charge and everything was fine now. I tried the inverter + tv. Voltage drop to 11.5v. Tried inverter on it own, nothing else on. Voltage drop to 11.6v??? This seemed odd to me. The batteries had held charge fine all night but couldn't cope with the inverter on it's own? This was highly unusual. So then I tried turning all my 12v stuff on at once, all my lights (including incandescent), my water pump, 12v laptop charger, fridge. The voltage was barely affected. Dropped to 12.7v. Then I turned everything off and put the inverter on again. Voltage drop to 11.5v and I noticed that the inverter fan kicked in immediately like it was overheating.

 

I've had to go out again now and I'm not back until tomorrow night. When I get back, I'll have the inverter off the wall to have a look at it. I guess it's full of dust and fluff? But my question is: Can an inverter really draw that much current? I'm sure the inverter didn't used to draw this much current, I'd have noticed.

 

All my voltage readings have been taken from the digital display for my solar system. I realise that this isn't perfect but when I've tested it against a proper voltmeter on the battery terminals it seems pretty accurate.

 

All help is appreciated.

 

Sounds like as your battery capacity has dropped to a small fraction of original and they will need replacing. In current state they will be quick to charge to a relatively high voltage as you found. They will also hold this voltage for a while due to high surface charge until a substantial load (inverter) is placed on them, shortly after which the voltage wIll plummet due to lack of capacity to sustain load.

 

What I find a little suspicious is that the engine alternator could not keep up with inverter demand. Wonder what it's current draw was v alternator output.

 

ETA: just read your post re immersion being on and consequent voltage with this high inverter load, which is entirely to be expected.

Nothing you have said therefore suggests anything amiss or unexpected, other than battery bank shot.

Edited November 5, 2016 by by'eck

[Top cat]

You might want to consider re wiring the immersion heater so that it can only be run when connected to shore power. That would prevent a repeat. If you dont fancy that fit a warning light somewhere prominent that switches on with the immersion. Another possibility is to fit a timer switch to the immersion, one press gets 15 minutes , 2 = 30 min etc

 

Top Cat