Can Inverters deteriorate?

[Postcode]

We were having power problems on Carrie Lou last April so in May we bought 3 new 110 amp hour sealed batteries since the ones on board were getting old. After a couple of cruises the new batteries were running down sooner than we expected. In between cruises they are trickle charged. We went back to the supplier on xmas eve but they didn't have anyone to check them.

 

We then went back at Easter when they drop tested them and said they were fine.

 

We then went back a couple of weeks ago and they replaced the isolation switch and said it was probably the inverter breaking down.

 

I haven't replaced the inverter. Today the batteries were fully charged when we left the marina. We cruised for 4 hours and watched tv for 4 hours before the batteries were below the voltage required by the inverter.

 

This voltage was also below that needed for the fridge.

 

I am an electrical ignoramus!

 

What should I do now?

 

Today

[Keeping Up]

It is possible, but extremely unlikely, that the inverter is the problem.

 

Next step - try the checklist I made out for you before.

[DeanS]

There are a few things that can cause the voltage to the invertor to be low.

 

1. Dirty battery terminals causing voltage drop.

2. Long runs of 12V wires which are too thin, so voltage drops.

3. The fridge could be drawing a lot of current.

4. The boat alternator may not be supplying current to the batts when you are cruising.

Edited June 22, 2013 by DeanS

[The Bagdad Boatman (waits)]

Hot weather and fridge use electric big time. Work out the amp ph the fridge uses. Modern lcd tv are greedy also. Buy more batteries. What charging system are you using?

Edited June 22, 2013 by The Bagdad Boatman (waits)

[DeanS]

If you only cruise weekends and can recharge batts during the week, then more batts is an option, else just get 1 big solar panel, and your "invertor voltage" will be sitting in the high 12's all day......( I have 4 and havent run my boat engine for batt recharging for 3weeks. I used to run it 3hrs a day, morn and evening)

[Hawkmoth]

WE used to get the problem of the 230V fridge start up bringing the DC voltage down. It never actually dropped out because we have huge batteries, but it was worrying. I had a good look around and managed to make the high power DC runs much shorter and it made a heck of a difference.

Bob

[Bodkin]

WE used to get the problem of the 230V fridge start up bringing the DC voltage down. It never actually dropped out because we have huge batteries, but it was worrying. I had a good look around and managed to make the high power DC runs much shorter and it made a heck of a difference.

Bob

Edit to say this belongs with my below post - trying to post on a new phone and failed!

Edited June 23, 2013 by Bodkin

[Charlotte Burnett]

Do you have any battery monitoring beyond a volt meter? You need to measure where the amps are going to figure this one out. A DC clamp meter is your friend in the absence of anything else. Boats nearby may have one if you don't but very useful for the toolbox. Turn everything off except the master switch, take a reading from the out side of the switch and leave it there. Then start turning things on, start running through your DC stuff first, if all of that looks ok, turn it all off and then do the AC side.

 

Post up what you get and it might be possible to figure out a fix for you.

[Bodkin]

Also being an electric ignoramus, can you explain what you mean by making the 'high power DC runs much shorter' are you talking about the length of wiring. We're at the point of thinking we need to replace our 12v Waceo fridge as it doesn't last longer than 20 mins before coming on, regardless of how much charge is in the batteries. (Apologies to the OP for going off on a tangent)

[Biggles]

Fridges are a monster user of power especially in the summer.

 

The DC runs are the hopefully very thick Very short cables probably red and black from the batteries to the inverter. They should be easy to identify .

[Charlotte Burnett]

How full your batteries are has precisely nothing to do with how often your fridge kicks in although how often your fridge kicks in has a lot to do with how full your batteries are. You may have touched upon the problem here.

 

How long have you had the boat, have you ever not had battery issues with it?

 

Your fridge has a thermostat in it. You have a knob to set this....normally 1=warmest and 5 =coolest but sometimes it is backwards to this, check your instructions. When the fridge warms up beyond the given point you have set (which rarely correlates with temperature in deg C) the compressor kicks in. When it reaches it's cool point, it kicks off. If the fridge is mainly full of air, it will retain coldness less well than if it is full. However, cooling a full fridge initially takes longer. If you don't liveaboard, consider filling up bottles with water and stuffing the fridge with them. I prefer to use gin and tonic bottles so as not to waste the cold. The rag and stick lot often stuff their fridges with extra insulation as well. Before you do this though, clean your fridge out thoroughly, check all of the seals carefully and make sure that the drain hole is clear. Then pull it out and hoover the back elements thoroughly, a dirty fridge will be inefficient. You should let it settle for 24 hrs before turning it on again to allow the coolant to settle.

 

Someone will be along shortly to tell you to jury rig some computer fans under your fridge...they have a point but ignore them right now, let's find the real problem first before we go crazy finding solutions to imaginary ones.

 

Biggles touches on another possible problem; how big are the cables going to the fridge from the DC distribution? Often they are undersized and this could be where all of your volts are running off to. If you can estimate the cable diameter we can make a guess as to the size. We also need to know what the distance between the distribution (fuse/breaker panel) and the fridge is and, ideally the model number of your fridge.

 

Bodkin - voltage drop is a huge issue with extra low voltage set ups (ie battery powered stuff.) The lower the original voltage, the worse the problem. By increasing the cable size, the voltage drop is less. Big cable is expensive and awkward and on very long cable runs, the maths of what is right does not necessarily agree with my multimeter! By reducing the length of the run, the voltage drop is less and therefore the appliance at the end of the cable uses less of your precious batteries up (a pedant will be along shortly to correct me.)

[Arthur Brown]

"I haven't replaced the inverter. Today the batteries were fully charged when we left the marina. We cruised for 4 hours and watched tv for 4 hours before the batteries were below the voltage required by the inverter.

This voltage was also below that needed for the fridge.

What should I do now?"

 

A failed inverter will likely show obvious signs, -total failure to function, smoke etc so if it works leave it.

How do YOU know that the batteries were full? Volts reading? Trickle charge reading? Does the trickle charge exceed the permanent fixed loads (bilge pump etc)?

What charge indication did you get during the 4 hour cruise, does the charging circuit really work? Is it charging both batteries (starter and house)

What current did you draw for the evening four hours. If the batteries were full at the end of the cruise then you emptied 330AH in four hours, which I think is a LOT.

 

How fat are the inverter DC supply wires? Thin wires drop a lot of volts at high current. (12.5v battery lose a volt in each lead and you have 10.5v at the inverter and it will shut off saying low battery but meaning thin wires. ) Inverter DC wires need to be as big or bigger than starter motor wires.

[by'eck]

We were having power problems on Carrie Lou last April so in May we bought 3 new 110 amp hour sealed batteries since the ones on board were getting old. After a couple of cruises the new batteries were running down sooner than we expected. In between cruises they are trickle charged. We went back to the supplier on xmas eve but they didn't have anyone to check them.

 

We then went back at Easter when they drop tested them and said they were fine.

 

We then went back a couple of weeks ago and they replaced the isolation switch and said it was probably the inverter breaking down.

 

I haven't replaced the inverter. Today the batteries were fully charged when we left the marina. We cruised for 4 hours and watched tv for 4 hours before the batteries were below the voltage required by the inverter.

 

This voltage was also below that needed for the fridge.

 

I am an electrical ignoramus!

 

What should I do now?

 

Today

 

Certainly sounds like your supplier is, remarking the inverter was breaking down?

 

Having said that can you not switch off the inverter and see how the batteries perform. A large inverter supplying AC to a modest load such as a TV may be quite inefficient. It could be that the quiescent (no load) current drawn from the batteries is greater than that taken by the TV.

[Arthur Brown]

An accurate remote diagnosis really needs some accurate figures to work with. Resting voltages for the batteries as charged and an hour after the inverter trips out. Charging voltage on shoreline and and on alternator charge.

[Hawkmoth]

Sorry, been away since my post about the high power DC runs. I think most of what needs to be said has been covered by others here.

I would just emphasize the need for THICK cables from the battery to the inverter. The shorter the better. By the way, what size is your inverter?

It might be worth you investing in a DC clamp meter, they're not expensive and will tell you where any power is being used, and how much. If you do go for one make sure that it will measure DC current, that's important.

Bob

[trackman]

Re your fridge, when it's warm ours probably runs one third to a half of the time. That is perhaps 20/30mins on then 30 off.

 

A 240V fridge running off an inverter will use a bit more power than a good 12V one, but the cable size for the 240V connection is much less critical. The cables that matter are the 12V ones as the currents in these are about 20 times greater for any given power use. This means proportionally higher voltage drops.

 

Finally, a given voltage loss is much more significant when the original voltage is 12V than if it's 240. Half a volt in 12 versus half a volt in 240 for example. So shorter fatter cables are optimal every time with 12V.

 

This applies between batteries & inverter or from batteries direct to 12V fridge. Our 12V fridge has cables about 4m long and they must be at least 15mm square, maybe more.

Edited June 23, 2013 by trackman

[smileypete]

Could be good to get hold of a multimeter and check the voltage at the batts when the engine is running, the batts need to see 14.4V for a good few hours to get reasonably well charged.

 

Whenever working around the batts do follow all the precautions in The Battery FAQ: http://www.batteryfaq.org/

 

cheers, Pete.

~smpt~

Edited June 23, 2013 by smileypete

[Theo]

WE used to get the problem of the 230V fridge start up bringing the DC voltage down. It never actually dropped out because we have huge batteries, but it was worrying. I had a good look around and managed to make the high power DC runs much shorter and it made a heck of a difference.

Bob

Might I just be a bit of an electrical pedant and remind people that the large cables from the battery are high current not high power.

 

Sorry.

 

N

 

 

Edited to add that such pedantry was entirely unhelpful. The advice given by lots of others is extremely helpful and to the point. Keep it up. I am sure that the problems will be sorted out and the educational process will be worthwhile and useful for the long term.

 

N

Edited June 23, 2013 by Theo
As in the post

[Postcode]

There are a few things that can cause the voltage to the invertor to be low.

 

1. Dirty battery terminals causing voltage drop.

2. Long runs of 12V wires which are too thin, so voltage drops.

3. The fridge could be drawing a lot of current.

4. The boat alternator may not be supplying current to the batts when you are cruising.

Thanks for the suggestions.

 

I cleaned all the terminals prior to visiting the boatyard.

 

The inverter was fitted by a professional using arc welder cable.

 

The fridge is the original 12v fridge and doesn't seem to be running excessively.

 

The batteries seem to charge which the boatyard confirmed when they replaced the isolation switch.

If you only cruise weekends and can recharge batts during the week, then more batts is an option, else just get 1 big solar panel, and your "invertor voltage" will be sitting in the high 12's all day......( I have 4 and havent run my boat engine for batt recharging for 3weeks. I used to run it 3hrs a day, morn and evening)

The batteries are on a smart charger all the time when we are not cruising.

Do you have any battery monitoring beyond a volt meter? You need to measure where the amps are going to figure this one out. A DC clamp meter is your friend in the absence of anything else. Boats nearby may have one if you don't but very useful for the toolbox. Turn everything off except the master switch, take a reading from the out side of the switch and leave it there. Then start turning things on, start running through your DC stuff first, if all of that looks ok, turn it all off and then do the AC side.

 

Post up what you get and it might be possible to figure out a fix for you.

I will try to get some figures when I get the boat back (being painted at the moment)

Sorry, been away since my post about the high power DC runs. I think most of what needs to be said has been covered by others here.

I would just emphasize the need for THICK cables from the battery to the inverter. The shorter the better. By the way, what size is your inverter?

It might be worth you investing in a DC clamp meter, they're not expensive and will tell you where any power is being used, and how much. If you do go for one make sure that it will measure DC current, that's important.

Bob

I have a clamp meter because I was advised it would be useful but I am not yet sure how to use it!

 

The trouble is the boat is 1 1/2 hours away so I can't just pop round after work.

[Postcode]

Apart from the batteries the equipment is all the same as before we changed them. We replaced them because the batteries were not holding charge which was confirmed by the boatyard when we replaced them.

 

Before we had issues the batteries would last for a couple of days without recharging with our usual usage.

 

I thought that the inverter breaking down was unlikely and possibly the boatyard clutching at straws to avoid replacing the batteries.

As soon as I can I will try to follow the checklist Keeping-Up has kindly sent me. My previous attempt was frustrated by my inability to decide whether a switch was on or off when open. A tap is on when open but I now realise a switch is off when open.

 

I will persevere.

[Theo]

Thanks for the suggestions.

 

I cleaned all the terminals prior to visiting the boatyard.

 

The inverter was fitted by a professional using arc welder cable.

 

The fridge is the original 12v fridge and doesn't seem to be running excessively.

 

The batteries seem to charge which the boatyard confirmed when they replaced the isolation switch.

 

The batteries are on a smart charger all the time when we are not cruising.

 

I will try to get some figures when I get the boat back (being painted at the moment)

 

I have a clamp meter because I was advised it would be useful but I am not yet sure how to use it!

 

The trouble is the boat is 1 1/2 hours away so I can't just pop round after work.

 

Just open the spring clamp and allow it to close so that the one wire through which you wish to measure the current is within the loop made by the clamp. Make sure that the right range is chosen and the ac/dc selector is on the right setting.

 

N

Apart from the batteries the equipment is all the same as before we changed them. We replaced them because the batteries were not holding charge which was confirmed by the boatyard when we replaced them.

 

Before we had issues the batteries would last for a couple of days without recharging with our usual usage.

 

I thought that the inverter breaking down was unlikely and possibly the boatyard clutching at straws to avoid replacing the batteries.

As soon as I can I will try to follow the checklist Keeping-Up has kindly sent me. My previous attempt was frustrated by my inability to decide whether a switch was on or off when open. A tap is on when open but I now realise a switch is off when open.

 

I will persevere.

Switches are off when open because the contacts are separated.

 

N

[Bodkin]

Fridges are a monster user of power especially in the summer.

 

The DC runs are the hopefully very thick Very short cables probably red and black from the batteries to the inverter. They should be easy to identify .

Super thanks:)