Power Options

[David R]

I could do with some advice on options for improving power availability for our 40' boat. We are not live-aboard and tend to spend 1 to 5 nights away.

 

Currently there are three batteries. 1 X 110Ah for cranking and 2 X 110Ah for domestic. These are charged from the alternator (I've tested this set-up and the batteries are being charged correctly).

 

There is a 300W inverter which we use for TV (LCD) + signal amp and the fridge.

 

Lights (fluorescent or halogen) water pump and radio are 12V and we also have a an 'electric' cool box for fridge overspill.

 

At the moment, the inverter reduces the charge on the domestic bank rather quickly (I have a feeling this unit is not all it might be since the output voltage drops to 205V AC even with the engine running!).

 

As I see it the options are:

 

1. Increase battery bank - there would be space issues for additional batteries but could be done.....I think a bigger/additional alternator might be required though. In addition purchase a new bigger inverter.......are cheaper units less efficient?

 

2. Put up with running the engine in the evening...it's a bit noisy and not terribly good for the old girl I understand???

 

3. Purchase a generator to provide 240V when required.

 

 

Any comments or better suggestions please?

 

Thanks

 

David

[blodger]

I think your situation has a lot in common with aspects in this other thread now running "Low Rev engine - alternators" in Equipment.

 

I might be repeating myself responding now; I'll wait for others to come aboard!

[Tony Brooks]

I could do with some advice on options for improving power availability for our 40' boat. We are not live-aboard and tend to spend 1 to 5 nights away.

 

Currently there are three batteries. 1 X 110Ah for cranking and 2 X 110Ah for domestic. These are charged from the alternator (I've tested this set-up and the batteries are being charged correctly).

 

There is a 300W inverter which we use for TV (LCD) + signal amp and the fridge.

 

Lights (fluorescent or halogen) water pump and radio are 12V and we also have a an 'electric' cool box for fridge overspill.

 

At the moment, the inverter reduces the charge on the domestic bank rather quickly (I have a feeling this unit is not all it might be since the output voltage drops to 205V AC even with the engine running!).

 

As I see it the options are:

 

1. Increase battery bank - there would be space issues for additional batteries but could be done.....I think a bigger/additional alternator might be required though. In addition purchase a new bigger inverter.......are cheaper units less efficient?

 

2. Put up with running the engine in the evening...it's a bit noisy and not terribly good for the old girl I understand???

 

3. Purchase a generator to provide 240V when required.

 

 

Any comments or better suggestions please?

 

Thanks

 

David

 

 

How old are the batteries and how did you establish they are being correctly charged. My guess (and I used to only have two x 110Ah domestic batteries)is that the batteries have lost capacity because of insufficient charging.

 

I suspect that before anyone is willing to give much more help we need to know exactly how you tested the charging system to conclude it was correct. We need your description WITH readings and times when they were taken.

 

My feeling is that you stand a good chance of wasting money until you do a power audit and tell us about your tests.

 

Sorry

[David R]

How old are the batteries and how did you establish they are being correctly charged. My guess (and I used to only have two x 110Ah domestic batteries)is that the batteries have lost capacity because of insufficient charging.

 

I suspect that before anyone is willing to give much more help we need to know exactly how you tested the charging system to conclude it was correct. We need your description WITH readings and times when they were taken.

 

My feeling is that you stand a good chance of wasting money until you do a power audit and tell us about your tests.

 

Sorry

 

Hi Tony - thanks for this. I used your own advice on Canal Junction and had the following results.

 

1. No load: 13.1V (I've tested the batteries individually too and the results are the same)

2. Didn't do the starter test since the cranking battery is fine.

3. Engine running charge - 13.6V once settled.

 

The batteries are all 12 months old and topped up correctly.

 

I have no real idea about the alternator's make or age I'm afraid. When starting in the morning after an overnight, the engine has to be revved quite hard before the charge warning light extinguishes - the (crude) voltmeters on then jump up to 16V (which is probably deeply inaccurate!)

 

Thanks again

 

David

[blodger]

Is it a fast/medium/slow running diesel?

 

Does the 13.6v you are getting rise in time and have you any way of ascertaining what amps the alt is delivering?

[David R]

Is it a fast/medium/slow running diesel?

 

Does the 13.6v you are getting rise in time and have you any way of ascertaining what amps the alt is delivering?

 

Hi Blodger - the diesel is a Honda 1250GD so runs fast/medium (to use a cricket term!) It's a generator/stationary engine design not an automotive one - Max revs is 2500.

 

The 13.6v is the steady reading after about 1 min of running.

 

David

[blodger]

Hi Blodger - the diesel is a Honda 1250GD so runs fast/medium (to use a cricket term!) It's a generator/stationary engine design not an automotive one - Max revs is 2500.

 

The 13.6v is the steady reading after about 1 min of running.

 

David

Well it takes a fair bit of time for the voltage to rise if the batts are discharged and what I am trying to figure is whether the alt regulator does get up to 14.2v or above as the batts near full charge before venturing an opinion on the alt's fitness for purpose or what could be done about it.

 

Pictures speak a thousand words; Any chance of a pic of the alt via a camera phone so that others can identify it?

 

I have just bought a back up 500watt inverter off Ebay for 17.98 inc P&P they are not expensive. I think the surge with a mains fridge when it starts up would hammer a small inverter and it surprises me that you have had one doing more than the fridge. IIRC when they started advocating mains fridges with inverters as cheaper than 12v/others the recommendation was for a 600watt one when they cost around a ton. Regardless, what I am suggesting is before your current inverter is totally knackered and still useable as a spare get one which can cope better and for your future needs. However, inverters use some juice on stand by and more because of their inefficiencies when in use plus whatever wattage you have plugged in so pull the battery volts down quite quickly with batt age, capacity numbers and SOC all factors.

 

So yes you will be into more batteries but as you are doing its important to make sure what you have is working optimally first IMO

 

Similarly, it's handy to not be totally dependent on the engine as we all find out, sooner or later when someat goes wrong, but take your time to acquire a quiet genny and charger(s) relevant to your needs and pocket.

[WotEver]

Seeing as no-one else has mentioned it yet. The line...

At the moment, the inverter reduces the charge on the domestic bank rather quickly (I have a feeling this unit is not all it might be since the output voltage drops to 205V AC even with the engine running!).

... suggests to me that the cables to the inverter might be too thin/long. Either that or the inverter's just being asked to deliver too much.

 

Tony

[wirren]

If money was no object -

You could start with a 12v fridge & a 12v TV .

Solar panels are a good way of topping the batteries up whilst you are away.

[Pretty Funked Up]

If the TV has an external PSU change it to run off of a DC-DC regulator. Get a bigger aerial and do away with sig booster all together.

Halogens and fluoresents are thirsty lighting if you have them on much, try LEDs or candles.

After that the solutions start getting pricey i'm afraid and really not worth it, considering how much you use your boat.

 

check to voltage coming off the alt. directly off the alt. terminals and see what that is.

 

Switch fridge to gas.

Edited October 27, 2010 by Pretty Funked Up

[David R]

Seeing as no-one else has mentioned it yet. The line...

... suggests to me that the cables to the inverter might be too thin/long. Either that or the inverter's just being asked to deliver too much.

 

Tony

 

Thanks - will investigate cable to inverter....length? About 2M at the moment and as for mm2...I dread to think....if like everything else on board when we got her....'the cheapest' option!!! What do you suggest for mm2 of cable?

 

Thanks

 

David

Edited October 27, 2010 by David R

[David Mack]

As I see it the options are:

 

1. Increase battery bank - there would be space issues for additional batteries but could be done.....I think a bigger/additional alternator might be required though. In addition purchase a new bigger inverter.......are cheaper units less efficient?

 

2. Put up with running the engine in the evening...it's a bit noisy and not terribly good for the old girl I understand???

 

3. Purchase a generator to provide 240V when required.

 

 

Or:

 

4. Reduce your power consumption.

 

The fridge is probably around half your total electricty use, so make sure you minimise its consumption. Typical points to consider:

 

• 
   
  
• check the fridge door seal and replace it if it is not making a good seal.
  
• make sure there is plenty of ventilation around the back of the fridge so that the heat extracted from the inside can escape.
  
• keep the fridge full - even just with bottles of water to fill empty space - so that you don't lose so much cold air every time you open the door.
  
• consider switching the fridge off at night. As long as you aren't opening the door the temperature won't rise much, and you'll save the rechilling until you have the engine running again.
  
• only put fresh (i.e. non-chilled) food in the fridge when the engine will be running for a while. That way the new food won't warm up what is already in there.
  

Coolboxes are usually horribly inefficient users of electricity. Try not to use yours, especially when the engine is not running.

 

Do you have access to the bottom plate anywhere (reasonably clean)? Things like beer and wine can be kept adequately cool there without needing to use a fridge or cool box.

 

David

[David R]

If money was no object -

You could start with a 12v fridge & a 12v TV .

Solar panels are a good way of topping the batteries up whilst you are away.

 

Thanks Wirren.....the fridge is one of those old 12v/240v/Gas jobs...could try running off 12V I suppose!

 

The TV is 12V in fact......uses a 240V>12V adaptor. Just not sure if such a unit would cope with the 'raw' feed from the batteries!

 

David

[Pretty Funked Up]

Use the fridge on gas if you can.

DC-DC reg for the tv

LED lighting.

[bottle]

he fridge is one of those old 12v/240v/Gas jobs...could try running off 12V I suppose!

 

No................. this type of fridge is designed to run on gas, they were originally for the caravan market.

 

Gas ......... works like any gas fridge.

 

240 v........ will cool and maintain thermostatically set temperature.

 

12v ...........will maintain (possibly) the temperature at the time of switching to 12v, it will not lower the temperature .

 

The scenario for use, caravan at home, connect 240v bring fridge down to working temperature, hitch to tow-car change to 12v, arrive site, change to gas or 240v if available.

They first emerged when it became illegal for the gas to be turned 'on' when the caravan was being towed.

[blodger]

Or:

 

4. Reduce your power consumption.

 

The fridge is probably around half your total electricty use, so make sure you minimise its consumption. Typical points to consider:

 

• 
   
  
• check the fridge door seal and replace it if it is not making a good seal.
  
• make sure there is plenty of ventilation around the back of the fridge so that the heat extracted from the inside can escape.
  
• keep the fridge full - even just with bottles of water to fill empty space - so that you don't lose so much cold air every time you open the door.
  
• consider switching the fridge off at night. As long as you aren't opening the door the temperature won't rise much, and you'll save the rechilling until you have the engine running again.
  
• only put fresh (i.e. non-chilled) food in the fridge when the engine will be running for a while. That way the new food won't warm up what is already in there.
  

Coolboxes are usually horribly inefficient users of electricity. Try not to use yours, especially when the engine is not running.

 

Do you have access to the bottom plate anywhere (reasonably clean)? Things like beer and wine can be kept adequately cool there without needing to use a fridge or cool box.

 

David

I concur with your view of coolboxes. Worthwhile carrying around should the fridge go AWOL/need defrosting but best used on a socket that is only live when the engine is running and near the back so you can get at the beer without the wife's assistance!

[Lady Muck]

Or:

 

4. Reduce your power consumption.

 

The fridge is probably around half your total electricty use, so make sure you minimise its consumption. Typical points to consider:

 

• 
   
  
• check the fridge door seal and replace it if it is not making a good seal.
  
• make sure there is plenty of ventilation around the back of the fridge so that the heat extracted from the inside can escape.
  
• keep the fridge full - even just with bottles of water to fill empty space - so that you don't lose so much cold air every time you open the door.
  
• consider switching the fridge off at night. As long as you aren't opening the door the temperature won't rise much, and you'll save the rechilling until you have the engine running again.
  
• only put fresh (i.e. non-chilled) food in the fridge when the engine will be running for a while. That way the new food won't warm up what is already in there.
  

Coolboxes are usually horribly inefficient users of electricity. Try not to use yours, especially when the engine is not running.

 

Do you have access to the bottom plate anywhere (reasonably clean)? Things like beer and wine can be kept adequately cool there without needing to use a fridge or cool box.

 

David

 

and defrost the fridge regularly, I do ours once a month when we are cruising, it's incredible how much electricity it wastes when it needs defrosting.

[WotEver]

What do you suggest for mm2 of cable?

500w = 42 Amps at 12V, plus say 20% for inverter inefficiency = 50A. Total run (there and back) 4 metres.

 

25mm Cable would be good, although you'd be okay with 16mm.

 

There. That's shocked you, hasn't it?

 

Tony

 

edit cos I carnt spel innefffishuncy

Edited October 27, 2010 by WotEver

[Guest User]

I re-did the 12V wiring to an Electrolux three-way fridge once ... what had once just about been a fridge on 12V, suddenly became a freezer and the nice new fat wires didn't get warm anymore like the thin old ones used to !

 

The 12V cooling is not thermostatically controlled on some (many?) three way fridges and the temp control is by switching the whole thing on or off, leave it on and you'll freeze everything ... and take a lot of electicity from the batteries.

 

By the way DavidR, how many hours cruising (i.e. battery charging) per day do you do when out and about ?

[David R]

Well it takes a fair bit of time for the voltage to rise if the batts are discharged and what I am trying to figure is whether the alt regulator does get up to 14.2v or above as the batts near full charge before venturing an opinion on the alt's fitness for purpose or what could be done about it.

 

Pictures speak a thousand words; Any chance of a pic of the alt via a camera phone so that others can identify it?

 

I have just bought a back up 500watt inverter off Ebay for 17.98 inc P&P they are not expensive. I think the surge with a mains fridge when it starts up would hammer a small inverter and it surprises me that you have had one doing more than the fridge. IIRC when they started advocating mains fridges with inverters as cheaper than 12v/others the recommendation was for a 600watt one when they cost around a ton. Regardless, what I am suggesting is before your current inverter is totally knackered and still useable as a spare get one which can cope better and for your future needs. However, inverters use some juice on stand by and more because of their inefficiencies when in use plus whatever wattage you have plugged in so pull the battery volts down quite quickly with batt age, capacity numbers and SOC all factors.

 

So yes you will be into more batteries but as you are doing its important to make sure what you have is working optimally first IMO

 

Similarly, it's handy to not be totally dependent on the engine as we all find out, sooner or later when someat goes wrong, but take your time to acquire a quiet genny and charger(s) relevant to your needs and pocket.

Al

Thanks again Blodger - seems like sound advice to me - I'll get some pics of the alternator when i'm next at Swanley. Also, I'll monitor the voltage to see if we can get to the 14.2V.

 

500w = 42 Amps at 12V, plus say 20% for inverter inefficiency = 50A. Total run (there and back) 4 metres.

 

25mm Cable would be good, although you'd be okay with 16mm.

 

There. That's shocked you, hasn't it?

 

Tony

 

edit cos I carnt spel innefffishuncy

 

Not too shocked Tony! But I AM grateful!

 

Thanks!

 

I re-did the 12V wiring to an Electrolux three-way fridge once ... what had once just about been a fridge on 12V, suddenly became a freezer and the nice new fat wires didn't get warm anymore like the thin old ones used to !

 

The 12V cooling is not thermostatically controlled on some (many?) three way fridges and the temp control is by switching the whole thing on or off, leave it on and you'll freeze everything ... and take a lot of electicity from the batteries.

 

By the way DavidR, how many hours cruising (i.e. battery charging) per day do you do when out and about ?

 

Hi Graham - that's interesting! I rewired the fridge to switch outlet for 12V with polar 2.5mm² cable but should have carried this thinking through to the other end on the switch panel which does get rather warm when running off 12V!

 

When we're out - usually 6 hrs in the Winter and 7-8 in the Summer.

 

David

[alan_fincher]

Your three way fridge is the killer, and using one of those horrible cool boxes as a back up will further add to the problem.

 

Run on either 12 volts or 240 volts those 3 way absorption fridges are massively inefficient compared to a compressor fridge. By that I mean they will drain your batteries perhaps 4 times as fast - they really are that bad.

 

You can't really solve this problem by throwing batteries at it, unless you have heaps of alternator capacity to charge them.

 

Run it on gas, if you are able, if not junk it, and replace with a modern 12 volt compressor fridge.

 

Try and get one that is big enough that you can also junk the nasty cool box too, and your problems should dissapear......

[Richard10002]

Given that your alternator only reaches 13.6v, this would suggest that it is an old model from a time when we only needed to charge an engine starter battery. AFAIK modern alternators are regulated to a higher voltage... 14.2V I think.

 

I had exactly the same situation on board a yacht over the summer of 2007, where I spent weeks at anchor.

 

For simplicity, I bought a Honda EU20i generator to provide 240v via the mains supply. Without needing to run the engine, this both charged the batteries and fed the 240v ring main. This is the most expensive option, but the quickest fix, and the most flexible.

 

Had I kept the yacht, I would have fitted a sterling alternator regulator, or some other form of smart charger... Adverc, driftgate etc. to provide more efficient charging from the engine.

 

In your situation, I would probably also look at changing the fridge to include a 12v option.

 

You could also fit a more up to date alternator, perhaps even blowing the budget on a Balmar.

 

I have no experience of canal boats yet, but am sure the principles are similar.

 

Cheers,

 

Richard

[Tony Brooks]

Hi Tony - thanks for this. I used your own advice on Canal Junction and had the following results.

 

1. No load: 13.1V (I've tested the batteries individually too and the results are the same)

2. Didn't do the starter test since the cranking battery is fine.

3. Engine running charge - 13.6V once settled.

 

The batteries are all 12 months old and topped up correctly.

 

I have no real idea about the alternator's make or age I'm afraid. When starting in the morning after an overnight, the engine has to be revved quite hard before the charge warning light extinguishes - the (crude) voltmeters on then jump up to 16V (which is probably deeply inaccurate!)

 

Thanks again

 

David

 

 

Right

 

13.1 volts at the batteries shows that you have tested them very soon after stopping charging. This reading is all but meaningless. Either put on a heavy load for a few minutes or leave them for several hours doing nothing, preferably overnight. I have a battery with two dead cells that shows over 13 volts straight off charge.

 

Now the charging voltage. Any alternator will give a low voltage reading for a period at the start of charging so unless that 13.6 was measured after several hours running it again is of little use. If it was after several hours I suspect either faulty batteries or a faulty voltage regulator in the alternator. Even on 30 year old alternators I would expect at least 13.8 volts once the charging current has fallen some way below the alternators rated output. If you have shorted cells in the battery the alternator might be running at maximum output and thus with lowered voltage all the time. If you are sure the charging voltage is only 13.6 with good batteries at the end of the day for goodness sake spend your money on a new alternator. My advice would be as large as you can up to 80 to 90 amps. Above that you starts to risk belt problems with ordinary V belts.

[Gibbo]

I'm a bit baffled by some of the replies in this thread. Some (most?) of them are completely missing the problem or offering partial suggestions to a tiny part of the problem.

 

Firstly I second Tony's post. I think the batteries are not being charged even remotely close to full so they're probably knackered now anyway.

 

The other major problem is that fridge. That type of fridge absolutely drinks power. They use about 3 to 5 times as much as a normal fridge.

 

Another problem is the 12 volt cool box. They also drink power.

 

Get rid of those two devices (or run the fridge on gas - I'm not going into the dangers of doing so here as I can't be bothered) and half the problems will go away.

[Pretty Funked Up]

If you absolutley need the extra space(coolbox) you could freeze some cold blocks in the fridge/freezer box (that you should be running on gas) and put those in the coolbox. Basically so you dont have to power it