Travelpower or inverter?

[dccruiser]

Hi, just looking for any fors and againsts .... am having a boat built shortly for c'cing and will have a washer/dryer and a domestic fridge and freezer on board, we are intending to c'c in its trueist sense so wont have access to shore power and dont really want to use a generator other than the little hoda suitcase i will have aboard for emergencies.

 

option 1 is a 3.5kva travelpower and a 1700 watt inverter i already have, this would mean washing on the move and using the travelpower to charge the cabin batteries and use of the inverter at night just to power the fridge , freezer and the lcd tv .

 

option 2 is a 160 amp 2nd alternator (standard on the engine we are getting) charging the cabin battery bank via either a pdar or alternator to battery charger and feeding a 3kw sterling pure sine inverter and possibly switching over to my 1700 watt inverter at night.

 

Any advice or experience of either setup would be most appreciated as i am close to the point where i need to specify whether or not i want the electric pack on the engine. The engine is a 50hp barrus shire and the boat is a 70' narrowboat

 

cheers

Rick

[chris w]

First of all, I would suggest that you switch to a 12v fridge.... they are around 30% more efficient than an equivalent wattage 240v fridge. A 240v fridge will consume about 20% more power in itself for the same cooling plus you can add another 10-15% wasted in the inverter required to power it. The 12v fridge is more expensive to purchase but much simpler to administer.

 

The problem with the Travelpack, IMHO,is that you won't get the expected power out of it at low revs. To get 3KW needs high engine revs. That won't make you very popular when moored and it's not practical when cruising to be at such high revs.

 

Chris

[Nickhlx]

ditto to what Chris said ... what happens when you are cruising along at ? 2000 rpm, washing machine running sweetly.. and you throttle down for a lock or to pass moored boats ? The power available drops to ? 1500 watts and the machine is wanting 2000 / 2500 watts - electrics throw a wobbly and at best, drop out, or at worst, drop out and destroy the electronics in the washing machine...

 

This is precisely the scenario I envisage and I so am looking at probably a 3000W Sterling sine wave inverter, loads of capacity through wet cell batteries charged by an advanced alternator, and big savings by not having the Electrolux Travelpower mains alternator option. I will probably have a smaller sine wave invertor as well, and even possibly a quasi sine wave invertor where possible to run those things which don't need sine wave, and enjoy the power savings from this more efficient type of invertor..

 

Nick

[Gibbo]

Travelpowers DO produce full power at tickover if they are pulley'd up correctly.

 

The fact that lots of people don't pulley them up correctly is not the Travelpower's fault. It's the fualt of the incompetent installer.

 

Gibbo

[Nickhlx]

Travelpowers DO produce full power at tickover if they are pulley'd up correctly.

 

The fact that lots of people don't pulley them up correctly is not the Travelpower's fault. It's the fualt of the incompetent installer.

 

Gibbo

 

 

Thats good to know - and check for - so if the engine idles at say 1000 rpm, and the alternators makes max power from say 3000 alternator rpm, with a 3:1 step up pulley arrangement, it will withstand a max engine speed of say 3000 rpm, and an alternator speed of 9000 rpm ? - I will root out the specs for both engine and travelpower alternators...

 

Thanks,

 

Nick

[chris w]

Thats good to know - and check for - so if the engine idles at say 1000 rpm, and the alternators makes max power from say 3000 alternator rpm, with a 3:1 step up pulley arrangement, it will withstand a max engine speed of say 3000 rpm, and an alternator speed of 9000 rpm ? - I will root out the specs for both engine and travelpower alternators...

 

Thanks,

 

Nick

 

..........................except that alternators typically produce maximum power at about 5000rpm AT THE ALTERNATOR, which would need a 5:1 pulley ratio to get that power at idle. Then the alternator may have to withstand 15,000rpm when the engine is at 3000rpm. Now you start to see the problems with pulleying.

 

Chris

[NB Phoenix]

Travelpowers DO produce full power at tickover if they are pulley'd up correctly.

 

The fact that lots of people don't pulley them up correctly is not the Travelpower's fault. It's the fualt of the incompetent installer.

 

Gibbo

 

In two years I have never had a problem with our travel power at any revs. We can have the washer/dryer on and slow down to tick over for boats or locks and everything keeps working fine.

 

I have an Indesit washer/dryer and an Indesit dishwasher both connected on a circuit running directly from the travel power. This is because we only have a 1200W inverter. We do not use both at the same time but both work very well on their own from the travel power at any revs.

 

Edit to say:- This setup is factory fitted on a Barrus Shire 45 engine.

Edited April 12, 2008 by NB Phoenix

[dccruiser]

thank you for the coments so far , personally i was waivering towards the inverter option , just wasnt sure what kind of power running a washer/dryer would take out of the inverter and what effect it would have on long term battery life.

 

I have a niggling thought that a travelpower may cause unnecessary strain on engine parts and may be prone to regular belt failures although this is probably not the case.

 

Chris thank you for the fridge info , i havent yet bought a fridge but was looking at a 12volt shoremaster earlier as for a freezer , i assume if it is reasonably stocked i can get away with switching it off through the night as it wont be opened and possibly do that on a timer

 

cheers

Rick

 

p.s. what size of battery bank would you envisage i will require, and using a washing machine how much running time would it take to replenish them? ... i know it is a difficult question but i am looking at worse case scenario because obviously there will be days we dont move on or get caught by stoppages, so i would rather be over capacity than running to a limit and having to run the engine on a mooring.

the only other equipment on the boat will be the pumps , webasto , lights and electric flush thetfords.

 

the inverter i currently have that i intend to use at night time is a 1700watt quasi wave , if i remember rightly i think it is made by adverc.

[Keeping Up]

i havent yet bought a fridge but was looking at a 12volt shoremaster earlier as for a freezer , i assume if it is reasonably stocked i can get away with switching it off through the night as it wont be opened and possibly do that on a timer

There's not a lot of point doing that, the power you save during the night will quickly be used as soon as you switch on in the morning, in getting the freezer down to the temperature that it would have been at if you'd left it switched on.

[Ex- Member]

There's also a consideration of how much you keep in the fridge, the fuller the better, we tend to put canned drinks and bottled water in it to keep it as full as possible, once a large amount of contents are cold the heat loss when opening the door is minimalised. If you do lose power for some time, because there's a lot on content already cold the fridge will stay cooler for longer. Of course to chill it all down will take a lot of power. I did read somewhere that cooling an empty fridge will require twice the power of cooling a full one.

[Ex- Member]

Just thought i would post a link to the 240 volt fridge we use for anyone considering a 240 volt system.

 

http://www.dooyoo.co.uk/refrigerator/bosch...8425gb/1041618/

 

Another link, pretty good price.

 

http://www.appliancedeals.co.uk/product_in...um=ProductFeeds

 

Just thought i would post a link to the 240 volt fridge we use for anyone considering a 240 volt system.

 

http://www.dooyoo.co.uk/refrigerator/bosch...8425gb/1041618/

 

Another link, pretty good price.

 

http://www.appliancedeals.co.uk/product_in...um=ProductFeeds

 

Found the power consumption figures too.

 

 

Energy rating: A+

 

Energy consumption: 117kWh/yr

[chris w]

Found the power consumption figures too.

 

 

Energy rating: A+

 

Energy consumption: 117kWh/yr

 

117KWh/yr plus around another 15KWh/yr for the inverter to run it = 132KWhr/yr. An equivalent 12v version would be approx 98KWh/yr. The difference equates to around an extra hour per day battery charging.

 

Chris

Edited April 12, 2008 by chris w

[Ex- Member]

117KWh/yr plus around another 15KWh/yr for the inverter to run it = 132KWhr/yr. An equivalent 12v version would be approx 98KWh/yr. The difference equates to around an extra hour per day battery charging.

 

Chris

 

 

Wow that's a surprise, do you mean an extra hour more than a 12 volt fridge?

[chris w]

Wow that's a surprise, do you mean an extra hour more than a 12 volt fridge?

 

I do. The difference is 34KWh/yr (ie: 34,000 Wh/yr) which is 93Wh per day. At 12v this equates to about 7Ah/day. Taking charging efficiency into account (70%) this means that you have to put back about 10AH extra per day into the batteries which will be about an hour's charging time.

 

Chris

[Gibbo]

..........................except that alternators typically produce maximum power at about 5000rpm AT THE ALTERNATOR, which would need a 5:1 pulley ratio to get that power at idle. Then the alternator may have to withstand 15,000rpm when the engine is at 3000rpm. Now you start to see the problems with pulleying.

 

Chris

 

No they don't. You keep saying this. In fact I think your RPM figure keeps increasing.

 

The reality is an alternator will NEVER produce its maximum output. Whatever speed it is run at it will always produce more power if you spin it faster (up to a point). So we have to be realistic. Most are at about 80% by 2500 RPM and 85% by 3000 RPM. Increasing from 3000 RPM to 5000 RPM makes little difference.

 

So if we take 3000 RPM as the speed to be aimed at, it's relatively simple to arrange the pulleys. Average tickover of a modern diesel is about 1000 RPM. Pulley it up at 3:1 (simple to achieve but makes a huge difference over the usual 2:1) and you have close to maximum power at tickover. At the engine red line of (say) 4000 RPM the alternator is doing 12,000 RPM. This is fine as most are good for 14,000 RPM before things start to go wrong.

 

http://www.prestolite.com/literature/alts/...2500_2800LC.pdf

 

Pulleying up alternators for decent power at tickover is only a problem on petrol engines where the rev range is much wider. On diesels it is no problem and there really is no excuse for the "marinisers" (read "engine painters") not doing it properly.

 

The alternator on Lionheart is pulley'd up at 8:1.

 

Gibbo

Edited April 13, 2008 by Gibbo

[Kraken]

The alternator on Lionheart is pulley'd up at 8:1.

 

Gibbo

 

 

I seem recall reading on your web site that you were going to try an alternator pulley diameter of 53mm. Did you? And how did it work out?

[Gibbo]

I seem recall reading on your web site that you were going to try an alternator pulley diameter of 53mm. Did you? And how did it work out?

 

What I finally did was took the alternator pulley to an old seasoned engineer and said to him "turn this down on your lathe to the smallest your experience tells you it will go no without falling apart". I really don't know what size it is now. But it is twin belt so slip isn't really a problem. I got the ratio by turning the engine by hand and counting the number of times the alternator spun round! Very technical.

 

Gibbo

[Gibbo]

Chris thank you for the fridge info , i havent yet bought a fridge but was looking at a 12volt shoremaster earlier as for a freezer , i assume if it is reasonably stocked i can get away with switching it off through the night as it wont be opened and possibly do that on a timer

 

I second julynian on this. It's pointless. Any power you save in the night, you'll just have to use in the morning instead. If the freezer isn't opened and you conclude from this that it won't warm up then it won't switch on anyway!

 

Gibbo

[Nickhlx]

On fridges and freezers that are built-in, I am sure it must be worth adding an extra slab of insulation around the sides and top ? I have for example, polystyrene slabs left over from other projects that are 25mm and 50mm thick and it seems reasonable that heat gain by the fridge would be reduced if 3 of the six surfaces could have the heat transfer reduced with extra insulation - obviously avoiding any areas where the heat extracted needs to get away.

 

A little time spent finishing it of around the front and it would look acceptable and the net result should be a little less electricity needed.

 

Nick

[Gibbo]

On fridges and freezers that are built-in, I am sure it must be worth adding an extra slab of insulation around the sides and top ? I have for example, polystyrene slabs left over from other projects that are 25mm and 50mm thick and it seems reasonable that heat gain by the fridge would be reduced if 3 of the six surfaces could have the heat transfer reduced with extra insulation - obviously avoiding any areas where the heat extracted needs to get away.

 

A little time spent finishing it of around the front and it would look acceptable and the net result should be a little less electricity needed.

 

Nick

 

Indeed. This was covered at some length on urw last year (or possibly the year before - I'm getting too old to remember). Something else that makes a big difference is ventilation to the back of the fridge. Holes cut in the floor so the rising air from the pipes at the back of the fridge pulls cold bilge air up from under the floor.

 

Gibbo

[Nickhlx]

Indeed. This was covered at some length on urw last year (or possibly the year before - I'm getting too old to remember). Something else that makes a big difference is ventilation to the back of the fridge. Holes cut in the floor so the rising air from the pipes at the back of the fridge pulls cold bilge air up from under the floor.

 

Gibbo

 

 

Thanks, Gibbo... I will have a search

 

Nick

[Ernie]

Indeed. This was covered at some length on urw last year (or possibly the year before - I'm getting too old to remember). Something else that makes a big difference is ventilation to the back of the fridge. Holes cut in the floor so the rising air from the pipes at the back of the fridge pulls cold bilge air up from under the floor.

 

Gibbo

Now that is a really good idea I will try that when I get a spare moment.

 

We have a 12v fridge and a 12v freezer, both built into kitchen units. It gets very warm behind them even though I have drilled a few 2” holes (discretely) at the top and bottom sides of the cabinets and added an old 12v computer fan (permanently running) to aid air circulation. Having some cool air coming up from the base plate should be a real help.

[chris w]

No they don't. You keep saying this. In fact I think your RPM figure keeps increasing.

 

The reality is an alternator will NEVER produce its maximum output. Whatever speed it is run at it will always produce more power if you spin it faster (up to a point). So we have to be realistic. Most are at about 80% by 2500 RPM and 85% by 3000 RPM. Increasing from 3000 RPM to 5000 RPM makes little difference.

Gibbo

 

Oh yes they do.....................

 

Here's the graphs for my engine (Isuzu 35). Note the horizontal scale is Engine revs and they come with a 2:1 pulley ratio, so alternator rpm is TWICE the horizntal scale. You will see that the alternator is giving its rated current output at 5000 rpm (alternator revs) as I stated above.

 

 

 

Chris

[Gibbo]

Oh yes they do.....................

 

Really? Then what is the maximum output of your alternator?

 

It is still increasing as it leaves the right hand side of the graph.

 

I didn't say "never reach rated output" I said "never reach maximum output".

 

It was you that said "alternators typically produce maximum power at about 5000rpm" which is incorrect. They never reach maximum output. You can ALWAYS get more output by increasing the RPM, right up to the point where the alternator destroys itself.

 

 

Here's the graphs for my engine (Isuzu 35). Note the horizontal scale is Engine revs and they come with a 2:1 pulley ratio, so alternator rpm is TWICE the horizntal scale. You will see that the alternator is giving its rated current output at 5000 rpm (alternator revs) as I stated above.

 

 

 

Chris

 

You're desperately clutching at straws now.

 

The graph shows that it is producing 71 Amps at 6000 RPM. 69 Amps at 5000 RPM and 60 Amps at 3000 RPM. 60 Amps is 85% of 70 Amps. Which is what I said. Thank you for confirming I was correct. Doubling the RPM from 2500 RPM to 5000 RPM produces a mere 15% increase in output. Not worth it.

 

Notice also that the graph is still rising, indicating that further increases in revs will still produce an increase in output. Which is what I said. Thank you for confirming I was correct.

 

There is no need to run an alternator at 5000 RPM as you seem to think. 3000 RPM is not only sufficient (which is what I said) but also easily achievable.

 

Gibbo

[Keeping Up]

That graph looks to me as if it passes exactly through the co-ordinates that Gibbo mentions