Large and small inverter?

[Bojangles]

From previous posts I know I need a 3000w pure sine wave inverter for the washing machine.

 

I wondered whether it's economic to use this large size inverter to run the gogglebox or should I buy a seperate small inverter for the TV, which will be a 15" flat screen.

[chris w]

From previous posts I know I need a 3000w pure sine wave inverter for the washing machine.

 

I wondered whether it's economic to use this large size inverter to run the gogglebox or should I buy a seperate small inverter for the TV, which will be a 15" flat screen.

 

 

The only issue with using a pure sinewave inverter when it's not really needed (eg: your TV) is that the current needed to run the inverter (its "quiescent" current in the jargon) can be 5-7 amps whereas for a modified sinewave inverter it's more like 1 amp - this is wasted power. (There will still be inefficiency losses on top of these figures for both types which will run at around 10% of the supplied current).

 

There is some clever marketing, with pure sinewave inverters, whereby you may see a low "standby" current for a pure sinewave inverter maybe less than an amp. Looks good eh? Not so......... what they do is that the inverter goes into a kind of "sleep" mode when no load is detected - this is the "standby" current. However when you are actually running some equipment, the quiescent current is as stated above and represents wasted battery power.

 

Some TVs may give a small line on the screen with modified sinewave inverters. My own experience is that the cathode ray (old type) TVs do but that my LCD TV does not.

 

Chris

Edited September 13, 2007 by chris w

[Guest]

The only issue with using a pure sinewave inverter when it's not really needed (eg: your TV) is that the current needed to run the inverter (its "quiescent" current in the jargon) can be 5-7 amps whereas for a modified sinewave inverter it's more like 1 amp - this is wasted power. (There will still be inefficiency losses on top of these figures for both types which will run at around 10% of the supplied current).

 

There is some clever marketing, with pure sinewave inverters, whereby you may see a low "standby" current for a pure sinewave inverter maybe less than an amp. Looks good eh? Not so......... what they do is that the inverter goes into a kind of "sleep" mode when no load is detected - this is the "standby" current. However when you are actually running some equipment, the quiescent current is as stated above and represents wasted battery power.

 

Some TVs may give a small line on the screen with modified sinewave inverters. My own experience is that the cathode ray (old type) TVs do but that my LCD TV does not.

 

Chris

Pretty much my findings with the 3kw Sterling. Very inefficient for small loads. Great for the washer though. Odd this but we leave a really ancient CRT telly on the boat and that gets a slight buzzing noise off the inverter but is OK on mains at home. To be fair it is probably knackered. Everythign else has performed fine off this inverter including other CRT tellies, radios, fridges, washers, vacuums blah blah.

[DHutch]

Yeah, ive thought of geting a little 300watt msw inverter just for running stuff off, camera chargers, laptops maybe, that sort of thing.

- Unfortunatly, cheap tho they are, there not quite dirt cheap yet and a really dont need one!

- That said, it would be easly enough to wire in, we've got a left over 16amp mcb, just have the one 240v outlet thats on it some where closeish to the batterys.

 

 

 

Daniel

[chris w]

Occasionally Maplin have inverters as one of their regular special price deals. I picked up a 600W modified sinewave inverter for £19.99 last year.

 

Chris

[DHutch]

Yeah ive heard about these.

- Had a look at there current line up, some of them dont look half bad.

- If i could get one for £20 that would be cool by me, then i just need the laptop!

 

 

Daniel

[anhar]

The only issue with using a pure sinewave inverter when it's not really needed (eg: your TV) is that the current needed to run the inverter (its "quiescent" current in the jargon) can be 5-7 amps whereas for a modified sinewave inverter it's more like 1 amp - this is wasted power. (There will still be inefficiency losses on top of these figures for both types which will run at around 10% of the supplied current).

 

There is some clever marketing, with pure sinewave inverters, whereby you may see a low "standby" current for a pure sinewave inverter maybe less than an amp. Looks good eh? Not so......... what they do is that the inverter goes into a kind of "sleep" mode when no load is detected - this is the "standby" current. However when you are actually running some equipment, the quiescent current is as stated above and represents wasted battery power.

 

Some TVs may give a small line on the screen with modified sinewave inverters. My own experience is that the cathode ray (old type) TVs do but that my LCD TV does not.

 

Chris

I'm sure your're right Chris about wasted battery power etc. but in my opinion it's worth it for the convenience. I get the feeling though that you are against pure sine wave inverters and mains circuits because of the wastage you perceive. I'd comment that the wastage doesn't matter provided the other elements of the system are designed to cope, that is, having an adequate size of the battery bank and the charging ability to match from alternator, shore power, generator or whatever.

 

My set up is with a Victron combi and a mains circuit with several house type sockets around the boat. The convenience of being able to use mains appliance such as microwave, TV, computer, standing lamp or whatever, knowing for certain that they will run because of the psw supply, is worth what the inverter consumes in my view. I don't have a washing machine but if I did I would stick with a similar set up, though with a larger inverter and battery bank plus probably a generator. Anything other than a psw supply, even if they consume less power internally, is asking for possible trouble because some appliances may not run properly. Personally, I have no wish for that to happen and am therefore content to incur the wastage you describe. Sometimes a bit of wastage is a good trade off for convenience.

 

Actually I think the word "wastage" is an emotive word in this situation and not really accurate. It suggests one is consuming electricity for no return but that's not the case. It's actually the cost of running the unit in return for the quality of its psw output. So I don't see it as wasted, you're getting something for it, namely a psw supply instead of something inferior. Yes if the battery and charging system can't cope then one could have problems with a psw inverter. But the key to it, as you'll probably agree, is designing it correctly from the start so that all the elements of the system, inverter, batteries, charging, match to give the desired results.

 

regards

Steve

Edited September 14, 2007 by anhar

[dor]

It varies a lot with the inverter.

 

I've a Powermaster 1800W PSW inverter which I often use just to listen to the radio. It doesn't appear to draw much more than 1 amp to put out this small amount of current. One of the reasons it won the Motor Boat Monthly inverter best buy. Nice people to deal with as well, really helpful.

[chris w]

I get the feeling though that you are against pure sine wave inverters and mains circuits because of the wastage you perceive. I'd comment that the wastage doesn't matter provided the other elements of the system are designed to cope, that is, having an adequate size of the battery bank and the charging ability to match from alternator, shore power, generator or whatever.

 

Actually I think the word "wastage" is an emotive word in this situation and not really accurate. It suggests one is consuming electricity for no return but that's not the case. It's actually the cost of running the unit in return for the quality of its psw output. So I don't see it as wasted, you're getting something for it, namely a psw supply instead of something inferior. Yes if the battery and charging system can't cope then one could have problems with a psw inverter. But the key to it, as you'll probably agree, is designing it correctly from the start so that all the elements of the system, inverter, batteries, charging, match to give the desired results.

 

regards

Steve

 

 

On the contrary I love pure sinewave inverters (PSW) - but it's horses for courses. For a device that needs a PSW inverter (eg: most washing machines) they are perfect. But why would one want to use a PSW to run a device that will run perfectly well off a somewhat more efficient and certainly less expensive Modified sinewave inverter (MSW)?

 

I don't have a washing machine on board so I don't need a PSW. Everything that I do run on board, that requires mains, runs off an 1800W MSW inverter and runs beautifully - eg: TV, lDVD, satellite, laptop, chargers, drill, hair dryer etc.

 

The only reason that a washing machine normally needs a PSW inverter is not because the output is "better". It's because to control motor speed the machine uses a device similar to a mains dimmer which happens to use the shape of the sine wave to achieve voltage control. It would be just as easy to design a motor control that didn't need a sinewave but since probably 99.99% of washing machines go into homes that do have mains....................

 

If that shape were unimportant then any MSW would run the nmachine.

 

For example, to dim my 12v lights efficiently (ie: without using a series resistor) I chop the 12v signal into a square wave at a particular frequency (500Hz) and vary the width of the square wave to achieve voltage control and hence dimming.

 

The chopped 12v is now an AC voltage but is no way close to being a sine wave. The lamp doesn't care, it just sees voltage for so many milliseconds - so it glows - and then nothing for so many milliseconds and it stops glowing. The human eye can't follow the speed so sees the lamp as dim.

 

Some devices utilise the shape of the sinewave because afterall, in a normal domestic situation, it's available. But it's not some God that is somehow better - it's just different.

 

I know you are hyper about Victron based on your posts. I'm sure it's excellent stuff and has a good reputation. But any electronics engineer can also see the "specsmanship" games they play just like most manufacturers. I could pick big holes in their "data sheets" but it doesn't make it bad stuff; it just makes it difficult for the layman (like you) to be able to fairly compare apples with apples.

 

Chris

[anhar]

On the contrary I love pure sinewave inverters (PSW) - but it's horses for courses. For a device that needs a PSW inverter (eg: most washing machines) they are perfect. But why would one want to use a PSW to run a device that will run perfectly well off a somewhat more efficient and certainly less expensive Modified sinewave inverter (MSW)?

 

I don't have a washing machine on board so I don't need a PSW. Everything that I do run on board, that requires mains, runs off an 1800W MSW inverter and runs beautifully - eg: TV, lDVD, satellite, laptop, chargers, drill, hair dryer etc.

 

The only reason that a washing machine normally needs a PSW inverter is not because the output is "better". It's because to control motor speed the machine uses a device similar to a mains dimmer which happens to use the shape of the sine wave to achieve voltage control. It would be just as easy to design a motor control that didn't need a sinewave but since probably 99.99% of washing machines go into homes that do have mains....................

 

If that shape were unimportant then any MSW would run the nmachine.

 

For example, to dim my 12v lights efficiently (ie: without using a series resistor) I chop the 12v signal into a square wave at a particular frequency (500Hz) and vary the width of the square wave to achieve voltage control and hence dimming.

 

The chopped 12v is now an AC voltage but is no way close to being a sine wave. The lamp doesn't care, it just sees voltage for so many milliseconds - so it glows - and then nothing for so many milliseconds and it stops glowing. The human eye can't follow the speed so sees the lamp as dim.

 

Some devices utilise the shape of the sinewave because afterall, in a normal domestic situation, it's available. But it's not some God that is somehow better - it's just different.

 

I know you are hyper about Victron based on your posts. I'm sure it's excellent stuff and has a good reputation. But any electronics engineer can also see the "specsmanship" games they play just like most manufacturers. I could pick big holes in their "data sheets" but it doesn't make it bad stuff; it just makes it difficult for the layman (like you) to be able to fairly compare apples with apples.

 

Chris

As a layman, the reason for a psw inverter is to be certain of running any appliance that one might use on the boat. I don't know enough about it but I've heard that some appliances may not work properly on non psw inverters, not only washing machines though I don't have one either. You say that all your equipment runs off msw but I have read comments by others that some sensitive devices may not, eg. laptop computers or TVs for example.

 

I'm no techie but I just didn't want to take chances that something might not work so I specified the psw inverter to be certain. That's the only reason for it in my case. I take your point that psw is not "better" but "different" but that technical difference dosn't matter to me. What matters to me is certainty, assurance, so why risk it? I need to be certain that any appliance I am likely to use will work properly. As I undertand it, only psw can deliver that assurance. So in going for psw I don't have "wastage" I have a power cost of running a psw inverter. The cost of my certainty that I can use any appliance. As long as the battery bank and charging can cope with that cost then it doesn't matter. In any event as you said earlier, the inverter is switched off when not required (my fridge and lighting are 12v) which most of the time it is not.

 

As for the brand, that's a separate issue, but it makes sense to me to go for psw whichever supplier is used. I didn't mean to get involved in a brand argument. But I'm surprised you advocate msw, can you guarantee it will alway work with any appliance that may be used on a boat, whereas psw does as far as I know? (which admittedly is not that far, I'm only a dumb accountant).

 

regards

Steve

Edited September 14, 2007 by anhar

[stuart]

You could always run the TV of 12v DC - no need for an inverter at all. Do a forum search I think there was a posting on using as 12v rectified DC supply.

[chris w]

But I'm surprised you advocate msw, can you guarantee it will alway work with any appliance that may be used on a boat, whereas psw does as far as I know? (which admittedly is not that far, I'm only a dumb accountant).

 

regards

Steve

 

I understand and agree with your argument Steve. I'm not advocating MSWs over PSWs per se. Both have their uses. For you who, as a layman, wants high certainty that everything will function with no hassle you have chosen a PSW. As you correctly point out you are trading off this certainty against cost and efficiency. But that's your choice and it's a valid one.

 

I am merely pointing out that most devices will function perfectly well on an MSW inverter which is considerably less expensive and somewhat more efficient than PSWs. Over 90% of all inverters sold are MSWs so they must work pretty well.

 

For me, it's not a question of cost, I am lucky enough to be able to afford either type - for me it's the relative greater effciency of a MSW that appealed, viz: my batteries will last longer. I have 400AH of domestic capacity and that lasts me 48 hours without recharging even if I'm running TV, Sat, my wife's hairdryer and the usual pumps, heating and lights etc. If I used a PSW to run the mains items, the batteries would not last me as long and I would gain no additional functional benefit.

 

So your choice and my choice are both correct - but different.

 

Chris

[Gibbo]

The only issue with using a pure sinewave inverter when it's not really needed (eg: your TV) is that the current needed to run the inverter (its "quiescent" current in the jargon) can be 5-7 amps whereas for a modified sinewave inverter it's more like 1 amp - this is wasted power. (There will still be inefficiency losses on top of these figures for both types which will run at around 10% of the supplied current).

 

There is some clever marketing, with pure sinewave inverters, whereby you may see a low "standby" current for a pure sinewave inverter maybe less than an amp. Looks good eh? Not so......... what they do is that the inverter goes into a kind of "sleep" mode when no load is detected - this is the "standby" current. However when you are actually running some equipment, the quiescent current is as stated above and represents wasted battery power.

 

Some TVs may give a small line on the screen with modified sinewave inverters. My own experience is that the cathode ray (old type) TVs do but that my LCD TV does not.

 

Chris

 

You're right about PSW using more power than MSW but your figures are a bit out.

 

Typical MSW 3000 Watt inverter = 1.8 amps no load.

Typical PSW 3000 Watt inverter = 3 amps no load.

 

The Mastervolt Dakar is an exception here as it actually consists of a small inverter and a big inverter in one box and switches between them as power requirements dictate. The result is that the low power drain is extremely good. Much lower than anyone else's.

 

Still a difference but not as much.

 

Gibbo

[chris w]

The PSW manufacturers (with little exception) still state a "standby" current to "hide" the true losses.

 

Chris

[Gibbo]

The PSW manufacturers (with little exception) still state a "standby" current to "hide" the true losses.

 

Chris

 

Indeed. PSW are also less efficient. Typically 85% as opposed to 90 to 95% for MSW.

 

Gibbo

[Guest]

Must admit that the only thing we have onboard that needs the pure sine inverter is the washer. All the other crap that we have onboard, computers and lcd tellies, satellite etc run fine even off the old genny, which is as rough as the proverbial. I think that there is an element of luck here though, or have I made my own luck

Edited September 14, 2007 by Guest

[dor]

I understand that some chargers can be sensitive to poor waveform. My electric toothbrush (yeah ok) charger was clobbered by a QSW inverter output.

[Guest]

I understand that some chargers can be sensitive to poor waveform. My electric toothbrush (yeah ok) charger was clobbered by a QSW inverter output.

True,we got a Sterlng Universal charger to run off the generator, as I had heard that certain chargers didn't like the rough sine wave of a genny such as ours. The Sterling is fine.

[anhar]

I understand that some chargers can be sensitive to poor waveform. My electric toothbrush (yeah ok) charger was clobbered by a QSW inverter output.

Good point dor. Whilst electric toothbrushes may be considered unimportant, readers elsewhere have reported that 'waves with electronic timers may not function properly either with other than a psw supply. (though I've got one with a mech. timer, not because I feared electronic won't work, it will on my psw supply, but because my natural parsimony led me to choose this £24 Tesco model, damn good value I might add) And I'm sure I recall reading or hearing similar things about some TVs and computers too. The point is that there is no guarantee that anything other than psw will work every time with every appliance. Personally, I want that guarantee particularly on a new boat where the whole electrical system requires design to cope with the usage. Doesn't everyone else? Apparently not. Why use something that may not work every time, money permitting which it very likely would be on a new build?

 

I remain very surprised that someone with ChrisW's knowledge and experience would suggest anything other than psw for a boat where a large range of appliances may be used. My view remains that, especially if one has a ring main with a series of mains sockets around the boat, like a house, that only a psw inverter supply is acceptable. This must be the best solution, a system designed to cope with anything that might be thrown at it. As I stress, I don't know dick about the techie side of all this but I do possess logic and that has to be the logical answer.

 

The reason given against psw is the higher consumption but that doesn't in my opinion supply a complete answer. If one is designing a system from scratch, it can be designed to cope with the inverter consumption by using the appropriate battery bank and charging methods. The inverter's consumption is just another piece of equipment to be incorporated in the design spec. like the fridge or whatever.

 

regards

Steve

Edited September 15, 2007 by anhar

[chris w]

I remain very surprised that someone with ChrisW's knowledge and experience would suggest anything other than psw for a boat where a large range of appliances may be used.

regards

Steve

 

I would refer you to the answer I gave some time ago. A MSW inverter will run virtually everything with the exception of anything that requires a true sinewave shape to operate as with washing machine timers etc.

 

The modern switched mode power supply adaptor/chargers for laptops, TVs etc, which are now generally universal on most items, couldn't give a dick about modified sinewave or pure sinewave because whatever they are hit with they convert it to high voltage DC first, then change it back to a very high frequency AC and finally transform this down to low voltage AC and rectify this to get the DC to run your laptop etc. Once the first conversion to DC takes place, the input waveform is irrelevant.

 

I'm NOT advocating either type. The advantage of the PSW is that it should run anything as you say. The disadvantages are a cost factor of 2-3 times over a MSW and a noticeably lower efficiency.

 

It's a bit like buying an expensive 4x4 car just in case you might wish to go off-road at some time in the future. If you can afford it and the usually poor fuel consumption then go ahead.

 

It's not just about having enough batteries; it's also about having sufficient charging current and sufficient time to charge, whilst cruising, to put back what you take out plus another 30% (charging is only about 70% efficient). And don't forget the Peukert effect which means you are taking a lot more out of your batteries than you imagine once you start using higher currents.

 

Buying and installing a relatively inefficient PSW is nuts IMHO if you don't need it. ie: it's horses for courses. You can have all the batteries you have room for but, as they start to get low, you'd better have a damn good charging regime or you're gonna get stuck.

 

I don't mean this to sound perjorative, but your not being technical can lead you into a false sense of security because you only have a (rudimentary) knowledge of the basic points and probably do not fully appreciate what is really going on with the charging, discharging and recharging of batteries. Your answer to this of "just get more batteries" is simplistic but doesn't address the other issues.

 

A 3000W inverter on a typical 400AH battery bank will last half an hour on full power before the batteries must be recharged (50% point). Even if you could recharge them at 40A continuously (which you won't be able to) they would still take up to 10 hours to recharge. So every percentage point of wasted power saved is not a throw-away line - it's a very important consideration.

 

Have you actually started cruising yet Steve or are you at this stage planning a boat? Either way, what's your battery bank capacity, your inverter size, your recharging scheme and your estimated AH usage per day?

 

Chris

[anhar]

...I don't mean this to sound perjorative, but your not being technical can lead you into a false sense of security because you only have a (rudimentary) knowledge of the basic points and probably do not fully appreciate what is really going on with the charging, discharging and recharging of batteries. Your answer to this of "just get more batteries" is simplistic but doesn't address the other issues.

 

A 3000W inverter on a typical 400AH battery bank will last half an hour on full power before the batteries must be recharged (50% point). Even if you could recharge them at 40A continuously (which you won't be able to) they would still take up to 10 hours to recharge. So every percentage point of wasted power saved is not a throw-away line - it's a very important consideration.

 

Have you actually started cruising yet Steve or are you at this stage planning a boat? Either way, what's your battery bank capacity, your inverter size, your recharging scheme and your estimated AH usage per day?

 

Chris

A few points Chris. I never said "just get more batteries" as a solution to powering a psw inverter. Instead, I said more than once that the whole system of batteries and charging has to be designed appropriately. You probably didn't read my comments fully. I do understand that much about it and said that system design is the answer, I never claimed it was merely more batteries and appreciate that it requires appropriate charging sources to match.

 

Also you talk of a 3,000w inverter on full power lasting half an hour to 50% battery capacity to prove your point. One has to be sensible in use. I don't have a washing machine on my boat and but full power is rarely required. Or if so it is very temporary, for example the 'wave is on for a few minutes. Someone with an inverter that large and appliances to match would, in designing their system, almost certainly have an onboard generator so that takes care of any charging when moored. They would be ill advised to rely purely on the engine alternator for charging.

 

I have started cruising, longest only about six days though, and can't go more than a night or two tops without charging. My answer to charging when moored up on a cruise will be to obtain a Honda EU10i portable generator in future. This then gives me sufficient power to avoid the batteries becoming discharged more than 50%. I am aware that I cannot rely on the engine alternator to recharge my battteries sufficiently and in any case don't wish to run it for lengthy periods when moored up on the cut for more than a day without moving. My boat is not an expensive one hence the lack of an onbard generator. If in future I go upmarket with a new boat, I would specify an onboard diesel generator.

 

So to repeat again it is about system design. The whole thing including the inverter type, the battery bank size and the charging sources including a generator if necessary have to be considered to produce the optimum answer, not just one aspect of it. As you say mating a 3000w psw inverter with a large battery bank but without adequate charging sources would be poor design. But I think you have taken a poor example to demonstrate your point. Howver that's not what I've been saying at all.

 

Maybe I have been excessive by specifying a psw inverter for my particular situation and it is entirely possible that I could have gone with msw. I'll never know. But I do know that psw will (I presume) never fail to work with any appliance merely because it is psw whereas I believed that anything else might just fail on occasion. I can't take that risk, I'd rather go excessive than risk it and money was not an object. A further point is that I was willing to install only Victron or Mastervolt because I believe them to be the best. I wouldn't have any other brand. And I believe those companies don't do anything other than psw. I don't think it matters if they consume more power, provided as I keep saying that one has the other components to match.

 

regards

Steve

Edited September 17, 2007 by anhar

[chris w]

Yes I have started cruising but haven't been out for more than a few days. I am based in a marina with a shore line which I plug in for charging. I have a Victron Phoenix Multiplus 1600/70a inverter/charger, 330 amp hour batteries, two alternators, one for the starter and one for the domestic batteries and they are separate, no linking devices. Appliances apart from the usual pumps, central heating, a 12v fridge and lights I have a mains microwave, mains TV, mains standing lamp for reading, a mains radio, mains laptop computer I'll be getting in future. There are sundry small appliances like a mains standing lamp, mains phone charger. The mains appliances are in use for only short times especially the 'wave of course.

 

My answer to charging when moored up on a cruise will be to obtain a Honda EU10i portable generator. This then gives me sufficient power to avoid the batteries becoming discharged more than 50%. I am aware that I cannot rely on the engine alternatore to recharge my battteries sufficiently and in any case don't wish to run it for lengthy periods when moored up on the cut.

 

regards

Steve

 

Steve

 

I assume you are aware that the Victron 1600 is not a 1600W inverter. It is 1600VA which (according to Victron) is 1200W @ 40degC continuous. Have you tried it with your microwave, because, for example, a 700W microwave will consume twice that in electricity (microwave cookers are only about 50% efficient) and will have a very high start-up current. 1200W will be marginal for most mains vacuum cleaners as well. I have an 1800W inverter which so far has run everything I have thrown at it including a 1400W vacuum cleaner.

 

For the amount of stuff on board, I would advocate you get at least one more battery to take you over the 400AH mark or else you will struggle to last a complete 24 hours without significant recharging. I assume you have 3 x 110AH to get your 330AH. Why did you not go for 3 x 135AH to get 405AH in the same space? They are about 50% more expensive than 110AH versions but worth it IMHO for the extra capacity with no space penalty.

 

As you have said, you must recharge at the 50% level so you only have 165AH effectively. Your fridge will be the most demanding single appliance. Assuming it draws say 4A @ a 50% duty cycle, then it will consume around 50AH of your 165AH each day.

 

To estimate how much your mains appliances will use, divide their wattage rating by 10 to get the current (which takes into account the inverter's inefficiency). So your TV, which may consume around 60W and which you may watch for say 4 hours per day, will consume around 24AH per day. Your laptop will be a similar consumption (24AH) and your lights and pumps typically around 60AH per day.

 

Your microwave (given that the inverter can even run it) will consume about 24AH per 10 minutes of running.That's it: the list above will have drained your batteries in one day so you will need good charging to put that all back.

 

Your Victron 70A charger will take many hours to replace that charge. It won't run at 70A continuously as it will go through the bulk and absorption stages. So if we say there may be an average current of 40A and given that charging is only 70% efficient, I estimate it will take around 6 hours to fully recharge your batteries. That's a long time to be running a generator.

 

What's the nominal output current of your domestic alternator and do you have an alternator controller on it? The maximum current you are likely to get out of your alternator, at typical canal engine revs, will be about 60% of its rated output. As the battery voltage rises and due to idling in locks etc, this current will decrease quite quickly. It would be safer to estimate say 20A or less as an average charging current over the day. This would take about 10 hours to recharge your batteries from the 50% level. So if you cruise for say 5 hours , you still need to run your generator for quite a few hours more to fully recharge the batteries. And if you don't fully recharge them, then you start off the next day with even less capacity to begin with. An alternator controller will hold the current up to a higher level for much longer and so will reduce the charging time necessary by maybe a factor of two.

 

Most 12v fridges nowadays have some kind of low-voltage warning alarm. That will probably be your first hint if you do encounter the situation above.

 

 

Chris

[anhar]

Steve

 

I assume you are aware that the Victron 1600 is not a 1600W inverter. It is 1600VA which (according to Victron) is 1200W @ 40degC continuous. Have you tried it with your microwave, because, for example, a 700W microwave will consume twice that in electricity (microwave cookers are only about 50% efficient) and will have a very high start-up current. 1200W will be marginal for most mains vacuum cleaners as well. I have an 1800W inverter which so far has run everything I have thrown at it including a 1400W vacuum cleaner.

 

For the amount of stuff on board, I would advocate you get at least one more battery to take you over the 400AH mark or else you will struggle to last a complete 24 hours without significant recharging. I assume you have 3 x 110AH to get your 330AH. Why did you not go for 3 x 135AH to get 405AH in the same space? They are about 50% more expensive than 110AH versions but worth it IMHO for the extra capacity with no space penalty.

 

As you have said, you must recharge at the 50% level so you only have 165AH effectively. Your fridge will be the most demanding single appliance. Assuming it draws say 4A @ a 50% duty cycle, then it will consume around 50AH of your 165AH each day.

 

To estimate how much your mains appliances will use, divide their wattage rating by 10 to get the current (which takes into account the inverter's inefficiency). So your TV, which may consume around 60W and which you may watch for say 4 hours per day, will consume around 24AH per day. Your laptop will be a similar consumption (24AH) and your lights and pumps typically around 60AH per day.

 

Your microwave (given that the inverter can even run it) will consume about 24AH per 10 minutes of running.That's it: the list above will have drained your batteries in one day so you will need good charging to put that all back.

 

Your Victron 70A charger will take many hours to replace that charge. It won't run at 70A continuously as it will go through the bulk and absorption stages. So if we say there may be an average current of 40A and given that charging is only 70% efficient, I estimate it will take around 6 hours to fully recharge your batteries. That's a long time to be running a generator.

 

What's the nominal output current of your domestic alternator and do you have an alternator controller on it? The maximum current you are likely to get out of your alternator, at typical canal engine revs, will be about 60% of its rated output. As the battery voltage rises and due to idling in locks etc, this current will decrease quite quickly. It would be safer to estimate say 20A or less as an average charging current over the day. This would take about 10 hours to recharge your batteries from the 50% level. So if you cruise for say 5 hours , you still need to run your generator for quite a few hours more to fully recharge the batteries. And if you don't fully recharge them, then you start off the next day with even less capacity to begin with. An alternator controller will hold the current up to a higher level for much longer and so will reduce the charging time necessary by maybe a factor of two.

 

Most 12v fridges nowadays have some kind of low-voltage warning alarm. That will probably be your first hint if you do encounter the situation above.

Chris

Hello Chris

 

I've had no problems using the wave from the inverter, neither on start up nor running.

 

On the inverter spec. I do understand that the 1600 refers to VA. The actual wattage outputs quoted by Victron are 1300 continuous at 25° and 1200 at 40°. Also, note that the peak power it can deliver is specified at 3000W which presumably is why it can handle the wave start up without problem.

 

I've discovered that I actually have 440AH worth of domestic batteries according to my spec., which is somewhat higher than I thought earlier so I can go for a bit longer than you say. And I don't use the TV or wave etc. for anywhere near the sort of times you quote. So generally I expect to be able to go for about 24 hours without charging and without murdering the batteries below 50%.

 

But in any case how long can anyone go without charging where they have a decent amount of modern appliances on board like inverters, TV, central heating (and use them of course) and so on in addition to the basics like fridge, lights, pumps etc? I can't imagine that many people can do much more than 48 hours. So most well equipped modern boats that are cruising, and stay anywhere more than a couple days, will have to charge by running their engines or use a separate generator if they don't have one built in. Even if cruising and staying no more than one night anywhere, it would require several hours using the alternator to recharge but on some days I might cruise only a short distance, insufficient to recharge. I'm sure this applies to many boaters as well.

 

Thus when I start longer term cruising, I will buy a Honda EU10i generator which I think is the most effective answer to the question. If I was buying a more expensive boat, I would have had a built in generator with auto start.

 

regards

Steve

Edited September 24, 2007 by anhar

[anhar]

.

Edited September 24, 2007 by anhar

[Gibbo]

I need to clarify something here.

 

The difference between VA and Watts is down the the load. It has NOTHING to do with the inverter.

 

A specification of 1000 VA on an inverter means it is capable of producing 1000VA/230 volts = 4.34 amps. Any more than 4.34 and it will shut down. A specification of 1000 Watts is completely and utterly meaningless.

 

A load of 1000 Watts with a power factor of 1 (say a heater) will work (because that is 1000VA). A load of 1000 Watts with a power factor of 0.5 (say a motor) will not (because that is 2000VA). It will shut the inverter down.

 

An inverter should be rated in VA. To rate it in Watts is completely and utterly non sensical.

 

To say "It's 1000 VA which is equivalent to 800 Watts" in relation to an inverter or generator is, to an electronics engineer, about as silly as saying "My car does 40 MPG which is equivalent to 3 people eating peanut butter on toast".

 

Gibbo