Power Inverters - Any good?

[Spartan]

We spend a fair bit of time on a swing mooring and therefore don't enjoy the benefits of shore power that marinas provide. My wife also tends to let my son and I do the sailing and, depending on the weather, can often be found below watching a movie on the laptop (until its battery conks out).

Anyway, I was recently in Maplin and noticed a power convertor that runs from a cigarette lighter and inverts the power to allow small TVs, laptops etc to be run from a car battery.

Have any of you guys had any experience with this type of kit on a boat? If so, is this something that is worth a shot - or are they a waste of time.

I currently have a small wind generator on my yacht that keeps my batteries topped-up but, even so, I won't want to start using this invertor if it has been proven to be a big drain on the batteries.

Any thoughts? Sorry if this subject matter has been covered before.

 

[Eygthene]

Whilst an inverter will allow you to produce a crude 240volt AC supply, which can power your laptop and recharge it via its usual mains adapter (though some laptops are reported not to survive), the conversion to 240V from 12v and then back down to perhaps 18v for the laptop is rather wasteful of battery power.

A more satisfactory solution is a laptop universal DC to DC converter, also available from Maplin etc., which also connects to the lighter socket, but can be set to output the right DC voltage for your laptop. The power lost in one of these is less serious.

 

[Stu Jackson]

http://www.westmarine.com/webapp/wc...&storeId=11151&catalogId=10001&page=Inverters

http://www.westmarine.com/webapp/wc...gId=10001&page=Sizing-Your-House-Battery-Bank

Inverters are helpful if you don't want to go the route of finding a direct 12V DC connector for your laptop. They use energy in conversion. Use your 240V AC in lieu of the 120V AC American in the link I provided.

Size your battery bank for your loads - do an energy budget.

 

[dmmbruce]

I have the same problem as you. I find the small inverter works well, mine is a 120watt, so it puts out 80 watt for the laptop ok. However it is probably less than 80% efficient.

My wind turbine does not cover this. However two 35watt semiflexible solar panels and an MPPT controller cope very well. My batteries suffered no problems last year.

Mike

 

[William_H]

Inverter

The concept is very seductive. However you need to understand the limitations and problems.
Cheap Inverters produce a square wave or so called modified sine wave. That means there are a lot of higher frequencies in the composite power apart from the 50 hertz you want. This can mean that the device you power will waste much of the power you put in. A domestic fridge for instance will not work well and is inefficient on 240vAC modified sine wave. Electronic power supplies for other devices vary in their efficiency on this " dirty" AC. some waste power some drop dead.
If you spend more money and get a true sine wave inverter you don't have such problems.

However you can not get away from the fact that an inverter will be at best about 90% efficient and worse at low power drain and even a small inverter 120 watt will draw more than 10 amps from your battery at full load.
To run a microwave oven puts you close to 100 amps from battery. You can see the point.

So an inverter can be cheap and can fill a useful role if used sparingly and carefully and don't let the ladies see it. They will never understand the current drain implications. olewill

 

[barnaclephill]

Whilst not contradicting OleWill in the square/pure sine wave and 90%max efficiency, there are other aspects.

Occasionally you might need to use a tool from home and there the inverter will power it, so long as you don't drain your batteries.

I had a 12V to multiple-select DC converter for a laptop, and a 300 W inverter for a while. Now I just use my 600 W inverter. It does the jigsaw, a non-12V drill and the angle grinder in both cutting and sanding modes. With 40W of solar panel and 100 A/hr battery capacity, I can't use the power tools for more than maybe half an hour, but that is enough to get the jobs done. Then the engine alternator or solar panel will recharge the battery over the following week or 2 till I next come to the boat. No shore power in the 9 years of owing this boat. Some jobs needing electricity are best done in the wet berth at the yard, or in the yard at haul-out time, while some others are easily tackled by the inverter in the season.

By example: my 500W angle grinder takes 500W divided by 12 equals about 42 Amps, if done for an hour will take about 42% of the battery capacity and shorten it's life. But on a 40W laptop, it'll be only about 4 Amps drain. It would be easy for someone to bring land-lubbing energy habits to a boat, and drain the batteries, but at times it's good to be able to use normal power tools, etc.

 

[Spartan]

Thanks for your responses guys (and gals). Most helpful.

Any other thoughts or suggestions (preferablly in plain or easy to understand english) would be most welcome. I'm not too electronically aware - hence my initial question.

 

[planteater]

As Dylan Winter pointed out in one of his Keep Turning Left videos, a lot of small rechargeable appliances (camcorders, phones, laptops etc.) can be charged quite happily from 120V. Many consumer items use the same charger that will work from Japan (90V) to UK (250V).

Cheap 120V inverters are readily available on Ebay and are more efficient than the 240V type.

 

[dylanwinter]

as the man says

As Dylan Winter pointed out in one of his Keep Turning Left videos, a lot of small rechargeable appliances (camcorders, phones, laptops etc.) can be charged quite happily from 120V. Many consumer items use the same charger that will work from Japan (90V) to UK (250V).

Cheap 120V inverters are readily available on Ebay and are more efficient than the 240V type.

I bought a v cheap and small american inverter - it runs stone cold - I use it for charging all the camera batteries I use which run off both 110 and 240

you will probbaly find that your laptop main lead will also be happy to accept 110volts as well

but...

when running the laptop I use a maplins laptop power unit that is designed to run stright off the 12 volts - I have used the laptop all through a winter evening and and it does not seem to dent the battery reserves very much at all

I think it was only about £12

or you could get another wife

up to you

Dylan

 

[barnaclephill]

or you could get another wife

up to you

Dylan

I almost choked on my coffee...

 

[philiphurst]

I use an inverter for charging camera and phone batteries and occasional laptop use.

Money-saving tip: mine is a Belkin. They have a lifetime guarantee which is pretty handy when using in a hostile environment. 350w. £22 from Amazon last year. (Great value as you only have to buy one!). Has a battery level indicator which, whilst unlikely to be very accurate, gives you some indication of the donor-battery state and cuts power when it is down to 10%.

Seems to work perfectly but I have never used it at anywhere near its limits.

After sales service from Belkin is superb. A friend of mine bought an ancientBelkin wireless router at a boot sale. It didn't work, he called Belkin for advice and they replaced it!

 

[boathead]

Thanks for your responses guys (and gals). Most helpful.

Any other thoughts or suggestions (preferablly in plain or easy to understand english) would be most welcome. I'm not too electronically aware - hence my initial question.

I use a 300 watt inverter on my boat, it runs the laptop and 'aint a problem to the batteries, though as previously suggested it's just as good (maybe better) the get a 'ciggy' lighter adaptor for this purpose. However as another reply has pointed out, an inverter can have it's uses. I run a small, 3ft x 2ft freezer (designed to be carried in a Truck or a Caravan) it's Gas or mains or battery powered, on it's lowest setting it runs happily via the inverter. Soldering irons are useful to me, they are fine too via the inverter as are other power tools.

As long as you are aware of their limitations which put really simply are: If you use them heavily they will drain your batteries, they are very, very useful. I have solar panels for charging, most of the time they cope well (obviously not in winter), as back up I carry a 12v booster pack (from Halfords) for emergency engine starting, though I carry this NOT because of the inverter.

Hope that's simple enough?

 

[Spartan]

Again, thanks for giving me more suggestions and food for thought.

"... or you could get another wife" Sorry although I appreciate your suggestion Dylan, that option would work out more expensive than a replacement yacht !! I know that from experience. Been there, done it, got the t-shirt and very happy with the new model I got !!

Changing the subject, Boathead, you say you have a 12v booster pack for emergency starting. Do lots of people have something like this - and is it something else I should be thinking about as a 'just in case I ever need it' ?