[copacabana]

I think my 2,000w inverter has died and I'm looking for a replacement. I really only use it to run a laptop and sometimes a power tool like a sander (but very rarely). I don't want to spend a fortune on a new one, but I would like something powerful enough. I suspect the 2,000w one was overkill for my needs. Would something like a 400w inverter be enough? Any suggestions for models or brands?
Thanks!

 

[findrichard]

I would think what ever your max wattage useage will be should determine how powerful of an inverter you need. So check the wattage of your sander and maybe add your computer wattage to that in the event they are both running at the same time.

 

[copacabana]

My grinder is 120v/900w. Would a 1000w inverter do the trick? I don't really plan on running the grinder off the inverter, but I'd like to know I could if I needed to.

 

[christian.hess]

depends on start up draw...thats the thing with electrical stuff...some things come with soft starts etc to help minimize initial draw

I think a 900watt grinder will more than likely overload a 1000watt inverter...safe bet there would be 1200-1500watt

 

[findrichard]

You can always call the manufacture of your grinder and they can tell you the max wattage your grinder needs.

 

[christian.hess]

you also have to account for losses...thought I read somwehere that its 5-10% depending on type and manfucaturer as well as how far from the batteries they are etc...

I wish I knew how to fix inverters...I need to fix my 2000watter

 

[AlanF]

Inverters will deliver roughly double their continuous power rating for a second or so, but electric motors can require roughly 3 times their constant draw when starting. So a 1000w inverter for a 900w motor is going to be a problem. 900w of lights, flat panel, etc., would be OK.

Also, a modified sine inverter is very inefficient for running motors, so take that into account when choosing.

Admittedly a tough call - they are expensive, but a good one will be around for a long time. My pre-Xantrex Heart from the late 80s is still going strong.

 

[Brewgyver]

+1 on AlanF's post. A common rule of thumb for electric induction motors is to take the RLA and multiply by 3, but some motors have even higher inrush current. For power tools on a boat, you might want to consider a small investment in a good set of lithium powered tools. I have several of the Ryobi 18 volt lithium powered tools, they have amazing power and longevity. A VSR drill, impact driver, angle grinder and lantern live in my truck. The one that I was happiest to find for my boat is an inflator. It does both low and high pressure, so I can pump up the inflatable in no time. Last fall, for the spiny lobster season, I had an air leak issue with the dink, so I just brought the inflator along with the hoop nets! For tires, it has a clamp on chuck and pressure setpoint control, with digital gauge. Clamp the chuck on the stem, set the pressure, start it and walk away. Cool stuff.

So, maybe get some nice toys, er I mean tools, and then keep a ~400 watter for computer, etc.

 

[hellosailor]

copa, if you haven't bought anything at this late date...

Buy a dc-to-dc converter for the laptop. They're inexpensive and reliable and efficient. See what your laptop needs, probably less than 100W and get something a bit bigger in case the next one needs a bit more. Several companies like Igo and Kensington make them with multiple tips available so you can use them with many brands and models.

There is no way that you should be using a 1000W inverter for a 100W computer, they are simply not efficient when running at such a low percent of capacity. A true waste. Plus, an expensive piece of equipment, or an unreliable one, or both. Buy the proper dc-to-dc converter for the laptop, and take your time buying a proper large inverter for large loads like the power tools. You'll be happier in the long run.

 

[copacabana]

Thanks for the tip Hellosailor. In the end my 2000w inverter isn't defective and seems to be working fine.
I have a 12v cigarette lighter power socket at the nav station and I'm going to see if I can find a cable to run the computer off that. Is that what you mean by DC-to-DC converter? I agree, running a laptop off a 2000w inverter is not very efficient...

 

[hellosailor]

"I'm going to see if I can find a cable to run the computer off that. Is that what you mean by DC-to-DC converter? "

Nope. While nothing in a modern laptop requires more than 5 volts to run, and nothing in most comuters in general ever required more than 12 volts to run, you can't run one off a 12v socket. Most are set up to require higher input voltage and you need a dc-to-dc converter, sold as a "car converter" or "airplane converter" or what have you, to run the computer off a 12vdc supply. It will look like a cigarette lighter, with a cord, and a brick, and another cord, with interchangeable tips to make that last cord work on different computers.
Typically $50-100 in the US, rarely less, sometimes more. Absolutely no need to buy the generally overpriced ones from whoever makes your laptop. Just make sure it is rated for more watts than your computer pulls.

 

[Brewgyver]

Or you could buy a 150 watt cig lighter inverter for $15-20.

 

[copacabana]

Brew, I just ordered a 150w cigarette lighter inverter (about 25 dollars). Thanks for the idea. Is 150w going to be powerful enough to run my laptop though??

 

[copacabana]

My laptop is 19v, 3.42a (which converts to 65w, if I'm not mistaken).

 

[Maine Sail]

Copa,

Please be very, very careful with these inverters. They draw a LOT of power for the "small contact area" they connect through. On boats corrosion sets in and I have seen a number of them nearly start boat fires...

A 150W plug in inverter can draw 13.0A at 11.5V. This is a typical "loaded" voltage for a bank getting close to 50% SOC. These inverters can also draw considerably more than 150W for short durations. Most marine 12V sockets are only rated for 10A and even that I don't consider safe as a continuous load. As a marine electrician I don't like to see 12V sockets loaded beyond about 6A..... This equates to approx a 65W plug in inverter.... Blue Sea makes 15A rated 12V sockets but I have measured these at hot as heck levels (well over 120F) pushing just 8-9A....

Do yourself a favor return it and buy a 12V Laptop Adapter for your laptop. Lind, iGo, Targus and many others make them. Lind is top quality, have less waste heat, but you pay for it. You can find 12V laptop adapters on Amazon for $30.00 - $100.00. They are usually laptop specific so search by your computer model. If you have a Mac Jeff at Marine Beam has 12V adapters for Mac's with the mag safe connectors...

Keeping it DC is MUCH more efficient. You will find you can save 25-40% over using an inverter and computers are ENERGY HOGS... I have some customers who's computers use as much as DC refrigeration in a day......

When I boarded this boat the smell of burning electrical and melting plastic was awful. It led me to this melted 150W inverter charging a 17" laptop computer.......

The 12V outlet also had 16GA wire and NO FUSE.......

I see melted inverters like this more regularly than you care to know about....

 

[copacabana]

Ouch, Mainesail ... I just ordered it and paid online! To be honest, I so infrequently use my laptop on board (and for a short duration when I do) that I might just give the little inverter a try. I will keep my eye on it like a hawk though, in case it heats up! Thanks for the warning.

Maine, I'm in Brazil and often I can't find the products you recommend up north. This was also the case when you kindly recommended some different solar controllers a while back. On my next trip up north I'll look for the Lind cable (and the other 20 or so things on my shopping list!).

 

[PeterJYC]

When it comes to power required for tools:

This isn't my picture but I have been using a set-up like this - inverter mounted directly above the battery for using power tools around the boat when away from shore power. I like it because you never need an extension cord and you can keep an eye on it for overheating, sparks, etc. I think I have 1,500 watts and have always had enough power to spool everything to 100% speed.

 

[copacabana]

When it comes to power required for tools:

This isn't my picture but I have been using a set-up like this - inverter mounted directly above the battery for using power tools around the boat when away from shore power. I like it because you never need an extension cord and you can keep an eye on it for overheating, sparks, etc. I think I have 1,500 watts and have always had enough power to spool everything to 100% speed.

Peter, I have a 2000w inverter installed in the engine compartment, but it's overkill for small charging needs like a mobile phone or running a laptop.

 

[hellosailor]

copa-
Maine has a point, some of the cheap inverters can be, well, dangerous junk. I think word has been slowly getting out over the past 20 years or so, that cheap stuff that plugs into electric sockets (wall or 12v) can and does start fires, so I wouldn't leave it plugged in unattended if it ran even warm to the touch.
If you don't use it often, a dedicated laptop converter can be expensive. But if you do use it on the boat, bear in mind that using a laptop's power brick plus a 12v converter, means you are using two converters and each one wastes power in the conversion process. By using a laptop dc-to-dc power supply, all in one unit, you cut that loss by at least 50%, whatever it may be.
Something to keep your eyes open for, so you can grab one if you see a good price on it. Even if that's not right now.
And I'd spray a little MacLube or silicon grease in the lighter socket, to help make sure there's no corrosion forming to add resistance (and heat) in there.

 

[JimsCAL]

You should be fine using a small inverter as long as you don't leave it plugged in unattended. I use one to maintain the charge my small laptop when onboard and have had no issues. Power supply is only 19v and 1.58 amps though, so about 30 watts. And my inverter is a good quality one.