New to inverters. Have some Q's.

[BigT]

OK, let me just preface this by saying that I've done multiple searches with little luck, so I'm going the direct route with this thread.  

Here's the deal: Among a few other things,  I want to charge my MacBook Air off my van's 12V system, but the little, $30 cigarette lighter units I see on Amazon, come with a multitude of bad reviews and warnings.  Apple doesn't recommend using them either, though that could simply be because they don't make them and they might void any warranty.

As for inverters...  Much as I expected, it's not recommended to get one that's powered off your vehicle's cigarette lighter / Acc outlet.  
Not only because you'll blow a fuse, but because the Acc outlet is notorious for making lousy electrical connections and loss of available power.  
For this reason, I'm looking for an inverter that either comes with Alligator clips or that I hardwire directly to the battery terminals and mount somewhere under the dashboard or to the console (the latter method being preferred).  

I'm also hearing that a "pure sine wave" design is better, though being the electronic moron that I am, I have no idea what that means, what the advantages are, or what they're "better than".  What's the alternative?  

The other items I'd like to charge off the van, are my razor/beard trimmer, and possibly, though rarely, a cordless tool/drill/saw.  
My iPone has no problem charging off my Acc outlets.  I also run my "Endless Breeze" fan off the rear 12V outlet with no issues.  
Honestly, it's just my laptop and maybe razor that are the concern right now.  OK, really just my laptop.  

I don't have much battery power in my van, just a single 75 Amp hour/Group 24 AGM under the hood and 190 Watts of solar on the roof, so my plan is to only use the inverter while driving so the alternator is backing it up.  

Money is no concern, to a point, so I'm not looking for the cheapest option available.  I tend to buy things I know I can grow into and/or use in the future for my next van build.  That being said, I also don't need the biggest, baddest, most powerful model in the world.  I just need something that will safely and efficiently run the few items I have.  

Unless, of course, running a more powerful inverter has little to no effect on the battery or charging system.  Then I'm fine with a super-powerful inverter with growth potential.  Honestly though, I'd like to keep the price below $200 - $300 if possible.  

I guess I should also mention that I don't live in my tiny Transit Connect cargo van.  I simply use it, or hope to use it, for short and extended road trips.  
That means I won't be running anything off the inverter constantly.  I just want a way to safely charge a couple of 110V items when I don't have access to shore power.  

So that's it.  That's my plan.  What do I need to make this work?  

 

[jimindenver]

The bigger the inverter the bigger the power drain while not in use. You really do not have enough battery to support a big inverter because a bigger load will drain it too quickly. You size a inverter by the largest item you want to run. Pure sine wave is a cleaner source of power than a modified sine wave. Some MSW are cleaner than others but for the size you are looking at you might as well spend the money.

The Morningstar 300 watt Pure sine wave inverter has no fan to annoy you and should charge up your computer, etc.

 

[BigT]

The bigger the inverter the bigger the power drain while not in use. You really do not have enough battery to support a big inverter because a bigger load will drain it too quickly. 

The ones I've been looking at have on/off switches.  Wouldn't they stop drawing off your battery if they were turned off?  

Also, if I only use them while the engine is running, would/could they still overpower the alternators charging ability and drain the battery??

I've heard, and it makes perfect sense, that the larger, more powerful the inverter, the faster it drains your battery, but is that an issue if the engine is running?

Since I'd only be using it while driving, the noise from a cooling fan wouldn't be an issue, but thanks for letting me know it's an option. 

 

[RVtrek]

Yes, they'll stop drawing power if they're shut off. Especially those with a physical switch instead of a button that toggles power on/off.

If you're looking at something in the sub 500-watt range (which you should be), your alternator can handle it, no problem.

 

[Almost There]

Because my inverter is housed in my 'electrical room' where it's not really convenient to turn it on and off, it's wired to a lighted switch inside my living quarters so that the switch ON the inverter stays in the on position and I control the power to the inverter from a convenient spot.

I also wired in a pair of duplex outlets in the living area that are simply wired with a plug on the end of romex and then plugged in to permanently to the inverter.

This gives me not only control of the inverter but access to it for use without having to fuss about getting in to the electrical area..everything is where I need it.

I see that you're only planning on using the inverter when the engine is running but it's worthwhile thinking about the little bit of extra work to make the whole system more accessible.

 

[Trebor English]

What I have done works fine for me.  I got a very inexpensive Harbor Freight 400/800 $25 inverter, $20 with a coupon.  My plan is to use that until I have a device that won't work with it.  So far everything has worked fine.  I do not have any Apple brand products.  I use it for a 10 inch Acer Aspire netbook.  I have an electric shaver, variable speed electric drill, jig saw, and a soldering iron.  I have a 3 speed incandescent light bulb, 50, 100, 150 watts, to use the inverter as a battery testing variable load.  I cut the 14 inch square hole in the roof and drilled the screw holes for the MaxxFan using the jigsaw and drill.  I have seen it actually put out 360 watts.  

I have recently started using it to run a Haier 1.7 cubic foot cube fridge.  The inverter has to be turned on without the fridge then, after a couple of seconds, it starts the compressor.  Turning on the inverter causes a 65 amp 12 volt surge, then the compressor start takes 75 to 80 amp surge.  Turning on the inverter with the fridge connected combines the two surges and it shuts off.

This inverter is not pure sine wave.  It is modified square wave.  I have had no equipment destroyed by it and it has worked everything under 360 watts I have plugged into it.  The 1000 watt space heater did not work but the inverter did not self destruct either.  

My plan is to continue to use it.  If I get a thing it won't work I'll consider a different inverter.  So far I have zero evidence that a $200 or more inverter would be any better for me than the cheap one.  Meanwhile I'll just hang on to the extra cash.

 

[tx2sturgis]

Pure sine wave means the output AC waveform from the inverter is very close to what comes out of the wall outlets in your house, but the downside is they cost more, and are slightly less efficient.

Modified sine wave (the opposite) has a less desirable waveform, close enough for some appliances, but usually bad for computers and sensitive electronics. But they are normally cheaper and more efficient.

But for your expensive computer, you really should buy a pure sine wave inverter....abbreviated on this forum as PSW. 

A 300 to 500 watt PSW inverter will easily do the job you want, but won't power a microwave, toaster oven, or A/C unit.

Stick with good brand names: Morningstar, Xantrex, Samlex, Renogy. There are others too.

Avoid cheap unpronounceable or generic no-names.

You will also need the connection cables to hook it up to your battery and mount it where its easy to access.

 

[BigT]

Thanks for all the helpful replies, everyone! Much appreciated! Seems pretty straight forward.

One more question (2 actually):
1- What gauge wire should I run between the battery and the inverter?
2- Should I run a fuse between the battery and the inverter? Or does the unit have its own, built-in breakers? I guess that was 3 questions.

The units I've seen come with cables and alligator clamps, but I figured/hoped that if long enough, I could just cut the clamps off and replace them with eyelets for the battery terminals.

 

[Trebor English]

1- wire gauge - depends on distance and how many watts you want to run.  Two feet, 120 watts, 10 amps, AWG #10 is small, #6 probably ok.
2- fuse - every wire connected to a battery needs a fuse to protect the wire.  If the wire chafes against a sharp edge and shorts only a fuse at the battery will protect it.  Fuses in the inverter will not protect the wire.  
- The wire that comes with it is at best marginal.

 

[tx2sturgis]

1: Depends on the size of the inverter. The manual will tell you, or if you buy an inverter with included cables, say, 20 feet long, they should be the correct gauge. We can also figure the wire gauge based on the expected amps and the length of cable, when you know what you will order. 

2: You should always fuse the positive line very close to the battery, even if the inverter has a built in fuse. This fuse near the battery will protect you and your vehicle if a short happens somewhere along the cable run to the inverter, like being pinched against the frame or heaven forbid if you are in an accident, and metal against metal happens right where that cable is.

 

[BigT]

Yeah, I figured a fuse on the positive wire was a good idea, but I wanted to confirm it because I read something about a breaker in the inverter.
Now I know, thanks!

I'm hoping to find a decent 300 or 400 Watt PSW and run only 4 or 5 feet of cable. My plan is to run the wires through the firewall, across the underside of the dash, and mount the inverter in the passenger side footwell somewhere.

I figure if I'm only going to charge things while the engine is running and/or I'm driving, I might as well mount it where it's easy to get at from behind the wheel.

I imagine the Amp of the fuse also depends on how powerful the inverter is?

 

[tx2sturgis]

Yep, so again, when you have the one you want, it will either have a cable with a fuse, or we can recommend a fuse based on expected current draw and wire gauge. For 300 to 500 watt inverters we are probably looking at a 25 to 50 amp fuse.

 

[BigT]

I found this --->  https://www.amazon.com/Samlex-Solar...2&sr=8-7&keywords=300+watt+sine+wave+inverter

Samlex Solar PST-300-12 PST Series Pure Sine Wave Inverter.

From the reviews and answered questions I've found on Amazon, it sounds like I want to run 6 AWG for 6' of wire and 4 AWG for wire lengths up to 10'.  
Not sure what size fuse to use, though.  

My MacBook is rated at 85 Watts with a peak of 100 Watts.  I'm not really sure about the beard trimer or cordless drill, but then those likely wouldn't see a lot of time, if any, on the inverter.  

The only downside to this particular model is that it appears to be quite large..  10" X 6" X 3"  So much for mounting it in the footwell.  This thing is going to require some serious room.   :s

 

[tx2sturgis]

If you order the one you linked to you can forget about the 12v power plug, I guess they include that cable for emergencies, but its not suitable at the 300 watt level. I dont know of any of those sockets that are fused and rated above about 15 amps.

My 300 watt Samlex is mounted under the driver seat, but this is a Ford E-250 with room under the seats. Does that van have a center console? If so, you could mount the inverter to either the front or back of the console.

 

[BigT]

From everything I've read, the Acc/lighter plug is only if your using less than 100 Watts, which theoretically should be enough for the 85-100W draw of the laptop, but just barely.  I have no intention of using that plug, though.  I'd much rather hardwire it straight to the battery.    

No room on the console in my Transit Connect, but I suppose I could mount the inverter to a piece of metal plate and stick it under the passenger seat.  
Should be enough room under there.  I was kind of hoping to bolt it down, though.  I'm not really interested in removing the seat if I don't have to.  

Given the lack of room, I may just run larger wire (4 AWG) for 10' and mount the system in the rear of the van.

Some guy on Amazon suggested that beard trimmers could draw as much as 500 Watts, but when I calculate the Voltage and milliamps, I get a much smaller number.  The trimmer is 4.0V & 100 mA.  With an Amps to Watts calculator that should be 4.0V / 0.1A = 0.4W.  Maybe he meant 500W when running.  IDK.

 

[frater secessus]

Maybe hardwire in a good quality 12v laptop supply for efficiency and add in a small inverter for tools and razor?

There are a couple brands of cordless tool battery chargers (like DeWalt, apparently) that can be damaged by MSW inverters. My Ryobi cordless chargers and other small items are happy on a $30, 300w unpronounceable inverter.

Sent from my R1 HD using Tapatalk

 

[RVTravel]

The inverter that Apple used to sell for their laptops was the Kensington Auto/Air Power Inverter with USB Ports. It is a regulated modified sine wave inverter.
https://www.kensington.com/us/us/4470/k38037us/autoair-power-inverter-with-usb-ports

 

[tx2sturgis]

Some guy on Amazon suggested that beard trimmers could draw as much as 500 Watts, but when I calculate the Voltage and milliamps, I get a much smaller number.  The trimmer is 4.0V & 100 mA.  With an Amps to Watts calculator that should be 4.0V / 0.1A = 0.4W.  Maybe he meant 500W when running.  IDK.

Well if some guy on Amazon said it, it must be true... (not!)

Think of it this way...if a beard trimmer was dissipating (using) 500 watts of power it would either be getting as hot as a 500 watt light bulb or make so much noise and vibration you could cut 2x4's with it.

Trust me, it's less than a few watts.

 

[jimindenver]

My full sized clippers for the dog say .19 amp at 120v. With inverter losses that would be 2 amps or so at 12v.

 

[John61CT]

There are a couple brands of cordless tool battery chargers (like DeWalt, apparently) that can be damaged by MSW inverters. My Ryobi cordless chargers and other small items are happy on a $30, 300w unpronounceable inverter.

Again, go direct off 12V or at least stick to DC-DC conversion.

I can't get my head around inverting from DC to AC then using a transformer to feed a device that is native DC to start with.

Yes there are exceptions, but cordless tools generally have an inexpensive 12V chargers direct from the mfg.

Personally I advocate keeping inverters to a minimum, often can be eliminated completely.

Buying a small/cheapest **one per** the few remaining must-haves is often cheaper, and usually **much** more power efficient than buying a big high-quality one for everything.