School me on inverters

[smlobx]

We are in the process of spec'ing a new Hallmark Everest but I think this question would apply to any camper.

Our goal is to make the unit as self sufficient as possible.
We are adding PV panels, extra battery, 2 way fridge etc. to allow us to stay off the grid as much as possible.

We don't anticipate much 110v electrical use other than a laptop. When we questioned Matt he said they could install an inverter (for around $800-1000) but reccomended we buy something like this instead:

http://www.donrowe.com/Samlex-PST-300-12-p/pst-300-12.htm

I'll be the first to admit my electrical ignorance so I am looking for advise from those of you that have some experience in this department.

Thanks!

 

[Happyjax]

I have heard good things about Samlex but have not owned one. The pure sine wave is a cleaner power version that the lesser expensive modified sine wave. It is better for electronics. This is a small inverter but should power your laptop and a few small items with no problem.

 

[iowahiker]

My understanding (not an expert) is "clean" power inversion is only important for non-battery powered electronics like desk top computers or display monitors (digital TV). We carry a small inverter ($35) to charge our laptop and and cell phone. We also purchased a 12 volt cell phone charger which is more efficient than using an inverter. If you get a large inverter, then you need a larger battery pack to supply it and a larger fuse in the campers 12 volt system to supply it. Our inverter has a 10 amp/12 volt fuse or 120 watts. Our laptop charger has an output of 20 volts and 4 amps or 80 watts. At startup (but not while charging), we slightly over amp our inverter so a 15 amp/12 volt inverter fuse would be better for us. Check the labels on your device chargers, convert to watts (amps x volts), and pick an inverter which has larger watts (fuse amps x 12 volts) while not exceeding the amp fuse rating on the 12 volt camper circuit you will connect to.

 

[Lighthawk]

Consider leaving 110v behind! Inverters are inefficient and from my limited knowledge either expensive or cheap.

We picked up a 12v adapter for our laptop, and all phones, GPS, bluetooth speakers and camera battery chargers are also 12v.
I modified our Hawk to make a charging station two years ago and it's been perfect for us.

FWC typically puts in one 12v outlet, usually on the face of the cabinet below the stove/sink, which doesn't really provide a platform to charge your device. I opted to put our charging station on the opposite side of the camper and added a shelf where we can place all those hungry electronic devices to get their fix.

 

[Casa Escarlata Robles Too]

I have a small 150w wired right at the battery. Easy to get to and use,Just charging lap top,camera and other battery's.
Also I use it to plug my coffee grinder in.It's just a bald grinder and works well.
Also I picked up a portable inverter that I can use in the truck cab or in the 12v outlet in the camper.
IMO I wouldn't spend a bunch of money on one. Wow $800/$1000 for that install!
Frank

 

[ntsqd]

I second Lighthawk, leave 120 VAC behind if you can. I tried and couldn't (at the time) so we have a couple small inverters. One that is mounted to run the navigation notebook and another loose one to charge camera batteries & occasionally run the string lights. Neither of these is a pure sine wave device and I've not had any issues in a couple of years. When it's time to replace the notebook I'll be revisiting this.

 

[wuck]

Generally speaking, a pure sine wave inverter is required for devices that use line transformers or AC motors. A square/modified sine inverter will cause these things to overheat and be noisy.

These days, nobody builds AC adapters for phones/laptops/etc with 60 Hz AC line transformers. They are all direct line switching supplies, there is a transformer involved but it is a high frequency, compact, lightweight design. How can you tell? Pick up an old AC adapter, compare the weight to your newest phone charger. The new one will weigh almost nothing. These type of adapters will usually operate fine off a modified sine inverter, with one caveat: Because of the waveform shape, the PEAK voltage output of a modified sine inverter will be larger than a pure sine inverter in order to keep the RMS output voltage at ~110 to 120 volts. This could cause problems with some adapters.

All that said, 12 volt adapters are pretty easy to find and way less expensive than a big pure sine inverter, I'll third the motion of going straight 12 volts.

 

[Bad Habit]

I opted out of a built on inverter on ours. In some ways I do wish I had one built in but it's not a big deal. We have a good portable one, ~350w I think that covers our needs. The only small down side is it's awkward for battery chargers, etc as to how they plug in in some case (i.e. the camera battery charges are always direct plug in units that sit at strange angles to the plug). My truck also has a built in ~150w inverter so I end up using that more times than not. Having something built in is nice because it's one less thing to store, deal with but for the, not worth it in my opinion.

 

[PaulT]

Add me to the list of losing AC 120v.

Converting between AC & DC, in either direction, involves loss of energy as heat. Losing battery energy hard won from solar as heat in the warmer months is strong incentive to find alternatives to inverters.

This may be as simple as choosing as your next laptop one that can be run directly from 12 volts DC.

Paul

 

[smlobx]

Thanks for all the replies! I've really learned a lot.

I read Lighthawk's previous posts and that got me to searching and I discovered a few things I didn't know before.

1. Laptops and iPads etc actually run on 12 volt
2. Going from 12v>110v>12v results in a loss of efficiency at each stage.
3. The iPad's actually need a different (stronger) charger than iPhones.

So it sounds like we're going to join the 12v club and just get the proper plugs!
Thanks again...

 

[fish more]

My new 2015 Ford Super Duty came equipped with a 110 invertor on the dash. It works great for charging almost anything.

 

[Old Crow]

I'm not sure if it's still true (I think it is) but when I bought my MacBookPro 13 in 2009 the only 12-volt chargers for them were aftermarket ones. I bought one off Amazon and it kinda works but charging is slow. I could run the laptop off it but couldn't both use it and charge the battery at the same time. On the other hand, my 150-watt inverter will do both. I can even plug in a nearly-dead laptop to the inverter and watch a movie on DVD and by the time the movie's over the battery is also fully charged. Same for while I'm using it online.

What my inverter WON'T do is run TWO laptops. It will for a while but eventually goes into an overload alarm. In theory my 150-watt inverter should handle both my MBP13's 60-watt draw and my wife's MBP15's 85-watt draw. It might if I run larger wires from a new lighter receptacle direct to the battery.

Personally, I prefer fan-less ('convection-cooled') inverters after having less-than-stellar experiences with noisy fans in the confined space of my van and my pickup cab. I've not seen fan-less ones above 150-watts so that appears to be a limit for those.

My ten-year-old West Marine fan-less unit is no longer available so I recently bought a Tripp-Lite PV150 ultra-compact unit for backup. But I don't yet have enough experience with it to say whether it's a worthy successor. I considered the slightly-more-expensive PV375 for its two receptacles and higher capacity but as soon as I saw it has a fan and read several complaints about noise in the reviews, I decided against it.

 

[iowahiker]

Your laptop is most likely 20+/- DC volts and your cell phone 5 +/- DC volts. The large inefficiency is going from 12 v DC to 120 v AC to 20 or 5 v DC (DC to AC to DC). Going from 12 v DC to another DC voltage requires less wasted energy. Our 12 volt / 10 amp / 120 watt no fan inverter has lasted a long time and worked for many different devices which is the only advantage for an inverter.

 

[takesiteasy]

Our Tacoma has a built in inverter (100 watts while driving, 400 watts while parked). I installed an outlet in the cab to run the computer for GPS navigation. We also use it to charge the cell phones while we drive. We use outlet all the time. We have several 12 volt outlets in the camper for charging while we are camped. I also installed an outlet in the camper connected to the truck inverter but we seldom use it as it requires the ignition to be on- inconvenient and it drains the starting battery if the engine isn't running. But it is nice on occasion to run 120v devices like tools and the rare occasional hair curler use by the spousal unit.

 

[Casa Escarlata Robles Too]

the rare occasional hair curler use by the spousal unit.

You just gotta have the "hair curler"
Frank

 

[Old Crow]

I've been reading the User Guide for the Samlex 300 inverter mentioned in post 1 and see it recommends limiting use to no more than 150 watts if installed using the supplied cables ( http://pdf.donrowe.com/pst-300-12-24_owners_guide.pdf , page 32). To get the full capacity of 300 watts, it requires at least 8-gauge wire and mounted within a 3-foot round-trip wire run of the battery. The manual goes on to say:

"- 12V power outlet in a vehicle is normally fused at around 15A. This limits the power draw from this outlet to around 150W.
- When powering PST-300 (rated at 300W) from the 12V power outlet in a vehicle, please ensure the AC load is limited to < 150W. Power draw > 150W will blow the 15A fuse in the vehicle."

I imagine many buyers don't realize that at purchase time and would assume they get the device's capacity with the cables in the box or by using similar-size wires when wiring it in.

Also- That info led to me wondering about the inverter I mentioned in post 12, the Tripp-Lite PV375 I had considered. It doesn't have wiring terminals so the only choice is to plug it in using the cigarette-lighter-style plug. So how does the manual handle the fact that a 15-amp-fused circuit won't handle the inverter's stated capacity?

( the manual is at http://www.tripplite.com/shared/techdoc/Owners-Manual/932230.pdf )

The 'Operation' section says (1) Plug Inverter into vehicle, (2) Turn on Inverter, and (3) Plug Equipment into the Inverter, then...

"Determine your equipment’s total wattage.* Do not connect more watts than your Inverter’s Output Power (Maximum Continuous Watts) rating..... See back page for typical equipment runtimes. Also see back page for important note concerning the limitations of vehicle electrical systems."

And on the back page, the important note says....

"NOTE: Due to the limitations of certain vehicles’ 12V DC lighter/accessory outlet electrical systems, you may not be able to continuously run a full load (375 watts) from PV375 models. If you regularly blow fuses, it may indicate your vehicle is not adequately wired to support a PV375 as it is designed. In this case, consult vehicle manufacturer recommendations for rewiring from the fuse block or battery with appropriate wiring (10 - 12 gauge) and fusing (at least 40 amp). All standard vehicle accessory outlet electrical systems can support full loads for PV150 models without any modifications."

-OC

PS- I really like the Samlex's detailed manual. Recommended reading. It has everything from C-rates and Peukert Effect to how the GFCI receptacles work to what the thread-pitch is on the set-screws of the DC terminals. Nice!

 

[Stalking Light]

I have a 17" MBP laptop and use an external firewire drive for photos and it sucks up a lot of power. I had a small inverter that I used in my Chaser but if would complain when I opened the photo editing software I use (Lightroom) so it wasn't an ideal solution. I have since found a 3rd party DC adapter for the Macbook Pro, but it also draws a lot of power and gets pretty warm during use.

When I bought my Eagle I decided to 'go big or go home' on power and had a GoPower 1500w inverter installed. So far I haven't wanted to run anything that requires near this big an inverter, but who knows. I recently installed a Dimetric and a test I need to do is see how much power the 3rd party 12v adapter draws vs the MacSafe adapter on the inverter.

I do like the occasional toasted bagel or Eggo waffle in the morning, though, so I do carry a toaster. (And yes, I have used the stovetop versions of camping toasters for years but far prefer an AC version). I also use power for charging my D4s camera batteries and I haven't found a DC charger for them yet.

 

[Old Crow]

Anybody want to add to this list of items that may need charging via DC chargers or an inverter (and the device's AC charger) while wandering the West? Perhaps the list will help us think through whether we have the bases covered in our trip planning.

- cell phone(s)--- (the 's' means don't forget to plan for the phones of everyone traveling with us!)
- iPads/tablets
- iPods/MP3 players
- phone and tablet add-on battery packs (for extended use)
- camera batteries
- satellite messengers (Inreach, Spot w/Nimh batteries, etc)
- CPAP batteries
- portable radio batteries (I'm thinking FRS, marine VHF, and portable Ham and scanner radios powered by rechargeable batteries)
- tool batteries
- rechargeable AA, AAA, etc battery charger
- kids electronics
- rechargeable 'tactical' flashlights, spotlights, and other lights (Streamlight, Fenix, etc)
- micro jump starters (AntiGravity, JumpNGo, etc)

Others?

(edited 11/9 to add mp3 players)

 

[craig333]

Keep in mind that some chargers won't be happy with the output of some inverters. So they say, I haven't had an issue yet. Camera battery and laptop are the only things I've found so far that I need to use the inverter for. Majority of stuff is 5v or 12v. I'd make sure I had a usb outlet first.

 

[ntsqd]

The cheep Cobra 150W inverter that we picked up at a truck-stop in Barstool on our way to our first Utah trip is what we use to charge camera batteries in the camper. When on the road the hard-wired 150W inverter keeping the 19VDC nav netbook running has enough extra juice to charge them too.

I've installed USB charging ports in both the truck and the camper. My current phone lasts significantly longer (3X-5X) on a charge from them than it does from a charge from the wall-wart charger.

Like a lot of things, I think moderate overkill in an inverter purchase is reasonable while massive overkill is just a waste of money. I've yet to run into anything that needed a pure sine wave inverter.