Power inverter

[thataway]

O'scopes for you:

Thanks, I had seen that first one, its a "kit"--certainly cheap enough.

The second is not a complex circuit, but mostly intended for audio:

" 150 Hz to 15kHz. Beyond this bandwidth, the displayed signals have a lower quality. Signals up to ±50V up can be injected on the input of the circuit."

Long time since I designed (tube type) circuits, but one could put small transformer and current limiter in and probably deal with 110V AC (60 Hz) with out damage to $700 smart phone. Not sure I want to take chances with that...(easy to test the voltage and current. Probably easy to bring the frequency response down to 60 hz and still see a decent curve). Some of the cheap ones don't have enough resolution to see a multi stepped wave vs a pure sine wave. But it looks as if this one (assembled) and has been used on 120 V AC without issues, for $80 is not a bad "buy".. I probably would put a resister or two in between the lead even using the 10X setting before 110 V attaching to leads.

 

[ssobol]

There are modules that connect to a smartphone that make it an O-scope. Not as inexpensive as the examples I posted earlier though.

 

[TyBoo]

We are cooking with induction!

The latest inverter works great. It is sitting on the waste basket in the pic but I have it secured semi-permanently and the wiring cleaned up now.



The cooktop runs on the highest power level while keeping the voltage drop less than the limit.



And I really think the coffee maker is a little faster brewing than it was with the previous inverter.



More later and maybe a question or two if I don't find the answers in the book.

 

[TyBoo]

What exactly do I connect the small grounding lug on the inverter case to? The only mention of it in the book states:

Operation of the inverter without a proper ground connection may result in an electrical safety hazard.
Chassis Ground (Grounding): Ground to vehicle chassis using #8 AWG wire.

On the previous inverter I had an 8AWG wire from the small lug back to the battery negative via a separate path than the inverter DC negative supply. Is that an adequate safeguard given that there is no true chassis to ground the inverter case to?

The inverter will power three appliances, one at a time - the microwave and the coffee maker which both have 3-prong plugs and the new induction stove that has a 2-prong plug.

 

[thataway]

The inverters have a floating ground, like the Honda Generators. Thus there is no true "ground" or "earth" was we have on the mains power.

But of course then your car or truck, is not really grounded either. There usually the ground is the same potential as battery negative. However there were some cars which had a positive ground. (Packard, Nash, Hudson, Pierce, and Studebaker)...plus most British cars up until the 70.s (not all--my Sunbeam. Alpine was negative ground)....

You will be OK either leaving the ground floating or tied into the negative. But I would take a volt meter on both AC and DC and double check to be sure that there is no potential from battery negative to "chassis ground" on the inverter.

Great to hear that it works.

 

[srbaum]

TyBoo,
I'm fixing to purchase an inverter, for the exact same uses that you are using yours for. Which inverter did you finally choose?

 

[TyBoo]

The one that works for me is this guy on Amazon.

It is long and heavy, but the shorter, lighter, cheaper ones didn't work with the cooktop.

 

[ssobol]

Wish they made small inverters with lugs for the output not sockets. I'd like to be able to wire to outlets in the boat. Yes, there are ways around this, but lugs on the inverter would be better.

I've only seen lugs on inverters that are way too large for a C-Dory.

 

[smckean (Tosca)]

I've been wondering why the induction plate is so picky in terms of the quality of its power source.

This is merely a guess on my part, but I'm thinking that since induction heating works by producing a magnetic field in the unit, which in turn induces electrical currents in the pan, the manufacturers design the induction plate to be picky in order to ensure that the magnetic field is just so, and to ensure they have good control over the magnetic field's parameters. Inconsistent input voltage (such as an irregular sine wave) could mess with their designed expected performance, so they don't allow anything but "clean" (expected) power input.

As I think about it, a traditional electric hot plate simply "smashes" electric current through a resistive material (burner coils) creating heat. That's a crude process that could care less about the "shape" of the input current. But an induction hot plate is actually doing some sophisticated electrical engineering processes to produce the magnetic field in the unit. The "big dumb" resistive heating process takes place in the pan, not in the unit.

 

[ssobol]

I've been wondering why the induction plate is so picky in terms of the quality of its power source. ...

Probably because it has some sort of microprocessor controller. Sags or insufficient voltage could keep it from working correctly.

 

[thataway]

Also the two induction burners I have, will not work if there is a non ferrous material on the plate. Sometimes even a test with a magnet is not enough. It appears that there needs to be a critical mass of iron to heat properly. I have one pot which is labeled with the induction symbol. It works on the New Wave burner, but not on the Duxtop, similar to what TyBoo owns.

Wish they made small inverters with lugs for the output not sockets

The Magnum I had used for many years in the RV had lugs, and the Victron I am currently use has lugs for the 110 V AC. I agree that they are large units, but also have large battery chargers but in--(110 and 80 amps respectively). Tight fit on the 25, but workable, with extra fans. Also the higher end inverters all have temperature sensors on the battery. This is an extra safety precaution.


Since the boat 110V wiring should be stranded wire, it is fairly easy to hook up the #12 wiring to a heavy duty 20 amp 110 V plug. Plug in those several plugs which you need. On my boat, the microwave and induction burners are on the inverter circuit. (The inverter has a built in transfer switch--it also adds power if the power from the dock is restricted and there is a voltage drop).

The water heater, battery charger and air conditioning circuits are not on the inverter circuit.

 

[TyBoo]

The inverter resides at the bottom of what was once a hanging closet. I added compartments and shelves to it over the years until it was almost useless as a closet, so the jumbo inverter dealt it the final blow. I will put a shelf above the inverter to protect it and another shelf above that and just wad the spare clothes up and stuff 'em somewhere.

 

[thataway]

Good looking--and a great use for the "closet"!

 

[colbysmith]

Resurrecting this thread, as I'm now thinking of adding an inverter to C-Traveler. I still have my generator, even with my solar panels. But would be nice to run the small microwave once in a while without firing up the generator. Also, while I'm not a coffee drinker, Rosanne is, and I might get her a little 5 cup Mr. Coffee Maker, that I see uses 650 watts. I think my microwave might be 1000 watts, if that much. Actually, may be 900 watts. Guess I should look and see. Anyway, I'm not sure I see the need for 2000 watts, and believe I can get by with 1000-1500 watts. I don't plan to change my two group 29 house batteries, and not sure if I'll mount the inverter back over the batteries and run 12 or 14 gauge wire for the 110 vt output to the cabin, or run the appropriate size wire from the batteries to the cabin and then mount the inverter inside. Seems it'd be better to mount it inside the cabin to protect it from moisture and I'd also like to put a switch in the 12 vt wiring from the batteries to the inverter, to completely shut it off when not needed. Either case, I would add separate 110 vt outlets from those already installed with shore power. I'm kind of looking at the Ampeak 1200W Pure Sine Wave Inverter on Amazon for $153. Just wondering if anyone else is using this one, or has any advice for me? Thanks. Colby

 

[thataway]

My findings are that the cheap inverters are "difficult" for the microwave. The run time is longer and there often a "buzz" from the microwave. Generally microwave outputs are less than the amount of current needed. We have also switched to induction stoves in both the Boat and RV--cooler in Fl heat, plus uses less fuel for the stove.

On my boats I put extra batteries (in today's world that means 100 amp hour LiFePO4 one of which equals the output of 2 group 31 AGM batteries. I mount both the extra battery and the inverter in the cabin, which allows for short cable runs.

My last boat I went with a 2000 watt inverter/charger from Victron, It also had an 80 amp charger, a boost function of 50 amps (If the end of the line voltage from a dock has dropped to 90 volts, and consequently electrical appliances do not run well, that the inverter boost the voltage back to 120. Finally the inverter can be wired thru its own transfer switch, so you can energize the outlets. Mounting in the cabin also allows for short cables of a smaller size such as OO instead of 000 3/0 or 0000. 4/0

 

[Robert H. Wilkinson]

Colby, I agree with Thataway - quality is best. You don't need another anchor - guys have said that here re. cheap generators which is why you see most using the honda exclusively. His setup using an invertor/charger is ideal if starting from scratch but I imagine you already have a charger setup.

Get a true sign wave - many electronics do not work well or at all with the cheap square wave units. They can also damage expensive electronics.

Install a class T fast blow fuse in line close to the battery. Carry a spare and beware they are not cheap.

Regards.

Rob

 

[colbysmith]

I do appreciate your advice Bob and Rob, but... let me restate what I'm looking for. A VW Bug rather than a Camaro or Cadillac. Again, I'm just looking to power up a small microwave for a few minutes, or a small coffee maker for however long it takes to make coffee, (one at a time), without the need to fire up my generator. I believe a 1200 watt pure sine wave inverter should be able to handle those power needs. And it looks like this one is decent: https://www.amazon.com/Ampeak-Pure-Sine ... deae8f9840 Tell me if I'm wrong about the amount of wattage or the specific inverter.
Then, is it too wet/humid to mount an inverter next to the batteries in the aft cockpit compartment? IF mounted in the cabin, requiring a 12-15' run of battery cable, what size cable are folks using? The only inverters I have experience with are 100-200 watt ones that I have plugged into an accessory outlet, and then charged up my laptop or electric shaver, or my cpap, before getting a 12vt adaptive power cord for it. Colby

 

[thataway]

If you want to stay with the cheap "pure sine wave" inverters (which are not really pure sine wave, they just have more steps than the "Modified Sine wave". Go for the 2000 watt version instead of the marginal (for microwave) one of 1200 watts. The 2000 watt is only $20 more.

 

[colbysmith]

If you want to stay with the cheap "pure sine wave" inverters (which are not really pure sine wave, they just have more steps than the "Modified Sine wave". Go for the 2000 watt version instead of the marginal (for microwave) one of 1200 watts. The 2000 watt is only $20 more.

I don't understand "steps", but the brand I'm looking at, the 2000 watt would be $100 more than the 1200. Also, the specs show the 1200 prefers a 200ah battery, the 2000 a 300. I believe my current battery bank has a capacity of 200ah, so that alone rules out going with a bigger inverter with my current battery setup. I am also aware that the 2000 would need larger battery wiring than the 1200, which would add more expense for additional power I would not need. Before I buy any inverter for this possible project, I will use one of those watt meters with the microwave to see what it's really pulling. I have read where inverters run most efficiently close to their rated power.
If I find out the microwave pulls more than 1000 watts, then I'm done considering this project. Just not willing to spend a lot on this.
I'd rather spend only what I need to have an operable system to meet my needs, and use the saved finances to buy more gas for more traveling. :wink: I really do appreciate the comments above, as I learn more about inverters, just as I learned about solar panels with that install. I don't want to buy "junk", but at the same time I do believe technology is continuing to evolve, and looking more to see what issues others have run into. I've already learned I want pure sine wave as opposed to modified, and that induction will require more sophisticated inverters. Still wondering where folks mount their inverters, and what size battery wiring are they using for runs of 12' or more. Or are most installing additional batteries in the cabin, which is something I'm not willing to do right now. It probably matters too when the inverter would be in use. With the microwave, it would usually be around supper time for only a few minutes when the batteries have a full charge. A coffee maker would likely be in the morning, when the batteries are at 75-85%. And the coffee maker would likely need to run longer than the microwave. That may make a big difference rather it's even worth installing an inverter with my current battery set up. Colby

 

[ssobol]

.... A coffee maker would likely be in the morning, when the batteries are at 75-85%. And the coffee maker would likely need to run longer than the microwave. That may make a big difference rather it's even worth installing an inverter with my current battery set up. Colby

Might be more efficient to use the induction cooker to heat water in a kettle for coffee than use the resistance heater in the coffee maker.