School me on power inverters

[MushCreek]

I'm trying to figure out how useful a 12V/120V power inverter would be during a blackout. I know you couldn't run any large appliances, but there are a lot of things, such as TV's and LED lights that don't use much power at all. I know Ohm's Law, so I can figure out watts vs. amps and 12V vs. 120V. What I don't know is how much usable juice there is in a car battery. If I was drawing say 200W at 120V., what does that translate to in terms of battery life? Obviously, car batteries aren't intended to be deep cycled, so I need to know what the approximate limits would be, or invest in a deep cycle battery.

We seldom have blackouts, but it would be useful for camping, and I would still need to know what the limits are. Could I make a pot of coffee without running down the battery? Could we watch a couple hours of TV without killing the battery?

 

[JRC3]

Here's what I use, for about 10 years now.

I have one of these little guys. When the power goes in the house I run an extension cord from a vehicle to power a lamp, TV, and charge my phone or flashlights. I've used it quite a few times and even for several days at a time. The thing was a great use of 20 bucks. https://www.harborfreight.com/200-w...-modified-sine-wave-power-inverter-61478.html

Mine came with a cig cord, not sure if they still do or not.

I've used one of these little ones for years. Was nice last Memorial Day when the tornados blew through us and the power went out. I had a regular table lamp and a 24" tv going all along. I've used it many times before on regular one and two day type power outages, but this time it was about safety.

I'm real close to just buying a deep cycle at Sam's for $100 and keeping it in the crawl space with a backup sump. And run a 12v outlet upstairs for the invertor.

When I bought it it was like 20 bucks. https://www.harborfreight.com/200-watt-continuous-power-inverter-66967.html

Yeah it's small, but it's all you need for overnight and whatnot.

 

[Showkey]

Just remember some devices are NOT going to happy (****) (buzz) with poor quality power ( modified sine wave) from some inverters.

As for battery life reserve capacity is a good starting point then the math works:

Reserve minutes, also called reserve capacity, is the number of minutes a fully charged battery can sustain a designated constant load — usually 25 amps — before it is fully discharged. For a 12-volt battery, that means battery voltage will have fallen to 10.5 volts.

Making coffee or toast with a 1500-2000 watt inverter is going to draw 125 amps on the 12 volt side +/- efficiency rating etc. 5 minutes coffee pot cycle... That would take 25 minutes off your reserve capacity. Typical battery might have 100 minute reserve capacity rating. Some of the low cost inverters might have 5-30% efficiency loss. Efficiency many times flows with cost.

One trick is run the inverter off the car running to charge the battery. Maybe not fuel efficient but gets the job done at a initial low cost in temporary situation. ( vehicle has to be outside)

There have been several post on trucks that come with a huge inverter from the factory that members have used to power the home in power outages.

Boiling water or making ice with battery power is very challenging.

 

[JRC3]

The 24"TV I use is .52A...What is that, like 60 watts? And then 60 watt equivelant LED for another 10 watts. So 70 watts with an invertor drawing from a group 27 battery with 100 amp hours is about 7 hours of run time. When I use mine I just go out every couple hours and let the vehicle run for 20 minutes or so. Sure it's hard on the battery, but it's only done like once a year or two.


I pull the truck close to the house in the driveway and hook the inverter directly to the battery and lower the hood to keep out the elements. Then an extension cord through the closest window. Quick and easy to setup up and just as quick to take down.

 

[dogdog]

There are only two type you need to be aware of.

Modified sine wave

and

pure sine wave (SPWM)


Spend a little more on the pure sine wave inverters... if they don't mention pure sine wave in the specs it will automatically means it's the modified sine wave ones.

SPWM are better on electronics power supplies and certain AC induction motors.
Modified sine wave probably will heat it up and destroy them.

keep in mind if you are doing the math... it's probably not 1:1 efficiency especially with Modified sine wave stuff..

 

[gungatim]

good topic. I don't know much about them but picked up a $39 750 watt unit for the truck to run my laptop and LTE modem off of when away from home. it works great.

they can be handy, I had to use a Dremel on an inop vehicle to cut out the bumper to get access to the radiator fan relay (Jeep Grand Cherokee) and used it for that. the Dremel ran great for the 10 minutes or so it took to cut.

it does get warm and runs the fan so that uses power too...

 

[nadogail]

In a pinch an inverter is very handy, but be aware of the battery drain. My 300 watt inverter came with a recommendation for a 50 Amp Fuse.

 

[Bretny]

1.5kw should run everything you state and possibly even a furnace. The battery dosnt really matter if your start the vehicle and let it run.

I have a friend that lives in a 3,000sqft house who kept his whole family warm and entertained durring hurricane Sandy with an inverter ran off a toyota sedan. Just parked it outside, let it run all night and locked it. Said it burned less than 1/4 of fuel.

 

[theoldwizard1]

If I was drawing say 200W at 120V., what does that translate to in terms of battery life? Obviously, car batteries aren't intended to be deep cycled, so I need to know what the approximate limits would be, or invest in a deep cycle battery.

First, quick and dirty (but gets you in the right ball park). Multiply the AC current draw by 10 to get the (approximate) DC current draw. If you are drawing 1A @ 120VAC it will take (at least) 10A @ 12VDC.

Batteries are rated in "amp-hours" (Ah - number of amps time the number of hours it took to draw the battery down). The usual test is for 20 hours, BUT the cut off voltage is LOWER than the recommend minimum by all battery manufacturers. (I know. It does not make sense.)

The ONLY TRUE deep cycle batteries commonly available are 6V golf cart batteries. Those dual purpose marine/RV batteries are a scam.

Just a SWAG. If you are drawing 200W @ 120VAC, that would be about 20A @ 12VDC. A pair of golf cart batteries are rated at about 220Ah, but the inverter will shut down at about 80% of that. You should get 8+ hours.

 

[MushCreek]

My microwave oven died when we tried to use it on the generator. I don't know if it was coincidence, or if it didn't like the quality of the power from the generator. Voltage was good, so I know it wasn't that. I've heard that generators can produce 'dirty power'. Our cheap $39 microwave wasn't bothered at all.

 

[theoldwizard1]

Just remember some devices are NOT going to happy (****) (buzz) with poor quality power ( modified sine wave) from some inverters.

The price of pure sine wave inverters keeps coming down. Some of the Chinese "brands" actually make clean power, but it is common that they are over rated.

4000W Off-Grid PURE SINE WAVE Power Inverter? Let's Find Out!


This "brand" is better. Positive reviews on multiple YouTube channels.

Reliable Brand(WZRELB) 3000W/6000W Surge OFF-GRID Power Inverter Tests!

 

[TonyJ]

I have a 10k peak inverter behind the seat in my truck and I have it hard wired in. We use it for power outages and also for camping. My truck is a 2004 crew cab Silverado so I installed the second battery tray and put a battery disconnect on the second battery that way if the first one the main one runs down to far to start the truck then I can flip a switch and start it with the second battery. 496 8.1l doesn’t like a low battery lol

 

[Bretny]

I have a 10k peak inverter behind the seat in my truck and I have it hard wired in. We use it for power outages and also for camping. My truck is a 2004 crew cab Silverado so I installed the second battery tray and put a battery disconnect on the second battery that way if the first one the main one runs down to far to start the truck then I can flip a switch and start it with the second battery. 496 8.1l doesn’t like a low battery lol

Better be careful with a 10kw inverter. That's almost 800a at 12.7v. You need serious serious cables to support that and your alternator is prob 500a shy at full tilt of actualy running that at max capacity.

 

[Denwood]

I've been down the same road with respect to inverters and generators..just sold my geny in fact. I've got a 2000 watt inverter/generator now for emergency power that powers up our high efficiency furnace (with digital control) and all the house electronics, including UPS units that did not like the generator. A few gallons of stabilized gas, and the inverter/gen unit can power our essentials for about 30 hours.

 

[TonyJ]

Better be careful with a 10kw inverter. That's almost 800a at 12.7v. You need serious serious cables to support that and your alternator is prob 500a shy at full tilt of actualy running that at max capacity.

Right. I’ve not really had any serious loads on it as of yet. Fridge and a deep freezer and the coffee pot all at the same time is maybe the biggest load I’ve had on it. I’m running 0 ga mining cable as my wiring and I have a 150a breaker in the line at the battery. Way over kill for most uses but beings I only have about $50 in the whole setup I can’t complain

 

[Lassen Forge]

I wiped out a battery and alternator with a 5KW inverter on my truck... went down to a 2KW, and if I need more, I have a generator.

 

[TonyJ]

I wiped out a battery and alternator with a 5KW inverter on my truck... went down to a 2KW, and if I need more, I have a generator.

Mine is the 5k 10k peak

 

[Robby321]

My God I hear a lot of making coffee with electric. Damn, hot water off a camp stove or fire place and INSTANT coffee! Being rural PNW get lots power outs winter, and have a 12 volt portable TV run off 12 Volt Battery (garden tractor fine, last days) hot coffee. Genny to keep fridge cold but noisy. Inverter from HF too but its noisy.

 

[dogdog]

Mine is the 5k 10k peak

I doubt that number is correct, might be some marketing ****... 12V 400AMP ... that would mean an awful big battery , big cable, and 100% efficiency. Modified sine wave inverters are not efficient in running electronics. Electrical sure... don't get too hung up on those numbers on the box.

 

[Showkey]

One note don’t confuse battery inverter and inverter generator.

Many inverter generators are perfect for sensitive electronics and motors and advertised as such:
“inverter technology ensures its power is closer to "line power" more than any other generator design. Our inverter generators produce power that is as reliable as the power you get from your outlets at home.”

Not all inverter generators are “clean” power as well. Non inverter generators are very sensitive to rpm changes which varies the frequency. Often linked to dirty power especially old units. Clean power and initial cost can also be related.

Where battery inverters are just the opposite.........proceed with extreme caution before using a battery inverter on $1000 TV or $2000-$3000 laptop or the $3000 furnace. Even the $250 TV might make you sad if you let the smoke out. Also when thinking TV your might have to power the cable box or modem which might not like the battery inverter.

500 watt Battery inverters can often had for $20-60.......with ad copy perfect for your laptop or TV. RV a guys are frequently mentioning dirty power and electrical noise from inverters.

 

[theoldwizard1]

I've been down the same road with respect to inverters and generators..just sold my geny in fact. I've got a 2000 watt inverter/generator now for emergency power that powers up our high efficiency furnace (with digital control) and all the house electronics, including UPS units that did not like the generator. A few gallons of stabilized gas, and the inverter/gen unit can power our essentials for about 30 hours.

BEST SOULTION ! Careful management of loads is all it takes.

Plus those little portable 2000w inverter generators are great for camping, cook outs, parties, etc.

 

[theoldwizard1]

Where battery inverters are just the opposite.........proceed with extreme caution before using a battery inverter on $1000 TV or $2000-$3000 laptop or the $3000 furnace. Even the $250 TV might make you sad if you let the smoke out. Also when thinking TV your might have to power the cable box or modem which might not like the battery inverter.

For (battery) inverters, there is no reason to "save a buck" and buy a modifies sine wave model. PURE SINE WAVE is the only way to go !

The "brains" of a pure sine wave inverter have been on a single "chip" that only costs a few dollars for almost 10 years. Yes, a lot more parts are required and there are DIY kits available on eBay for very little money (NOT for rookie DIYers).


Like I said before, even the cheap ones make "clean power" (they all use the same chip). Cut the advertised power by 50% and you will be in the right neighborhood.

 

[Bigblockyeti]

I haven't put a scope on my genny yet but being an ancient, brushed alternator 4Kw Onan leads me to believe it's probably pretty nasty. My primary concern would be first the fridge and second, one or two furnaces if it was really cold.

 

[theoldwizard1]

I haven't put a scope on my genny yet but being an ancient, brushed alternator 4Kw Onan leads me to believe it's probably pretty nasty.

I can't say I have scoped a standard generator output, but from a electrical "noise" standpoint they should be "clean".

In an alternator (AC generator), the field spins and the stator stay stationary. The field is powered through slip rings. No commutator so there is no sparking.

The biggest problem with this simple style alternator is that the voltage and frequency varies with engine speed and electrical load. For "voltage regulation", the simple ones rely on inertia of the spinning mass of field.

 

[Bigblockyeti]

I can't say I have scoped a standard generator output, but from a electrical "noise" standpoint they should be "clean".

In an alternator (AC generator), the field spins and the stator stay stationary. The field is powered through slip rings. No commutator so there is no sparking.

The biggest problem with this simple style alternator is that the voltage and frequency varies with engine speed and electrical load. For "voltage regulation", the simple ones rely on inertia of the spinning mass of field.

It certainly has plenty of mass! I've adjusted the governor so its no load output is 121V. Plugging in a couple 1500W resistive heaters drops it to 113V and an inductive load added to bring the total to very close (if not over) 4Kw drops output to 109V. I need to get a scope on it to confirm I'm getting 60Hz. My non-contact tach isn't very fancy but it's showing me 1800rpm +/- 15rpm so I know I'm close.

 

[theoldwizard1]

It certainly has plenty of mass! I've adjusted the governor so its no load output is 121V. Plugging in a couple 1500W resistive heaters drops it to 113V and an inductive load added to bring the total to very close (if not over) 4Kw drops output to 109V. I need to get a scope on it to confirm I'm getting 60Hz. My non-contact tach isn't very fancy but it's showing me 1800rpm +/- 15rpm so I know I'm close.

If the voltage dropped, you are no longer getting 60 Hz !

Not only the mass of the field winding but also the mechanical governor of the motor control both voltage and frequency.

I would put your heater back on it and adjust the speed of the engine so that you are a bit closer to 120V. Don't worry about the no load voltage as long as it is below 134V (you want to be within +/- 20% of 120V)

 

[Denwood]

If the voltage dropped, you are no longer getting 60 Hz !

Not only the mass of the field winding but also the mechanical governor of the motor control both voltage and frequency.

I would put your heater back on it and adjust the speed of the engine so that you are a bit closer to 120V. Don't worry about the no load voltage as long as it is below 134V (you want to be within +/- 20% of 120V)

I went through both frequency and voltage tuning on my Champion generator (using a Fluke multimeter) with partial loads, and it still caused issues with UPS units (they cycled on and off until depleted) and our new (digital control) furnace. These are not issues at all with the new inverter generator though.

 

[Bretny]

A word on that HF inverter. If you put a load on it your output voltage will drop. They dont make 60hz and even with hardly any use mine didnt last long. About 2yrs.

I now have a Xantrex 1200w that I can run a 7A shop vac on and it still shows 119v. It also has a whole bunch of features I didnt know I really needed until I had them. Selectable low voltage cut off and power shut off after a set amount of time with no load.

 

[mobetta]

I do have a cheapo inverter or two, but I grabbed a ryobi 900w propane inverter genny when it was on sale for $300.

I havent even unboxed it yet but i always have some grill gas around and the carb should never gunk up from ethanol!!

I also have a honda iu2000 that ive used once or twice to keep the innnernets on during brief outages.
I just figured its easier to store LP long term.

 

[sberry]

If it was a serious truck would order the ambulance package,,, ha, alternator, switches, wire, all ready and strip it out. I was hoping to see more ready made inverters, it was on the way before the 2008 crash and seems to went by the way. The nature of the small inverter welder makes this possible. Some of the early proto was 14KW single phase, a guy could plasma from it, weld full blast also. Service trucks could get so much lighter today without the demand for heavy air can be done with battery tools now for sooooo much less cost.

 

[sberry]

I dont have a little one but they are neat. What would be cool is to have a battery, inverter, hooked to that thing by demand auto start. Hobart had a version of that in a battery powered wire welder. It was a good idea, personally think Miller should have brought it but was a little ahead of its time in some respect,,,, but they had a scheme would recognize the size of an inverter, it also would weld from batteries and battery assist which actually made it output more than a 140,,, could pull 20 from the wall and also from its batteries.

 

[sberry]

Hey Jack, I wondered how much window AC a 2000 watt gen will run?

 

[theoldwizard1]

Hey Jack, I wondered how much window AC a 2000 watt gen will run?

6,000 BTU. You do have to shop carefully, but there are more and more low power consumption window A/C units on the market.

Solar Shed: Running a Cheap Air Conditioner

The real issue is starting current. This has been discussed several time on GJ, but most compressors (A/C, refrigerator, etc.) have very high starting currents. Large start capacitors do NOT help inverters or generators, they actually hurt !

What is needed is a true "soft starter" like a Micro-Air EasyStart. This actually LIMITS the "in rush" current. You A/C might take a few extra seconds to start, but it won't hurt your inverter or generator.

 

[sberry]

I wondered if anyone ran AC on one?

 

[Showkey]

I wondered if anyone ran AC on one?

Yes......multiple RV guys have tried it.......is it possible YES......is it practical NO......is it sustainable NO

Here’s a YouTube with some numbers, comments and conclusions
:

There are dozens of other examples........

 

[sberry]

That was from inverter,,, I was wondering about the inverter generators. EU 2000 type.