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harbor freight power inverter, 2000 / 4000 watts ?


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5 replies to this topic

#1 johnceggleston

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Posted 16 June 2013 - 09:25 PM

this harbor freight power inverter is good for 2000 watts.

(discount coupon = 20% off.)

 

we lost power again this week., only one day this time.

 

since i don't know much about electricity,

what kind of alternator would i need to supply it with enough 12v amps? to actually get 2000 watts = 120v x 16amps ?

 

i am assuming that it is not a magic machine that can make power out of nothing.

 

 

http://www.harborfre...6Ijg5MzAifQ==

 

from reading the reviews, it seems needs to be connected to multiple batteries with #2awg cables.

then an alternator or generator, or solar panel would recharge the batteries.

i guess how long it last is dependent on how many, how big the batteries are.

 

thoughts?

 

thanks.


Edited by johnceggleston, 17 June 2013 - 08:50 AM.


#2 Tsuru

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Posted 17 June 2013 - 01:59 PM

Yes, Exactly.

A good bank of batteries (preferably deep cycle, like marine or golf cart batteries) is best, these can be charged through a bank charging system, connected to the mains, Or Solar panel, or wind turbine, or harvested from a stream or river using hydro turbines,  or a generator (redundant there, since you could just power from the generator directly)

Ideally you would also have a break-over switching panel that connects the inverter to your house circuits.

Such a panel would have to be wired in by someone who knows what they are doing. what it does is ISOLATE your house from the power companys lines into your home. and transfers to receiving power from your "In house" power supply.

 

That is if you wish to run a few selected outlets in your home from the in house bank.

Otherwise, just run (heavy duty) extension cords for essentials (big screen tv, xbox, margarita blender...)

 

Many use golf cart batteries in pairs, (they are six volts each)

that way if a cell fails in a battery they are not replacing a full six cell 12 volt battery, only a three cell six volt unit.

It can be quite a spendy thing, 

OR

it can be done on the cheap.

After hurricanes Ivan (and consequentially Katrina)

Damaged our home in Florida we all pooled our resources, food, gas grills, coleman lanterns, radio gear, chainsaws, etc.

a couple of folks had inverters that clipped onto the cars battery, we all learned that they can suck a cars battery flat in no time at all.

generators were shared, those inverters ran a small fan (so we could sleep at night) clipped to a battery set on the floor, then during the day, those of us lucky few with generators (and fuel to power them) used the 12 volt ports to charge neighbors batteries.

 

Back to topic...

 

You can just run car batteries and connect the inverter, but they use a lot of juice.

Also keep in mind that some electronics, (laptops, cellphone chargers, gaming systems) will run on such an inverter, but they will overheat, and in some cases fry your electronics.

the reason is that the 110 Volts being produced is a "clipped" or "square wave" 60hz as opposed to a "full wave" 60hz.

that that means to the electronics is that there is a brief interval (60 times a second) where the electrical power is not flowing smoothly (on an oscilloscope this can be seen as more of a square, sharp wave. electricity from your outlet is a true sine wave, undulating sensuously across the screen, full bodied and oh so curvy.

This soothes your electronics, keeping them happy (who wouldn't be?).

The square wave that is artificially generated actually induces heat into the electronics. 

The Harbor Fright unit reads as a "Modified Sine Wave" that might not be any easier on the electronics aspect of things. But please read the fine print on that and see if its really compatible with electronics.

If you are only going to run appliances that do not have electronics, refrigerators, manual control (not electronic keypad) air conditioners, household lighting, and the like you should be fine.

 

http://www.homestead...-inverters.html

 

http://www.survivali...ad.php?t=249054   

 

Hope this helps somewhat.



#3 nickb21

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Posted 18 June 2013 - 01:25 AM

What are you trying to run? 2kw is a good amount of juice to be sucking out of batteries, especially if it is a high duty cycle.

 

While there are inverters that put out 'pure' sine waves, they also cost a lot. Stepped or Modified sine wave power is common on most generators, inverters, etc. Depending on the inverter though, some will have more/smaller 'steps' and be closer to a pure wave, vs fewer/larger steps (more $ = better quality). Like Tsuru said, motor loads, heating elements, simple circuits could care less. It's the electronic loads that are more sensitive.

 

With that amount of capacity you'll need a pretty good power source for recharging, especially for extended outages- either generator or line power. And it should be smart enough to charge the batteries 'smartly'. I can't really speak to solar/wind/hydro, but I can imagine that at least for solar you'd need some serious panels setup (=$).

 

Personally, I have 1 or 2 small (less than 5A) loads that I'd like to ensure always have seamless power, even when I'm not around - so i've been looking into these: http://www.tripplite...SeriesID=818    They are really nice, but also pretty darn pricey. :(

 

What fuel storage/access do you have? Large propane tank, natural gas, fuel oil? Regular generators that size can be had cheap. And you can put tri-fuel carb kits on them to run gas/ng/propane. I've even seen fairly cheap 5kw diesel sets. Then of course there are the honda/yamaha inverter 'lunchbox' generators. They'll run ~7hrs at 1kw on a gallon or two of gas, but there is that price tag...

 

I guess the other question is to do some calculations and figure out how much battery capacity (amp-hours) you'll need. That could increase battery cost significantly.

 

Just some food for thought.


Edited by nickb21, 18 June 2013 - 01:28 AM.


#4 nickb21

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Posted 18 June 2013 - 01:46 AM

Re-read your post, not sure, but may have ignored your original question. Were you thinking of running an alternator to drive the inverter directly (or with a minimum of batteries inline)? It's kinda late, but the power/RPM/fuel/etc required for a 12V alternator to drive a 2kw load is gonna be a lot. Like.. 160A from the alternator a lot.

 

Your amperage draw on the DC side will be different from the AC side since you have to step up the voltage. You'll also lose, I dunno, 10%? converting from DC to AC...



#5 johnceggleston

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Posted 18 June 2013 - 07:12 AM

i have a much smaller inverter i keep in the car which fits in a cup holder.

it makes enough power to recharge a cell phone or ipod or the like.

i have only used it when the car is running and something else was plugged into the ''power outlet''.

i knew it used 12v, duh, but i always associated it with the alternator, not the battery.

 

so when i saw this , not TOO expensive, inverter i started wondering .....

 

we lose power fairly often. 2 - 3 times a year.

usually for only a day or two, but recently for a longer period every year.

on the up side, this forces us to clean out our freezer and refrigerator fairly often.

but the obvious down side, it is an expensive forced cleaning.

 

using the new ''twisty'' light bulbs dramatically reduces the need for electricity for lighting, so almost any inverter will light a room.

but being able to run the freezer for a couple, several,  hours a day would be great.

and then unplug that and plug in a coffee pot for 15 minutes.

but in my situation, i would be limited to the battery and alternator in my 97GT with the engine running as a 12v power supply.

and idling a car is not a very efficient way to generate electricity, but it does work.

 

any electronic use would have to be in the form of games, recordings, or other self contained stuff since we lose cable / internet / phone when we lose power. but given the risk involved using an inverter for this is a little scary.

 

so i don't really have a specific need, i was just exploring the possibility and wanted to learn something about inverters.

 

thanks for all the info and the links.

i have learned a lot.


Edited by johnceggleston, 18 June 2013 - 07:13 AM.


#6 nickb21

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Posted 18 June 2013 - 02:00 PM

Like you said, not efficient to run at idle, but it works. I wonder what the amp/rpm curve looks like for the alternator? I would wager a guess it only puts out 20A tops at idle. Which only give you 200-300watts AC. Certainly enough to charge stuff and run lighting small appliances. Maybe enough to run a fridge or freezer depending on running vs startup load.

 

You don't like the semi-yearly fridge/freezer clean out? Can't be all bad _having_ to eat all that ice cream. :)

 

I think we overstate the risk with regard to electronics. I've run laptops, TV's, etc, never had an issue. That's how most RV's operate when you think of it (on generator power). I would say an inverter is maybe a bit more reliable, since you don't have engine rpm regulation to deal with. (With that said I probably wouldn't fire up a $1000 LCD TV).

 

You might also consider an older APC or TrippLite UPS (one with bad batteries). Many (most?) of the higher enterprise/data center units put out very clean power. Find one with dead batteries and you could probably hack it apart and hook up your own battery storage.

 

Some off-the-cuff calulations:

 

Figure a fridge is 5A-AC running (600watts) - which might be a bit high; also 'listed' startup/surge current for fridges can be as high as 10-15A. Convert to DC-Amps 600/12 = 50A-DC. 10% DC-AC conversion loss, so let's say 55A-DC. How long does the fridge need to run? I'll admit I have no idea what the cycle is; maybe 4hrs a day total runtime? So 4hrs*55A-DC is 220Amp-Hours (needed).

 

Some quick googling says Walmart Marine batteries are rated for ~100A-hrs. Probably don't want to discharge these much below 50%, so they're good for 50A-hrs each. So you would need 5-100A-hr batteries to run the fridge for 4hrs/day.

 

I did some reasearch a while back, so I think these number are right. Maybe someone can check my math. :)

 

If you've got a clamp on multimeter you can figure out what the current draw of an appliance is, or grab one of those kill-a-watt devices and you can get a daily electricity usage.

 

Cheers!


Edited by nickb21, 18 June 2013 - 02:02 PM.





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