Running Fridge/Lights from LEAF

[travelover]

...........According to Consumer Reports, yes, some of them are just as good, although the warranty does not last as long.
...........

I was amazed to see that. I really wonder about the long term durability of the electronics in the Harbor Freight generator though.

 

[NW-Bound]

What is even more amazing to me is the following 1000W inverter generator under the brand Sportsman that you can get for $149.


For that price you not only get inverter technology, but also a 4-cycle engine, not a 2-cycle. How the heck can anyone build and sell one for such a low retail price? And it weighs 20 lbs, a lot less than the common 2-cycle generator that sells for $99.

And the thing is CARB-approved!

Most buyers are happy with it. I am so intrigued, I looked a bit more, and found a Youtube review that shows how it's built.

 

[Maenad]

I did not know the LEAF has a DC/DC converter that can recharge the 12V battery from the propulsion battery

It sure does. And if it goes bad, your Leaf turns into a brick in the parking lot. Ask me how I know!

The warning lights and codes on a Leaf are truly amazing and intimidating.

 

[NW-Bound]

Obviously, I had not thought much about this. How else would an EV get its 12V juice? And the 12V is needed for all lighting, electronics, etc... There's no alternator. Duh!

Even in a hybrid car, a DC-DC converter would allow deleting the 12V alternator, and that's a good trade. I was not thinking again.

 

[travelover]

.......Even in a hybrid car, a DC-DC converter would allow deleting the 12V alternator, and that's a good trade. I was not thinking again.

In my Escape hybrid the DC-DC converter was water cooled and rated at 120 amps.

 

[samclem]

What is even more amazing to me is the following 1000W inverter generator under the brand Sportsman that you can get for $149.

For that price you not only get inverter technology, but also a 4-cycle engine, not a 2-cycle. How the heck can anyone build and sell one for such a low retail price? And it weighs 20 lbs, a lot less than the common 2-cycle generator that sells for $99.

And the thing is CARB-approved!
....
Most buyers are happy with it. I am so intrigued, I looked a bit more, and found a Youtube review that shows how it's built.

That's an interesting little unit, and the price is right. 800W continuous would power my furnace blower (I'm not sure if it would start it--it's an electronically controlled unit, so maybe), or freezer+lights+room fan. Not bad at all, and pretty handy. Here's a video Here's a video of a guy using this little generator to run a small AC unit and to use extra capacity from the unit to provide 4 amps at 12VDC to charge a battery.

The claimed continuous HP (1.3 HP) is believable (based on 4-stroke aluminum air-cooled engines: Lycoming to VW to Honda to Briggs&Stratton, they all require 31-36 ccs per continuous HP due to engine head heat limits. This engine is 31cc/HP).

1.3HP = 969 watts (at 100% conversion efficiency), so the claimed 1000 peak watt output could only come by trading some engine kinetic energy for short-term output (that is, getting more output through a short-term drop in RPM).

The claimed fuel efficiency of the unit is terrible compared to larger air-cooled engines. The mfgr claims the .55 gal tank lasts 6.3 hours at 50% output. If we assume this equates to an engine output of 0.65 HP, that gives a BSFC of 0.8 lbs/hr/HP. In larger air-cooled 4-strokes, we typically see about .45 lbs/hr/HP.
BUT--high specific fuel consumption is unavoidable with tiny engines. It's still a lot better than the 700/900 watt Harbor Freight 2-stroke which, at 50% power, burns about 5 times as much fuel (2.5 lbs/hr/HP).

I wonder how efficient it is to run my 6cyl car engine to get 8 amps from the alternator? Despite all the sophisticated FI and the tight tolerances that water cooling allows in the car engine, I'd bet the little cheapy 800/1000w 4-stroke genset makes power more efficiently due to less internal friction compared to the much bigger car engine.

Good find, thanks!

 

[NW-Bound]

I am so tempted to buy this little guy at $149 from Walmart to play with, although I have no immediate use for it.

I have not looked at fuel efficiency, but suspect that a larger 2kW generator would be better in this aspect. If you have an inverter/battery setup like I suggested, then you want a unit that can provide more than your consumption, so that the genset can charge the battery while it also runs the load. Then, you can shut down the genset to cruise on the battery overnight.

This little guy will make a cheap and handy backup genset to the larger 2 or 3-kW unit.

 

[Walt34]

I am so tempted to buy this little guy at $149 from Walmart to play with, although I have no immediate use for it.

I know exactly what you mean. It is so tempting to buy it just because it's so cool, and cheap at that price, but I have no idea what I'd actually do with it once the novelty wore off.

 

[samclem]

I have not looked at fuel efficiency, but suspect that a larger 2kW generator would be better in this aspect.

Surprisingly, the Harbor Freight 2000W inverter generator has about the same fuel burn. Its 1 gal tank lasts 12.5 hours, but that is at 25% output. The Sportsman 1000W unit at 50% power, .55 gal tank, lasts 6.3 hours. So, about the same. The Honda 2000i model with a .95 gal tank at 25% power was supposed to be good for 8.1 hours, so it was thirstier yet. I'd take all these claims with a grain of salt.

If you have an inverter/battery setup like I suggested, then you want a unit that can provide more than your consumption, so that the genset can charge the battery while it also runs the load. Then, you can shut down the genset to cruise on the battery overnight.

This little guy will make a cheap and handy backup genset to the larger 2 or 3-kW unit.

There are some good options out there, I need to think about the smartest way to do things.

 

[samclem]

I know exactly what you mean. It is so tempting to buy it just because it's so cool, and cheap at that price, but I have no idea what I'd actually do with it once the novelty wore off.

Buy 10. Also buy 10 small room air conditioners that they can run, this will be about $3k total. Pre-position them in Tampa. When the next big hurricane hits FL and power is out for a week and it is 95 deg F day and night, move all to the affected location and start the bidding.

Maybe bring some "muscle," too. Folks get a little grumpy under these circumstances.

 

[njhowie]

That Sportsman generator is really nice for what it is and the price.

However, when we lose electricity, I don't want to fuss, I don't want to run extension cords. I certainly don't want to rig up a $30k+ hybrid/EV...that's one expensive battery for an inappropriate use that the auto manufacturer will certainly not honor warranty for should anything go wrong.

We live on the outskirts of the residential area, last to be plowed, last to get electricity turned back on, etc. I knew this when we bought our home 18 years ago, and one of the first things I did was to buy a great Cummins Onan 8kw industrial generator and had an electrician install a transfer switch. Wife thought I was crazy and it was a waste of money, joked about it with township inspector once the job was done. After the first couple times the electricity went out, wife wasn't joking about it any longer. We'd use it about twice a year on average. Then when Sandy came and the generator ran for 7 straight days without a hiccup while our entire area was without power, I was the one joking about it. During Sandy, the thing not only powered our home, but I ran about 300 feet of extension cords to our closest neighbor to give them enough power for their fridge, some lights, and small appliances.

Anyhow, short of getting a real generator and transfer switch setup, I'd highly recommend that Sportsman generator before messing with the LEAF.

 

[NW-Bound]

For emergency, one does not need a generator that large.

Home Depot sells a 7.5kW Generac generator for $1,999 and it even comes with an 8-circuit automatic transfer switch.

That amount is a fraction of the cost of the solar/battery storage that I am building (for fun).

The problem with any genset is the fuel supply for it. I don't know how reliable the natural gas line is during a disaster. I would install my own ground-mounted propane tank to be safe.

 

[NW-Bound]

Come to think of it, why is that residential 7.5kW generator so inexpensive compared to RV generators?

Out of curiosity, I look up the price of the 4kW Onan genset I have in my class C motorhome. It's $3000.

PS. The motorhome genset would be my emergency power supply if I ever need one. I would need to fill up the 55-gal tank of the motorhome though.

 

[Walt34]

Come to think of it, why is that residential 7.5kW generator so inexpensive compared to RV generators?

Out of curiosity, I look up the price of the 4kW Onan genset I have in my class C motorhome. It's $3000.

Is your RV generator powered by a diesel engine? That could account for much of the difference. If the RV set uses an inverter for a true sine wave that also adds to the cost. And I'd wager the Onan is designed to last a lot longer than the Generac set, so that comes at a price too.

 

[NW-Bound]

No, the motorhome engine runs on gasoline, and so does the genset. It's also the old type that runs at a constant speed of 3,600 rpm, and is not the inverter type.

 

[NW-Bound]

When traveling, I never run that RV genset for long to care about its fuel consumption. For home emergency use, one would need to know how much fuel to keep on hand. So, here are the numbers.

Full load @ 4 kW -> 0.7 gal/hr

Half load @ 2kW -> 0.5 gal/hr

The engine is 304cc, rated at 9.5HP.


PS. A gallon of gasoline has the energy of 33.7 kWh. At full rated output, the Onan RV generator has an efficiency of 17%, dropping to 12% at 2kW output.

For comparison, Toyota claims to have an automobile engine with an efficiency of 38%, using the Atkinson cycle.

 

[NW-Bound]

Surprisingly, the Harbor Freight 2000W inverter generator has about the same fuel burn. Its 1 gal tank lasts 12.5 hours, but that is at 25% output. The Sportsman 1000W unit at 50% power, .55 gal tank, lasts 6.3 hours. So, about the same. The Honda 2000i model with a .95 gal tank at 25% power was supposed to be good for 8.1 hours, so it was thirstier yet. I'd take all these claims with a grain of salt...

For comparison with the Onan 4kW RV genset:

HarborFreight 2kW inverter at 500W output -> Efficiency = 18.5%

Sportsman 1kW at 500W output -> Efficiency = 17%

Honda 2000i at 500W output -> Efficiency = 12.7%

HarborFreight 2-cycle at 50% (350W) -> Efficiency = 5% *

* Using specifications of 1.1 gal tank, 5 hrs of run time at 1/2 load.

 

[samclem]

When traveling, I never run that RV genset for long to care about its fuel consumption. For home emergency use, one would need to know how much fuel to keep on hand. So, here are the numbers.

Full load @ 4 kW -> 0.7 gal/hr

Half load @ 2kW -> 0.5 gal/hr

The engine is 304cc, rated at 9.5HP.

PS. A gallon of gasoline has the energy of 33.7 kWh. At full rated output, the Onan RV generator has an efficiency of 17%, dropping to 12% at 2kW output.

One HP = 746 watts, so a 9.5 HP engine has an output of 7100 watts. If this genset only puts out 4kw, and if the engine makes 9.5hp, then the mechanical-to-electric conversion has very low efficiency. 4000w /(9.5hp x 746) = 56%

The little Sportsman 1000/800w has a 40cc engine that puts out 1.3 HP.
800w/(1.3hp x 746) = 82%.



The Onan's 304 cc has approx the same cc/HP (about 31, like the Sportsman). If it had the same conversion efficiency, it would be making 5.8kw.

Or, it seems equally likely that the Onan isn't actually making 9.5 HP. Perhaps it has been de-rated (governed to an RPM lower than peak HP, or with a lower compression ratio, etc) just to make it last longer. It's a pricey unit and folks expect them to last for many many hundreds of hours. Keeping the head temps and bearing stresses reasonable is the best way to do that.

 

[NW-Bound]

Even in the winter, if the sky is clear, my 5.5kW solar array produces about 18 kWh/day.

Using a genset efficiency of 17%, that's equivalent to 3 gallons of gasoline.

 

[NW-Bound]

... Or, it seems equally likely that the Onan isn't actually making 9.5 HP. Perhaps it has been de-rated (governed to an RPM lower than peak HP, or with a lower compression ratio, etc) just to make it last longer...

I suspect the above. It's not running max out when producing 4kW.

 

[ERD50]

...


PS. A gallon of gasoline has the energy of 33.7 kWh. At full rated output, the Onan RV generator has an efficiency of 17%, dropping to 12% at 2kW output.

For comparison, Toyota claims to have an automobile engine with an efficiency of 38%, using the Atkinson cycle.

I've thought about this. An auto engine needs to run under all sorts of conditions, from idle to full acceleration, to cruising, and I assume lower emissions than a generator. A generator runs constant speed and limited power range. It seems the generator should be able to be more efficient than an auto engine, even w/o all the fancy variable cam timing, lift, etc.

My guess is that it just doesn't make economic sense. A generator runs a few hours at a time, sometimes months between runs. Just build 'em cheap and let 'em suck up the fuel.

-ERD50

 

[samclem]

It seems the generator should be able to be more efficient than an auto engine, even w/o all the fancy variable cam timing, lift, etc. . . .

My guess is that it just doesn't make economic sense. A generator runs a few hours at a time, sometimes months between runs. Just build 'em cheap and let 'em suck up the fuel.

I think that's a big part of it. Plus, an air-cooled engine is going to have lower efficiency than one that is water cooled. The much higher/less uniform temps of an air-cooled engine preclude the tight tolerances found in a modern water-cooled car engine. There's much more blow-by (past the rings) in an air-cooled engine.

 

[NW-Bound]

... My guess is that it just doesn't make economic sense. A generator runs a few hours at a time, sometimes months between runs. Just build 'em cheap and let 'em suck up the fuel.

-ERD50

This.

I think large industrial diesel generators would be better, as they are often used to run 24/7 in remote areas. One of us needs to look up some numbers.

A similar thing happens with RV air conditioners. They are just awful compared to residential units. A big part of the inefficiency is caused by the size constraint on the condenser and evaporator coils (it needs a low profile above the roof as well as inside), but I think it also does not make sense to put a lot of money on something that does not get used all that often, then gets junked along with the vehicle.

 

[ERD50]

Come to think of it, why is that residential 7.5kW generator so inexpensive compared to RV generators? ...

An acquaintance of mine had a propane generator installed at his business, which is out in the sticks a bit, and would have outages from time to time. They needed power to keep their business running.

I forget the numbers, but an "industrial" genset was maybe $12,000, while the residential Generac was < $2,000?

He had some odd problems when they had an outage, and I worked through it with him, and learned a lot in the process. The problem was, their office computers were on their own UPS, yet, if power was out overnight, and the genset kicked in, all the computers were dead with dead UPS batteries. Hmmm - why was this, if the generator was running?

One clue was - the computer UPS all ran fine when the well pump kicked in. Then started beeping warnings when the pump turned off. Curious.

Well, you get what you pay for. The Generac pulled some clever engineering 'tricks' to get burst power and as long a life as they could out of a relatively small/cheap engine. They would run the engine at slower RPM on a light load, and at a higher RPM as the load increased. So they saved engine life on light loads, but could get extra power with higher RPM into the generator when needed. But this meant the 60Hz varied quite a bit. Not a problem for most things, but the computer UPS decided that was not "good" AC, and switched to their UPS battery, and ran it down after an hour or so. The well pump running loaded it to the point that the speed was close enough to 60 Hz for the UPS to be happy.

Not a knock against Generac, they are giving the customer back up power at a fraction of the cost of an industrial unit. But there are compromises. Some forums had some ideas for modifying the controller board to keep the RPM more constant, but we didn't mess with that. Not sure what the solution was, I think he got UPSs that were not so picky about the incoming frequency.

-ERD50

 

[samclem]

Well, you get what you pay for. The Generac pulled some clever engineering 'tricks' to get burst power and as long a life as they could out of a relatively small/cheap engine. They would run the engine at slower RPM on a light load, and at a higher RPM as the load increased.

Interesting.
I saw some owner YouTube videos of the little 1000w Sportsman unit that NW-Bound found, and their meters showed 'em staying dead-on at 60Hz despite the obviously changing engine RPMas they varied the load. The newer "true sine wave" inverter circuits must be darned accurate compared to counting on a constant engine RPM and a fixed ratio to get 60Hz.