Running Fridge/Lights from LEAF

[ERD50]

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.

Absolutely. The inverter is no doubt controlled by a crystal oscillator, and even the cheapest crystals (IIRC) are good to ~ 200 ppM ( +/- 0.012 Hz out of 60 Hz). Consider a $5 clock movement, or digital LCD clock - only off by a minute or so a month, if even? Amazing accuracy at almost zero cost. I could look it up, but I even in modest quantities, those crystals are probably less than 10 cents.

Sine wave inverters are great in that regard.

-ERD50

 

[travelover]

Better generators (that don't use inverters) run at 1800 rpm and have double poles to get the 60 Hz output. Their advertised horsepower may be rated at 3600 rpm, even though they are actually governed at 1800 rpm. This might explain the discrepancy on the motor home generator.

 

[NW-Bound]

Constant-RPM gensets rely on a governor to increase the throttle opening when the electrical load increases. Mechanical things have some finite response time, and cannot be instantaneous. Hence the rpm and frequency momentarily drop when the load suddenly increases.

Inverter-type generators generate the 60-Hz output using electronics. Its frequency is therefore not load-dependent, as ERD50 describes.

However, the voltage of the AC output will sag, if the motor does not rev up fast enough to provide the juice for the electronics to convert to AC. And that's why inverter gensets have a switch to turn off the "economy mode", in order to keep the speed a bit higher to be ready to provide that surge in load demand.

 

[NW-Bound]

Better generators (that don't use inverters) run at 1800 rpm and have double poles to get the 60 Hz output. Their advertised horsepower may be rated at 3600 rpm, even though they are actually governed at 1800 rpm. This might explain the discrepancy on the motor home generator.

My 4kW RV Onan gennie runs at 3600 rpm. I remember seeing some larger RV Onan's running at 1800 rpm. These employ 2 cylinders of 600cc total to provide 5.5kW, while mine has only 1 cylinder of 300cc.

 

[NW-Bound]

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...

OK, it's a dirty job, but someone has to do it.

I found the specs on a large generator with a diesel engine by Mitsubishi, rated at 2900 HP using 16 cylinders of 65L total displacement.

It produces 2MW of power, while burning 159 gal/hr. There's 22 million BTU in that amount of diesel, which is equivalent to 6.5 MWh.

The efficiency is therefore 31%. That's almost 2x that of our little personal generators.

 

[NW-Bound]

At 159 gal/hr (2.7 gal/min), the above generator will burn through a tanker truck worth (9000 gal) in a bit more than 2 days.

Each of the 16 cylinders is 4 liters, larger displacement than the total in most V6 automobile engines.

 

[NW-Bound]

OK, so you think that the 2MW generator is a bit more than you need?

How 'bout this military surplus 15kW generator that you can tow behind your EV? That's less than 1% of the BIG megawatt generator.

Only $8K on eBay.

PS. Oops, forget about towing it with an EV. Dry weight is 2100 lbs, without the trailer.

 

[samclem]

OK, so you think that the 2MW generator is a bit more than you need?

How 'bout this military surplus 15kW generator that you can tow behind your EV? That's less than 1% of the BIG megawatt generator.

Only $8K on eBay.

PS. Oops, forget about towing it with an EV. Dry weight is 2100 lbs, without the trailer.

And bring some hearing protection. I'm still coughing up diesel soot charcoal briquettes from the big brother of one of those that was running outside my tent for months. It powered the air conditioners for several 20 person tents in 95 F weather for months, and it burned a LOT of fuel.

 

[NW-Bound]

And bring some hearing protection. I'm still coughing up diesel soot charcoal briquettes from the big brother of one of those that was running outside my tent for months. It powered the air conditioners for several 20 person tents in 95 F weather for months, and it burned a LOT of fuel.

I looked some more, and it appeared that above the 10kW level up to the 2MW level, diesel generators typically have about 30% efficiency in converting diesel fuel thermal energy to electricity.

I doubt that they can improve the diesel engine further, given that this is a mature technology. The only thing left for the military to do is some research on tents with better R-insulation values, if it wants to reduce fuel usage.

 

[Telly]

Constant-RPM gensets rely on a governor to increase the throttle opening when the electrical load increases. Mechanical things have some finite response time, and cannot be instantaneous. Hence the rpm and frequency momentarily drop when the load suddenly increases.

Inverter-type generators generate the 60-Hz output using electronics. Its frequency is therefore not load-dependent, as ERD50 describes.

However, the voltage of the AC output will sag, if the motor does not rev up fast enough to provide the juice for the electronics to convert to AC. And that's why inverter gensets have a switch to turn off the "economy mode", in order to keep the speed a bit higher to be ready to provide that surge in load demand.

Our little Honda e2000i 2kW will stumble but recover if I have it on Eco-throttle, and the refrigerator starts up. It doesn't take too much parallel load, maybe 100w, on Eco-throttle for it to be pretty smooth when the refrig starts. It's that sharp transition, from no-load at all, to refrig start load that makes it stumble an instant. Just need to get it up from idle speed.
We once talked here about how it would be a neat idea if you could parallel an external battery to help power the inverter portion to help start-up demands. Of course, that would be added cost and complexity, and the inverter portion would need to have an input voltage compatible with a convenient battery voltage. And it would need to work and be stable with/without the battery.

 

[travelover]

............
We once talked here about how it would be a neat idea if you could parallel an external battery to help power the inverter portion to help start-up demands. Of course, that would be added cost and complexity, and the inverter portion would need to have an input voltage compatible with a convenient battery voltage. And it would need to work and be stable with/without the battery.

Yamaha makes an inverter generator that uses its own starter battery to provide a temporary boost to handle surge loads. Victron and some other manufacturers make an inverter that passes through generator input and boosts as needed. These are used on boats and also allow a boat to run off a small extension cord while in dock.

 

[NW-Bound]

... We once talked here about how it would be a neat idea if you could parallel an external battery to help power the inverter portion to help start-up demands. Of course, that would be added cost and complexity, and the inverter portion would need to have an input voltage compatible with a convenient battery voltage. And it would need to work and be stable with/without the battery.

The DC voltage that an AC sinewave generator needs to generate the 115VAC is 115xsqrt(2) = 163V. For a 2kW inverter generator, you will need a DC-DC converter that converts 2kW worth of power from 12V up to that 163V. It can be done but adds to the cost.

Yamaha makes an inverter generator that uses its own starter battery to provide a temporary boost to handle surge loads. Victron and some other manufacturers make an inverter that passes through generator input and boosts as needed. These are used on boats and also allow a boat to run off a small extension cord while in dock.

Yes. Victron inverters are quite neat. If I had that, would be able to run my RV AC from a 2kW genset. The inverter will provide the boost needed when the AC compressor starts. The cost of a 3kW Victron inverter is $1500, which is not bad if I were an RV full-timer.

 

[NW-Bound]

Hmmm... Here's another project for me to do when I am done with my solar/storage system.

Hack the $149 Sportsman inverter generator to add the boost from an external 12V battery. It may not be that hard, as one can "borrow" the DC-DC converter circuit from a cheapo modified-sine-wave inverter.

PS. Victron inverters will add their own power to the external generator. This is similar to wiring in parallel two synchronized AC sources.

The simpler way I was thinking above is still going through the genset sinewave inverter, and the power output is still limited by the latter. It only provides the momentary power surge while waiting for the engine to rev up.

The external DC power source [-]may[/-] will interfere with the load sensing of the genset, so some experimentation is required.

 

[samclem]

Hmmm... Here's another project for me to do when I am done with my solar/storage system.

Hack the $149 Sportsman inverter generator to add the boost from an external 12V battery. . . .
The simpler way I was thinking above is still going through the genset sinewave inverter, and the power output is still limited by the latter. It only provides the momentary power surge while waiting for the engine to rev up.

Would it be possible to have the inverter handle loads without the engine, using just a 12v battery? That would provide some "quiet time" where small loads could be handled by the battery. On starting the engine, the 4A/12vdc output could be used to recharge the battery while bigger loads are being serviced with the main AC output. Run the freezer for a few hours, the furnace blower, etc, then go quiet and let the battery run lights and maybe a room fan. In addition to the quiet and convenience, fuel would go farther by letting the genset run at a higher, more fuel efficient, output.
It isn't a big deal (small inverts aren't expensive and would allow the same functionality), but this would involve less hassle and eliminate one component.

 

[NW-Bound]

There may be a market for such an integrated product, which has the same function as the large solar/storage/inverter that I am building, but sans the solar portion.

Such an inverter/generator will allow one to add more lead-acid batteries in parallel as one needs. And it will start itself up automatically to recharge the batteries when the latter are depleted.

Certainly doable for less than $1K, and does not require any earthshaking invention.

PS. A 12V marine battery will provide less than 500Wh, which is not that much. You will need several to power a fridge overnight without the generator running.

 

[ERD50]

There may be a market for such an integrated product, which has the same function as the large solar/storage/inverter that I am building, but sans the solar portion.

Such an inverter/generator will allow one to add more lead-acid batteries in parallel as one needs. And it will start itself up automatically to recharge the batteries when the latter are depleted.

Certainly doable for less than $1K, and does not require any earthshaking invention.

PS. A 12V marine battery will provide less than 500Wh, which is not that much. You will need several to power a fridge overnight without the generator running.

Now imagine if we standardized on some basic configurations of Lithium power packs, say 24V.

Since cordless tools and appliances are no longer 'toys', we have more and more of these around the house, yet most of them are used only occasionally. Make a standard module size that pops in/out easily, and you could slip those packs into your charger when needed for an emergency.

It really seems silly to me that I have a couple batteries for my cordless drill, our new cordless vacuums have built in batteries, and many people have other cordless tools like lawn mowers, trimmers, etc. Modules could just snap together to form higher capacities, and snapped apart to fit in small appliances.

Our power outages have been few and far between, I sort of hate to maintain a bunch of lead/acid batteries which will likely need to be replaced before I ever need to use them. I have one on an inverter on a sump pump, that's my limit for now.

-ERD50

 

[travelover]

If I had that, would be able to run my RV AC from a 2kW genset. The inverter will provide the boost needed when the AC compressor starts.

Actually for $200 you can buy a soft start kit for the AC and run it off a 2000 watt inverter generator easily.



https://www.microair.net/collections/easystart-soft-starters

 

[NW-Bound]

Now imagine if we standardized on some basic configurations of Lithium power packs, say 24V.

Since cordless tools and appliances are no longer 'toys', we have more and more of these around the house, yet most of them are used only occasionally. Make a standard module size that pops in/out easily, and you could slip those packs into your charger when needed for an emergency.

It really seems silly to me that I have a couple batteries for my cordless drill, our new cordless vacuums have built in batteries, and many people have other cordless tools like lawn mowers, trimmers, etc. Modules could just snap together to form higher capacities, and snapped apart to fit in small appliances.

Our power outages have been few and far between, I sort of hate to maintain a bunch of lead/acid batteries which will likely need to be replaced before I ever need to use them. I have one on an inverter on a sump pump, that's my limit for now.

-ERD50

Batteries for cordless tools, even lawn mowers, are too small to be backup power sources.

About standardization, there are several companies selling LiFePO4 (lithium iron phosphate) batteries that look like a 12V lead-acid battery, and have a compatible voltage too. LFP batteries have a cell voltage of 3.2V, and 4 of them in series give you 12.8V, which make them replaceable for lead-acid in most applications.

In contrast, lithium cells of other more common chemistries have a cell voltage of 3.7V, and you cannot come close to 12V either with 3 cells or 4 cells in series.

The problem is cost! A 12V 100Ah lithium battery costs around $1000, to provide 1kWh. One such battery is shown below.

 

[NW-Bound]

Now imagine if we standardized on some basic configurations of Lithium power packs, say 24V.

Since cordless tools and appliances are no longer 'toys', we have more and more of these around the house, yet most of them are used only occasionally. Make a standard module size that pops in/out easily, and you could slip those packs into your charger when needed for an emergency.

It really seems silly to me that I have a couple batteries for my cordless drill, our new cordless vacuums have built in batteries, and many people have other cordless tools like lawn mowers, trimmers, etc. Modules could just snap together to form higher capacities, and snapped apart to fit in small appliances.

Our power outages have been few and far between, I sort of hate to maintain a bunch of lead/acid batteries which will likely need to be replaced before I ever need to use them. I have one on an inverter on a sump pump, that's my limit for now.

-ERD50

Batteries for cordless tools, even lawn mowers, are too small to be backup power sources.

About standardization, there are several companies selling LiFePO4 (lithium iron phosphate) batteries that look like a 12V lead-acid battery, and have a compatible voltage too. LFP batteries have a cell voltage of 3.2V, and 4 of them in series give you 12.8V, which make them replaceable for lead-acid in most applications.

In contrast, lithium cells of other more common chemistries have a cell voltage of 3.7V, and you cannot come close to 12V either with 3 cells or 4 cells in series.

The problem is cost! A 12V 100Ah LFP lithium battery costs around $1000, to provide 1kWh. A few of these batteries are shown below.

 

[NW-Bound]

Actually for $200 you can buy a soft start kit for the AC and run it off a 2000 watt inverter generator easily.

https://www.microair.net/collections/easystart-soft-starters

This is something I would look into, if my Onan 4kW genset croaks and I have to replace it with a portable 2kW unit.

 

[ls99]

Presume these LiFePO4 batteries need specialized chargers.

 

[ERD50]

Batteries for cordless tools, even lawn mowers, are too small to be backup power sources. ...

Yes, after posting that I did a google search and a quick calc - those power tool batteries are pretty wimpy.

Would still like to see them standardized, to share across tools/appliances.

-ERD50

 

[NW-Bound]

Presume these LiFePO4 batteries need specialized chargers.

Yes. LFP cells cannot be taken to over 3.6V, or they are ruined (but will not burst into flames).

This means no more than 14.4V for 4 cells in series. Many lead-acid battery chargers do not have the output voltage controlled that precisely, if at all.

 

[ls99]

Yes. LFP cells cannot be taken to over 3.6V, or they are ruined (but will not burst into flames).

This means no more than 14.4V for 4 cells in series. Many lead-acid battery chargers do not have the output voltage controlled that precisely, if at all.

Then Even if willing to pay for one for a car, would get ruined. In my Caddy and Colorado the indicated battery charging voltage from the computer's monitor often shows 14.6 or even 15.2 volts.


And for solar install at my camp I then I'd need the custom charger. My Golf cart storage batteries are on their last legs. Still I'll consider it. No water level checks are a plus.

Looking at one spec., claims 5000 deep cycles, or around ten to twleve year life.

 

[NW-Bound]

The above LiFePO4 batteries are meant for use in RVs or boats, not in automobiles, at least not to be installed under the hood. Temperatures above 140F will shorten their life.

You also should not discharge them below 2.8V/cell.

I maintain mine within the operating voltage of 3V/cell min for discharge, and 3.45V/cell max on charging. They should last a lot longer.


PS. Cells in series also need balancing, so that not any single cell is operated outside the safe voltage range. Measuring the total pack voltage is not enough. The commercial packs of 12V usually have internal cell balancing circuits to help the cell voltages to match.

Cells are usually matched when fresh. With age, their capacity may drift apart, and a weaker cell may get discharged or charged to the limits before the others.