Gas Generators

[solar226]

I have 2X Blueetti 1500's and 2X Maxoak K5's. What would be the best gas Generators to charge my equipment?

 

[Minimoose]

I have 2X Blueetti 1500's and 2X Maxoak K5's. What would be the best gas Generators to charge my equipment?

By 1500 do you mean EB150? They only use 200 watts to charge with the adapter. So you're talking less than 600 watts for all four. The tiniest Harbor Freight 1400 watt generator would cover that. A 2500 watt Champion like I have could run on eco-mode and charge that little amount. I'd make sure it's an inverter generator though.

 

[Nobodybusiness]

I have 2X Blueetti 1500's and 2X Maxoak K5's. What would be the best gas Generators to charge my equipment?

Don’t they have wall adapter?
Any small generator should work.

 

[solar226]

By 1500 do you mean EB150? They only use 200 watts to charge with the adapter. So you're talking less than 600 watts for all four. The tiniest Harbor Freight 1400 watt generator would cover that. A 2500 watt Champion like I have could run on eco-mode and charge that little amount.

 

[solar226]

I was thinking about getting a 2500 dual fuel inverter champion as well.
What are your thoughts about using propane as well as gas for charging the generators I need charging?
I've never used propane before but I read that you could use it in longer durations than gas but I heard it's tricky to store in an area like a garage.

 

[solar226]

I was thinking about getting a 2500 dual fuel inverter champion as well.
What are your thoughts about using propane as well as gas for charging the generators I need charging?
I've never used propane before but I read that you could use it in longer durations than gas but I heard it's tricky to store in an area like a garage.

 

[Minimoose]

I was thinking about getting a 2500 dual fuel inverter champion as well.
What are your thoughts about using propane as well as gas for charging the generators I need charging?
I've never used propane before but I read that you could use it in longer durations than gas but I heard it's tricky to store in an area like a garage.

I got the champion dual fuel as a backup to run and charge small loads in case the sun doesn't shine. It will run longer on one gallon of gas than my old school 5000 watt will run on 5 gallons. Being able to use propane is a big plus for me. You can store propane for years without issue. Not to mention it is way more quiet than my large generator and only weighs about 50 lbs.

 

[Symbioquine]

When comparing gas and propane generator efficiency, you may find some interesting data in this thread: https://diysolarforum.com/threads/how-efficient-is-your-generator.50418/

 

[Minimoose]

When comparing gas and propane generator efficiency, you may find some interesting data in this thread: https://diysolarforum.com/threads/how-efficient-is-your-generator.50418/

I know I can expect about 200 watts less efficiency on propane as compared to gas, but I'll only be running light loads with the small generator.
1850 running watts and up to 11.5 hours run time on gasoline, and 1665 running watts and up to 34 hours on propane on eco mode. I can run this on eco mode with my battery chargers if there is no sun. I only have this for a secondary backup system. I have a couple of Ecoflows and a Bluetti. I believe in backups for my backups. Maybe I'm being over cautious? lol

 

[time2roll]

Back up for a backup? I would go all propane to avoid gasoline carburetor issues and maintaining old gasoline. Best to store the propane cylinder outside. Generator can be inside.

Propane is not less efficient necessarily as much as it contains less thermal energy per gallon.

 

[Minimoose]

Back up for a backup? I would go all propane to avoid gasoline carburetor issues and maintaining old gasoline. Best to store the propane cylinder outside. Generator can be inside.

Propane is not less efficient necessarily as much as it contains less thermal energy per gallon.

Yes. I keep my generators inside. My large one is 10 horsepower pull start. I found out years ago how hard it was to pull start it with thick oil in very cold weather! I plan on using propane only on the small generator.

 

[Symbioquine]

Propane is not less efficient necessarily as much as it contains less thermal energy per gallon.

The thread I linked so far only contains data to the contrary.

In that thread, I (and others) have aggregated some data that suggests that the peak observed propane efficiency is around 15% - compared to up to 20% with gasoline and up to 25% with diesel. Those efficiency numbers already take into account the density of chemical energy in the various fuels because the calculation is the actual generated killowatt-hours divided by the potential chemical energy in a unit of fuel.

@time2roll Perhaps you have datapoints you can share showing higher propane efficiency?

 

[time2roll]

Actually I did not see a great comparison of BTU input compared to kWh output.

I do know a gallon of propane has 84,250 BTU per gallon and gasoline is 116,090 BTU per gallon.
The lower propane BTU alone accounts for 27.5% less power out per gallon.

 

[Symbioquine]

Actually I did not see a great comparison of BTU input compared to kWh output.

I do know a gallon of propane has 84,250 BTU per gallon and gasoline is 116,090 BTU per gallon.

The thread I linked uses the kWh versions of those numbers - for the amount of chemical energy in a unit of each fuel - but it is the same math/data as you're talking about.

The 84,250 BTU number you mention is actually the one for natural gas btw.

A gallon of propane is 91,500 BTU or 26.816 kWh. (In that thread I've been using 27.988 kWh - I can't remember where I got that, but that just means the efficiency numbers I've been calculating may be a bit lower than the real values.)

 

[Rocketman]

My guess of why propane shows less efficiency in the conversion cycle than gas than diesel has to do with engine design.

Propane is usually ran in gas designed engines, even though they are close enough to do that, I believe you would get better efficiency from a propane designed engine. (Plus gas has MANY more years and people getting all the efficiency out of it they can).

Diesel is more efficient with the much higher compression factor.

But the biggest thing is what works best for your situation. Propane will store for years and won’t go bad. But will/may be harder to source and it’s usually more expensive. For generators you should be using ethanol-free fuel (helps cut down on issues). But I would not store that for fuel.

Good Luck in your decision.

 

[Symbioquine]

Great points @Rocketman!

I believe you would get better efficiency from a propane designed engine.

That's why I've been really hoping that more folks with straight propane generators would provide their usage/efficiency numbers.

Unfortunately, as you highlight many of those are probably also just retooled gas engine designs. Most are going to be backup generators and it mostly isn't critical for a backup generator to have maximum efficiency - and just using existing gas designs could help a ton with the production cost.

 

[Checkthisout]

LPG/NG motors need to run higher compression ratios than gasoline to get their best efficiency.

That's really the only thing that can be done to help.

Also, lpg/ng have higher combustion efficiency than diesel or gas.

In other words you send very little partially burned (co) and unburned (hc) fuel out the tailpipe along with basically zero soot production so oil stays cleaner, less abrasive scrubbing cylinder walls etc...

 

[Checkthisout]

Also, engine fuel consumption is given in lbs, not gallons. If you compare fuel weights, gaseous fuels net you the best efficiency so long as they are burned in an engine that optimizes their high octane rating.

Albeit, I understand for our purposes, we need to compare gallons consumed and the cost per gallon since that is how the fuel is sold to us.

 

[DPC]

Great points @Rocketman!



That's why I've been really hoping that more folks with straight propane generators would provide their usage/efficiency numbers.

Unfortunately, as you highlight many of those are probably also just retooled gas engine designs. Most are going to be backup generators and it mostly isn't critical for a backup generator to have maximum efficiency - and just using existing gas designs could help a ton with the production cost.

Sharpen your pencil.....

Without looking at it I assume its a small block clone ( Champion )
Not much I can do without know exactly what clone but its probably a GX160.
You can swap the head gasket out for one from Honda Gx200 to tighten up the combustion chamber a little but this is very very little.
That and advance the timing a couple of degrees ( its probably around 25 Btdc now, but it might not be clones can be all over the place you need to get a timing light on it and find out exactly where it is ).

Mostly with a tiny charger you turning propane in noise and green house gasses.

I loath alternators for charging because they are so dam inefficient, but anything is better than a trickle charger and inverter generator.
This is something made to charge batteries, but good luck buying one here....

YK60A-1 Digital Inverter Battery Charger Gasoline DC Generator (DC 12V-60A, 17Kg) - SHANGHAI YANGKE IMP. & EXP. CO., LTD.

YK60A-1 (12V-60A) Portable gasoline dc generator. Digital inverter battery charger. Compact design, weight only 17kg. Rare earth p... Ships from China.

www.ecplaza.net

Your likely stuck with an alternator build.
A few things you can do....
Get a small block 196 clone with electric start and buy a dual fuel carb for propane.
14cc head from Chinese GX160 clone and the Honda Z4M flat top piston.
This will yeild near 10.5 to compression with thin .010 head gasket.
Also check your timing and set it around 25 BTDC this is a good number and the machine will still burn pump gas ( but it should be premium if not on propane )

You may nee to play with the plug gap sometimes your have to close it up a little if you get a miss at light loads.

Chose a good alternator in the 60-80 amp range you can mount an external adjustable marine regualtor so you can charge a weak battery at an appropriate rate.

If your feeling up too it, you could buy a relay like this

And you add a solenoid and spring and make your governor somewhat responsive to load.
You have a high and low speed for a high and low charging load.
This can improve efficiency a little, but its still an alternator...

A direct drive with a lovejoy coupling can be about 10% more efficient than a V belt drive.
But you will need to look at set of tables to find out whats going to work at what RPM.

This is all a real hassel isn't it?
Inverter with the little charge is an option again....

You could look for an old generator with saturated field and exciter cranked.
Kohler made a pile of 3RM21 units in gas and NG and I still see them on Kijjiji all the time pretty cheap
Down side is that thristy 18 cubic inch flat head ( upside is power to spare and AC available while you charge in a remote start unit )

Or you can do a modernization of a unit like than with a purpose built OHV engine for Propane.
( way off down the wabbit hole now )


The takeaway here is the unit has that big exciter and two stage charger that can provide as many if not more amps....

Way back in the day Onan made a unit called an LK and it has a big exciter in it too.
Although Onan said not to use them as battery chargers Winnebago wired them up in RVs and used them to do just that.
They were good for about 10 amps ....

Oh ya the LKs usually come with a low compression head, but if you find the left head off a CCK-B tractor that a high compression engine head that will save you some propane and still give the capacity to burn pump gas ( as built the LK could burn 80 octane fuel on purpose they were weakened like this to keep you from overloading them because they could easily pull over 3000 watts with that High head )

No one will ever steal a cast iron monster and they are pretty easy to work on if you ever need too.
You can fog them up and oil them and ignore them for years and they will generaly start without much fuss
Try that with an Inverter generator lol...

Propane and NG are kind of a hassel to use in a small electric plant unless its built for that purpose.
I think its more a gimic that of any value.
For one thing its a wet fuel and if you ever heard that you make about a litre of water for every Litre of gasoline you burn that is correct. lighter fuels like propane even more so.
This means you want to get that engine under a load and warmed up to drive off the moister.
Engines will rust from the inside out if they run on propane for short light loads and never get up to temperature.
Sometimes you see it in the oil its all milky....
SO get that engine working, use more power if you have to get it loaded up for the 1st half hour so it warm enough to stay dry as the charging load tapers off....

Chain oil often especialy in winter if your using it alot 25 hours... Change oil no matter what it looks like, its full of water....

 

[Symbioquine]

@DPC all that is pretty interesting, but perhaps you can comment on what total efficiency one might expect by going deep down that rabbit hole? I mean there's a lot to be said for having standard easily obtainable self-contained system components too...