diy solar

diy solar

Small ~2kw Diesel Generator to run on waste oil

One thought I had was using a DC charge controller. There are now some that work with wind and hydro alternators. If we put a full wave rectifier on a "normal" AC generator output, we would end up with about 170 volts on a 120 volt output, or 340 volts from a 240 volt output. If we feed that into a DC charge controller to feed straight into the batteries, it should work. To make good use of my old 5,000 watt generator, I think it could push 3,000 watts. That is under 10 amps off of the rectified 240 volt. A 400 volt solar charge controller dialed in to 50 amps of charge current for my "48 volt" battery should do quite well. Fully discharged is 51 volts and charged up I stop at 57 volts. 57 volts x 50 amps = 2,850 watts. I think I will be looking for a cheap 400 volt 60 amp charge controller to try some experimenting.
 
If my batteries needed topped up and I was out of waste oil, I could even burn diesel in it, in a pinch!

I also have my Honda 2kw inverter genny, and could just plug one of the AIO's into it to charge batteries. Doesn't take care of my waste oil issue.

My dad owned a bio diesel factory here in the UK, also ran WVO (waste veg oil) in our car for years and years.

I don't know much about it, but he's pretty knowledgeable, I could pass you on his email if youd like ?
 
My dad owned a bio diesel factory here in the UK, also ran WVO (waste veg oil) in our car for years and years.

I don't know much about it, but he's pretty knowledgeable, I could pass you on his email if youd like ?
Thank you for the offer, I will pass though.

I'm well enough versed in running WVO that I'm not interested in doing so, even in a $200 diesel engine. I'm aware of how weird that is, since I'll run waste motor oil. WMO might carbon things up, but won't turn to plastic in the fuel system.
 
Thank you for the offer, I will pass though.

I'm well enough versed in running WVO that I'm not interested in doing so, even in a $200 diesel engine. I'm aware of how weird that is, since I'll run waste motor oil. WMO might carbon things up, but won't turn to plastic in the fuel system.

How are you cleaning the motor oil ? Are you cutting it with anything

We call it black diesel over here
 
How are you cleaning the motor oil ? Are you cutting it with anything

We call it black diesel over here

I'm sorry for giving the impression that I'm already doing this. Re-reading my post, it can definitely be taken that way. I haven't done it yet, just at the "looks doable on paper" stage.

I would likely filter via settling, and gravity feed through a toilet paper type filter. I probably wouldn't de-water at all.

The whole process would have to largely be set and forget, and not burn through expensive filters. Going to the recycling center is a pain, but not hugely out of my way if I route my trips right. How much WMO can be filtered through a filter before it needs replacing, and how much diesel will the cost of that filter buy? Doesn't take much time or cost consumed before I'd be better off just taking the oil to the recycling center and buying diesel.
 
I'm sorry for giving the impression that I'm already doing this. Re-reading my post, it can definitely be taken that way. I haven't done it yet, just at the "looks doable on paper" stage.

I would likely filter via settling, and gravity feed through a toilet paper type filter. I probably wouldn't de-water at all.

The whole process would have to largely be set and forget, and not burn through expensive filters. Going to the recycling center is a pain, but not hugely out of my way if I route my trips right. How much WMO can be filtered through a filter before it needs replacing, and how much diesel will the cost of that filter buy? Doesn't take much time or cost consumed before I'd be better off just taking the oil to the recycling center and buying diesel.

denim works well as a cheap pre filter, takes the oil down to 15 micro if I remember

But after the denim you're going to want two of these 10 inch filter housings , a 10 micron then a 5

, you can either gravity feed or pump it through


Screenshot_2022-11-19-17-17-43-602-edit_com.amazon.mShop.android.shopping.jpg
ge-wp-zs-10-20-1238938-ge-depth-cartridge-filter-10-micron-plain-end-20-length-2983169.jpg



After filtering you will need to get the water out some way or another (otherwise you'll knacker your engine) Buy a water block filter, or make one using Fuller's earth cat litter .. (you can reuse the cat litter over and over, just dry it out in the sun) . Remember oil floats on water , so your cat litter wants to be low in your homemade water block filter

You're other option is to by a small centrifuge, they're cheap enough, that avoids filtering & dewatering



It needs thinning with some form of solvent, kero, white spirit , petrol ( don't use anything that dissolves rubber seals like acetone),

normal unleaded petrol is best because it's guaranteed engine safe ( or gas if youre American)

5% 10% 20% depends on your engine & how cold it is there , start with 5% build up, you'll have to play with it

Black diesel is great for diesel engines, they love it. Get it right and it'll run great
 
Last edited:
As for
How much WMO can be filtered through a filter before it needs replacing, and how much diesel will the cost of that filter buy?

It can be anywhere from 100 litres to 1000 litres of oil before you have to change the filters

Your filters last a lot longer if you pre filter through cloth. Old pillow cases from the charity shops are good , don't wash them , throw them away . When we do veg oil I burn them, make great fire starters , but obviously wouldn't do that with engine oil ;-)
 
Thanks for the input, you've saved me some time and hassle

If that's what it takes to run WMO successfully, I'll pass on the whole venture. Not even close to worth the trouble for me.
 
Thanks for the input, you've saved me some time and hassle

If that's what it takes to run WMO successfully, I'll pass on the whole venture. Not even close to worth the trouble for me.

bloody hell fuel must be cheap over there then ? it's £1.95 a litre (£7.22 a US gallon) here
 
About £5/US gallon here, if I'm doing the conversion right.

I was only approaching this from the aspect of getting rid of the waste oil that my friends and I generate, while getting some use out of it myself, and providing yet another backup power option. A waste oil heater would check those first two boxes as well.

My daily driver is gasoline powered, and I spend ~$150/mo on fuel. Doesn't take much hassle or cost to make alternative fuels more trouble and cost than that.
 
Last edited:
About £5/US gallon here, if I'm doing the conversion right.

I was only approaching this from the aspect of getting rid of the waste oil I and my friends generate, while getting some use out of it myself, and providing yet another backup power option. A waste oil heater would check those first two boxes as well.

My daily driver is gasoline powered, and I spend ~$150/mo on fuel. Doesn't take much hassle or cost to make alternative fuels more trouble and cost than that.

Waste oil heater is a good idea . Have you looked into biogas ?
 
Only in passing. I know what biogas is, and have seen the home methane digesters that look like a waterbed mattress. What are your thoughts?
 
Only in passing. I know what biogas is, and have seen the home methane digesters that look like a waterbed mattress. What are your thoughts?

Fantastic stuff, I'm yet to try it out . But from my research it's cheap, easy and well worth doing

I love the idea of turn garbage, grass clippings, horse poo, food waste, into a usable product

Theres a man your side of the pond, sells plans for what he calls the 'liberty generator' , he digs big long trenches, encloses them, fills them full of muck and harvests the gas to run propane generators. He sells the power to the grid, produces enough electricity to make a full living off it, all he has to do is feed the digesters some organic material every couple of days

Truly free & self sustaining power , well worth a look
 
Love the idea, no clue why more of this isn't done on a commercial scale. I know landfill gas is utilized for a lot of things.
 
Love the idea, no clue why more of this isn't done on a commercial scale. I know landfill gas is utilized for a lot of things.

So wasteful . I live next to a huge cow farm, they have literally millions of gallons of slurry in a pit. All that gas coming off not being used, probably enough to power a small town
 
One thought I had was using a DC charge controller. There are now some that work with wind and hydro alternators.
So that’s anninteresting point.. a charge controller intended to work with a wind or hydro turbine must be ok accepting a lot of waviness on its input. Now i wonder if they are designed differently to ‘endure’ that, or there is no issue there and they are simply programmed different as far as how to ‘manage’ it for MPPT..
 
I did a little hunting, and now I came to a slightly different conclusion. My use case is a little different. It is a rare thing for me to need to fire up my generator, but the more I thought about it, why do we need a sophisticated charge controller at all?

What we need is a way to get charge current from an engine driven generator. And being able to choose the charge current makes more sense than tricking an MPPT. Any "normal" engine/generator is going to try to put out 120volt, 230 volts, or 120/240 split phase. In my case, it varies a bit due to an unstable governor, but it stays within +/- 10% on voltage, but the frequency can bounce from 45 to 70 Hz. But a dumb power supply does not care about frequency. Most switching supplies just convert it to DC anyways. So I came up with this idea.


Same brand lists several other options for different voltage ranges and power ratings. I need the "up to 60 volts" version, which limits my choices, and I also want over 2,000 watts.

Dial the no load voltage to the maximum bulk charge voltage of the battery bank. Then connect it to the battery and adjust it to the desired charge current rate. This one will go up to 60 volts, perfect for my 57 volt full charge setting. And the current will go to 41.6 amps. That gives me over 2,000 watts of charge power out of my old generator, putting it close to it's 50% load max efficiency area. The power draw from the generator will increase a little as the battery voltage climbs, and then the load will drop off once bulk voltage is reached and the current falls off. My old generator can't do auto start, but I could have a relay trip the low oil engine kill wire once the battery reaches 57 volts. No need to keep the thing running once the battery is full. Simple CV/CC charging works just fine, no need for MPPT search.

My generator still runs on gasoline for now, but I am looking at a propane carb for it. If this thing ever dies, I will look into a Diesel engine for it. It is a big old tank, but it just plain works. If I needed it more often, I might be more inclined to upgrade it. I just can't justify the cost for a decent inverter type or a new dual fuel or diesel one since this works.
 
I am running ~2300w of PSUs into my 48v pack off an okd 5000w generator as we speak, so i am just fine with this idea. ?

Main difference is in my case it’s 4x 500w psu + 4x100w psu. None have current limit, only the 500w have adjustable voltage. I have this because i pieced it together over time. The only advantages of the multiple small psus are price (about $220 total for all of them), redundancy (single failure won’t take the whole thing out), and adjustability.

What i mean by adjustability is, while i have no current limits i can stagger the voltage adjustments of the 4x500w supplies if i chose to. I’ve found i need maybe 1-2volts of differential between PSU and battery voltage to max out the PSU current. As the battery gets close to psu voltage current drops and when battery passes psu voltage they ‘idle’ at about 4w each for the 500w ones. So if i set 3 to 49.8, and one at 52.7 i would have ~2000w of charging below about 48.5v, but it would taper off quickly to 500w at ~50v. Add in the 4 x100w chargers @54.6 and it goes:

~2400w @ <48.5v
~1300w @ ~49.3v (guesstimated rate of taper there)
~900w @ 50v
~400w @ >52.7v

It’s not a grand design, i just pieced it together with multiple <$40 purchases while experimenting before i decided “yeah this works” and slapped em all together. If i had already known it would work out when i started, i may very well have bought a single larger, more adjustable PSU for the purpose such as what you showed.

Although, again when you buy a big enough PSU you run into the irony that now for $100 more you could buy an entire 5000w 48v all in one inverter charger that has ~60-80a of ac charging built in and has other abilities you could ‘grow into’. But, you could ONLY feed 220-240 to it. Not useful for a 120-only generator.

$520 48v AIO
 
Last edited:
I haven't read on all the posts but in my opinion the best way to use the waste oil is to mix it 50/50 with fresh diesel and centrifuge it. Filtering can never remove the smallest carbon particles or suspended water.
 
Back
Top