Does a medium sized SE exist that could charge 12 V car battery properly?

[Spacefog_]

If not, how many small SE would it take to do so? Looking for things on the market today, things that have been built in the past, DIY's; anything. Working fluid being air (preferably not pressurized).

[Stroller]

8 amps would be a good charge rate for a 12V car battery. That's 12*8 = 96 Watts
An unpressurised SE using air making 100W might be fairly chunky unless its of Andy Ross level sophistication. Possibly bigger and heavier than my 40 year old Honda EG550 sidevalve generator, which will make 450W continuous power on around 12oz of gasoline an hour. I picked mine up off the 'bay for £50. Another option would be the Yamaha EF600 600W.

An unpressurised SE using air making 100W will be quieter, but it won't be silent, and it'll use a lot more fuel. How much does some noise matter in your application?

https://youtu.be/m7J2MUGIwfw

[Tom Booth]

8 amps would be a good charge rate for a 12V car battery. That's 12*8 = 96 Watts
An unpressurised SE using air making 100W might be fairly chunky unless its of Andy Ross level sophistication. Possibly bigger and heavier than my 40 year old Honda EG550 sidevalve generator, which will make 450W continuous power on around 12oz of gasoline an hour. I picked mine up off the 'bay for £50. Another option would be the Yamaha EF600 600W.

An unpressurised SE using air making 100W will be quieter, but it won't be silent, and it'll use a lot more fuel. How much does some noise matter in your application?

https://youtu.be/m7J2MUGIwfw

Letting your pants down petrol shill?

I'm pretty sure Spacefog_ didn't join the forum for advice on fuel efficient gasoline generators.

This is not a recommendation but I managed to get 8 volts open circuit from this engine before it blew a seal.

It went up to 8 volts off camera when I held it down to reduce vibration, but then a little plug blew out before I could move the camera.

https://youtu.be/sjDE4pf1zNY?si=fo5pHE1ues2ieN-P

Don't be fooled by the propane torch. I was trying to see what I could get the engine to do with as much heat input as possible, but it runs on MUCH less heat. The extra from the propane torch didn't really help that much.

https://youtu.be/546LT0AnL40?si=xazwJbafk3qqn593

These small Stirling battery chargers were available but are currently sold out of something I guess

https://www.ebay.com/itm/204296343706

[Tom Booth]

BTW, that eBay engine looks bigger than it actually is.

There is a pretty big compartment underneath just for housing the burner.

Compress_20240510_115838_8453.jpg (21.64 KiB) Viewed 107 times

[Stroller]

15Watts for $499. Plus $150 shipping.

petrol shill

What are you planning on firing your 15W generator with Tom? How much do you think it'll use?

[Tom Booth]

This is a nice little semi-DIY engine with 12v output potential.

Based around some cheap stainless steel cooking pots but would obviously take some skilled machining to actually build.

Compress_20240510_180457_7583.jpg (19.32 KiB) Viewed 56 times

https://youtu.be/QcppEhp2RfA

[Tom Booth]

15Watts for $499. Plus $150 shipping.

petrol shill

What are you planning on firing your 15W generator with Tom? How much do you think it'll use?

There is room for a lot of improvements. The displacer chamber and the displacer itself, I found, are made of ordinary steel, not stainless. Bolted to cast iron. Sheer losses due to conduction alone are unacceptable IMO.

Hardly any more output than the little engine with a SS displacer & chamber.

Unfortunately there have not been many options. Mine isn't a generator anyway. It's a Kyko type fan but the same engine.

I was lucky to find one locally on Facebook marketplace cheap from someone who had a friend who brought a couple with him on the plane back from Pakistan.

[Tom Booth]

This engine made from water bottles, according to the description, is charging two 12 volt batteries.

https://youtu.be/CXsFAB77Mzo

Only a few watts though.

How do you define "properly"?

Almost any wattage will charge a battery eventually.

Most common car battery chargers are between 2 amps (trickle charge) and 10 amps(fast charge).

One thing about Stirling engines many people don't realize is that they adapt to a load. In other words, running no-load for a while, you could stop one with a feather. But if the load is gradually increased the engine will build up more and more torque.

Case in point my little model above. When I got it it wouldn't light the little LED supplied with it, even with a propane torch, or would just barely.

But increasing the gear ratio, it not only lit the LED but could charge a cell phone, apparently at a rate higher than my wall charger.

[Tom Booth]

I first became aware of this ability of Stirling engines to "grow stronger" under a gradually increasing load reading a VITA publication authored by William Beale:

PDF:

https://pdf.usaid.gov/pdf_docs/pnaas739.pdf

Compress_20240510_200747_7072.jpg (51.69 KiB) Viewed 43 times

This is probably the result of the added work output gradually increasing the engines internal temperature difference.