Heavy duty AC to DC converter required

[dmills]

Were I making browns gas for some reason I would be looking to build say 6 * 50V stacks rather then a single 300V one, then use telecom rectifiers as the power supplies.

Compact, efficient, isolated and (on the surplus market) all kinds of cheap. The Eltek Twinpacks seem to be widely available and relatively well documented (2,500W each).

Regards, Dan.

[mche1997]

Hi Dan, thanks for the advise, sorry again it's far too big and heavy, ok for static but its to go inside an enclosure the size of a 2 drawer filing cabinet and always gets transported around.
6  smaller stacks might work with lower voltage but not sure if it can produce the same amount of gas and temperature wise when running for over 1/2 hour.

[TopLoser]

Tell us how much equivalent commercially available systems sell for?

[mche1997]

From £1500 up to £8000

[dmills]

There will be a reason for that cost...

As to the size of the telecoms rectifiers, I have several 2kW units (Eltek Flatpack 2HE) that are about 1.7 inches high, 4 inches wide and maybe 12 inches long, three of those would get you ~6kW (120A @ 54V) which should get it done, I seem to recall paying £25 each for them.

My use is radio shenanigans, not inefficient gas generation, but whatever.

I take it you have considered the effect of hot H2 on most steels? Hydrogen Embrittlement is a thing you know. 

Regards, Dan.

[mche1997]

Hi Dan, holy !, I must have looked at the different ones on the internet, they're big stacks like the size of a shoe box. Thanks for the extra info, I'll have another look tomorrow.
If I can't find the appropriate ones like you mentioned, can you sell me some ?

Thanks

[tron9000]

...but its to go inside an enclosure the size of a 2 drawer filing cabinet and always gets transported around...

So something like this:


this is a 19" rack mounted case, 19" rack mounted stuff is pretty standard, save you from having to design your own enclosures: http://sierracases.com/19-inch-rack-mount-transit-cases

[oldway]

Choosing a voltage lower than 300V is a much safer solution ....
 
The switching power supplies for telecommunication have a nominal voltage of 56V, it's a great choice.

This is another approach to the problem that you had imposed in your first post.

First buy the used AC / DC converter (s) then do the electrolyser project according to what you have found...

The only limitation is the availability of such converters at a cheap price, especially if you want to make multiple copies.

[BravoV]

Hi Dan, holy !, I must have looked at the different ones on the internet, they're big stacks like the size of a shoe box. Thanks for the extra info, I'll have another look tomorrow.
If I can't find the appropriate ones like you mentioned, can you sell me some ?

Thanks

Hint where to look for, try find cellular base stations installers/contractors, do few social engineering communication either thru email or phone calls, with the main purpose of getting informations on who/where/how cellular operators disposed/dismantled their outdated towers.

Not sure in UK, but there must be someones that do these cleaning and installing job as cellular towers get refreshed quite often.

This is how I got my quality industrial PSUs, some are even bigger wattage or higher voltage, even used, they're still very usable.

Most important thing is they're dirt cheap.

Example my hoards last year, got few of these for <$30/pcs.

Most of these quality PSUs are "designed" capable of running in series, parallel, master & slave & etc.

Just google the below PSU for it's new price.   



Wish you good luck on your hunt.

[dmills]

There are some 4kW Eltek SMPSU 4000 on ebay at the moment, not the smallest things I have ever seen and very slightly off the pace for efficiency, but very solid kit, and good for 85A @ 48V each!

IIRC somewhere in the region of £125 quid each, and brand new, you couldn't build it for twice that!

Alternatively there are Eltek flatpack HEs, but they want a little too much money, they are however compact.

I would second talking to telecoms service types, cell base stations are mad for every point on the power efficiency they can win, you not so much, and the telcomms gear tends to be REALLY nice stuff.

Regards, Dan.

[oldway]

Choosing a max voltage of 56V, your new electrolyser must have 20 cells and need a current of 66A to produce the same amount of Brown's gas as your actual 300V / 12A electrolyser.

Try to stay with a low density current of 0.2A / cm² (electrodes of 330 cm² - 27.5 x 12 cm²)

[mche1997]

Great, lots of ideas now and I will start hunting, thank you all guys.

[schmitt trigger]

The only advise that I would give you with respect to used cell tower PSUs, is to open them up and thoroughly clean them inside.
And I mean thoroughly.
You will not only find dust and dirt, but the occasional life form which was attracted by the warmth and decided to crawl inside, only to be duly shocked.

I know. I used to work at a place where we built and refurbished Telecom supplies. I wish I still had the picture of a power rack, which had been installed somewhere in India, which had a thick snake, almost 5 feet long, completely fried.
Small rodents are quite common.

[mche1997]

Oh, that is scary, thanks pal