DC power supply

[Rick Hughes]

I'm looking into a winch project (separate post) ........ if I opted to use a 12V winch ... type that bolt onto a 4x4 for recovery work.

To avoid having a car battery battery hanging around all year for very occasional use .. (cost) .......... is it reasonably practical to use a

220v ac to 12V DC converter. The current would need to be in region of 85A if I opted for 1.3hp / 1kW winch.

I'm guessing that will not be a small or cheap unit ............... unless anyone knows better I may have to go with a 12V battery and keep it on trickle charge.

[Andrew Gabriel]

Battery and charger is almost certainly going to be cheaper. Switched mode PSUs of this rating used to be commonly used in minicomputers 25 years ago, but nowadays, computers of this size use 48VDC distribution, and tiny local DC-DC converters (switched mode PSUs running in MHz region) to generate the lower voltages.

[newshound]

+1.

1 kW will pull over 200 kg force at 1 mph (maybe a bit less allowing for friction). Do you definitely need this much power?

Simplest mains power supply option might be one of these

these should be robust against overload from starting currents.

[John Williamson]

That'll be the cheapest way, even allowing for a proper float charger. A normal trickle charger will rapidly cook the battery.

The good news is that you will only need a cheap car battery, unless you're running the winch for an hour at a time..

85 Amps is jump starter territory, and they often need a battery in circuit or they won't let the power out, unless you know enough to be able to bypass the protection circuit.

[Jules Richardson]

Even the older stuff tended to use a modular approach with lots of supplies providing DC rather than one enormous unit, though - e.g. a mid- sized DEC might have 5-10 PSUs*, and each of those would contain a handful of regulators to provide various DC voltages (each regulator being around the physical size of a modern PC's PSU).

• a KL-10 of the early '70s with the additional memory option seems to be seven 7420 PSUs and 33 regulators (and that's not counting supplies in the storage units and other peripherals).

cheers

Jules

[harry]

These are a specialist item,ie devised for the one purpose of automive mounting. It would be really difficult touse them in any other environment.

[Andy Bartlett]

Farnell have one for £379

some others ...

[The Natural Philosopher]

Hmm. Google for 13.8V PSUs. There area few 'replace a 12v battery' type units out there designed for boosted CB radio usage..

But remember your STARTING current will be up to 800A. That winch is a starter motor in essence. So you will need a car battery anyway

[Archibald]

A PSU is a little over the top for the application. See if someone can connect a transformer and a 100A bridge up. You may need a slight refinement to stop any back EMF or inrush current from doing your diodes in, but a 1kVA transformer shouldn't break the bank.

A winch would not benefit much from a stabilised ripple free PSU.

HN

[Theo Markettos]

bought a 1KW 12V PSU for 200 quid, but that's with data sheet, manufacturer support etc.

If you aren't bothered by that, grab a surplus server power supply from ebay. They're pretty cheap, and you can get 1-2KW versions. You may have to do some googling/investigation to work out pinouts, how to switch the thing on, etc, as they're usually specials for HP, Cisco, etc.

I have no idea how well they'll cope with seriously inductive loads, though.

Theo

[Toiler]

I use a jump-starter to run my winch and it works fine see

have smaller units but I needed one to start my Discovery

[meow2222]

Loads that apply inductive kickback require a psu to be designed to cope with it, and that's not likely in a computer psu. It could be an expensive move.

NT

[GB]

Surely, if this is just occasional use, you'd be better off with something man-powered? A decent block and tackle will only set you back a few pounds.

For more security, there are those clever chain thingies with the two pulleys with different diameters welded together concentrically. That will set you back a fair bit more, but it will last several lifetimes.

[damduck-egg]

As the OP has a boat I wonder how much he associates with other marine types, Someone may have a surplus manual sail capstan or small anchor drum winch that could be bolted down and a couple of blocks or rollers in strategic places. There is a lot to be said for manual operation if it does the job. Power operation can go pear shaped in a blink of an eye ,sometimes painfully.

G.Harman

[The Other Mike]

70 quid ish for a transformer, another 30 for the rectifier (just a couple of prices from industrial suppliers I've used in the past)

Agreed, but is this hypothetical 'cheap psu' going to have some form of regulation such that the car battery is fed a voltage that won't boil the electrolyte?