To be honest, Brian … I think your best bet would be a 12V sealed lead-acid battery with a trickle charger.

Other, wiser, folk will hopefully be along soon … to support or discredit my opinion.

MichaelG.

PC power supply. Cheap. Google PSU from atx power supply. It's an easy job

server computer power supplies costing ?10 or so from usual sources can supply 80A at 12.2V – I have a couple that will supply 150A at 12.5V

You will need to know how much current the motor takes so you can obtain a power supply capable of driving it.

Les.

Frances, I was referring to the ATX PSU, not a server unit but please advise your usual source.

Emgee

+1 for the ATX – pc power supply and there are plenty of videos on youtube or infoon the internet showing how to set them up.

I used one for my dehumidifier project (photos in my library ) but found when testing this unit using 3 halogen headlight globes in parallel the unit wouldn’t fire up as it was detecting a heavy current flow so it shut down suspecting a dead short . I would use a cheap PWM controller between the power supply and motor as this will allow the power supply to fire up without any current flow and you get the added bonus of speed control on your spindle . Even the old 550w unit i used was rated at 20 A @ 12 volts and they are dirt cheap to buy new if you don’t fancy using a second hand unit which can usually be scavenged for free from an old pc .

Hi Michael,
Thanks for pointing out the information I missed in the first post. One point about using PC power supplies is that some of them require some load to be put on the +5 volt output before the rated current can be drawn from the +12 volt output..

Les.

Plenty of wiring diagrams out there to fix that .

**LINK**

If you don’t want a certain voltage rail like 3.3v or 5 v or a negative rail just leave it disconnected .

When you open up a supply just identify the voltage you want by either wire colour code or looking at the board as it is sometimes written on it and unsolder the wires from the other pads then trim off the wires you won’t need from the supply rail you won’t use or as i did remove all the wires and solder on some heavy duty cable to the solder pad for the voltage i wanted to use .

Seriously these power supplies are something that many model engineers overlook because we don’t understand how they work or don’t know how to utilise their ability, you can get a 20amp , 12 volt pc power supply for under $50au here in OZ from just about any computer shop and even more power is not that much more expensive considering my local electronics shop would ask well over $100 au for something similar in their power supply units .

P.s , Dave slotted in a reply while i was typing this and as he says – the OP is not electrically minded so the power supply that Dave shows is the  simplest approach – i have never had a problem running motors off them and my cnc engraver uses the exact same type for its spindle motor but utilised the voltage control potentiometer  as an RPM control via a remote potentiometer instead of the trimpot on the circuit board .

Edited By XD 351 on 31/08/2019 10:44:37

Edited By XD 351 on 31/08/2019 10:54:39

a charger for a 12V lead acid battery will deliver near 14V if old fashioned type – modern chargers will sense output + current and may not like a motor connected as no voltage on initial startup looks like a shorted battery

Hi William,
I don't think that is really suitable for your purpose. It will be designed to control the speed of a motor designed for around 180 to 220 volts. It will provide no isolation from the mains. It will probably use phase control so when it is set to a low speed (Low AVERAGE voltage.) the output will be short pulses of a much higher peak value than the average output voltage. I am assuming that your saw is designed for an 18 volts battery.

Les.

My 3D printer uses a PC power supply with a couple of power resistors to keep it happy. One nice thing is I added a switch in the standby circuit.

For my astro I have a nominal 12V 150W psu like the one in SOD's post. I deliberately went for one greatly over-rated for my needs. I run it at a higher voltage to mimic a car battery then have two switching regulators to give me 12V and 5V for other devices.

Neil

Good point, whilst old-fashioned battery chargers are simple beasts that don't care about the load the same can't be assumed about today's magic boxes. I've not taken one apart yet, but a fast-charge unit I looked at in a shop recently was too light to contain a hefty transformer. As with wall-warts, I suspect transformers are being replaced by switch-mode power supplies, and once that's done it's trivial to specialise the electronics to do proper battery charging.

So a new battery charger could well be a close relative of a LED PSU with the added disadvantage of throwing a wobbler if the load doesn't behave like a charging battery. Although a smart charger refusing to run a motor properly because it's profiling volts and amps might be seen as a step back, at least the new one is clever enough not to damage batteries as is possible with a simple transformer/rectifier. Maybe!

Dave