110 volt to 12 volt

[qmdv]

I have a 12 volt motor that draws 15 amps and want to run it without using a battery. Can I just use a battery charger or is there some trick expensive device I need to use instead.

 

[Dustball]

12 volt AC or DC?

 

[qmdv]

DC. It is a fuel pump that goes into a 100 gallon slip tank

 

[californiaHank]

The short answer is that battery chargers are designed to charge batteries, and not run motors.

If you connect a battery to the charger and then connect the motor to the battery, it will probably work, depending on the size of the battery and the design of the charger.

If you omit the battery it might work, but depending on the motor and the charger it may not work, and it may fry the charger or the motor.

The better alternative is to use a constant voltage DC power supply rather than a battery charger. The power suply should be large enough to handle the motor starting current, which is probably significantly larger than the full load running current of the motor. DC motors typically have high starting currents.

 

[a_whale]

<deleted>

 

[Sumboodie]

I had similar on a 500 gallon tank. I just had a battery and brought it in to charge when it would be low. Maybe 2-3x a year.

BTW. It's 120v in the USA.

 

[nadogail]

If it was my problem, I would use a battery and a charger, all of which I have in my garage or equipment shelter.

 

[qmdv]

Always in my airplane hangar or outside in good weather. Awe yes 120 volt. 15 amps at 12 volts is 180 watts. That would be a pretty good transformer

 

[qmdv]

What think of one of these https://www.superbrightleds.com/mor...1000w-enclosed-power-supply-12v-dc/2246/5345/
Consider the price of a new 12 volt battery these days

 

[dcg9381]

There are a few power supplies (12v) on Amazon in the 30A range for pretty reasonable amounts:

https://www.amazon.com/12v-30a-power-supply/s?k=12v+30a+power+supply

 

[Terry D]

You have two reasonable options here:
A 12V transformer-based power supply, or a 12V switching power supply.

The transformer-based power supply will be more weatherproof and long lasting. Honestly, you could just get a 12V transformer, a 30A bridge rectifier, mount it in a metal box, bolt the bridge rectifier to the inside of the box with a heat sink on the outside, and be done with it. I wouldn't even put capacitors on it. Or buy a 12V transformer supply. These are very common.

The switching power supply will be more efficient, much lighter, but less weatherproof and probably won't last 30+ years like the transformer will.

What kind of environment would the power supply be in? Outdoor? Under a roof? Etc

If I remember correctly from school, and its been a long time. When building your own power supply with just a 12 vac power supply and a bridge rectifier, you will get a lower voltage of 12 vdc at the output. I just cant remember how much lower, I do remember .7 and 1.414 for the math, anyway the addition of a capacitor will bring the output voltage back up.

 

[John T]

I use one of these in my garage to power a 12 V Dewalt battery charger.

Works great.

Schumacher 1216 12V 15 Amp Power Converter https://www.amazon.com/dp/B0066COXY0/?tag=atomicindus08-20

Mine is 15 A so you might be pushing it with your pump motor

They probably make them in different sizes/higher amps

 

[a_whale]

<deleted>

 

[Dustball]

What think of one of these https://www.superbrightleds.com/mor...1000w-enclosed-power-supply-12v-dc/2246/5345/
Consider the price of a new 12 volt battery these days

I've used Mean Well before without issues. Here's the same one for half the price- https://www.mouser.com/ProductDetai...OPeo77wgsgjBWL3Utf3gM8kRjXflWI%2BFbgKS/2Nhg==

 

[rlitman]

We speak of AC in terms of RMS. Because it is pretty close to a perfect sine wave, you can simply use the square root of 2 (i.e. 1.414) to calculate your AC RMS voltage from the peak-to-peak measurement...

Just to clarify this (for those who don't know this in their sleep):

120VAC is already the RMS voltage, but the peak-to-peak voltage if you probe your outlets with an oscilloscope is 169V (hope you have a 100x probe before you try this).

Transformer that down to 12VAC, and it will already be 17V P-P, because the RMS is 12V, so you don't need to multiply by radical 2 here.

As for rectifying it, well, RMS does apply to DC as well (since we're really worried about the "thermal power" of the waveform, rather than the P-P voltage), so, at first glance, you would think that 12VAC run through a bridge rectifier would give you 12VDC. However, there's also almost a volt lost through the diode losses to consider (that's why the rectifiers generate heat).

Here's a thought that nobody has considered yet above. Brushed universal motors generally work on BOTH AC AND DC. Unless there's some electronics in there that are DC only, it might work better on 12VAC off your transformer, than it would through the rectifier.

 

[HeadsUp]

There has already been a lot of good suggestions. I've used many old computer power supplies for such an occasion. You may not have to buy anything.

 

[rlitman]

There has already been a lot of good suggestions. I've used many old computer power supplies for such an occasion. You may not have to buy anything.

It'll have to be pretty old. Back in the AT days, computer power supplies had a simple switch. Ever since ATX, they've had a low standby power that's always on (for WoL purposes), and require communication with the MB to turn on.

Fanless 12V power supplies are pretty inexpensive, but the devil is in the details. Cheap fanless supplies are perforated for natural convective airflow, and will burn up if enclosed, plus they're rather sensitive to contamination, so outside of a "clean" environment, they don't last.

Knowing that, I'd suggest something fanless, with a solid aluminum heat-sink case. Like this maybe (with the outputs connected together):
https://www.amazon.com/dp/B07X52WNJC/?tag=atomicindus08-20

IF you really need DC. If AC will work, I'd suggest a landscape lighting transformer. Those are already well ruggedized for outdoor use.

 

[a_whale]

<deleted>

 

[Sevenhills1952]

Just a battery, switch, pump.
I've used this one for years, lithium battery Walmart had on clearance $5.

Sent from my SM-S205DL using Tapatalk

 

[HeadsUp]

It'll have to be pretty old. Back in the AT days, computer power supplies had a simple switch. Ever since ATX, they've had a low standby power that's always on (for WoL purposes), and require communication with the MB to turn on.

Fanless 12V power supplies are pretty inexpensive, but the devil is in the details. Cheap fanless supplies are perforated for natural convective airflow, and will burn up if enclosed, plus they're rather sensitive to contamination, so outside of a "clean" environment, they don't last.

Knowing that, I'd suggest something fanless, with a solid aluminum heat-sink case. Like this maybe (with the outputs connected together):
https://www.amazon.com/dp/B07X52WNJC/?tag=atomicindus08-20

IF you really need DC. If AC will work, I'd suggest a landscape lighting transformer. Those are already well ruggedized for outdoor use.

All good points. From the link posted... Wow! <$.20/watt May not be an issue for the OP but I'd question the longevity of the power supply. It's been a while but last time I researched quality power supplies they cost $1/watt.

 

[rlitman]

All good points. From the link posted... Wow! <$.20/watt May not be an issue for the OP but I'd question the longevity of the power supply. It's been a while but last time I researched quality power supplies they cost $1/watt.

It's about the economics of scale. Led strip lighting power supplies are being mass manufactured nowadays, which has driven down the price of 12VDC and 24VDC supplies made for that market.

I don't ever (since the 80's) remember computer power supplies being anywhere near $1 a watt either. Maybe before my time.

Anyway, don't take my link as a recommendation for a specific product, or me vouching for it's longevity. But with a name like "SHNITPWR", how bad can it be?

 

[TractorJeff]

An "Old Fashioned" Battery Charger was a transformer and half wave rectifier. I know it would work because as Kids, We used one to run automotive heater fans/blowers. We even "motored" a Delco Generator with it.
I still have one that I use occasionally to "force charge" Batteries when a NEW Electronic Charger won't power up on a Battery.

 

[walta]

If you decide to try a battery charger make sure it is an old fashion dumb charger as the new smart chargers do not put out any power until they see a battery in the circuit.

It sure looks hard to beat Sevenhills cordless tool battery and a switch.


Walta

 

[AntonLargiader]

An old RV power converter and a battery as a capacitor sounds like a cheap solution.