O/T 12 Volt DC question

phat46 · March 28, 2006, 08:24:17 PM

I need to know if it is o.k. to run a 12 volt DC motor that pulls 7 amps at 6 amps. Will it hurt the motor?

enjenjo · March 28, 2006, 08:42:39 PM

It won't develop full power, and may heat up if loaded heavily.

phat46 · March 28, 2006, 09:10:04 PM

Quote from: "enjenjo"It won't develop full power, and may heat up if loaded heavily.

Kinda what i was worried about. It's a motor on a water pump for an RV type application. I saw a converter for 120 AC to 12 VDC but it is one amp off. The pump is to be used at my deer camp for the water system, two sinks, occasional toilet flush, but no long time running; ie: no shower or tub...it is deer camp after all

donsrods · March 28, 2006, 09:16:05 PM

What are you trying to do exactly? Do you have 120 Volts at the camp, or or you using a generator to make this power?

Don

phat46 · March 28, 2006, 09:41:51 PM

Quote from: "donsrods"What are you trying to do exactly? Do you have 120 Volts at the camp, or or you using a generator to make this power?

Don

We have 120 at camp, and right now we have "city" water. As of Oct. 31 this year they are cutting the water line a few miles down the road. Camp is at the end af a "road" that is about nine miles off the pavement. Back in the early-mid part of the last century the area was booming with money from iron mining. The city closest to our camp built a huge water system with all the tax money from the mines. The last mine closed in the late '60's i believe, and the whole area is really hurting for money now. The city can't maintain the old, built in the 20's-30's, water system and they have decided to stop water service to remote areas like ours. i am putting a water tank in the camp and I have a 12 VDC pump out of a motor home to use. I can't justify putting a lot of money into the camp that is only used a few weeks a year, so I am trying to do it as cheaply as possible.

donsrods · March 28, 2006, 09:50:56 PM

Go to Northern and buy a 120 volt water pump for like $35.00 to maybe $ 50.00 and it will move more water than you need. We bought one a few years ago for a scallop business we were starting, and it really moved the water.

They probably have small demand pumps for what you need for less money than you will spend for the convertor.

Just a thought, and it would be more dependable too, I bet.

Don

And if you have your heart set on using the 12 volt pump, why not use an old car battery to run it, and hook up a small battery charger to keep it up? You could get all the amps you need this way.

phat46 · March 28, 2006, 10:15:20 PM

Quote from: "donsrods"Go to Northern and buy a 120 volt water pump for like $35.00 to maybe $ 50.00 and it will move more water than you need. We bought one a few years ago for a scallop business we were starting, and it really moved the water.

They probably have small demand pumps for what you need for less money than you will spend for the convertor.

Just a thought, and it would be more dependable too, I bet.

Don

And if you have your heart set on using the 12 volt pump, why not use an old car battery to run it, and hook up a small battery charger to keep it up? You could get all the amps you need this way.

I'll have to look at Northern again, I didn't see any 120 pumps there, I'll check again. The reason i was gonna use the 12VDC pump was that i had it, it was a freeby, and i found a 120VAC to 12VDC converter today for $19.95. If i can find a 120 volt pump for around $50 that would be the better way to go! Thanks for the idea!

purplepickup · March 28, 2006, 10:30:18 PM

Joe, I got a 3/4 hp harbor freight pump recently for $59 on sale. Right now they're $79 but they go up and down. It only draws 4 amps and I'm planning to use it at the cabin with a 2k generator. A friend drove a shallow well in his shop and has had one that has worked for years without a hitch. http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=2955 Their 1hp one is only $69 right now.

Here's a 20% off coupon that's good thru tomorrow at the store. The stores usually honor the catalog sale price. http://ww2.harborfreightusa.com/showpage_retail.taf?pageid=214&email=

phat46 · March 29, 2006, 06:30:50 AM

Quote from: "purplepickup"Joe, I got a 3/4 hp harbor freight pump recently for $59 on sale. Right now they're $79 but they go up and down. It only draws 4 amps and I'm planning to use it at the cabin with a 2k generator. A friend drove a shallow well in his shop and has had one that has worked for years without a hitch. http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=2955 Their 1hp one is only $69 right now.

Here's a 20% off coupon that's good thru tomorrow at the store. The stores usually honor the catalog sale price. http://ww2.harborfreightusa.com/showpage_retail.taf?pageid=214&email=

George, is that a demand type pump? Or would it require a pressure switch of some sort? I am a city boy, with no experience with wells/pumps :oops:

Varicam · March 29, 2006, 11:56:07 AM

If a 6 amp power supply is used for a 7 amp motor it's not going to hurt the motor. Might take a little longer to start under load, and it might pump a bit less in a given time. This is assuming that the motor rating is for peak load which will be of very short duration. If it's a continuous rating, peak load will be several times higher and a 6 amp power supply won't be able to start it. In either case the power supply itself might overheat and/or trip a cb if the max output is exceeded.

Mr Cool · March 31, 2006, 10:25:35 AM

If running a 7A pump on a power supply that can deliver smaller currents use a maximiser (or MPPT), same as what we use on solar powered pumps. Solar panels vary the supply current with cloud etc and the pumps still work fine, even running under load is no problem. They just run slower thats all.
Just go to a local solar pump supplier over there and ask for a 12v pump maximiser, over here they start at around $50. these basic units work by supplying a pulsed DC power to the pump at full power, commonly called PWM or pulse width modulation supply.