I have reviewed the AC /DC motor guides found in the archives and still need a little help.

I have a pump that has a 1/2 HP motor , rpm 1725 , 115 VAC, amps 7.8
I would like to replace this motor with a DC motor for portability.
With the pump loaded, the AC motor only draws 5.8 to 7.0 A. at any time.
The time factor is critical, since portable batteries run down quickly. A 30 minute window would be enough to complete the job.
By my calculations, I would need a 24 volt DC motor and accompanying batteries to have any chance of working.
Am I full of it or will something like this work?

Thanks for any advise given!

 

Assuming each motor has about the same efficiency, the 24VDC motor will draw 115/25 * (5.8 to 7) = 26.7 to 32.2A from the 24V battery. Thus you would need a minimum battery capacity of 16.1AH for a half hour of operation. You should approximately double that for margin. I would think two deep-discharge type marine batteries in series, which typically have a capacity greater than 30AH, should work.

Don't use standard auto batteries as they won't last long under heavy discharge type use such as this is.

 

Unfortunately, I am trying to make it more portable by downsizing the batteries to those similar to a 18-24V drill battery. Will have to re-think the motor needs and possibly the pump itself. Thanks for the info.

 

Have you tried running a battery powered electric drill at full load for 1/2 hour? Mine won't do it. Batteries go dead first.

 

You either going to need larger batteries or a much smaller pump if you want to use drill type batteries.

How much liquid do you need to pump and at what pressure?