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# Power Inverter Wattage Vs. Amperage

## Power Inverter Wattage Vs. Amperage

#1
02-03-13, 10:33 AM
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Join Date: Feb 2013
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Power Inverter Wattage Vs. Amperage

Hi Folks,
I have a small 12 volt submersible pump that uses quite a lot of amperage. It has a variable output, but can use up to 40 amps at high speed. The manufactuerer recommends operating it off of a car battery while the vehicle is running. He says that I could use a 12 volt deep cycle battery, but that I would likely need several of them to get through a full day of operation. He said that a typical gasoline generator would not produce enough amperage to run the pump, but was not sure about using a power inverter. So my question is, will a commercially available power inverter make the amperage that I need, and if so, how much wattage do I need?

Thanks a ton for any and all responses!

#2
02-03-13, 11:35 AM
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Location: Wet side of Washington state.
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An inverter changes direct current (generally from a battery) to alternating current. Most inverters change 12 volts DC to 120 volts AC so they would have no use with your 12 volt pump.

Wattage in DC circuits is simply volts times amperes so your pump is rated at 480 watts.

If what you want is to run your pump on regular house current (120 volts AC) then you need a AC to DC power supply with more than 480 watts capacity. That may be a bit difficult to find.

What exactly is your application? We may be able to suggest a better method.

#3
02-03-13, 11:39 AM
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Welcome to our forums!

An inverter is not what you need.
Because your pump is already 12 volts dc an inverter will convert 12volts dc into 120 volts ac that you would have to convert back to12 volts dc!

A 31 series marine/deep cycle battery has about 155 amp.hrs of capacity.
This means that you could operate your pump at 40 amps for about 4 hours continuously.
A 2000 watt generator would allow you to use a 20 amp battery charger.

One thing is if you had a 2000 watt generator you could easily operate your main sump pump if it is 1/2hp or less.

#4
02-03-13, 01:25 PM
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Join Date: Feb 2013
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Thanks for the Replies!

Hi Guys,
Thanks for the help! Yeah, I got to thinking after my post and realized that an inverter would not get me where I wanted to go (silly me). I did think about hooking a charger up to my generator, but that seemed a little convoluted. It sounds like that might work though... I am using this small 12 volt pump as a portable well sampling pump, so the system needs to be both mobile and able to run for 5-6 hours a day for several weeks. I have a brand new NAPA 8240 deep cycle battery (I'm not sure how many amp hours it is good for), and am currently running a test with the pump set at a med. setting to see how long it will last. If I wind up making this a permanent system that generator/charger/battery system may work, or 2 deep cycle batteries might be the way to go. Are there any other possibilities? Thanks again!

#5
02-03-13, 01:37 PM
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That battery is the smallest dual purpose battery rated at 120 min reserve capacity.....That is 25 amps of draw for 120 min.
A 31 series dual purpose would be around 200 min reserve @ 25 amps.

#6
02-03-13, 01:46 PM
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OK, a bigger battery...

So I need a bigger battery to operate longer. We will be working from Polaris Ranger UTV's, will the charging system for the on board battery make enough amps to run the pump? You guys are really helping me out a lot here!

#7
02-03-13, 02:31 PM
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With the battery you have if you were to draw it down to 11.8 volts which would be completely depleted it would take about 120 minutes at a 25 amp charge rate to replenish the battery.
Unfortunately 25 amps into a small battery like yours is too high a rate and would overheat the battery and would likely damage the alternator on the utv.
A 15 amp rate is more reasonable and would take between 3 - 4 hours to charge.
This is the advantage to a larger battery because it can take a slightly higher charge rate.

Two 31 series batteries at about 200 min reserve each should run your pump between 6-7 hrs.
You would almost need two sets of batteries and visit the site daily to swap them out and a large enough charger to recharge overnight.

#8
02-03-13, 03:04 PM
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For 5 hours use at 40 amps you need 200 amp hours worth of battery reserve. You should not discharge the batteries more than 50% and less than that is even better, so you need a minimum capacity of 400 amp hours.

You could use 4 golf cart batteries 6v each. Connect 2 sets in series to get 12 volts and connect those 2 sets together in parallel. If the amp hour rating of 1 battery is 220 AH then connecting them together in that manner will give you 440 AH of which you could use 220AH without serious harm to the batteries.

They would have to be charged overnight after each days use. Batteries used in this manner require much care in their maintenance and charging unlike the battery in your car. A good charger that monitors battery temperature and voltage and adjusts accordingly and prevents overcharging is a must to get the most life out of them.

For the kind of money all that would cost, a small generator capable of 2000 watts (120v@15 amps) and a 120v pump would be a lot less hassle with less maintenance. You could buy a generator for the cost of just the 4 batteries.

Working around water would require safety issues be dealt with, ground fault protection, watertight wire connections etc. Maybe the reason your already on the DC trail ?

#9
02-03-13, 03:04 PM
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Since the manufacturer recommends operating from a running car while connected to the car's battery, what about connecting to the Polaris Ranger UTV battery and leaving it running like the car?

#10
02-03-13, 03:15 PM
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What's the amperage output of the vehicles charging system?

#11
02-03-13, 04:04 PM
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I wish I knew... I took a quick look at the manual on-line and can only say that there are several 20 amp fuses/circuit breakers. I guess we'll just have to try it! This particular set-up is all new equipment for me. Sorry to monopolize all your time. If you ever need advice on groundwater sampling just ask!

#12
02-03-13, 05:03 PM
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Join Date: Jan 2013
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I see they have a 50 amp alternator available as an "accessory". That should do it for you. You'd need the appropriate gauge wire and breaker to handle the current.

I'm thinking if they offer this as an accessory, a stock alternator could be much less amps and would not work for you.

The link no longer works, but here is some info posted on a Ranger forum about 4 years ago.

Features

* Easy To Install
* Kit Includes Everything Required
* Provides 50 Amps Of Power
* Mounts HIGH under Seat
* Marine Grade Alternator is Water Resistant
* Anodized Black Aluminum
* Complete Enclosed Belt To Protect From Elements
* No Other Parts Or Upgrades Needed To Work
* Will Work With 2003 to 2008 Rangers Including the 2009 Models
* FITS 700cc ONLY (WILL NOT FIT 500cc UNITS)

Benefits

* Do Not Have to Purchase Expensive H.I.D. Lights
* 12 Volt Inverters Can Be Used
* Only Need One Battery
* Can Run All Accessories; Stereo, Spotlights, Navigation, Winch, Etc.
* Works with Factory Stator
* Gives Power For Life Saving Rescue, Police, Fire, Fish and Game, Etc.

#13
02-03-13, 05:12 PM
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OK, I'm out of questions... Thanks for your time! Enjoy the big game!

#14
02-04-13, 01:20 PM
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Thanks for your reply. Our issue is pumping speed. Some of these wells need to be purged very slowly (less than 0.1 gallon per minute), and 120 volt pumps will just not go that low. We do have a golf cart on site, so I will look closely at that option. Thanks again!

#15
02-04-13, 02:31 PM
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Our issue is pumping speed. Some of these wells need to be purged very slowly (less than 0.1 gallon per minute), and 120 volt pumps will just not go that low
But a low voltage DC pump can be run on a battery kept charged by a 120 volt DC charger.

#16
02-04-13, 03:19 PM
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So is the 40 amp estimate for your pump quite high?

It's getting a bit confusing I think but based on your use it would make most sense to size the battery(s) to allow a day or so pumping time.
Unless you plan to stay at the site for an extended amount of time trying to charge discharged batteries from a vehicle would likely mean you would have to sit there and watch batteries charge.....Can you do this?

There is a maximum rate at which you can charge the batteries without overheating and at best you are looking at about four to six hours to recharge a 24 series battery.
Can you sit there to do this?

Exactly what pump are you using and how often do you need to visit the site?