Basic Question

[slothman]

I may be missing something obvious here, but I have a 1/2 Hp ( @370 watt) , 230 volt deep well water pump. I need to back it up with a battery....probably 24 volt.

Question; Do I only need to consider the power output of the battery (ie I x V) to ensure that the battery can operate the pump, or, do I need to factor in some kind of relay to ensure that the battery voltage is stepped up to the 230'ish level.

Thanks in advance!

 

[Skogsgurra]

Yes, you are missing something very obvious.

Unless you involve an inverter to change your battery to 230 V, you will never see that pump turning. Also, a simple 24 V DC/230 V 50 Hz inverter doesn't produce a very nice waveform. And it is possible that your motor doesn't like it at all.



Gunnar Englund

http://www.gke.org

 

[itsmoked]

and... 370W/24V = 15Amps => a really large battery to support 15amp draw for the time periods a deep well pump will want to run unless you only turn it on to get a subsistence gallon of water from occasionally. You would be better off using a generator probably.. Which has other advantages as well.


Keith Cress
Flamin Systems, Inc.- <

http://www.flaminsystems.com>

 

[slothman]

I am not concerned about the amps since I will connect in parallel the number required.

The big voltage delta is my concern. As far as generators, it was my understanding that a generator can easily overpower (system tolerances of gen) the starting current drawn by the pump...possibly burning it out....?


Thanks to all for the feedback.

 

[ScottyUK]

Slothman,

Consider the following:

Generators of a given size cope with motor starting rather more gracefully than an inverter of the same rating. The genny may slow down a little and the voltage may sag, but the motor will probably start. An inverter would just shut down unless it was oversized to ride through the starting current drawn by the motor.

It is easier to store a days worth of diesel than a days worth of batteries.

Consider how the UPS industry deals with long runtime applications: there is a battery to carry the critical load until a diesel generator starts up. The reason? It is not economical to use storage batteries for long runtime applications.

If you are considering paralleling batteries, consider putting them in series instead and running a VFD by direct feed onto the DC bus of the drive.

----------------------------------

I don't suffer from insanity. I enjoy it...

 

[itsmoked]

Ditch the batteries. Realize that they are a large maintenance headache! They wear out and die just sitting there "ready".

Use a propane or Nat. gas fired generator. That way you have no fuel sitting around for two years going bad and gumming up the carb before actually being needed.


Keith Cress
Flamin Systems, Inc.- <

http://www.flaminsystems.com>

 

[slothman]

All,

Thanks for the advice...it is very much appreciated.

The location basicall prohibits the use of a generator...to much pain involved in getting it there....I will eventually probably look into some solar panels to charge the batt's.

Thanks again!

 

[waross]

You said " I need to back it up with a battery."
Is this in case of failure of the regular supply or is the battey going to be the prime power?
You may consider a tower or storage tank. The tower would supply water by gravity and store enough to last out a power failure.
The ground level storage tank will store enough water for a power outage and you can use a small 12 volt pump for delivery. These pumps are available from the pleasure craft industry and used to be used in motorhomes. Probably still are but I haven't seen a motor home up close for a while.
As for

The location basicall prohibits the use of a generator...to much pain involved in getting it there

By the time you get to your site with enough batteries to run a 1/2 HP pump for a reasonable length of time and enough solar panels to charge the batteries in a reasonable length of time, you will know the true meaning of pain.
I had some experience with a shallow well pump (which will deliver a given volume of water in a fraction of the time that a deep well pump takes) and solar power. I got involved when the owners "Bit the bullet" and bought a small diesel generator. The "Pain of delivery" was sea shipping to Central America and then about a 200 mile flight in a small plane to a grass strip near a small hospital in the moskito coast. The generator was unloaded by hand and dragged with a rope by manpower to the installation site. Even though it was sized for other planned loads and was about 7 or 8 times as large as would be required for the pump alone, the weight of the generator was similar to, the and volume of the generator, was less than the batteries and solar panels that were not adequate for the waterpumping chores.
Let me put it another way; The batteries and the solar panels were not adequate for pumping water with a pump that was only about 20% to 30% as demanding as your deep well installation. The genset was at least 6 times as big as you require for the deep well pump. I don't think that the battery bank and the solar panels would have fitted into the plane that brought the genset.

Ditch the batteries.

good advice
ps; There are several small diesel sets avaiable that are well worth the extra money. In my experience a gas set lasts 2 to 5 years. A small diesel lasts 10 or 15 years.
If you can't lift the set, tie a pole to it and get some friends to help you lift the pole.
yours

 

[Skogsgurra]

The fundamental issue is that you do have a 230 V motor for that pump. A 230 V motor is, at least in my eyes, an AC motor. Batteries are DC. So it is not only a question about voltage - it is also a question about frequency and wave-form.

It is possible that you referred to some kind of inverter when you asked "do I need to factor in some kind of relay to ensure that the battery voltage is stepped up to the 230'ish level?" but you have to bee very open-minded to read "inverter" into that.

I get a feeling that you want to make things as difficult as possible. Why on earth should you use solar panels to charge the batteries? Isn't there a 230 V grid available now and then? Use that to charge your batteries. Or better still, take a genset there. A 3 kW set is more than adequate and kan be lifted by one hand. I cannot see any problems at all there. And your concerns about burning out the pump because of overvoltage are pure fantasies. The motor protection will trip long before that happens.

You came here for advice. Then take the advice offered. The guys around here know lots about these things.


Gunnar Englund

http://www.gke.org

 

[jraef]

Just to play devil's advocate here, it could very well be a remote water collection site such as a well or flume on a mountain stream, where the primary power source is intermittant at best. I have worked on such sites at group campgrounds where they collect water from a stream and pump it into a holding tank for showers, cooking etc. Power lines go down quite frequently because of wind and tree branches, but if the site is unattended you don't find out until someone arrives to prepare for a camp session and there is no water. Back woods utilities sometimes take days to respond and fix the problems. Engine driven generators may be prohibited in high fire danger areas as well, or it might be highly impractical to haul fuel to the site.

slothman, there are plenty of solar powered water pumps on the market, and 370W is not too big to do even at 12V. The trend in that industry is to use DC motors because of the better overall efficiency compared to storing DC and converting to AC. It's then real simple to run a 12 or 24VDC motor from an AC power source, that technology is much more simplistic and rugged by comparison. Do a google search on solar powered pumps.

Eng-Tips: Help for your job, not for your homework Read faq731-376

 

[itsmoked]

The usual is:
1) a tank
2) day only solar
3) DC pump down hole
4) Tracking solar to maximize pumping.

This recipe maximizes pumped water for the dollar.
No batteries that waste a lot of precious energy in charging and die in a few years.

Example:

http://www.poweriseverything.com/product/dankoff-sunrise.html

Keith Cress
Flamin Systems, Inc.- <

http://www.flaminsystems.com>

 

[mkinnes]

"I am not concerned about the amps since I will connect in parallel the number required."



I hope your fire insurance is up to date

 

[waross]

Hi slothman
For comparison, if you're in the US or Canada, go down to the local battery supply house and ask to see an 8D battery. Try to pick it up. Try to pick up two or three 8D batteries.
Go over to Lowes Hardware and ask to see a 3Kw genset. Pick it up with one hand.
Now go over to your favorite solar supply store and ask to see enough solar cells to charge a couple of 8D batteries in a day or so. Try to pick them up. Go back and pick up the 3 Kw gen-set with the other hand.
On the other hand I was involved with the installation of a battery bank for a UPS in a nuclear plant. Each cell weighed 235 lbs. There were several hundred of them. The normal duty cycle was a few seconds until the standby diesel generators came on-line, but there was a reserve in case of a generator failure concurrent with a failure of the normal supply. Yes, you can probably do anything with batteries that you want to.
Respectfully