Troubles powering a water pump of a battery/inverter

System · January 2012

For the past month i have a been slowly trying to make a successful solution to power my water pump from an alternate source (solar and/or wind + battery + inverter).
Its a standard 240v 3.8a pump that has been giving me lots of problems.

Battery: 100ah, gel, deep cycle
Solar panel: 120w 12v dc
Inverter: Pure Sine Wave 3000W/6000W Max 12V-240V Power Inverter
Water pump: HP65-06T
http://www.davey.com.au/site/DefaultSite/filesystem/documents/datasheets/D985-1%20Torrium%20on%20HP.pdf

My system so far is a solar panel connected to its regulator which charges the battery (100ah deep cycle) and then to the 3000w pure sine wave inverter (originally using 1200w pure sine wave inverter but did not seem to be sufficient). With this system that i presumed should be more than suitable the pump does not work properly, when i connect the battery to the inverter it continues to perform its start up repeatedly and does not stop until i turn off the inverter.
When the pump is powered by mains it performs its start up and then goes into standby until it is used (a tap is opened).
With the inverter it performs the start up and then goes into standby but then repeats the process every 2-3 seconds.

One thing i have noticed when the pump is connected to the inverter is that the battery's voltage drops each time it starts up and each time it goes back into standby it almost reaches its original value.
eg: battery starts at 13.4v
on start up: 12.6v
on standby: 13.2v

each time it repeats this process the voltage lowers (that's why i disconnect it after a while)

any help with this would be greatly appreciated (running out of ideas).
My only solution so far is to buy another 100ah battery and connect it in parallel with the original battery to try and reduce the voltage drop.

westbranch · January 2012

Re: Troubles powering a water pump of a battery/inverter

I am not sure after reading about this interesting 'new' pump what the problem is.
As far as I know they are not available here, so the rest is a guess.
Read the link and the best I can deduce is that you have not reached max pressure yet.
Maybe it is set too high..."Torrium® measures the pump shut off head each time the pump stops, and sets the cut-in pressure at 80% of shut-off head"
What is it & how is it set?

HTH

petertearai · January 2012

Re: Troubles powering a water pump of a battery/inverter

Looks to me your battery is not big enough for the big start-up currents that motors can have. Bigger battery will help, but you will also need to increase your solar.
What make and brand inverter? What size cables from your inverter to battery? and length.

westbranch · January 2012

Re: Troubles powering a water pump of a battery/inverter

Right, based on what Peter noted, running, it pulls 900W and at 12 V that is ~70 A, out of a 100 Ah battery. you are really abusing that small battery. Don't know what they really mean by 'locked rotor' but I have to assume they mean a 'stuck/jammed' rotor and it will pull 12A or 2.8 Kw @ 12 V =~ 240A. That battery can not support that load.

Agree that you should have more battery and solar to make this work.

icarus · January 2012

Re: Troubles powering a water pump of a battery/inverter

3 amps/240v=720 watts. That is ~60 amps from 12 vdc plus inveerter loses, add in starting current and it might be 180 amps or more. Bottom line, your battery is too small by a lot! Remember that strong currents are much higher than running currents. The large starting current sends the invert to LVD, probably dropping the apparent battery voltage way below 10 vdc. You are going to have to consider more battery, more PV and or a smaller pump.

Tony

System2 · January 2012

Re: Troubles powering a water pump of a battery/inverter

Hey, Thank you for your great inputs and time. Makes me feel quit stupid that i couldn't see the problem right before me.
I seem to have been calculating things a tad wrong

Thank you heaps for your help and i shall go over this a bit more to see whether i should bother spending so much extra money on my little project.
(i thought this was going to be such a simple thing to do)

and about the increase in power input (the solar panel) i had originally a 300w wind turbine connected but it did not seem to be charging the battery, i presume it had a dead regulator.
if someone knows where to order a 3 phase ac regulator for a descent price that would also be quiet helpful.

mikeo · January 2012

Re: Troubles powering a water pump of a battery/inverter

Don't know what they really mean by 'locked rotor' but I have to assume they mean a 'stuck/jammed' rotor

Locked rotor amps is the starting current when the rotor is starting from a dead stop. The current tapers off quickly as the motor comes up to its operating speed. If powering with battery and inverter, the locked rotor amps defines the size of the inverter surge needed to start the motor. The battery also has to be rated to handle the surge plus the run time of the motor between charging.

mike95490 · January 2012

Re: Troubles powering a water pump of a battery/inverter

For this large load, you should be looking at 24V system, at least. build it out of 200ah, 6V golf cart batteries, they should be cheap. if you can't get golf cart batteries, consider going o 48V, with 12v batteries. That will reduce the current demand more, and cut losses. (17amps @ 48v vs 70a @ 12V)

And that pump may need a pure sine, to be even happier. With mod-sine, it will draw ~ 20% more power.

petertearai · January 2012

Re: Troubles powering a water pump of a battery/inverter

Could you achieve your desired outcome with a 12 volt pump?. I run a sureflow 12 volt pump to header tank about 10 m lift. Has run for 5 years now without a hitch.

Troubles powering a water pump of a battery/inverter

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