Follow up questions about well pumps and selecting a modern inverter

vinthewrench

New Member
Hi I am new to the forum. first of all i want to say thank you for all the great posts, the imformation is priceless.

I have seen a few questions about well pumps (https://diysolarforum.com/threads/need-240-volt-inverter-recommendation-for-well-pump.22770/)
but i want to re-ask it both with what is available today and a slightly different problem.

I have a 3/4 HP motor that supplies a pressure tank from my home well cistern. Filing the cistern is another 1/2 hp pump. Both are running from utility 220v. I have a backup generator that I can to manually start to run the pressure tank during power failures., but t seems like a total waste to run all the time, since it only needs to build pressure when we are using water.

what I would like to do is put together a charger, inverter, battery setup that can run the pumps during power failures. It not in a location that gets much sun, so I don't really care about solar panels in this application. I will just charge the batteries from either utility or generator. So this is more like a UPS than anything else.

I can easily wire in a relay that prevents both pumps from running at the same time giving priority to the pressure tank pump (3/4 hp). I can probably also use setup a relay to trigger when neither pump is calling to run, thereby allowing the inverter to power down and save battery when it is idle.

So my questions are:

1) I'd like a recommendation for an appropriate inverter that can provide 220v for 3/4 hp plus the surge current for the pump. It would be ideal if the inverter has a shutdown/enable input so I can save idle drain.

2) Should i go with 24v or 48v? and if so what is a good battery charger that I can use to take care of the popular LiFePO4 cells that Will has done a fantastic job describing how to put together?

The rest I can work through, an I promise I will write an article about on the forum describing how it came together.

Many thanks.

Vinnie
 

snoobler

Solar Honey Badger
Hi I am new to the forum. first of all i want to say thank you for all the great posts, the imformation is priceless.

I have seen a few questions about well pumps (https://diysolarforum.com/threads/need-240-volt-inverter-recommendation-for-well-pump.22770/)
but i want to re-ask it both with what is available today and a slightly different problem.

I have a 3/4 HP motor that supplies a pressure tank from my home well cistern. Filing the cistern is another 1/2 hp pump. Both are running from utility 220v. I have a backup generator that I can to manually start to run the pressure tank during power failures., but t seems like a total waste to run all the time, since it only needs to build pressure when we are using water.

what I would like to do is put together a charger, inverter, battery setup that can run the pumps during power failures. It not in a location that gets much sun, so I don't really care about solar panels in this application. I will just charge the batteries from either utility or generator. So this is more like a UPS than anything else.

I can easily wire in a relay that prevents both pumps from running at the same time giving priority to the pressure tank pump (3/4 hp). I can probably also use setup a relay to trigger when neither pump is calling to run, thereby allowing the inverter to power down and save battery when it is idle.

So my questions are:

1) I'd like a recommendation for an appropriate inverter that can provide 220v for 3/4 hp plus the surge current for the pump. It would be ideal if the inverter has a shutdown/enable input so I can save idle drain.

Welcome to the forum.

No one can make a sensible recommendation until you can supply the actual surge current or locked rotor amps (LRA) of your pumps. Not all pumps are created equal, and it's not uncommon for the surge to be 5X the run current. The inverter has to be sized for this surge.

2) Should i go with 24v or 48v? and if so what is a good battery charger that I can use to take care of the popular LiFePO4 cells that Will has done a fantastic job describing how to put together?

Depends on how much power you need. LFP may not be the best choice for a "standby" system and they degrade when stored fully charged. AGM are cheaper and love to sit there fully charged.
 

vinthewrench

New Member
Thank you
No one can make a sensible recommendation until you can supply the actual surge current or locked rotor amps (LRA) of your pumps. Not all pumps are created equal, and it's not uncommon for the surge to be 5X the run current. The inverter has to be sized for this surge.

YEs I understand, I am using a Goulds 10GS07412CL pump. I bet they are using the CentriPro 3 wire 4" submersible motors, best I can tell. I will try and find out what the motor LRA is speced at. Hindsight is 20/20 in this case, two years ago when I built the pump house I would have picked out a motor with a lower LRA.

Given that, lets say the unit pulls around 32 A LRA. what would you suggest for an inverter box.

AGM are cheaper and love to sit there fully charged.
thank you. that's good advice. OK so now what is a good charger for these. and is 24v the correct thing or should i go to 48v?

many thanks again.
 

snoobler

Solar Honey Badger
32A * 240V = 7680W

That's going to need a low frequency inverter with wicked surge capability.


This is an inverter/charger, so it will keep the batteries topped off and even act as a UPS in the event of an outage, i.e., if the pumps are running, and you lose power, they will continue to run. This unit has a 12-18kW surge capability for several seconds and is available in 24/48V models.

Cons:
HEAVY (but necessary good surge with large transformer, so not really a con)
Relatively low efficiency compared to higher end models, 85% vs 90-95%.
High self-consumption, i.e., it burns about 100W just being turned on with no loads on it.

Pros:
Inexpensive for the power.
Made by Sigineer, which has a good reputation and makes AIMS inverters.
Should have no problems with running both pumps at the same time, even if they try to start at the same time.
120/240V split phase output would allow for more flexibility in an outage if you need to power another 120VAC device.
 

Hedges

I See Electromagnetic Fields!
If you do an inverter based system, might as well have it provide backup to other household loads as well.
If just pushing a small amount of water from cistern occasionally, a 12V 3 gpm pump and deep cycle battery could do the job inexpensively.


I don't know the lift requirements to fill the cistern, but probably generator occasionally would take care of that.
 

vinthewrench

New Member
If you do an inverter based system, might as well have it provide backup to other household loads as well.
If just pushing a small amount of water from cistern occasionally, a 12V 3 gpm pump and deep cycle battery could do the job inexpensively.

I agree but this is in a separate structure, so while it would be useful for other things, it not worth wiring back to the other buildings.

good thought though.

funny thing is I am using that same pump to feed my garden from an above ground tank/
 

vinthewrench

New Member
That's going to need a low frequency inverter with wicked surge capability.


This is an inverter/charger, so it will keep the batteries topped off and even act as a UPS in the event of an outage, i.e., if the pumps are running, and you lose power, they will continue to run. This unit has a 12-18kW surge capability for several seconds and is available in 24/48V models.

very cool.. exactly what I was looking for. many thanks. and I guess I will get a few AGM batteries for this. Any suggestion on those ?
 

snoobler

Solar Honey Badger
very cool.. exactly what I was looking for. many thanks. and I guess I will get a few AGM batteries for this. Any suggestion on those ?

@Hedges has a brand of AGM for which he has a deep fondness, and the few times I've looked at the datasheets, they look very impressive.

Important that you size them assuming 50% usable capacity and some acceptable level of run time. If you expect only infrequent use and a cycle life of 300-500 cycles is enough, you can likely assume 80% usable capacity.
 

vinthewrench

New Member
@Hedges has a brand of AGM for which he has a deep fondness, and the few times I've looked at the datasheets, they look very impressive.

Important that you size them assuming 50% usable capacity and some acceptable level of run time. If you expect only infrequent use and a cycle life of 300-500 cycles is enough, you can likely assume 80% usable capacity.

I believe you are talking about the Sun Xtender® PVX AGM Batteries http://www.sunxtender.com/12_volt.php
yes these look pretty cool.. maybe @Hedges can suggest a source to purchase from in the US?

thank you again, you have been generous with your knowledge I hope to return the favor sometime.
 

Hedges

I See Electromagnetic Fields!
Yes, it is SunXtender.
I have a 12 year old 104 Ah bank that has only ever been periodically recharged or kept on float, and a 1 year old 405 Ah bank on my four Sunny Islands which I've cycled a small number of times.

Looks like I got my recent purchase from here. I had simply done a Google, picked best price with shipping so their location made a difference.


A proper charger with temperature compensation will be key.
The technical manual recommends a non-standard charge cycle if charged below 0.2C, so you might get something which can charge at the target rate.

Do all your buildings get fed from one grid connection? If you put in a central UPS system, it could feed those. But you'd want to run a signaling wire to disconnect unimportant loads.
 

MichaelK

Photon Sorcerer
Here is a pump data table that another poster, Mike94052, previously posted elsewhere. Looking at the table, a 3/4hp 3-wire pump has a starting surge of 31.4A at 230V. That is very close to your 32A guestimate, and is about a 7200W surge.

For my own well-pump, which as a 37-38A surge, I'm successfully powering that with a Schneider XW+6848 inverter, previously with a Trojan L-16 bank, but recently upgraded to Rolls. I power this from 8am till 4pm with a 4500W array.
 

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vinthewrench

New Member
Yes, it is SunXtender.
I have a 12 year old 104 Ah bank that has only ever been periodically recharged or kept on float, and a 1 year old 405 Ah bank on my four Sunny Islands which I've cycled a small number of times.

Looks like I got my recent purchase from here. I had simply done a Google, picked best price with shipping so their location made a difference.


OK thanks.. I'll dig into it

Do all your buildings get fed from one grid connection? If you put in a central UPS system, it could feed those. But you'd want to run a signaling wire to disconnect unimportant loads.

you would think so. but unfortunately no. this is just for the pump house and maybe some wifi devices.
 

vinthewrench

New Member
Yes, it is SunXtender.
I have a 12 year old 104 Ah bank that has only ever been periodically recharged or kept on float, and a 1 year old 405 Ah bank on my four Sunny Islands which I've cycled a small number of times.

I hunted around, it looks the the SunXtender high end batteries are many months out for shipping. I bet they are having supply line chain issues like everyone else. Can you suggest any other alternatives to the Sun Xtender PVX-2580L AGM. Some folks tried to sell me on the NorthStar BLUE+ series. what you you think of these?

thanks.
 

Hedges

I See Electromagnetic Fields!
With a quick search I find listing and can put batteries in a shopping cart, don't see "out of stock" going that far.


I don't work with batteries enough to know which are particularly good.
I think Rolls Surrette FLA is supposed to give particularly long cycle life, making it more cost effective than AGM.
But I see what you mean - this page says 26 weeks lead time.


I favor using PV panels to power things directly, and then you can get by with second hand automotive starting batteries to supply surge. Stop running pump when it would drain battery. But you say you don't get enough sun.
 

Hedges

I See Electromagnetic Fields!
One vendor of Rolls Surrette on eBay, "more than 10 available"

 

snoobler

Solar Honey Badger
Another good vendor, but I can't confirm stock:


I can attest to the awesomeness of Rolls batteries. Yes, they do require maintenance, but it's really not that big of a deal, especially since you'll be in standby most of the time vs. cycling.

I have 4X S-605 in 2S2P config. I abuse the crap out of them and do the minimum for maintenance and often hold them at 70-80% SoC for extended periods.
 

vinthewrench

New Member
Thank you @Hedges and @snoobler,

I ordered a set of Rolls Flooded 6V cells S6 L16-SC - 6 Volts, 487 Amp-hours. - I would have liked to use AGM, but they are not to be found in stock anywhere given the current supply chain failures these days,. And the monster inverter charger from Energetech came in (87 lbs of it)

I will also add in a victron smartshunt. I like those things. I'll appreciate the advice and will write a review on how it goes.

any other suggestions?
 

MichaelK

Photon Sorcerer
I ordered a set of Rolls Flooded 6V cells S6 L16-SC - 6 Volts, 487 Amp-hours. - I would have liked to use AGM, but they are not to be found in stock anywhere given the current supply chain failures these days.
When I ordered my new 4V Rolls, and my supplier told me it was 6 weeks delivery. He emailed me about a month later and told me my batteries had just come in. Made an appointment with him, and he delivered them right to the front door.

I think they were ordered directly from the Canadian factory, and it was a month getting to me.
 

Hedges

I See Electromagnetic Fields!
any other suggestions?

Fuse. With interrupt rating a least as high as the short-circuit current of the battery. You can study the documentation and figure out what that is.

Car batteries are rated 600 or 800 A cranking current at 8.5V, which works out to about 3000A at zero volts.
I've read 100 Ah AGM can put out about 4000A.
Not sure current is linear with capacity; interconnect to terminals will matter.
For lithium with 0.17 milliohm typical and 3.5 volts per cell I calculate 20,000A

I'm using class T, which can interrupt 20,000A at 125 VDC.
That would be more than sufficient for yours, or you can find other fuses perhaps 10,000 AIC if you decide your battery would put out no more than that.

Have you selected a charge controller or inverter/charger? Make sure it has a good FLA setting, preferably customizable to specs for your battery, and it uses a battery temperature sensor.
 
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