well pump conversion

[OffGridNewbe]

I have a 1/2 hp 115v well pump that l want to convert to batteries and an inverter. I have a 3000 watt 110v inverter and a 100ah battery system that will not power the pump motor. What else do I need in the system, more batteries, a larger inverter, or both?

 

[42OhmsPA]

Likely both.
A low frequency inverter or overrated hf.
I'd start with an inrush clamp meter to determine pump draw at startup, then I'd price a grundfos pump vs new inverter.

 

[OffgridMatty]

My 1/2 hp pump works with my growatt 3000w 24v inverter. I needed two 24v lifepower4 batteries to get the voltage it wanted to start up. With a single battery it would fault with a low voltage warning at start up. It has run fine since adding the second battery. It's my biggest load in a small off grid cabin.

 

[OffGridNewbe]

My 1/2 hp pump works with my growatt 3000w 24v inverter. I needed two 24v lifepower4 batteries to get the voltage it wanted to start up. With a single battery it would fault with a low voltage warning at start up. It has run fine since adding the second battery. It's my biggest load in a small off grid cabin.

Thanks, that is more of what my research has shown. Is there any way I can build a system that uses my 12 volt inverter ? Also, what amp hour are the batteries?

 

[OffGridNewbe]

Likely both.
A low frequency inverter or overrated hf.
I'd start with an inrush clamp meter to determine pump draw at startup, then I'd price a grundfos pump vs new inverter.

Thanks, the site is remote and difficult to reach with well service trucks so a new power system is probably more practical. Is there anywhere I can get a diagram of a battery and inverter setup? Something that shows wiring and fuse or circuit breaker setups.

 

[OffgridMatty]

Mine are liFepo4 24v 5.1 KWh 200AH batteries from Signature Solar. I'm not sure about the 12v question. I'm just getting into solar as well and I only have last summer under my belt. My place is seasonal for the most part so I'm only using the system late spring to early fall.

 

[OffGridNewbe]

Mine are liFepo4 24v 5.1 KWh 200AH batteries from Signature Solar. I'm not sure about the 12v question. I'm just getting into solar as well and I only have last summer under my belt. My place is seasonal for the most part so I'm only using the system late spring to early fall.

Thanks

 

[42OhmsPA]

Thanks, the site is remote and difficult to reach with well service trucks so a new power system is probably more practical. Is there anywhere I can get a diagram of a battery and inverter setup? Something that shows wiring and fuse or circuit breaker setups.

Mine is attached. I'm not an electrician, just a guy with lots of common sense and diy mentality.

 

[12VoltInstalls]

Question:

Is there any way I can build a system that uses my 12 volt inverter

Answer:

I'd start with an inrush clamp meter to determine pump draw at startup, then I'd price a grundfos pump vs new inverter.

But I get the issue of truck access.

So this is a budget version of a low frequency inverter.

 

[OffGridNewbe]

Thanks for the suggestion, but I'm not very sure of what you are talking about since l have limited electrical knowledge and experience. I was hoping that additional batteries and maybe a different inverter would take care of it. My confusion only grows.

 

[12VoltInstalls]

was hoping that additional batteries and maybe a different inverter would take care of it

It might. But the specs of said pump determine that probability

 

[OzSolar]

I assume LiFEPO4 battery? Guessing that your battery's BMS is limiting you to 100 amps of discharge. (others jump in to correct me if needed)

100a x ~12.8 v = 1280 watts so I don't think you ever stood a chance of running that well pump.

You could try to parallel two more 100 AH batteries via a bus bar arrangement which would allow you to get 300 amps to the inverter but IMHO you should dump the 12v inverter and move onto something like this 24 Aims Inverter and at least one more battery.

Please share any details about the pump that you can. Is it a submersible or surface (jet) pump? Depth to the water?

edit to add my comments about the pump.

 

[OffGridNewbe]

Thank you, and you are close to what some other recommendations have been. It appears that adding 3 more 100ah batteries, wire them in a series to 48v, and adding a 48v inverter might be the solution. I assume the 48v setup is safe for the well pump motor?

Franklin Electric model 244504 2 wire prefix motor
670 to 960 watts
12 amp
.37kw

 

[OffGridNewbe]

Submersible pump set at 240 feet pumping into a 33 gallon pressure tank

 

[OzSolar]

Thank you, and you are close to what some other recommendations have been. It appears that adding 3 more 100ah batteries, wire them in a series to 48v, and adding a 48v inverter might be the solution. I assume the 48v setup is safe for the well pump motor?

Franklin Electric model 244504 2 wire prefix motor
670 to 960 watts
12 amp
.37kw

You won't regret stepping up to a 48v system today. If you add 3 more 12v batteries it's advised to use a battery balancer.

You may be money ahead to step up to a 48v server rack battery put 12v system the "lessons learned" shelf.

Depending on your budget just adding one just battery to get you up to 24v, getting something like that 24 Aims inverter that I suggested and replacing your current pump with the Grundfos SQ Flex may be better on paper. And you might even be able to change it yourself if the water level is 100' or less and installed on poly pipe.

It all depends on much more you think this system is going to grow and how much you want/can to spend today.

 

[AHTrimble]

I was in almost the exact same situation...120vAC 1/2hp well pump @200' that I had been using a genset on. I crunched the numbers on a 24v solar set-up...and then thankfully a buddy talked me through a DC well pump with 1000w PVs.
I now have a 1/2hp DC pump sitting in the well with 4 used 250w PVs running it. It works flawlessly and for less money and zero issues or headaches. I am so glad I went with a DC well pump set-up!

 

[OzSolar]

I was in almost the exact same situation...120vAC 1/2hp well pump @200' that I had been using a genset on. I crunched the numbers on a 24v solar set-up...and then thankfully a buddy talked me through a DC well pump with 1000w PVs.
I now have a 1/2hp DC pump sitting in the well with 4 used 250w PVs running it. It works flawlessly and for less money and zero issues or headaches. I am so glad I went with a DC well pump set-up!

I love solar water pumps! Such a thing of simplicity. Sun shines, water moves. Have enough storage to get through your needs then do it all over again the next day. What pump did you use?

 

[MichaelK]

Here's a pump chart to help guide you. Look at the specs for a 1/2 hp pump at 120V. Starting amps is 42.5A. That works out to be 5100W for the first 500 milliseconds or so.

Very doable on just a 24V system. Forget about 12V completely. You'll need a high surge-capacity low-frequency inverter for this. I have Schneider's Conext 4024, and it can surge to 7000W for 5 seconds. That will handle your pump. 48V is even better, but I don't really think you need that much power. I do however run my 1hp 240V well pump on my XW+6848 inverter. That can surge to 12,000W for 60 seconds.

I like to recommend the 2X rule to everyone. Assuming your pumps runs on 960W as you mention above, I've have double those watts, or 2000W of panels. That's what I have for my own 24V system, which has been working very well. I don't run my well-pump on it, but it does easily handle a 1.6hp air-compressor.

If you do go the 48V route, I'd have at least 3000W of panels for it. Don't buy panels retail. Shop on Craigslist, and shop for panels locally, with cash and carry pickup. I'd expect you to get panels in 1000W increments for between 260-400$.

 

[OffGridNewbe]

Here's a pump chart to help guide you. Look at the specs for a 1/2 hp pump at 120V. Starting amps is 42.5A. That works out to be 5100W for the first 500 milliseconds or so.
View attachment 122300
Very doable on just a 24V system. Forget about 12V completely. You'll need a high surge-capacity low-frequency inverter for this. I have Schneider's Conext 4024, and it can surge to 7000W for 5 seconds. That will handle your pump. 48V is even better, but I don't really think you need that much power. I do however run my 1hp 240V well pump on my XW+6848 inverter. That can surge to 12,000W for 60 seconds.

I like to recommend the 2X rule to everyone. Assuming your pumps runs on 960W as you mention above, I've have double those watts, or 2000W of panels. That's what I have for my own 24V system, which has been working very well. I don't run my well-pump on it, but it does easily handle a 1.6hp air-compressor.

If you do go the 48V route, I'd have at least 3000W of panels for it. Don't buy panels retail. Shop on Craigslist, and shop for panels locally, with cash and carry pickup. I'd expect you to get panels in 1000W increments for between 260-400$.

With the inverter you mention, how many and what type batteries do l need?

 

[MichaelK]

With the inverter you mention, how many and what type batteries do l need?

A good rule of thumb is the size of the battery should be proportional to the load applied to it, and the load applied to it should be no more than the maximal charging/discharging rate.

Suppose for example you settle on flooded lead-acid as a battery chemistry. That's what I'm using for my well-pump. Assume the maximal charging/discharging rate is 1/8th of C, with C being the 20hr battery capacity. Assume it's a 24V system using the Conext 4024 inverter.

So, that means you need a battery that is at least 8 times bigger than the amp load pulled out of it to run your pump. If your pump draws 960W while running, the amp draw out of the battery would be 960Wh/24V = 40Ah. A battery that's 8 times bigger than 40Ah would be 40A X 8 = 320Ah. A Trojan L-16 battery is typically in the 380-420Ah range, so four 350$ Trojans would fit nicely here.

Suppose instead you went with Li, with a max charge/discharge rate of 1/4th C. Then the battery size would be 40Ah X 4 = 160Ah.

It's always better to have a bit more than a bit less, so I'd recommend getting a lead-acid battery in the 400Ah range, or a LiPO4Fe battery in the 200Ah range. The bit extra covers system losses/inefficiencies.

With 2X solar capacity, you are looking at the 4024 inverter mated to a 200-400Ah battery at 24V and 1800-2000W of solar panels. You'll need a charge controller that can handle 60-80amps at 25-26V charging. I have a Midnight200V model for my system. You might also look at Epever's Tracer series, maybe the 6420AN or the 8420AN. That would allow you to wire eight 250W grid-tie panels 4S2P.