off grid deep well pump

offgridnewbe

I have a 1/2 hp 115v well pump that l want to run off of battery and inverter power. I have a 3000 watt 12v inverter and a single 100ah battery that will not run the pump. I would like to know what l need to do to this setup in order to power the pump. Do l simple add more battery power ? Do l use a different inverter with higher voltage? l simply don't know. l have searched but can't find a simple wiring diagram or list of components to solve this problem. The well is for a remote cabin.

littleharbor2

A simpler solution would be to get a DC powered pump. No batteries, charge controller or inverter needed. Also you eliminate the maintenance required with batteries and controller.

offgridnewbe

Thanks but that is not practical for this application. The expense of replacing the pump would be greater than batteries and an inverter. The site is remote and very difficult to get equipment in to replace the pump. It is an existing system that has been run off a gas powered generator.

706jim

If it runs ok off a generator my guess is that the battery voltage sags when you try to run it from the inverter.

In other words you probably need more/larger battery.

One last thought: Modified sine or pure sine inverter? Modified sine will run an induction motor but they are happier with pure sine current.

offgridnewbe

Thanks. that is what I've been thinking and is close to what my research has shown. I'm just new at this and not sure about things. I already plan to get more batteries, but don't know if l should just add 12v batteries and wire them parallel or go up to a 24v or 48v inverter and wire the batteries in a series. I'm just surprised at how difficult the solution is to find. I would think this is a very common situation with battery and solar power applications becoming so common.

Horsefly

offgridnewbe said:

I have a 1/2 hp 115v well pump that l want to run off of battery and inverter power. I have a 3000 watt 12v inverter and a single 100ah battery that will not run the pump. I would like to know what l need to do to this setup in order to power the pump. Do l simple add more battery power ? Do l use a different inverter with higher voltage? l simply don't know. l have searched but can't find a simple wiring diagram or list of components to solve this problem. The well is for a remote cabin.

I also have a 1/2hp 120V well pump. You need to understand the inrush current for an induction motor is much higher than the running current. Your inverter & battery need to be able to provide this inrush current for only a fraction of a second, but most of the less-expensive inverters simply can't do it.

If I recall correctly, the inrush I measured with my cheap peak-capturing clamp meter was something around 37A. At 120V, that's well over 4000 watts. My inverter (Schneider SW4024) is rated only 3400W continuous, but is spec'd to handle up to 7000W for up to 5 seconds. It's never had a problem starting the well pump. 

I'd actually question if this can be done safely with a 12V inverter and a 100Ah battery. Assuming your inverter is 85% efficient and assuming your inverter can handle the >4000W surge, you'd be pulling something over 4000/12/0.85 = about 400A. 

offgridnewbe

Horsefly, what charger controller, battery and panel set up are you using?

littleharbor2

Horsefly said:

offgridnewbe said:

I have a 1/2 hp 115v well pump that l want to run off of battery and inverter power. I have a 3000 watt 12v inverter and a single 100ah battery that will not run the pump. I would like to know what l need to do to this setup in order to power the pump. Do l simple add more battery power ? Do l use a different inverter with higher voltage? l simply don't know. l have searched but can't find a simple wiring diagram or list of components to solve this problem. The well is for a remote cabin.

I also have a 1/2hp 120V well pump. You need to understand the inrush current for an induction motor is much higher than the running current. Your inverter & battery need to be able to provide this inrush current for only a fraction of a second, but most of the less-expensive inverters simply can't do it.

If I recall correctly, the inrush I measured with my cheap peak-capturing clamp meter was something around 37A. At 120V, that's well over 4000 watts. My inverter (Schneider SW4024) is rated only 3400W continuous, but is spec'd to handle up to 7000W for up to 5 seconds. It's never had a problem starting the well pump. 

I'd actually question if this can be done safely with a 12V inverter and a 100Ah battery. Assuming your inverter is 85% efficient and assuming your inverter can handle the >4000W surge, you'd be pulling something over 4000/12/0.85 = about 400A. 

That DC direct (battery free) well pump is sounding more like a viable solution. Thet're known to run for decades with very little maintenance.

BB.

OffGridNewbe,

If you are on a desktop computer, LittleHarbor2 has it in his signature:

• 2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.
  

If you are on your phone, the signatures do not display (you can turn on "desktop mode" (3 vertical dots in upper right of window).

-Bill

Horsefly

offgridnewbe said:

Horsefly, what charger controller, battery and panel set up are you using?

I've got a Schneider XW60-150 charge controller, and a Schneider CSW4024 inverter/charger. I've got 6 Canadian Solar 260W panels, configured in three strings of two panels. My battery is a custom built 24V 230Ah LiFePO4 battery, with a JK BMS (Battery Management System) and a thermostatically controlled heater pad under the battery cells.

jacki412

interesting information