Battery question, flooded vs LiFePO4 for well pump use.

[dieselrealtor]

I am trying to see if it is feasible to have a battery/inverter backup for my 230v well pump.

According to the pump mfg it draws 230v at 6a max, startup draw 630% max so rounded up to 8700 watts max for startup.

The LiFePO4 I am looking at are 100ah batteries with a 1280w max discharge rate, which would require 7 batteries to not exceed the max discharge rate. 7+ batteries are well out of my budget for storage.

Looking quickly at specs for a 27 series flooded deep cycle battery on Menards site shows 680cca 884mca. Am I understanding this correctly to be the max rate of discharge? If so 1 battery equates to 8160w cca & 10608w mca.

This doesn't seem right to me so I am hoping someone knowledgable can clear this up.

If this is correct, 2 of the 31 series batteries should be sufficient for occasional well pump use on battery/inverter?

Thanks in advance.

 

[gassprint1]

220 is not very optimal when it comes to inverters or battery. You figure your workung 2 110v lines at once, start up is more but balanced out after running. 110 is going to be more practical. Check your pump motor for the 110v hookup. I'd suggest a small generator to operate the water pump and furnace unless you have a wood burner, then you can leave it at 220v.

 

[indyjohn]

I would really like to help you on this topic, however the entirety of my experience is in 120v.

That being said, I cannot say enough good things about the LiFePO4 battery technology. I did a bunch of research on a well installation based on a battery driven 2200w inverter @ 120v and arrived at this combination:

Grundfos 10SQ05-160-115V, 10GPM, 1/2HP, 115V, 2 Wire, 96160167, 3" Stainless Steel Submersible Well Pumps

3-inch submersible pump for all residential groundwater needs. Several built-in protection features and soft start to reduce stress on the pump and electrical service.

www.aquascience.net

AIMS LiFePO4 12V 200Ah Lithium Battery with Bluetooth

Provide off-grid systems and powersports vehicles with reliable backup power by using this lithium battery with Bluetooth monitoring from The Inverter Store.

theinverterstore.com

I have 2 of these batteries tied together in parallel and they deal with the pump draw with no problems. With the overall discharge/recharge characteristics being superior to the deep cycle technology and their average 4,000 +/- charge cycle life, the LiFePO4 batteries are really the way to go. The pricing on them gets better all the time, so maybe they will come into your range sooner than later.

 

[dieselrealtor]

Thanks for the replies, from what I am gathering the flooded lead acid batteries are able to handle a much higher amperage draw, (what I will call a surge draw) than the lithium.

A generator is a consideration but really looking for something that won't require fuel if needed longer term.

The pump I have is a Grundfos 230v, planning to sell this place so not really looking to put money/work into a different pump.

 

[russc2542]

(Based on following a bunch of solar power FB groups and reading their debates)
(48v being the general standard for consumer-safe "low" voltage.)

The limit for most LI battery types is actually the battery management system (BMS): 100a is pretty common/standard. I'm guessing the one you're looking at is 12v? 12v * 100a is 1200w (add a little since that's "nominal" voltage, actual operating voltage is higher just like FLA 12v is actually 12.6-12.8).

100a BMS at 48v will yield 4800w (+) per battery and be more efficient in the inverter (less energy lost to heat) not to mention using much smaller cables. You're now looking for 2 batteries.

FLA starting batteries may be much cheaper to accommodate the surge but have much lower overall capacity partially because you can discharge a LI battery 80% without problems but FLA deep cycle need to be less than 50% discharged. IE you can get (safely, reliably, long term) 80ah out of a 100ah LI battery but only 40-50 out of a 100ah FLA. You haven't mentioned the actual AH capacity of the FLA batteries you're looking at. Generally, as CCA goes up, AH goes down. Deep cycles are physically made different than starting batteries.

Also, 220 and 230 equipment nowadays actually runs on 240v That bumps the startup to 9072w... convert that to 12v and you have 750a on startup and (1440w) 120a running (plus safety and inefficiency margin). biiiig cables. bump up to 48v and you have higher efficiency in the inverter and you're looking at 190a startup and 30a running.