Sump pump battery backup - AGM or Lithium?

[couch67]

Hello,

Getting close to sump pump season around here. Although with the amount of snow we've got, it might be a shorter season than usual.

Checking on the backup battery and acid level (level ok) , I noticed its been a while since its been replaced - mfg date 2011. I recall testing last year during peak pump season, and the backup pump ran only for about 45 minutes straight before the low voltage cut it out. I recall when new, I got about 4-5 hours with the pump running intermittently and keeping up with water level, and probably had more to go but I stopped the test early. So definitely time for a replacement.

Looking at lithium batteries as a potential replacement. Seems like a good application for them, as they can be depleted much closer to 0? Still need to research more, as I'm still not 100% sure about fire safety. Any comments from the GJ masses are welcome.

 

[PCustoms]

Agm.

Why waist the money on benefits of lithium for such a basic application?

And I don't think you can deplete a lithium to 0%. You're probably thinking of the power curve

 

[BillK]

Call me old fashioned but for a critical application like that I would stick with a traditional lead acid battery like the one you have. I fly radio control planes and have seen how a Lithium battery can just decide to go bad for no reason at all with no warning. Traditional lead acid batterys rarely just fail like that. Dont have any experience with AGM.

 

[dogdog]

You got money ??? Go with lithium… they are a bit cheaper now but still expensive.

heck I wouldn’t even go AGM but just a very large wet cell, that you can add distill water to top it off once a year. And exercise it once a year. Just get a good charger maintainer.

if you go Agm or lithium make sure your charger maintainer is compatible.

 

[My Old Tools]

I just put two 100ah LifePo4 batteries in the boat for the trolling motor. They are perfect for deep cycle applications and for situations where they sit a lot. They don't lose charge on the shelf very fast. You can charge LifePo4 on the AGM setting on your charger. I ordered mine from Walmart online. They will let you return to the store instead of shipping them back if you aren't happy. Mine were no more than a good deep cycle wet battery, about $135 each, no shipping charge.

 

[PCustoms]

I just put two 100ah LifePo4 batteries in the boat for the trolling motor. They are perfect for deep cycle applications and for situations where they sit a lot. They don't lose charge on the shelf very fast. You can charge LifePo4 on the AGM setting on your charger. I ordered mine from Walmart online. They will let you return to the store instead of shipping them back if you aren't happy. Mine were no more than a good deep cycle wet battery, about $135 each, no shipping charge.

That's dirt cheap for a lithium....

My 100ah AGM was $212 in 2022, best ah/cost combination I could find at the time.

 

[My Old Tools]

That's dirt cheap for a lithium....

My 100ah AGM was $212 in 2022, best ah/cost combination I could find at the time.

Dropping all the time.

 

[PCustoms]

Dropping all the time.

Still seems cheap.

Link?

 

[InsanePyro]

https://www.batteriesplus.com/productdetails/battery/marine-and-boat/deep-cycle/sli31dtmagmdc

Thats what I'd use personally

 

[Monza Harry]

For batteries I'm still a little old fashioned [HUGE surprise I know]. For that application I'd go like @InsanePyro listed above or bigger! I would add a (small) solar charger (secondary) and potentially solar/wind back up on top of that. A properly sized on- line electric trickle charger/maintainer is a must as primary protection. Harry

 

[theoldwizard1]

I just put two 100ah LifePo4 batteries in the boat for the trolling motor. They are perfect for deep cycle applications and for situations where they sit a lot. They don't lose charge on the shelf very fast. You can charge LifePo4 on the AGM setting on your charger.

I am not saying you can't, but you will never get to a full 100% charged.

I ordered mine from Walmart online. They will let you return to the store instead of shipping them back if you aren't happy. Mine were no more than a good deep cycle wet battery, about $135 each, no shipping charge.

As stated, the prices are dropping all of the time.

Don't be afraid of unknown brands. Check out Will Prowse channel on YouTube.

 

[75gmck25]

Also take a look at the feasibility of using one of the water-powered sump pumps that will operate as long as you still have water supply pressure. They are connected into your house municipal water line, and use water pressure to run the pump. They do not rely on POCO electricity.

I do not have one and have minimal knowledge of them, but this link seems to have some good information. https://www.watercommander.com/articles/water-powered-backup-sump-pump-ultimate-guide

 

[My Old Tools]

I guess I got an intro deal. They are at $179 now, and AGM is $169. As to getting a full charge, I don't need to. Even at a partial charge I'll get more useable power than a wet battery because the LifeP04 batteries will run full voltage until just about depleted. However, I'm not sure you are correct. My Minn Kota MK 18PC charger shows a charge voltage for AGM to be 14.4v until full, then a float at 13.5v. That appears to be in the sweet spot for LifePO4.

 

[PCustoms]

I guess I got an intro deal. They are at $179 now, and AGM is $169. As to getting a full charge, I don't need to. Even at a partial charge I'll get more useable power than a wet battery because the LifeP04 batteries will run full voltage until just about depleted. However, I'm not sure you are correct. My Minn Kota MK 18PC charger shows a charge voltage for AGM to be 14.4v until full, then a float at 13.5v. That appears to be in the sweet spot for LifePO4.

Not sure who said get a full charge.

I mentioned you can't typically fully discharge lithium. Not sure if the lifePO4 are different

 

[couch67]

Thanks for all the replies. Man I wish batteries were that cheap here in Canada. AGMs start in the 300's, and any lithium ion battery is going to be 4-$500. I will probably take the advice of sticking to the larger wet cell, as that has worked for me in the past. My old battery was a class 31 'deep cycle' marine, so I might just get the same one.

@75gmck25 thanks for the tip on the water powered pump. I'm on a well so it wont work for me, but it's a great backup for somone on municipal water...

 

[GrayFlattop]

I've gone with deep cycle marine batteries - both wet and AGM over the years. Wet is easier to maintain (assuming that you do maintain them). If you are concerned over run-time, wire two batteries in parallel. Most of the marine batteries are dual-post, making the parallel configuration a piece of cake.

I would not want to use large Lithium Ion batteries inside of the house.

 

[dcg9381]

I mentioned you can't typically fully discharge lithium. Not sure if the lifePO4 are different

You cannot. Well, you should not. Many modern lithium batteries self-protect with an internal management system.
The existing "low voltage" disconnect may not be right for lithium.

Difference is lithium will have enough amps to do the job at 20% remaining capacity.

In my experience lithium will give you better total lifetime.

Lithium will likely require a different charger and low voltage protection setup, so factor that in.

I would not want to use large Lithium Ion batteries inside of the house.

Use LiFE04. They don't do what you're worried about.

 

[dogdog]

if you are going to parallel the Lithium batteries... other than the right charger / maintainer, they advise you to get the same brand and capacity and not Mix and match.