Worth Buying Used AGM Batteries?

[Cali Carlos]

So I just bought 8 of these 4.0 batteries and was just curious if it was worth it or not. $50 a piece.

https://www.alpha.com/products/equipment/outside-plant-power/item/alphacell-hp

They are nearly 5 years old but were used strictly for emergency backup for communication systems so they've hardly been cycled and were kept on float. When I found them they were sitting right at 13v which seems to be normal for these batteries and a digital load tester says they test between 800 and 1000 cca. I'm waiting on my gs6 but my system will strictly be for emergency backup as well and I dont really see it drawing more than 4000 watts. From my understanding AGM batteries can last over 10 years if not really cycled. Did I just waste $400 or should I go buy more for that price? 

[NotMario]

I'm quite familiar with the use case. Cell towers, for instance. They are meticulously maintained, however, i do know that they go bad even without cycling, eventually. I hear about banks not performing to spec all the time -- but when you have 80 banks, that tends to happen.

Essentially you've bought a bank with a max capacity of 11kWh. You don't want to cycle that past 50% if it can be avoided, so for regular use, it's less than 5kWh.
For $400, that's a pretty good price, assuming you really get that performance. The cost per cycled wH will still be higher than LI, but since you're using this for emergencies, that doesn't really come into play. Having said that, most people start out that way -- then they inevitably go off-grid.

For the off-grid use case, there is almost no excuse to use LA batts anymore. Save up to buy LI - you'll end up spending far less in the long run.

So TLDR, i'd say you got a decent deal for your use case. Lots of variables for their condition, so hopefully that will work out.

Edited October 29, 2022 by NotMario

[Cali Carlos]

27 minutes ago, NotMario said:

The cost per cycled wH will still be higher than LI, but since you're using this for emergencies, that doesn't really come into play.

My thoughts exactly. They'll die due to calendar life before they die from cycle life and even LI has a calender life.

[Sid Genetry Solar]

Assuming they still have full capacity, that's a great price for energy storage.  At ~114Ah each rated, that gives you ~11kwh of batteries for $400, or a cost of $36/kwh.  I thought I did real good with LiFePo4 at ~$100/kwh (but to be honest, those Tenergy 32650-cell LiFePo4s now at at least 5 years old, show absolutely no signs of degredation nor have they needed any maintenance). 

Most commercially available LiFePo4 setups are in the $300-600/kwh range, making them quite pricey.  So $36/kwh is real cheap...assuming they have the full capacity.

However, just because they're kept at float doesn't necessarily mean they're in great condition.  I'm not the best lead-acid expert--or even fit to be called a lead-acid expert.  What I know is that a set of 8 Datasafe 12HX505 batteries, never deeply cycled to my knowledge (though that doesn't mean they couldn't have been cycled a few times) ended up after a couple of years with only about 30Ah of capacity.  Sure, I am aware they were gassing a bit when connected to a solar system for a couple years (TS-MPPT-60 settings I guess!), but whatever happened, their capacity was basically nothing after about 5 years.

[NotMario]

6 minutes ago, Sid Genetry Solar said:

I thought I did real good with LiFePo4 at ~$100/kwh

That is quite the deal. But i guess that's what you can manage with a 32650 wall.

My configuration was about 240$/kwh. The biggest issue was getting the damn things shipped here, being a hazmat item.
So far i have been extremely pleased with the performance, given the pricing and origin. They have lived up to their specs and no signs of degradation yet.

[Cali Carlos]

1 hour ago, Sid Genetry Solar said:

What I know is that a set of 8 Datasafe 12HX505 batteries, never deeply cycled to my knowledge (though that doesn't mean they couldn't have been cycled a few times) ended up after a couple of years with only about 30Ah of capacity.

Ya there's definitely a risk with used batteries, especially when it comes to lead acid. Only time will tell with my batteries.