Do 8 year old batteries need replacing?

[wibbleypants]

Hello all.
I have a bank of 24 Hoppecke 910ah 2v batteries. As soon as they start to discharge, the voltage drops to 45. A few kW of load will soon drag that down to 43 and then the inverter shuts down (Victron).
I just went up into the loft to check electrolyte levels and see that about half of the cells have electrolyte resembling soup (midday sun) and most of the rest are not quite so soupy. However, one of the cells' electrolyte looks completely clear.
Should I just bite the bullet and bin the lot? Or replace the non-fizzy cell?
Let's see if I can embed photos of two cells here:

 

[Mattb4]

I would guess that you should recycle them. I do wonder about where you keep them and if they are subjected to a high amount of environmental heat. The soupy electrolyte in particular sounds like the batteries are boiling from high rate of charge in a hot room. That or you did not use good quality distilled water to keep them topped up. The clear electrolyte cell could be checked to see if normal voltages are present. It could be OK or so dead that no internal activity is happening to stir the electrolyte.

 

[wibbleypants]

They are in the loft. Currently at 24ºC. I'm using all Victron kit (mppts) with the recommended voltages. I'm thinking of replacing the la with lithium (6 x 3.5kWh). Although the capacity will be less, at least it will be usable. What upsets me is that everyone says the la batteries should last 20+ years. Eight seems like a very short life, considering the investment.

 

[Mattb4]

It is a rare situation that FLA will last 20+ years. Maintenance, environment, initial quality and usage all play a role.

 

[OzSolar]

10 yrs or less is pretty common. I've dabbled in off grid battery/solar projects for 30+ years. I only had a few packs make to 15+. My personal pack is 23 years and still in good shape but I consider that a total outlier in my experience.

You might be able resurrect them with lots of equalizing or you may not. Step one would be to use a high quality hydrometer and make sure you're properly charging them. Find the specs for those batteries but I bet you need to be taking them to 60+ volts on a regular basis.

 

[wibbleypants]

10 yrs or less is pretty common. I've dabbled in off grid battery/solar projects for 30+ years. I only had a few packs make to 15+. My personal pack is 23 years and still in good shape but I consider that a total outlier in my experience.

You might be able resurrect them with lots of equalizing or you may not. Step one would be to use a high quality hydrometer and make sure you're properly charging them. Find the specs for those batteries but I bet you need to be taking them to 60+ volts on a regular basis.

Yes, I do boil them every now and again. The charging voltages are as per the Victron standards. I recently dropped the voltage by one volt as they needed topping up every 2 weeks. They've been noisy since they were new.

 

[OzSolar]

Yes, I do boil them every now and again. The charging voltages are as per the Victron standards. I recently dropped the voltage by one volt as they needed topping up every 2 weeks. They've been noisy since they were new.

That means almost nothing. Specific gravity is what you really to be watching.

 

[wibbleypants]

That means almost nothing. Specific gravity is what you really to be watching.

A couple of years ago, the electrolyte density dropped quite a bit on one cell and the hoppecke guy said to boil the batteries a few times. This did the trick in the short term. The density was pretty even across all 24 cells. Since the pandemic, the hoppecke service no longer exists, hence my coming here. We are 440 metres above sea level and the av temp is quite high, which seems to confuse the issue. Or maybe that's a red herring.

 

[Zwy]

A couple of years ago, the electrolyte density dropped quite a bit on one cell and the hoppecke guy said to boil the batteries a few times. This did the trick in the short term. The density was pretty even across all 24 cells. Since the pandemic, the hoppecke service no longer exists, hence my coming here. We are 440 metres above sea level and the av temp is quite high, which seems to confuse the issue. Or maybe that's a red herring.

While EQ will remove soft sulfation, it will not remove hard sulfation. Most hard sulfation ends up at the bottom of the battery when it separates from the plate.

I've written quite a bit about lead acid used on solar systems. This is one example: https://diysolarforum.com/threads/c...o-one-battery-bank-off-grid.40477/post-756598

And this one: https://diysolarforum.com/threads/flooded-lead-acid-revitalization.61730/post-770590

Using lead acid can work, however it should be 2 banks where one bank is receiving absorption to full charge without any loads and the other being used to power loads. Once absorption is done on the first bank, use it for loads and charge the other bank. If done correctly, there are many cases where lead acid batteries lasted over 20 years. This does require constant attention/monitoring to achieve however.

Moving to LFP, it actually likes running between 20% to 90% SOC. No mess, no corrosion, accepts high bulk charge rates, doesn't need absorption, has more usable capacity, no adding water, no EQ, doesn't require constant attention/monitoring, voltage sag less than lead acid,no need for venting. Many more items where LFP is superior to lead acid for solar systems.