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Lead acid... it's dead isn't it?

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paulca:
Again, lead acid batteries.  I hate them.

100Ah Marine battery on the solar panel, just turning 2 years old.  It's not being loaded at all over winter as their is barely enough sun to run the charge controller!

Well, I was leaving it until it started to fully charge again.  It has done that now, 3 days in a row.  Even getting to run for over an hour in float 13.6V.   Suggesting it's fully charged.

However running just the charge controller (<100mA) over night the battery fell to 12.35V which doesn't sound good.

Running the garage lights off the battery last night pulled the voltage down to 12.11V.  That's only a 1.5A load.  I expect a 2-3 Amp load will drop it below 12V.

I need a new one, again, don't I?

Is there a chance it will get better now the temperature is rising again?  It's suffered 2-5*C for the past month.

They aren't cheap to replace every 2 years, but Lithium options are still 5 times the price, maybe less taking the gamble on LiFePO4 100Ah cells from AliExpress - who are reportedly mixing second hand industrial cells into orders.

tszaboo:
13.6 is not fully charged, 14.4V would be for regular lead acid.
Sudden drop of voltage is expected for these, after the charging is done.
If you dont want to rip out all the electronics, just try to replace the battery with Enersys Cyclon batteries. They are the duck's guts when it comes to lead acid batteries. Not cheap, but it might be cheaper than buying a new battery every two year or replacing the entire electronics. Or blowing up your property with some junk grade batteries.

CJay:
What's the alternative though, as you say Lithium ones are 5 times the price, LiFePo are more expensive and a gamble unless you pay top price from a reputable supplier, so calculate the lifespan of the alternatives, work out the cost per year of each and see where the numbers lead you.

I've a feeling you may be surprised at how well lead acids fare in the comparison.

Plus, a decent brand/quality lead acid should last longer than two years if it's specified, charged, discharged and installed/stored correctly.

Personally I'd consider getting friendly with a UPS engineer, one of the guys who works on building size installs where batteries are made up of hundreds of 2V cells and have capacities measured in the hundreds of AH per cell, for instance we recently disposed of 24 of these during a telephone system renewal, I don't think they'd ever been used in anger:[attach=1]

CJay:

--- Quote from: NANDBlog on February 24, 2021, 10:51:49 am ---13.6 is not fully charged, 14.4V would be for regular lead acid.
Sudden drop of voltage is expected for these, after the charging is done.
If you dont want to rip out all the electronics, just try to replace the battery with Enersys Cyclon batteries. They are the duck's guts when it comes to lead acid batteries. Not cheap, but it might be cheaper than buying a new battery every two year or replacing the entire electronics. Or blowing up your property with some junk grade batteries.

--- End quote ---

Cyclons are the balls, absolutely excellent, years ago I made myself a booster pack from a pile of junked Cyclon cells out of DEC/Compaq/HP SAN cache battery packs that were replaced on scheduled maintenance, it was a sad day when they moved to LiIon and my supply dried up.

Renate:
I've run on solar panels and batteries for years now.
It's been a learning curve.

Long term insufficient charging will kill your batteries.
They need to see 14.4 V for a few hours, then 13.8 V for more hours.
You have to look at how much current is going into them.

You're running a light load so maybe LiFePO4 would be overkill (or over-budget).
The one thing that LiFePO4 do well on solar is that they can absorb any electrons you want to offer them.
A lead acid hits 14.4 V and it says, "I'm full" and starts slowing down.
You have to coax if for hours, "Aw, wouldn't you like another 20 Ampere-hours for dessert?"
This difference is significant if you only have a few hours at the end of a (solar) day to recharge a battery.
A lead acid takes its time and won't get the job done, a LiFePO4 will greedily suck down the electrons.

Current setup: 2 x 300 W solar, 2 x 6 V, 224 AH GC2 ("golf cart") AGM batteries
Next battery: 4 x 3.2 V, 280 AH prismatic LiFePO4 battery cells.

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