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Flooded Lead Acid deep cycle batteries coming out of storage

Justkeepitsimple

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Joined
Mar 12, 2024
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47
Location
Southwest USA
Hello everyone. I have (four) 12 Volt 270AH Group 4D deep cycle lead acid batteries.

They’re manufactured by EastPenn (Deka) for NAPA auto parts

NAPA part # BAT 8274

East Penn part # 904D

https://www.napaonline.com/en/p/BAT8274
DFAFED42-CF64-4570-AD7B-4F17C654DB1D.jpeg

I bought them back in November in preparation for the final assembly of our off grid solar system. I was able to stack points rewards that were about to expire, some old bulging trash batteries for core credit, and a holiday sale to get a good price and seized the opportunity even though I knew the final assembly of the project would be some months away.
They’ve been stored in a cool dry place out of elements and direct sunlight. But we did have ambient temps +90 fahrenheight for a few months this summer.
When I bought them they all had a resting charge of 12.63- 12.65V (98-100% SOC). I have never charged or discharged them.

Currently they have a resting charge of 12.5 - 12.53V (88-90% SOC).

My question is what is the best way to treat them coming out of storage before final installation in the solar system? I’ve read a lot of the articles on battery university and mined the archived posts here.
This is some information on Lead Acid batteries I’ve gathered:

-For prolonged storage conditions it’s best to remove the electrolyte while fully charged (😬 didn’t do that unfortunately). Best to store dry because the sulfuric acid electrolyte stratifies. You get a very rich layer of acid toward the bottom of the plates and higher % concentration of purer H20 higher up on the plates which is not ideal when you go to recharge.

-Flooded Lead acid batteries self discharge over time; this rate of self discharge is exacerbated by temperature extremes and electrolyte stratification.
-Lead Acid batteries need a controlled four stage charge cycle (Bulk, Absorption, Float, occasional equalization about every 30 days) To maximize cycle life and maintain maximum capacity.

-Flooded lead acid batteries ideal charge rate (for Bulk and Absorption stages) is 0.1 C of their total rated current. A good battery charger/ solar charge controller will taper back significantly and progressively to top off the final 10-15% at a lower C rate (0.05 to 0.01C) until reaching 100% SOC and holding float voltage.

-For battery life size system for a minimum 10% depth of depletion to a maximum 50% DOD when sizing overnight load requirements.

The design philosophy I implemented when designing they system was essentially to power our chest freezer and devices <500w continuous daytime only. Taper back to essential loads (lighting, Starlink router, and device chargers <300w conservatively, for about 4 hours after sunset. Inverter shut down at bedtime. According to my calculations this will keep our overnight consumption to less than 10% DOD on the battery bank. I really want to maximize the longevity and utility of our battery bank.

System is 12 volt

-1000 watts of solar panels feeding solar charge controller

-SCC Is Morning star Tri star MPPT 60AMP (800W max output to battery bank @12 volt)

-Battery bank is the (4) 12 V 270aH flooded lead acid batteries

-Inverter is Morningstar SureSine 12V 700W inverter

-Cloudy day/ overnight top off battery charger is 12 Volt 55AMP IOTA with 4 stage charging algorithm

I am thinking to hook up two of the four batteries in parallel at a time (540 Ah) and give them a full charge cycle from the IOTA 12V 55AMP battery charger before hooking them up together (~0.101 C rate) on the SCC bus bar to give them a full capacity start. Once the whole bank is fully charged then the 60AMP solar charge controller should give them a 0.05C rate which should be enough to keep them charged up after nighttime 10% DOD and run daytime loads.

I can’t emphasize enough that I designed and plan to utilize the solar system/ battery bank to not cycle down more than 10-15% DOD at a time. From what information I’ve gathered that will get me the maximum cycle to capacity to longevity utility out of it.

I’m pretty sure I should fully charge the batteries before I hook them up on their maiden journey in the completed system?

Should I attempt to “stir” the electrolyte before I recharge the batteries?

Should I run an equalization cycle on them since they’ve been sitting for so long?

Obviously make sure they’re all topped off with distilled water.

Long post. Thanks for reading and input- knowledge building. I started with essentially zero solar knowledge 9 months ago and thanks to the lot of archived posts on this forum and people answering my questions along the way. I’ve learned a lot and really want to optimize our solar system for longevity and utility.
 
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Yes, check the water level first and give them a stir. Your charging plan sounds good and once they've been fully charged they'll level out while the other set is charging up. Once they've been fully charged and the water topped up an equalization wouldn't hurt at all.

It's a long process but it'll start you out at the best place.
 
Congrats on getting to where you are!

Unfortunately, any battery that has a CCA rating is not a true deep cycle battery. These marine batteries will be fine given the parameters you've listed plus you've got them so you might as well use them!

One of the biggest favors you can do for yourself is to install something like the Victron Smart Shunt. Preferably an actual Victron Smart Shunt.

I bought them back in November...
...12.63- 12.65V (98-100% SOC). I have never charged or discharged them....Currently they have a resting charge of 12.5 - 12.53V (88-90% SOC)
Voltage is not a good indicator of state of charge. Specific gravity is the best. Get a quality hydrometer, check each cell, note it then check them all every few months for at least the first year.

1724779843071.png

Obviously make sure they’re all topped off with distilled water.

Actually, don't ever "top them off". Topping them off now will result in electrolyte overflowing out as they become fully charged.

Just make sure the plates are covered until your are sure they are fully charged. Once you are sure they are fully charged then you add until the level indicator inside the cell filler tube.

Here's some good reading that will really help you.

 
Yes, check the water level first and give them a stir. Your charging plan sounds good and once they've been fully charged they'll level out while the other set is charging up. Once they've been fully charged and the water topped up an equalization wouldn't hurt at all.

It's a long process but it'll start you out at the best place.
Practical question: how does one give them a stir? Is there a right way? Maybe a plastic rod through the water service caps? Use turkey baster to jet-stir each cell? Obviously don’t stick anything metal in there, and I don’t think a guys is going to shake-shake a 97lb battery.
 
Thank you for that manufacturer manual. Honestly once I learned some of the fundamental electrical and solar specific background concepts, literature from quality manufacturers is some of the greatest material to learn from (after I bounce what I think I’ve learned off forum members to double check veracity of my conceptual assimilation).
Unfortunately, any battery that has a CCA rating is not a true deep cycle battery. These marine batteries will be fine given the parameters you've listed plus you've got them so you might as well use them!
Got it. I started figuring that out after I bought them and did more research. In the future with what I know now I would go with some proper L16’s. Another good reason to keep the daily DOD on them to less than 15% and immediately get them on the generator powered battery charger if they dip below 25%.
One of the biggest favors you can do for yourself is to install something like the Victron Smart Shunt. Preferably an actual Victron Smart Shunt.


Voltage is not a good indicator of state of charge. Specific gravity is the best. Get a quality hydrometer, check each cell, note it then check them all every few months for at least the first year.

View attachment 239614



Actually, don't ever "top them off". Topping them off now will result in electrolyte overflowing out as they become fully charged.

Just make sure the plates are covered until your are sure they are fully charged. Once you are sure they are fully charged then you add until the level indicator inside the cell filler tube.
Victron shunt would be nice but currently maxed out on solar budget hardware spending so for now I’ll have to do with conservative wattage calculations to meter after-insolation-hours battery consumption. I figure between that and monitoring inverter voltage input from Bluetooth app I should be able to figure a safe consumption margin. Not perfect as battery voltage should be measured at rest , and as you noted specific gravity of each cell is really the most accurate for long term tracking of overall heath. I can definitely invest in a fine tune hydrometer. I have one of the cheap “floating beads” hydrometers for testing car batteries I’ll see about getting one more like this for tracking battery health over time when I do monthly battery checkup/ maintenance:

Duly noted about electrolyte levels. Don’t want a big mess boiling out.
 
Practical question: how does one give them a stir? Is there a right way? Maybe a plastic rod through the water service caps? Use turkey baster to jet-stir each cell? Obviously don’t stick anything metal in there, and I don’t think a guys is going to shake-shake a 97lb battery.

Before I switched to LFP, I "stirred" my L-16's (100 lb each) by gently rocking them back and forth in the long dimension a few times, checking first that the electrolyte level wasn't so high as it might leak out. You can put something in the middle about a 1/2" or so to make a pivot to rock on.
 
Stir them by charging them up and letting them bubble for a while with an equalization charge.

Don't add (distilled only) water until they are fully charged, electrolyte expands as the batteries charge and will spill out if you fill them before charging. The only time to add a little water is to barely cover the plates if they are dry before you start charging, but I doubt you have that problem.

Don't overthink it, those batteries are fine, just charge them, equalize them, add water to the bottom of the split ring (you'll see the meniscus form, it'll be obvious), and put them into service.
 
Your panel size and charger size seems a bit small for the amount of AH . did you ask east Penn for a charge profile ?
I use a turkey baster style hydrometer, use that to stir up the electrolyte.
 
Sounds like you did all the necessary homework. Ironically all the legwork in the world on the research phase can't outweigh or undo months of physical neglect on lead acid, but since all of yours are still at 12.5+ id say the degradation during storage was probably very minor!

I dont think there's any 'good' method to 'de-stratify' the electrolyte other than the agitation of equalization charging. Anything else seems like a ton of physical effort for unproven results. At least, i havent seen anyone say "i took my dormant FLA and measured significant change in SG near the top of the electrolyte after gently rocking them back and forth". Based on my unscientific practical experience of mixing liquids (mostly drinks in clear/translucent cups! lol) id say it has a low chance of accomplishing much of anything with the types of movement you can provide by hand. Just my .02.
 
Your panel size and charger size seems a bit small for the amount of AH . did you ask east Penn for a charge profile ?
I use a turkey baster style hydrometer, use that to stir up the electrolyte.
Admittedly it is if I run the batteries down more than 10-15% DOD and necessitate a bulk charge stage. The current setup will only supply about 0.05C when the battery bank really needs 0.1C to do Bulk charge at a healthy rate. 0.5 C should be enough to do a healthy Apsprbtion and Float charge stages with the current setup.

I’m going to see if my daily wattage estimates and design concept works to keep the batteries above 85-90% SOC after nighttime consumption.

Will see what happens. If i am chronically using more than 20% of my battery bank capacity overnight then I will either take two batteries out of the bank (So that the current insolation can charge the bank at 0.1C), Or get a second 60AMP MPPT run in parallel to the battery bank and another 1000 watts of panels to bring the total Solar input up to 120 amps worth for Bulk stage.
 

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