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after 2 years of dependable use my lead acids have died. can i do better ?

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roaming ram

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Jul 24, 2022
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i have three 12 volt lead acid batteries in parallel with 200 watt renogy solar panels with supplied charge controller. i have fuses on all components directly wired to batteries. they run fridge/freezer, water pump, lights, propane heater and a 2k inverter. when i first started using the system i could go 3 days without recharging batteries just testing the limitations. it stayed that way for almost 2 full years. charging the batteries with solar even through the winter when there is no usage. going into this third summer they couldnt maintain their charge. i added distilled water and still no storage of energy. i just assume they have reached their max cycles. i know i could try trickle charging them but i also would like to know if there is a better way to approach this. i do live at altitude. i camp mostly 7k to 11k feet above sea level. the cost of these lead acid batteries was maybe 150 each. this has worked well for me. so dependable that i sold my honda generator i had as backup. i am good with spending 500 again, but would rather not spend a grand or more unless i am educated enough to make a better decision. thank you for your help and i am looking forward to learning how to build a better system. 20220625_163905.jpg
 
How does your depth of discharge and number of cycles compare to published specs?

I use SunXtender AGM for grid-backup. Spec is 650 cycles to 70% DoD and 10 year float life.
My usage is rare deep cycle, float the rest of the time.
If you avoid deep cycling, mostly draw power during the day and limit night time draw to 15% or 20% DoD, should lasts a very long time.

If they died early, could be failed to get full charge and absorption, or lost water due to overcharging or charging and not topping off. Or due to over-discharge.

LiFePO4 is an alternative, can be close in capital cost these days. More tolerate of being left in various states of charge and number of cycles.
 
Hedges said:
How does your depth of discharge and number of cycles compare to published specs?

I use SunXtender AGM for grid-backup. Spec is 650 cycles to 70% DoD and 10 year float life.
My usage is rare deep cycle, float the rest of the time.
If you avoid deep cycling, mostly draw power during the day and limit night time draw to 15% or 20% DoD, should lasts a very long time.

If they died early, could be failed to get full charge and absorption, or lost water due to overcharging or charging and not topping off. Or due to over-discharge.

LiFePO4 is an alternative, can be close in capital cost these days. More tolerate of being left in various states of charge and number of cycles.
Click to expand...
my system is small and mostly simple. i do not go that in depth to record stats and check against specs. i did determine running the fridge freezer would require 3 batteries and that seemed to work out well. now i am researching 6 volt batteries which are heavier but true deep cycle. i am also very interested to see of all charge controllers are basically the same or if some are better than others. lithium at high altitude very much concerns me.
 
What voltage did your battery reach by morning? Or how long did PV take to recharge it?

I think fridge could coast through the night, much less battery needed if that load is only operated when the sun is out.

Consider these batteries for higher priced longer life AGM: http://sunxtender.com/
People talk about "silicate salt" lead-acid batteries, I think another type of gel cell. Claimed figures may be an improvement over other gel or AGM for some applications.

diysolarforum.com

Silicate Salt Batteries

Hi guys, I purchased a 22kwh battery bank from watts247 and they've been great to work with. The one thing I can't seem to find or get an answer on is a voltage to SOC chart. These are the batteries...
diysolarforum.com diysolarforum.com
 
Hedges said:
What voltage did your battery reach by morning? Or how long did PV take to recharge it?

I think fridge could coast through the night, much less battery needed if that load is only operated when the sun is out.

Consider these batteries for higher priced longer life AGM: http://sunxtender.com/
People talk about "silicate salt" lead-acid batteries, I think another type of gel cell. Claimed figures may be an improvement over other gel or AGM for some applications.

diysolarforum.com

Silicate Salt Batteries

Hi guys, I purchased a 22kwh battery bank from watts247 and they've been great to work with. The one thing I can't seem to find or get an answer on is a voltage to SOC chart. These are the batteries...
diysolarforum.com diysolarforum.com
Click to expand...
my fridge runs 24/7 and the propane forced air heater runs most of the night as well because i camp where it still gets cold at night.
 
Any reason you can't switch off refrigerator during the night? Maybe have a second thermostat to re-enable if freezer compartment gets too high, otherwise let ice maintain temperature? H2O (and optional NaCl) are much cheaper than Pb or Li.

LiFePO4 of course is not supposed to be charged below freezing, would be damaged.
One forum member said he found it accepts very little current at normal voltage when cold.
Lot of mass, won't change rapidly in temperature, and insulation would moderate changes. LiFePO4 doesn't dissipate much power, so limited self heating.
You would want a BMS that prevents charging below 32F, and some have heater, divert charge current to heating when cold.

If you need more than 500 deep cycles, LiFePO4 may be the more economical approach and worth taking care of use in cold.
I selected AGM for zero maintenance in backup application. FLA would have been cheaper and longer life.
 
So 2 things that come to mind:
1: 200w of panels is only good for about 800wh in an average dat best case. That's not going to be enough to fill 3 batteries in a day and lead does NOT like to sit empty OR be drained below 50%.

2: Many SCC's will try to run an equalizing charge on FLA's every 30 days or so cooking off the water inside. If you leave that unattended for months at a time you'll dry out the batteries and destroy them.

It sounds like the batteries were too dead for too long and you'll want to make sure you can fully charge the battery bank with enough panels and SCC to fully top up those batteries as fast as possible. The other thing to ensure is that you're not running any equalization charge when you're not around. If your SCC has an AGM setting that Should prevent boiling off.
 
How low is the voltage when the generator is finally run? Are the batteries getting charged to 14.4 to 14.6 volts and held there for an hour? Common problem with lead-acid is over discharge and incomplete charging. This allows sulfation to build up and permanent loss of capacity.

More solar would help. If you camp extensively I recommend a lithium battery but that will cost a bit more than $500.
 
Rednecktek said:
So 2 things that come to mind:
1: 200w of panels is only good for about 800wh in an average dat best case. That's not going to be enough to fill 3 batteries in a day and lead does NOT like to sit empty OR be drained below 50%.

2: Many SCC's will try to run an equalizing charge on FLA's every 30 days or so cooking off the water inside. If you leave that unattended for months at a time you'll dry out the batteries and destroy them.

It sounds like the batteries were too dead for too long and you'll want to make sure you can fully charge the battery bank with enough panels and SCC to fully top up those batteries as fast as possible. The other thing to ensure is that you're not running any equalization charge when you're not around. If your SCC has an AGM setting that Should prevent boiling off.
Click to expand...
cool. thank you for that info. i was assuming having the 3 batteries would keep me above the 50% drainage point. i did not run tests so i cant be sure of that but i do run solar daily so if there is a drain on the system, which 6 months out of the year there is, i assume i am pretty close to their max cycles anyway. can i daisy chain another set of 200 watt panels, get new lead acid batteries and possibly double or better their life span ? they can handle colder temps much better than lithium. even heated lithium is still going to see some temps below recommendations but only a handful.
 
time2roll said:
How low is the voltage when the generator is finally run? Are the batteries getting charged to 14.4 to 14.6 volts and held there for an hour? Common problem with lead-acid is over discharge and incomplete charging. This allows sulfation to build up and permanent loss of capacity.

More solar would help. If you camp extensively I recommend a lithium battery but that will cost a bit more than $500.
Click to expand...
i am concerned about the temperature range with any lithium variety of batteries. when it gets cold they dont like to charge. we get temps to -10 a handful of times a year but even heated LiFePo4 hanve a range of -4 to 135. not quite where i need to get to. i also live at 7k ft and camp higher then that all summer, up to 11k. i like the idea of adding more panels and just replacing the marine lead acids especially if it will double their life span. 500 bucks every 4 years seems efficient to me, but i dont really know any better yet
 
roaming ram said:
i am concerned about the temperature range with any lithium variety of batteries. when it gets cold they dont like to charge. we get temps to -10 a handful of times a year but even heated LiFePo4 hanve a range of -4 to 135. not quite where i need to get to. i also live at 7k ft and camp higher then that all summer, up to 11k. i like the idea of adding more panels and just replacing the marine lead acids especially if it will double their life span. 500 bucks every 4 years seems efficient to me, but i dont really know any better yet
Click to expand...
Yes I understand. If the space is available consider a set of 4x GC2 golf car 6 volt batteries. I think a set of four at Costco is under $500.
These are better designed for cycling to 50% vs the common marine deep cycle combo batteries.
 
Hedges said:
Once again, why run refrigeration at night? Can you store cold as ice in freezer compartment instead?
Last page of technical manual indicates 3500 cycles to 15% DoD, so could last 10 years if mostly shallow cycled, using PV direct to load most of the time.

Click to expand...
i could shut the fridge off at night, but the heater will still run pretty frequent all night the majority of the summer months because of elevation. my goal would be to have a system that works without making adjustments in a perfect world but if that is what it takes, so be it
 
For $500 you should be able to get a 12V/100Ah LFP battery that would match the deep discharge capability of three Group-21 batteries. Build an insulated box or put it in a good cooler with a ~5W heating pad that runs when you have solar.
 
One thing that may help is to always recharge to 100% from mains power after returning from camping. In the past, I've gotten several years from 12v fla batteries without solar, just with alternator charging and trickle charging at home.
 
time2roll said:
Yes I understand. If the space is available consider a set of 4x GC2 golf car 6 volt batteries. I think a set of four at Costco is under $500.
These are better designed for cycling to 50% vs the common marine deep cycle combo batteries.
Click to expand...
I was also going to recommend Costco cart batteries. that why I asked what 12v he currently had to see if he had the room. I have a set of them That I removed from my RV that is currently running my container/shop. They are 5 years old and still working. But they are 58lbs each so he may not want that extra weight.
 
6v GC2 are far more durable than automotive 12v. if you can handle the space and weight, they're solid. you'll need them in series pairs. i have two in place of a single 12v in our motor home, and have been happy so far. but, we never really use battery power. $90ea at sams club.

4x would give you ~200ah of usable 12v power.
 
Jack Rabbit Off Grid said:
I was also going to recommend Costco cart batteries. that why I asked what 12v he currently had to see if he had the room. I have a set of them That I removed from my RV that is currently running my container/shop. They are 5 years old and still working. But they are 58lbs each so he may not want that extra weight.
Click to expand...
i didnt really want to add weight as my trailer is already over 4k lbs but what is another 60 lbs ? haha. sounds like i would be running them both in series and in parallel to keep my 12 volt system. i think i would also have to daisy chain more panels too.
 
I just bought a 140ah 12v battery for $400 on amazon, because i waited a little too long and let the discount to $370 expire. I would recommend going to lithium and making the minor accommodations to keep it functioning in your climate.

Honestly, unless your battery bank was functioning one day and not functioning the next, i suspect what happened is you were 'away' from the setup (or not watching it) during a period where it sat at low soc AND endured cold temps and it put a quick end to what was already an 'aged' pack. It's possible if it had not gone through that, they would last longer.

I think going to true deep cycle lead acid would be an improvement, but as mentioned that doesn't change anything about them not liking to sit at partial SOC, so it may be more prudent to focus on keeping them full (i.e. reliably fully replacing the energy you used, preferably quickly) than buying a slightly more tolerant or higher capacity lead acid design.

But, all of the above would be good, with an upgrade to lifepo4 and some protective measures against the temp, being the optional but ideal capstone.
 
Last edited:
Jack Rabbit Off Grid said:
I was also going to recommend Costco cart batteries. that why I asked what 12v he currently had to see if he had the room. I have a set of them That I removed from my RV that is currently running my container/shop. They are 5 years old and still working. But they are 58lbs each so he may not want that extra weight.
Click to expand...

Vigo said:
I just bought a 140ah 12v battery for $400 on amazon, because i waited a little too long and let the discount to $370 expire. I would recommend going to lithium and making the minor accommodations to keep it functioning in your climate.

Honestly, unless your battery bank was functioning one day and not functioning the next, i suspect what happened is you were 'away' from the setup (or not watching it) during a period where it sat at low soc AND endured cold temps and it put a quick end to what was already an 'aged' pack. It's possible if it had not gone through that, they would last longer.

I think going to true deep cycle lead acid would be an improvement, but as mentioned that doesn't change anything about them not liking to sit at partial SOC, so it may be more prudent to focus on keeping them full (i.e. reliably fully replacing the energy you used during the day, preferably quickly) than buying a slightly more tolerant or higher capacity lead acid design.

But, all of the above would be good, with an upgrade to lifepo4 and some protective measures against the temp, being the optional but ideal capstone.
Click to expand...
so what i am getting from all of your valuable and greatly appreciated responses is that i should upgrade my scc to 30 amp so i can have 400 watts of panels. get 200 watts more in panels. get 4 6volt costco batteries and go through my system much closer so i know what my actual usage is and figure out watt hours per day. pretty sure it is astronomical somewhere close to 4k is my guess.
 
I like the idea of flooded lead acid batteries maintained with measurements from a hydrometer to know when you are supposed to equalize these batteries. For my area of Arizona, I found that I used 1000 watts of panels to reliably charge those four golf cart sized FLA batteries, which gave me 2.5 kwh of power, about 220 ah of usable power. The panels may seem overkill, but helped much for cloudy days.

I even had 400 watts of ground panels I angled at and moved with the sun that outperformed the 1000 watts of roof panels.

Lead acid batteries will need to be limited to charging to whatever the battery spec said, in my case 60 amps or 13%.
 
Vigo said:
Since you are already incorporating a new charge controller, i would just try to get one that will track the usage for you so you can skip most of the math.
Click to expand...
While this approach does work, doing the math becomes a whole lot more important the bigger a system gets.
 
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