After watching Will's 2019 video on a beginners solar generator, I used his guide to building my first solar generator. I made the mistake of allowing my SLA battery to fall below 50% power and now when I charge it, it will register 100% charged but as soon as I disconnect the solar panel it falls to 84%. The when I turn on the inverter and plug something in, it falls to around 77% immediately. I realize I have damaged the battery. Question is - when I purchase a new battery could I hook it up in parallel with the damaged one to use what power it does hold?
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- Thread starter CmdrMike
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Thanks, I don't have any experience with electrical things. I don't know of any use for the damaged battery, seems like a waste. My bad.
Hedges
I See Electromagnetic Fields!
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- Mar 28, 2020
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Nothing wrong with drawing SLA down to 50% SoC or a fair amount lower.
0% SoC causes damage faster. 30% or 20% SoC cycling would give fewer cycles, but not much fewer Ah of cycling (DoD x number of cycles)
It should be recharged shortly after; don't leave below 100% SoC.
My system is configured to disconnect loads at 70% DoD, completely shut off inverter at 80% DoD. It has SunXtender AGM, and I should get several hundred cycles with these settings.
Your "100%" and "84%" are probably voltage readings translated to SoC?
Of course voltage drops when you stop putting current into it, but if it drops to an indicated 84%, that suggests not fully charged.
Double check SCC settings for absorption voltage and time.
What "C" rate do you charge at, current vs. Ah capacity?
AGM and Gel batteries need different charge voltage (and maybe current) compared to FLA. So your charger settings might not be correct.
The other possibility would be if cells are of different SoC, so they settle to different voltages, some much lower.
That doesn't happen early in properly-charged life of a battery, but develops over time. (Or if abused, left at low SoC.)
How old is this battery? If practically new, I think you could parallel another. But only after charging and observing it has returned to expected voltage. If voltage remains low, then yes it would drag down a new battery.
0% SoC causes damage faster. 30% or 20% SoC cycling would give fewer cycles, but not much fewer Ah of cycling (DoD x number of cycles)
It should be recharged shortly after; don't leave below 100% SoC.
My system is configured to disconnect loads at 70% DoD, completely shut off inverter at 80% DoD. It has SunXtender AGM, and I should get several hundred cycles with these settings.
Your "100%" and "84%" are probably voltage readings translated to SoC?
Of course voltage drops when you stop putting current into it, but if it drops to an indicated 84%, that suggests not fully charged.
Double check SCC settings for absorption voltage and time.
What "C" rate do you charge at, current vs. Ah capacity?
AGM and Gel batteries need different charge voltage (and maybe current) compared to FLA. So your charger settings might not be correct.
The other possibility would be if cells are of different SoC, so they settle to different voltages, some much lower.
That doesn't happen early in properly-charged life of a battery, but develops over time. (Or if abused, left at low SoC.)
How old is this battery? If practically new, I think you could parallel another. But only after charging and observing it has returned to expected voltage. If voltage remains low, then yes it would drag down a new battery.
MichaelK
Solar Wizard
In the examination of a problem for failure analysis, the common strategy is to identify the root cause of your problem. You problem is a dead/sick battery, but that's not the root cause of your problem. The root cause appears to be a too small battery, being charged by a too small solar array. Since your battery was being drained to less than 50%, that's an indication it was not sized right for your loads. Since this battery was not immediately recharged to 100% it suggests your not pumping enough watts into it.
Before anything else, you should document your loads and how long you expect to run them. That will allow us to determine the appropriate sized battery to support those loads. Once we know how big the loads are and how big the battery needs to be, we'll be able to figure out how many watts of solar you should install.
So, do not buy a new battery until you have first answered these questions. Then you can design a properly functioning system that is not going to let you down.
Before anything else, you should document your loads and how long you expect to run them. That will allow us to determine the appropriate sized battery to support those loads. Once we know how big the loads are and how big the battery needs to be, we'll be able to figure out how many watts of solar you should install.
So, do not buy a new battery until you have first answered these questions. Then you can design a properly functioning system that is not going to let you down.
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