Gel batteries capacity on 25% after 2.5 years of light use - what am I doing wrong?

[i_papp]

Hi guys,
I have a question regarding the way I use my gel batteries, as they are causing issues after 2 years :-(
I've replaced them twice already, and now I am a bit desperate if should take the same route again.
So I rely on you now

My off-grid system in my weekend house looks like this:

• 3 PV panels of poly 140W, connected in parallel. According to the specification, they are 18V, 7.7A each.
• Epever XTRA3210AN charge controller, 30A, 12V, MPPT. It is configured for GEL batteries, equalization is turned off.
• Sinus 12V inverter of 1000W, with 1500W surge, Nova Tech NV-P1000.
• 2 JYC GE100-12 batteries, connected in parallel.

The system was initially designed and set up by a professional, after mapping my devices and needs.

I have the following devices:

• Alarm system consuming 5W. It is on 24/7. (it is connected to Load terminals of the charger, 12V)
• From May till October, I have the following consumers that are used occasionally
  • 9 LED bulbs of 8W each, used only in the evening, and not simultaneously (up to 5 simultaneously)
  • 1 fridge of 70W, which runs for 10 minutes every hour, from May till September.
  • water pump of 500W, which runs 10-15 times per day when we are in the house. One run is ~30 seconds to fill the water tank. When the pump starts, the surge power is up to 950W according to a meter I installed. After a second or so, it goes back to 500W.

The caveat is that yearly we spend ~15 days and nights in the weekend house. So in my view, the system is not heavily used or stressed.
Only the alarm system is on when I am not there, and the fridge is on only during summer. So most of the year I am not using the house.
The temperature in the weekend house is between 26 degrees Celsius in the summer, and down to 4 degrees Celsius in the cold winter. But it never goes below 0 degrees.

When the batteries are new, there is no issue, and all of the equipment and devices work as expected. This usually lasts for a year, or a year and a half. After that, sometimes in the evening, the bulbs blink when the pump turns on. Then also when the fridge turns on. And as a final stage, e.g. after 2 years, and usually at night, the inverter shuts off due to low battery voltage when the pump or the fridge turns on.
The batteries went down to 20% after 3 seasons of use. This was measured by a local company I bought them from.

Before I buy a new set of batteries, I wanted to check with you if there is something wrong with my system.
Help, friends!

 

[Mattb4]

Possibly your Epever is not doing a good job of charging up your batteries or possible overcharging them. The other possibility is when you are using the batteries that you are discharging them more than 50%. Either situation can lead to early demise of a lead acid battery type.

You might want to monitor your battery voltages to see if you can isolate what is going on. You might also consider replacing your batteries this time around with LiFePO4.

 

[Bluedog225]

Excellent first post. Great info.

Matt’s points are all I could offer. We would need charging voltages, and resting voltages, absorb, float. To dig in a little.

 

[i_papp]

Thanks, I spent a lot of analysis prior to this post
The boost voltage is set to 14.4V, the floating voltage is set to 13.7V. I set them according to the battery specification.
When the sun goes down, it settles at 12.9V if no load connected. It may decrease during night to12.6V while the batteries are usable, but goes lower (12.5V, 12.4V) when the batteries are EOL (by my scale).

 

[mikefitz]

GEL batteries need a long absorbtion period where the charge voltage is held constant at the absorbtion voltage of 14.2 volts maximum. The default absorbtion period for Epever is 2 hours, this is lower than recomended for some GEL batteries under cyclic operation.
The manufactures JYC, recomended charge voltages of 14.4 to 15 volts, these are higher than some other manufactures recomend for GEL, Epever default charge voltage for example is 14.2 volts for GEL .
It's suggested by some that GEL batteries should be charged at 14.2 or 14.1 volts to reduce early failure. (2.35 volts per cell )
Without knowing the typical solar yield compared to daily load its difficult to suggest the batteries were
under charged. For example is there shading on the panels for some part of the day?, is the inverter idle current accounted for? are there often several days of poor solar input, cloud/rain?

Assuming for most of the time the only load is 5 watts at the battery, it's possible at the daily charge at 14.4 volts , the batteries were over charged. Epever don't have variable absorbtion period so even after a slight overnight discharge the battery was subjected to a prolonged charge.

My guess is the charge voltage of 14.4 caused degradation despite the manufactures advice for this value.

Mike

 

[Mattb4]

Researching this battery I find the specs here: https://jycbattery.com/wp-content/uploads/Specifications/GE/GE100-12S (29.7KG).pdf and I note the cycle service life under different discharge scenarios. (image posted below) This particular battery is not really designed for routine discharging but instead as a float battery. It is not a good choice for a solar power system. I would guess between you usage and the Epevers charging it is why the battery has such a short lifetime.

 

[i_papp]

GEL batteries need a long absorbtion period where the charge voltage is held constant at the absorbtion voltage of 14.2 volts maximum. The default absorbtion period for Epever is 2 hours, this is lower than recomended for some GEL batteries under cyclic operation.
The manufactures JYC, recomended charge voltages of 14.4 to 15 volts, these are higher than some other manufactures recomend for GEL, Epever default charge voltage for example is 14.2 volts for GEL .
It's suggested by some that GEL batteries should be charged at 14.2 or 14.1 volts to reduce early failure. (2.35 volts per cell )
Without knowing the typical solar yield compared to daily load its difficult to suggest the batteries were
under charged. For example is there shading on the panels for some part of the day?, is the inverter idle current accounted for? are there often several days of poor solar input, cloud/rain?

Assuming for most of the time the only load is 5 watts at the battery, it's possible at the daily charge at 14.4 volts , the batteries were over charged. Epever don't have variable absorbtion period so even after a slight overnight discharge the battery was subjected to a prolonged charge.

My guess is the charge voltage of 14.4 caused degradation despite the manufactures advice for this value.

Mike

Thanks Mike, this was also one of my suspicions, as my use case is neither standby, nor cyclic use. But the battery specs discouraged me from letting the boost voltage as per Epever settings for GEL.
The panels face south, without shading (no nearby trees or buildings).
The inverter idle current is up to 0.4A, but it is on only when the fridge is on (summertime).

@mikefitz You mentioned that the Epever doesn't have a variable absorption period - is that some I need to worry about e.g. if I buy LiFePO4 battery instead?

Istvan.

PS: I tried to reach JYC for further clarification on the voltages. As soon as they figured out that I am not a company, they stopped responding :-(

 

[i_papp]

Researching this battery I find the specs here: https://jycbattery.com/wp-content/uploads/Specifications/GE/GE100-12S (29.7KG).pdf and I note the cycle service life under different discharge scenarios. (image posted below) This particular battery is not really designed for routine discharging but instead as a float battery. It is not a good choice for a solar power system. I would guess between you usage and the Epevers charging it is why the battery has such a short lifetime.

View attachment 135440

The following link (Application section) states that the battery is intended to be used for solar:

12V 100Ah Gel Battery Manufacturer - JYC Battery

The gel battery with the advantage of deep cycle life adopts agm gel technology that can fully immerse the plate in the electrolyte.

www.jycbattery.com

The batteries were dimensioned for cca. 30% DOD overnight, which should be in the safe range.
Though I am not sure what counts as a cycle in my case (on a yearly basis):

• In summertime when we are there, like 20 days a year => 20 cycles?
• Or when the inverter and fridge are working (5 months = 150 days) => 150 cycles?
• Or all the time, even when only the 5W alarm is on => 365 cycles?

None of these numbers fits the expected numbers, the battery fails like it is always drained 80% or more, which is for sure not the case.
Any thoughts on this?
Istvan.

 

[Mattb4]

The following link (Application section) states that the battery is intended to be used for solar:

12V 100Ah Gel Battery Manufacturer - JYC Battery

The gel battery with the advantage of deep cycle life adopts agm gel technology that can fully immerse the plate in the electrolyte.

www.jycbattery.com

The batteries were dimensioned for cca. 30% DOD overnight, which should be in the safe range.
Though I am not sure what counts as a cycle in my case (on a yearly basis):

• In summertime when we are there, like 20 days a year => 20 cycles?
• Or when the inverter and fridge are working (5 months = 150 days) => 150 cycles?
• Or all the time, when even when only the 5W alarm is on => 365 cycles?

None of these numbers fits the expected numbers, the battery fails like it is always drained 80% or more, which is for sure not the case.
Any thoughts on this?
Istvan.

My only thoughts are that sealed LA batteries are a iffy choice for long term solar power usage. I know from my own experience that I had SLA batteries go bad after a couple of years. The folks that seem to get really long battery life in a solar setup are those that go the FLA route with routine maintenance. Now it seems that LiFePO4 based batteries are supplanting the old standby providing deeper cycling, less maintenance and long life spans.

 

[i_papp]

My only thoughts are that sealed LA batteries are a iffy choice for long term solar power usage. I know from my own experience that I had SLA batteries go bad after a couple of years. The folks that seem to get really long battery life in a solar setup are those that go the FLA route with routine maintenance. Now it seems that LiFePO4 based batteries are supplanting the old standby providing deeper cycling, less maintenance and long life spans.

Would the SOK Marine LiFePO4 206Ah battery be a good drop-in replacement for my gel batteries?
Without changing the rest of the solar system?

 

[Mattb4]

Would the SOK Marine LiFePO4 206Ah battery be a good drop-in replacement for my gel batteries?
Without changing the rest of the solar system?

Nice battery with a 7 year Warranty. It would effectively double your battery storage. Your Epever has lithium battery charging settings so that is not a problem. My only concern is your solar may not be enough if you add additional loading.

 

[Bluedog225]

That’s what I got. It seems to be a nice battery from will’s review of the SOK line. Though I’ve had no issues, the owner of currentconnected.com has participates here and has a good reputation.

 

[Bluedog225]

It’s also light enough not to spring a hernia.

 

[i_papp]

Nice battery with a 7 year Warranty. It would effectively double your battery storage. Your Epever has lithium battery charging settings so that is not a problem. My only concern is your solar may not be enough if you add additional loading.

How safe is it to overpanel my charger? E.g. add another panel, or replace these with more powerful?

 

[rodrick]

How safe is it to overpanel my charger? E.g. add another panel, or replace these with more powerful?

Epever states that over paneling is acceptable check your model specs but on mine the manual said up to 50%
just stay under maximum voltage this can’t be fudged if you go over you will smoke it

 

[Hank Waconda]

So your 12 volt PV panels the VOC is 18vdc and the ISC is 7.7amps? That could be 23.1 amps going into the charge SCC maybe more if really cold.....I would have the panels configured in series. The SCC current for the 3210 AN I think is 30amp...Maybe over paneling up to 45 amps on output of SCC. IMHO I think if the VOC gets up to 22VDC you may have to much current for the 3210 AN SCC input.

 

[i_papp]

If I put the panel in series, does that mean I should change the system configuration from 12V to 24V?
Meaning I would need 2 batteries in series, new inverter?

 

[mikefitz]

The variable absorbtion is not really relevant for lithium, the absorbtion, boost, period is typically 30 minutes for lithium.

The Epever solar controller can accept panel voltages up to 100 volts, it converts panel power to a suitable voltage for the battery. Thus there in no need to change to a 24 volt system.
I think you have enough solar with the three panels,
The SOK battery would be a good choice.

Mike

 

[Hank Waconda]

If I put the panel in series, does that mean I should change the system configuration from 12V to 24V?
Meaning I would need 2 batteries in series, new inverter?

No you don't need to change battery configuration, just make sure to disconnect solar before anything. The SCC will do the rest. What is the VOC & ISC (voltage open circuit, short circuit current) of your solar panels?

 

[i_papp]

No you don't need to change battery configuration, just make sure to disconnect solar before anything. The SCC will do the rest. What is the VOC & ISC (voltage open circuit, short circuit current) of your solar panels?

As far as I recall (I don't have the spec anymore) the VOC is around 22V, while the ISC is less than 9A.
Seems that most of the polycrystalline 140W panels have these specs.

This means that in my setup I could:

• connect my three panels into a series, which would generate up to 3x22V = 66V, and up to 8A
• connect the panels to the SCC
• the SCC will take care of converting the input voltage/current from PVs (66V, 8A) into 12V-level output for the battery (14V and current of up to 30A - like a DC/DC converter).
• This configuration would help to extract additional power from PVs in case of a cloudy sky or evening hours.

Is my understanding correct?
Istvan.