Gel battery dropping capacity with no load

[Tronco]

In December 2022, I installed a 24v system with the following components:

2 x 12v Gel batteries
30Amp Epever Xtra 3210N charge controller
340W JA Solar mono panel,

According to the display on the charge controller, the batteries have always been dropping capacity (from 5 bars when full to 3 bars) immediately or within an hour after sunset or when I disconnect the solar panel even without load and a voltage of 27,5 volts. I turn my inverter on in the evenings and it runs overnight for lights and I also use it for minor charging during the day. In the morning there are still 3 or 2 bars battery capacity. I have never discharged the batteries 100%

Is there a problem with my batteries or my system?

 

[sunshine_eggo]

The % readout/bars on the charge controller are worthless. It is purely based on voltage and doesn't mean anything.

Are you charging to no higher than 28.2V?

When the system is at 28.2V, is each GEL at 14.1V?

 

[Tronco]

The % readout/bars on the charge controller are worthless. It is purely based on voltage and doesn't mean anything.

Are you charging to no higher than 28.2V?

When the system is at 28.2V, is each GEL at 14.1V?

Thanks very much for the response. My charging voltage is around 27,5V and has never reached 28V. Maybe it is because the battery bank is almost always full and the charging system doesn't get to spend lots of time in Boost stage. The batteries have less than 5 months of use

 

[squowse]

The state of charge indicator on those charge controllers is pretty rough. The voltage will drop slowly after charging stops. That’s normal

 

[Tronco]

The state of charge indicator on those charge controllers is pretty rough. The voltage will drop slowly after charging stops. That’s normal

Thank you. So I guess it's a game of wait and see for me then.

 

[squowse]

Thank you. So I guess it's a game of wait and see for me then.

I wouldn’t worry about it. Can you check the battery voltage and compare it to charts. Needs to be the resting voltage when its not under load and definitely not being charged.

 

[Tronco]

I will do that. Thanks a lot

 

[squowse]

What does your battery manufacturer recommend for charging voltages? 28V sounds a touch low. This is what rolls recommend for their gel batteries- https://support.rollsbattery.com/en/support/solutions/articles/222287-battery-charging-gel

 

[DIYrich]

I have never discharged the batteries 100%

Gel batteries shouldn't be discharged more than 50%

 

[pollenface]

Pay no attention to Epevers SOC readout.

Also, it would be ideal if they saw 28v everyday.

 

[Tronco]

Pay no attention to Epevers SOC readout.

Also, it would be ideal if they saw 28v everyday.

I will check the settings when I take a trip there, I don't remember them getting past 27,5V. Maybe I should have a look at the settings

 

[Tronco]

What does your battery manufacturer recommend for charging voltages? 28V sounds a touch low. This is what rolls recommend for their gel batteries- https://support.rollsbattery.com/en/support/solutions/articles/222287-battery-charging-gel

They recommend 28,2V - 28,8V boost and 27V - 27,6V float. So I don't know why my controller does not get up there.

 

[pollenface]

I will check the settings when I take a trip there, I don't remember them getting past 27,5V. Maybe I should have a look at the settings

It would be really good to spend a couple of days observing how the system behaves. Knowing your charge settings and the panels open circuit voltage would be handy.

Periodically check it every 30mins as the day progresses to see how it's doing and take note of the battery voltage and current.

The standard GEL profile may be okay depending on the depth of discharge, but if you're still seeing a lot of current going into the batteries towards the end of the "boost duration" you will have to make some changes. I had to set my Epever mppts to equalize @ 14.2v/180min and boost @ 14.2v/180min to get 6hrs of "absorption" time. Also my setting of 14.2v at the controller makes about 14.0-14.1v at the batteries with wiring losses. It's a lot of observation, trial and error until you get it close to perfect.

Lastly, if you don't already have one, consider getting a Ha01 24v balancer. I have used them with much happiness in my 24v lead acid setups.

 

[sunshine_eggo]

Thanks very much for the response. My charging voltage is around 27,5V and has never reached 28V. Maybe it is because the battery bank is almost always full and the charging system doesn't get to spend lots of time in Boost stage. The batteries have less than 5 months of use

If that's intended, you are charging to a float voltage, which typically takes > 24 hr to fully charge and is not recommended for cyclic systems.

Boost should be set to 28.2V and float to 27.6V. If you're not seeing the boost voltage set in the controller, you are using more than you have available, or your solar is insufficient.

Didn't address the second issue directly. I'll ask it another way:

When the system is at peak voltage, are both 12V voltages identical?

I'll second @pollenface 's HA01 recommendation, but only after you've determined their current state.

 

[Tronco]

If that's intended, you are charging to a float voltage, which typically takes > 24 hr to fully charge and is not recommended for cyclic systems.

Boost should be set to 28.2V and float to 27.6V. If you're not seeing the boost voltage set in the controller, you are using more than you have available, or your solar is insufficient.

Didn't address the second issue directly. I'll ask it another way:

When the system is at peak voltage, are both 12V voltages identical?

I'll second @pollenface 's HA01 recommendation, but only after you've determined their current state.

I haven't checked their individual voltages when system is at peak, but when I installed them, there was a slight difference. About 0,2 Volts I think. Seller said voltage difference was insignificant.

I am going to check the voltages for both batteries in series and the individual batteries, then compare to the MPPT readings. At the moment, I am not happy the voltages. Feels like the batteries are being undercharged, probably the reason for a quick drop in capacity indicator after sunset

 

[sunshine_eggo]

I am going to check the voltages for both batteries in series and the individual batteries, then compare to the MPPT readings. At the moment, I am not happy the voltages. Feels like the batteries are being undercharged, probably the reason for a quick drop in capacity indicator after sunset

No. The reason is because you are using a worthless gauge. If you just put 15 gallons in your car gas tank to fill it, but as you accelerated from the gas station, you saw your gas gauge go from full to 50%, would you think you just burned 7.5 gallons of gas? Wouldn't you conclude there is a gauge problem and not a fuel consumption/capacity problem?

Yes, you may be failing to fully charge; however, even if you knew you were getting fully charged, you would see the same behavior on the shitty, worthless gauge.

I really mean it. Ignore the gauge. It's worthless. If you care about your actual state of charge, get a quality battery monitor with a shunt that factors in Peukert's law and temperature efficiency factors. The only one I know of is a Victron smartshunt.

 

[squowse]

They recommend 28,2V - 28,8V boost and 27V - 27,6V float. So I don't know why my controller does not get up there.

What settings have you got in the controller? Its also possible that you’re not generating enough to finish charging the batteries every day.

 

[Tronco]

What settings have you got in the controller? Its also possible that you’re not generating enough to finish charging the batteries every day.

I selected the Gel Option in the controller settings.
Boost voltage is 14,2V (battery manual requires 14,1V-14,4V) and float voltage is 13,8V (battery manual requires 13,5V - 13,8V). I have attached the screenshot for both.

NB I don't stay where the system is installed. Can't rule out that someone might have tinkered with the settings.

 

[sunshine_eggo]

I selected the Gel Option in the controller settings.
Boost voltage is 14,2V (battery manual requires 14,1V-14,4V) and float voltage is 13,8V (battery manual requires 13,5V - 13,8V). I have attached the screenshot for both.

NB I don't stay where the system is installed. Can't rule out that someone might have tinkered with the settings.

Gel setting should be fine, though I would prefer 14.1V. Important to confirm that it's actually getting to 28.4V. You may need to watch it like a hawk and/or use a separate meter to confirm volts.

 

[Tronco]

Gel setting should be fine, though I would prefer 14.1V. Important to confirm that it's actually getting to 28.4V. You may need to watch it like a hawk and/or use a separate meter to confirm volts.

Thank you very much. I am going to watch the system. When I installed it I only had 24hours with the system, but I was also concerned with the rate at which the bars dropped from 5 to 3 (100% down to 60%). It was too rapid for a 24V 200AH with a load of less than 20 Watts on a 400w inverter