Jump to content

Solar Gel Batteries won't keep voltage


Felix Merz

Recommended Posts

Hello community,

My name is Felix and I live in Egypt. I'm new in this forum and I would like to ask you guys for your opinion.

I'm running an off-grid pv system on my kitesurfing boat. Installation in April 2018. It was performing quite well for a few months, then after 5-6 months I noticed that my batteries slowly started decreasing it's capactity and finally after 9 months my batteries only provide less than 20% of their expected capacity! 

My setup:
48V system
16 x 275W TrinaSolar panels
12 x 12V, 150ah/C20 Newmax Deep Cycle Gel batteries - SG1500H
  2 x Axpert MKS 5kva (parallel)
  ... ICC 2.3.0 on Pi3 for monitoring

My daily average load is 15-25kwh (10-15kwh during day-time, 5-10kwh during night-time). 
- Water pumps: 1 x 1hp fresh water, 1 x 1hp bilge pump, 1 x 0.5hp salt water pump for toilets, 1 x 1.5hp waste water pump
- Air Compressor: 1.5hp for inflating kite
- Fridge/Freezer: 2 x big, 2 x small
- Water kettle: 2kw
- Coffee machine: 1.3kw
- Sound system: 50-60w
- Some ventilators: 50-60w
- 20-40 LEDs during the night - 3-7w
- And some computer- and phone-chargers...

Talking to my solar provider/installer... he tries to explain me, that I damaged my batteries by using the water kettle and the coffee machine! Or that I finished the cycles of my batteries. Both I can't and I don't want to believe.

According to the data sheet, the cycle life characteristics of my batteries are 800 cycles at 80% DOD,1500 cycles at 50% DOD or 3000+ cycles at 20% DOD.
During the last 9 months (270 days) I maximum discharged my batteries as follows:
  20 x 20% DOD
100 x 50% DOD
150 x 80% DOD

Of course, during a normal day, the total load is sometimes higher that the input from the panels, because I have some electric motors for pumps. But this always happens only for a very short time - seconds to minutes... But during a normal day, my battery SOC never drops below 95%.

If from any interest, all historical monitoring data from ICC are available on 
https://www.centurionsolar.co.za/emoncms/
usr: Tornado
pwd tsci2018

Anyone have an idea, why my batteries lost their capacity way too early?

Any help is highly appreciated.

Thanks,
Felix

 

Link to comment
Share on other sites

9 hours ago, Felix Merz said:

12 x 12V, 150ah/C20 Newmax Deep Cycle Gel batteries - SG1500H

Three strings. My feeling is that you might be dealing with only two or three bad batteries that is affecting the whole thing. I also wonder what kind of effect this might have had on the batteries, because multiple strings like this almost always means one string is overcharged while at least one other string is also undercharged, causing the entire thing (or the weakest link in any of them) to degrade faster. It's just a guess though. But it might be a good idea to take individual strings out of the whole and test the batteries on their own.

Link to comment
Share on other sites

11 hours ago, Felix Merz said:

Anyone have an idea, why my batteries lost their capacity way too early?

It could be the premature float bugs, if you are using factory firmware. Sorry, I could not get the historic graphs to make sense (to me) to see if that was the case. The bugs will cause your battery to be chronically undercharged. If you're using the inverter's SOC measurement, it's very approximate, and not to be trusted. Are your batteries getting to the absorb voltage most days?

See also Can I update my firmware, and if so to what?

Link to comment
Share on other sites

12 hours ago, Felix Merz said:

Hello community,

My name is Felix and I live in Egypt. I'm new in this forum and I would like to ask you guys for your opinion.

I'm running an off-grid pv system on my kitesurfing boat. Installation in April 2018. It was performing quite well for a few months, then after 5-6 months I noticed that my batteries slowly started decreasing it's capactity and finally after 9 months my batteries only provide less than 20% of their expected capacity! 

My setup:
48V system
16 x 275W TrinaSolar panels
12 x 12V, 150ah/C20 Newmax Deep Cycle Gel batteries - SG1500H
  2 x Axpert MKS 5kva (parallel)
  ... ICC 2.3.0 on Pi3 for monitoring

My daily average load is 15-25kwh (10-15kwh during day-time, 5-10kwh during night-time). 
- Water pumps: 1 x 1hp fresh water, 1 x 1hp bilge pump, 1 x 0.5hp salt water pump for toilets, 1 x 1.5hp waste water pump
- Air Compressor: 1.5hp for inflating kite
- Fridge/Freezer: 2 x big, 2 x small
- Water kettle: 2kw
- Coffee machine: 1.3kw
- Sound system: 50-60w
- Some ventilators: 50-60w
- 20-40 LEDs during the night - 3-7w
- And some computer- and phone-chargers...

Talking to my solar provider/installer... he tries to explain me, that I damaged my batteries by using the water kettle and the coffee machine! Or that I finished the cycles of my batteries. Both I can't and I don't want to believe.

According to the data sheet, the cycle life characteristics of my batteries are 800 cycles at 80% DOD,1500 cycles at 50% DOD or 3000+ cycles at 20% DOD.
During the last 9 months (270 days) I maximum discharged my batteries as follows:
  20 x 20% DOD
100 x 50% DOD
150 x 80% DOD

Of course, during a normal day, the total load is sometimes higher that the input from the panels, because I have some electric motors for pumps. But this always happens only for a very short time - seconds to minutes... But during a normal day, my battery SOC never drops below 95%.

If from any interest, all historical monitoring data from ICC are available on 
https://www.centurionsolar.co.za/emoncms/
usr: Tornado
pwd tsci2018

Anyone have an idea, why my batteries lost their capacity way too early?

Any help is highly appreciated.

Thanks,
Felix

 

If you are in a hot place, you should consider battery temperature. Each increment of 9ºC over 25ºC reduces a half battery lifespan. In some places, we are installing air conditioner, where battery bank is installed. Consider it.

Edited by Javi Martínez
Link to comment
Share on other sites

4 hours ago, Javi Martínez said:

hot place

In my mind Egypt definitely rates as a hot place. I mean I haven't been there, but I've seen pictures... and it looks more like Namibia than it looks like other places in the world 🙂

Link to comment
Share on other sites

1 hour ago, plonkster said:

In my mind Egypt definitely rates as a hot place. I mean I haven't been there, but I've seen pictures... and it looks more like Namibia than it looks like other places in the world 🙂

Then, temperature compensation can be critical and Axperts arent able to do it.

Link to comment
Share on other sites

Thanks guys for your feedbacks. Highly appreciated.

Actually I gave you just a brief idea about my problem. Here some more details...

Already for a while I could notice and see from the monitoring data, that the capcacity of my batteries are slowly decreasing. Means, that when running off-grid and no panel power, the battery Voltage and SOC going down faster than in the beginning, although not taking too much power from the batteries. That's the situation I could notice for a while already...
 
Then a couple of weeks ago - on Dec.10 - after going off-grid around 8am we might have stressed the batteries a bit during the morning by accidentally running a 2000W electric water heater, and then in the afternoon around 4pm, after sunset, still using some ~3000w for a short while suddenly the battery had a huge voltage / SOC drop like never before. That was just before the boat came back to the marina and went on-grid again! After that day the boat was operating daily for a couple of days and everything seemed to be normal because during day trips we are using mainly solar power and not using the batteries. But the next time when the boat stay outside overnight (off-grid) the battery didn't keep the voltage anymore and SOC/voltage dropped low within one hour without using much power... The battery didn't recover from this bevaviour anymore. Since then they charge toooo fast and discharge toooo fast... Below some reports from the ICC-Monitor (historical data in emoncms)   
 
 
Battery SOC / Voltage - 10.Dec.2018
 
Inline image
 
 
Battery Amps / Watts - 10.Dec.2018
 
Inline image
 
 
Load Watts / PV Watts - 10.Dec.2018
 
Inline image
 
 
Here a diagram of battery SOC vs Voltage for the past months:
 
Inline image
 
 
Is this information helpful for you? 
 
Thanks for your support
Felix
Link to comment
Share on other sites

16 hours ago, plonkster said:

Three strings. My feeling is that you might be dealing with only two or three bad batteries that is affecting the whole thing. I also wonder what kind of effect this might have had on the batteries, because multiple strings like this almost always means one string is overcharged while at least one other string is also undercharged, causing the entire thing (or the weakest link in any of them) to degrade faster. It's just a guess though. But it might be a good idea to take individual strings out of the whole and test the batteries on their own.

After the situation I just described above - mid December 2018 - I checked all batteries and found one with a voltage drop. The 1. battery on the positive side of the middle string had only 10.7V instead of 12.8 like all the others. So, I took that one out, replaced it with one from the 3.string and ran the system with only 2.string (8 batteries). But still the same behaviour, i.e. the batteries seem to charge tooo fast and discharge tooo fast. 

Link to comment
Share on other sites

14 hours ago, Javi Martínez said:

If you are in a hot place, you should consider battery temperature. Each increment of 9ºC over 25ºC reduces a half battery lifespan. In some places, we are installing air conditioner, where battery bank is installed. Consider it.

Thanks Javi, I thougt about this also. Yes, in summer it can get quite hot in Egypt. But not extremly hot...

Klimatabelle_700x280.gif

Well, on non windy days it can get to 40°C sometimes in July/August.

The batteries and inverters are installed in the engine room of my boat. But we are not moving much with the boat and so the engine room doesn't get really hot.

An air conditioned box for the batteries... hmmm... possible. 

But still, could warm/hot temperatures kill new batteries within 9 months?

Link to comment
Share on other sites

3 hours ago, Felix Merz said:

Is this information helpful for you? 

It probably would be, if we could see the images. I think you need to allow access to other than yourself somehow. Digging a little, I get EC-4008, which seems to be associated with  "authorization error".

Link to comment
Share on other sites

Sorry... here the same post again. But with images accessible

Thanks guys for your feedbacks. Highly appreciated.

Actually I gave you just a brief idea about my problem. Here some more details...

Already for a while I could notice and see from the monitoring data, that the capcacity of my batteries are slowly decreasing. Means, that when running off-grid and no panel power, the battery Voltage and SOC going down faster than in the beginning, although not taking too much power from the batteries. That's the situation I could notice for a while already...
 
Then a couple of weeks ago - on Dec.10 - after going off-grid around 8am we might have stressed the batteries a bit during the morning by accidentally running a 2000W electric water heater, and then in the afternoon around 4pm, after sunset, still using some ~3000w for a short while suddenly the battery had a huge voltage / SOC drop like never before. That was just before the boat came back to the marina and went on-grid again! After that day the boat was operating daily for a couple of days and everything seemed to be normal because during day trips we are using mainly solar power and not using the batteries. But the next time when the boat stay outside overnight (off-grid) the battery didn't keep the voltage anymore and SOC/voltage dropped low within one hour without using much power... The battery didn't recover from this bevaviour anymore. Since then they charge toooo fast and discharge toooo fast... Below some reports from the ICC-Monitor (historical data in emoncms)   
 
 
Battery SOC / Voltage - 10.Dec.2018
 
t1.png
 
Battery Amps / Watts - 10.Dec.2018
 
t2.png
 
Load Watts / PV Watts - 10.Dec.2018
 
t3.png
 
Here a diagram of battery SOC vs Voltage for the past months:
 
t4.png
 
Is this information helpful for you? 
 
Thanks for your support
Felix
Link to comment
Share on other sites

This is quite helpful, thanks. The basic problem seems to be that that day at least, you never reached absorb voltage from PV. You need to be at some 56.4 V (14.1 V per 12 V module) for an hour or so to have the battery soak up charge. That peak of battery voltage when you got to shore power (I assume that was soon after 17:00) should have happened at about 11:30 when the load dropped off. Maybe you just didn't have enough solar power to cover your loads and charge the battery properly that day. 

In fact, your loads are quite high. Your solar panels add to 4400 W nominal, of which you could count on perhaps 3 kW in the best hours, times perhaps 5 hours in summer. So that's only 15 kWh, and you say you use 10-15 kWh during the day. So you can barely cover the highest usage days, even with good panel orientation. In a boat, I imagine that your orientation will be highly varied when at sea. I note you barely reached 2.3 kW on Dec 10th. So I think that you could use more panels or less load. 

But there seem to be days like Dec 9th when the battery had a small discharge, and no charge at all. So I think your settings must be off. Please post your settings. 

Link to comment
Share on other sites

7 hours ago, Coulomb said:

This is quite helpful, thanks. The basic problem seems to be that that day at least, you never reached absorb voltage from PV. You need to be at some 56.4 V (14.1 V per 12 V module) for an hour or so to have the battery soak up charge. That peak of battery voltage when you got to shore power (I assume that was soon after 17:00) should have happened at about 11:30 when the load dropped off. Maybe you just didn't have enough solar power to cover your loads and charge the battery properly that day. 

In fact, your loads are quite high. Your solar panels add to 4400 W nominal, of which you could count on perhaps 3 kW in the best hours, times perhaps 5 hours in summer. So that's only 15 kWh, and you say you use 10-15 kWh during the day. So you can barely cover the highest usage days, even with good panel orientation. In a boat, I imagine that your orientation will be highly varied when at sea. I note you barely reached 2.3 kW on Dec 10th. So I think that you could use more panels or less load. 

But there seem to be days like Dec 9th when the battery had a small discharge, and no charge at all. So I think your settings must be off. Please post your settings. 

Well, Dec. 10. was quite a special day, because that day there was accidently running a 2000W water heater, which was normally never active when were off-grid. 

On normal days, when using 15-25kWh in 24 hours, the panels could cover that loads. Yes, you are absolutely right, nominal power of my panels is 4400W and they provide a maximum of 3kW at noon-time. The panels are flat mounted on the roof of the sun deck. So, of course not max. efficiency!

Kite-Adventure_09.JPG 

But still, we have a lot of sun here in Egypt - pretty much every single day... 😉 On a sunny summer day my panels can produce 25kWh. And also, on normal days my batteries always reached absorb voltage from PV easiely... Ok, there were a very few days, when this was not the case. But in general, I feel that the sizing of my system is not too bad.

Another point I would like to ask:
As mentioned in my first post, I have a coffee machine (Nespresso 1300W), and a water kettle (2000W). Nespresso machine has been used around 15-25 times per day for 1-2 minutes. Water kettle has been used 3-4 times per day for 2-3 minutes to make hot water.
Now, my solar dealer/installer here in Egypte just tried to explained me, that "heating devices like coffee machine, kettle, water heater etc. are very dangerous for batteries and defect them fastly!" He says that this the reason why I had one battery whit a voltage drop, and that my batteries are nearly end of life!

Is that through, that a coffee machine or a water kettle can severly damage my batteries, so that they give up after 9 months? Is a coffee machine - running for 2-3 minutes on 1300W, worse than air compressor - running for 2-3 minutes on 1500W?  For me, watt is watt, amp is amp. And of course, heating devices are never economic and not good to run from batteries. But can they destroy the batteries?

Thanks for any enlightenment...  

Link to comment
Share on other sites

28 minutes ago, Felix Merz said:

Is that true, that a coffee machine or a water kettle can severly damage my batteries, so that they give up after 9 months?

I fixed your question a bit, the way I think you intended 🙂

Of course larger loads stresses a battery more... that is true.Neither of those loads are even C/10 when considering the full 450Ah capacity. So it should have been just fine... IF the batteries were well treated (ie was always properly charged).

Edited by plonkster
Link to comment
Share on other sites

4 hours ago, plonkster said:

I fixed your question a bit, the way I think you intended 🙂

Of course larger loads stresses a battery more... that is true.Neither of those loads are even C/10 when considering the full 450Ah capacity. So it should have been just fine... IF the batteries were well treated (ie was always properly charged).

Thanks @plonkster , that is also my opinion. Yes, I always tried to treat my batteries well...  

Link to comment
Share on other sites

2 hours ago, Javi Martínez said:

I would say one cell, or some, is short. What about warranty?

That is also my suspicion. And that is what I'm currently discussing with my solar dealer.
After the situation on Dec. 10. which I described above, I checked the voltage of all the batteries individually and found one with a low voltage 10.7V, while all the others had 12.8V. I took that battery out from the system and operate the system with only two strings since then. In the meanwhile I tried to charge that battery seperately with a proper smart charger. But even after 10 hours on the smart charger, that battery still only have a voltage of 11.1V.
Could that mean that that battery has a broken cell?
Can a battery with a broken cell ruin a whole battery bank?  

Link to comment
Share on other sites

5 hours ago, Felix Merz said:

Could that mean that that battery has a broken cell?

Yes, definitely. It's toast. 

5 hours ago, Felix Merz said:

Can a battery with a broken cell ruin a whole battery bank?  

I'm no expert on lead acid, but I think yes, it might. The other strings will discharge trying to overcharge the short string. All the other cells in the short string will go closer to or even past the gassing voltage, so they will likely have lost most of their water, so the acid will be dilute.

Your two remaining strings might recover somewhat with a good charge, now that they don't have the bad string weighing them down. If you have absorb time settings, try a long absorb time for a week or two. 

Link to comment
Share on other sites

10 hours ago, Felix Merz said:

That is also my suspicion. And that is what I'm currently discussing with my solar dealer.
After the situation on Dec. 10. which I described above, I checked the voltage of all the batteries individually and found one with a low voltage 10.7V, while all the others had 12.8V. I took that battery out from the system and operate the system with only two strings since then. In the meanwhile I tried to charge that battery seperately with a proper smart charger. But even after 10 hours on the smart charger, that battery still only have a voltage of 11.1V.
Could that mean that that battery has a broken cell?
Can a battery with a broken cell ruin a whole battery bank?  

I agree @Coulomb

Link to comment
Share on other sites

On 2019/01/20 at 11:10 AM, Coulomb said:

This is quite helpful, thanks. The basic problem seems to be that that day at least, you never reached absorb voltage from PV. You need to be at some 56.4 V (14.1 V per 12 V module) for an hour or so to have the battery soak up charge. That peak of battery voltage when you got to shore power (I assume that was soon after 17:00) should have happened at about 11:30 when the load dropped off. Maybe you just didn't have enough solar power to cover your loads and charge the battery properly that day. 

In fact, your loads are quite high. Your solar panels add to 4400 W nominal, of which you could count on perhaps 3 kW in the best hours, times perhaps 5 hours in summer. So that's only 15 kWh, and you say you use 10-15 kWh during the day. So you can barely cover the highest usage days, even with good panel orientation. In a boat, I imagine that your orientation will be highly varied when at sea. I note you barely reached 2.3 kW on Dec 10th. So I think that you could use more panels or less load. 

But there seem to be days like Dec 9th when the battery had a small discharge, and no charge at all. So I think your settings must be off. Please post your settings. 

Hi Coulomb,

Sorry, I was a bit busy the last days...
You mentioned my inverter setting. Actually my solar installer just recommended me to leave all inverter settings on default - except

05 AGM
28 PAL (because I have 2 inverters in parallel mode)

 But now, after I investigating a bit in why my batteries lost their capacity I checked the charging settings, which are default:

02 60A (Max. charging current)
11 30A (Max. utility charging current)
26 56.4V (Bulk charging voltage)
27 54.0V (Float charging voltage)
29 42.0V (Low DC cut-off voltage)

But since I have Gel batteries and I read that these batteries can be a bit sensitive against over-/undercharging, I am wondering now if there could be a problem.
The data sheet for my batteries says:

Recommended charging (@ 25°C) 
- Cycle use: 2.40-2.45V/Cell (+-5.5mV/°C/Cell) / 57.0A max.
- Float use: 2.20-2.24V/Cell (°-3.3mV/°C/Cell)

Does that mean that my settings should rather be like this:

05 USE
26 57.6V-58.8V (2.40 x 6 x 4 = 57.6   /  2.45 x 6 x 4 = 58.8)
27 52.8V-53.8V (2.20 x 6 x 4 = 52.8  /   2.24 x 6 x 4 = 53.76)

Could that make a difference for performance and life-time of my batteries?

Thanks for any comments or recommendations

Link to comment
Share on other sites

5 hours ago, Felix Merz said:

 But now, after I investigating a bit in why my batteries lost their capacity I checked the charging settings, which are default:

02 60A (Max. charging current)

This was fine for 3 strings, but while you are running 2 strings, I'd reduce that to 40 A.

5 hours ago, Felix Merz said:

But since I have Gel batteries and I read that these batteries can be a bit sensitive against over-/undercharging, I am wondering now if there could be a problem.
The data sheet for my batteries says:

Recommended charging (@ 25°C) 
- Cycle use: 2.40-2.45V/Cell (+-5.5mV/°C/Cell) / 57.0A max.
- Float use: 2.20-2.24V/Cell (°-3.3mV/°C/Cell)

Does that mean that my settings should rather be like this:

05 USE
26 57.6V-58.8V (2.40 x 6 x 4 = 57.6   /  2.45 x 6 x 4 = 58.8)
27 52.8V-53.8V (2.20 x 6 x 4 = 52.8  /   2.24 x 6 x 4 = 53.76)

Could that make a difference for performance and life-time of my batteries?

Yes, that's what the recommended voltages translate to. I'd stick to the low side of these numbers, since Egypt has a hot climate. Those figures of X mV/°C/cell should be minus only; lead-acid battery voltages should reduce as temperature increases (this is called temperature compensation; ideally you should have a temperature probe and the inverter should apply the compensation automatically. In practice, adjusting the settings a little for Winter versus Summer around equinox time is OK).

The absorb ("cycle use") figure is a bit on the high side for gel cells, so I'd maybe even reduce them a little more (say 57.5 V). 52.8 V sounds good for the float voltage, although it seems low compared to other gel cells. I guess you just have to trust the manufacturer.

Yes, it could make a difference for the performance and/or life of your batteries.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...