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Inverter System Not Lasting 4 Hours - Please Advise


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Hi all

I'm hoping someone on here can help me.

We used to have a Schneider Inverter 24V 1500VA – Homaya Hybrid with 2 Deep Cylce batteries. This lasted us 6 - 8 hours if we kept the load under 300 W during power outages.

During the middle of last year we upgraded to the following system (and we've just been experiencing problems ever since):

  • 4x Solar panel 455W
  • The Sun Pays Inverter 5.5kw (5.5kW 100A Axpert Type Pure Sine Wave Inverter High voltage)
  • 4x Battery Royal 1150K (Deep Cycle)

Output Source Priority:     Solar + Line (PAL)

  • Recently we added an additional 4 batteries (used but still new) to the above system in an attempt to improve the endurance of the system, but to no avail.

With our load being under 300 W during power outages and load shedding, the system almost doesn't make it to 4 hours at night and starts giving the Low Voltage Warning. And sometimes it almost doesn't even make 2 hours (like this morning).

 

Our electrician who did the installation has tested the batteries and said that they're all 100% fine. But something is still not right.

I've logged some information on various dates to compare.

 

On the new system, with 4 batteries, I tracked the following:

Date / Time Battery Voltage Load On Inverter In Watts Battery Level Indication Notes
28 Feb 2023        
19:00 50.8 284    
19:30 50.3 231    
20:00 50.1 233    
20:30 49.8 231    
21:00 49.4 266    
21:05 49.2 263   Electricity back
2 Mar 2023        
19:00 49.4 172 3  
19:30 47.1 162 3  
20:00 44.5 175 1  
20:30 44.3 174 1  
21:00 44.1 139 1  
21:05 44.6 140   Electricity back
8 Mar 2023        
AM  
09:00 54.8 204 3  
09:05 52.2 205 4 Electricity off
09:30 50.2 202 4  
10:00 47.5 201 3  
10:30 45 210 2  
11:00 44.7 202 1  
11.:05 44.7 201   Electricity back
PM  
19:00 51.1 405 4  
20:00 45.6 320 2  
21:00 43.2 386 1  
21:05 45.2 277   Electricity back

 

 

With the 8 batteries, I tracked this:

Date / Time Battery Voltage Load On Inverter In Watts Battery Level Indication Notes
18 Mar 2023        
21:00 52.5 587 4  
21:30 50.5 298 4  
22:00 50 300 3  
22:30 47 281 3  
23:00 45.2 270 2  
23:05 45.9 279   Electricity Back
29 Mar 2023        
17:00 52.1 496 4  
18:00 50.5 183 4  
19:00 48.7 242 3  
19:30 45.4 241 2  
20:00 45.1 245 2  
4 Apr 2023        
19:00 52.1 397 4  
19:30 50.5 300 4  
20:00 50.3 247 4  
20:30 46.3 248 2  
21:00 46.1 252 2  
7 Apr 2023        
21:00 51.4 411 4  
21:10 50.3 402 4  
21:30 50.2 406 4  
21:45 50.3 218 4  
22:00 49.7 209 3  
22:15 46.7 208 2  
22:30 45.7 149 2  
22:45 45.6 144 2  
23:00 45.5 142 2  
11 Apr 2023        
18:30 50.3 261 4  
19:00 50.5 228 4  
19:30 50.3 212 4  
20:00 46.6 208 2  
20:30 45.1 250 2  
21:00 45 248 2  
21:10 44.9 252 1  
21:30 44.8 202 1  
22:00 44.5 202 1  
22:45 44 196 1  
23:00 43.8 194 1  
23:10       Electricity back
23:15 43.8 287 1 Electricity off
18 Apr 2023        
18:00 50.55 142 4  
19:00 47.5 212 3  
19:01 46 219 2  
19:05 46.7 212   Charging
22 Apr 2023        
21:00 51.6 180 4 Electricity goes out
21:15 50.9 180 4  
21:30 50.9 184 4  
21:45 50.7 197 4  
22:00 50.7 194 4  
22:15 50.6 191 4  
22:30 50.4 233 4  
22:45 49.8 232 3  
23:00 45.8 235 2  
23:10 46.3 236 2 Electricity back
23 Apr 2023        
05:00 51.4 410 4  
05:30 49.8 520 3  
06:00 45.6 294 2  
06:15 44.6 320 1  
06:30 43.5 191 1  
06:45 43.2 189 1  
06:50 42.8 333 0 Warning beeping started
06:55 43.5 103 1 Solar started but showed 0 W - still beeping
07:00 43.5 107 1 Solar watts = 6 W
07:15 43.4 107 1  
07:30 43.5 107 2 Beeping off
07:45 45 102   Charging

 

The electrician made some changes to the settings and it seems like it is performing even worse now. Unfortunately I'm not sure of exactly all the parameters he changed and what to. Feels like he's grasping at straws at this point to try make the system work.

 

We cannot afford Lithium batteries at this time, and considering our old system pulled through easily on the Deep Cycle batteries it's hard to understand why the current ones aren't holding out the way they should.

 

Attached are some graphs for a visual comparison of the above charts.

 

We are at a loss. Has anyone experienced anything similar? 

Can someone suggest any useful advice?

 

NOTE: During the day time the Solars pull the load and we don't have much trouble then, the above-mentioned issue occurs when there is no Solar input/Battery only.

Battery (V) vs Load (W) Comparison-4 Batteries.png

Battery (V) vs Load (W) Comparison-8 Batteries.png

Edited by GeorgeP
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29 minutes ago, GeorgeP said:

Hi all

I'm hoping someone on here can help me.

We used to have a Schneider Inverter 24V 1500VA – Homaya Hybrid with 2 Deep Cylce batteries. This lasted us 6 - 8 hours if we kept the load under 300 W during power outages.

During the middle of last year we upgraded to the following system (and we've just been experiencing problems ever since):

  • 4x Solar panel 455W
  • The Sun Pays Inverter 5.5kw (5.5kW 100A Axpert Type Pure Sine Wave Inverter High voltage)
  • 4x Battery Royal 1150K (Deep Cycle)

Output Source Priority:     Solar + Line (PAL)

  • Recently we added an additional 4 batteries (used but still new) to the above system in an attempt to improve the endurance of the system, but to no avail.

With our load being under 300 W during power outages and load shedding, the system almost doesn't make it to 4 hours and starts giving the Low Voltage Warning.

 

Our electrician who did the installation has tested the batteries and said that they're all 100% fine. But something is still not right.

I've logged some information on various dates to compare.

 

On the new system, with 4 batteries, I tracked the following:

Date / Time Battery Voltage Load On Inverter In Watts Battery Level Indication Notes
28 Feb 2023        
19:00 50.8 284    
19:30 50.3 231    
20:00 50.1 233    
20:30 49.8 231    
21:00 49.4 266    
21:05 49.2 263   Electricity back
2 Mar 2023        
19:00 49.4 172 3  
19:30 47.1 162 3  
20:00 44.5 175 1  
20:30 44.3 174 1  
21:00 44.1 139 1  
21:05 44.6 140   Electricity back
8 Mar 2023        
AM  
09:00 54.8 204 3  
09:05 52.2 205 4 Electricity off
09:30 50.2 202 4  
10:00 47.5 201 3  
10:30 45 210 2  
11:00 44.7 202 1  
11.:05 44.7 201   Electricity back
PM  
19:00 51.1 405 4  
20:00 45.6 320 2  
21:00 43.2 386 1  
21:05 45.2 277   Electricity back

 

 

With the 8 batteries, I tracked this:

 

Date / Time Battery Voltage Load On Inverter In Watts Battery Level Indication Notes
18 Mar 2023        
21:00 52.5 587 4  
21:30 50.5 298 4  
22:00 50 300 3  
22:30 47 281 3  
23:00 45.2 270 2  
23:05 45.9 279   Electricity Back
29 Mar 2023        
17:00 52.1 496 4  
18:00 50.5 183 4  
19:00 48.7 242 3  
19:30 45.4 241 2  
20:00 45.1 245 2  
4 Apr 2023        
19:00 52.1 397 4  
19:30 50.5 300 4  
20:00 50.3 247 4  
20:30 46.3 248 2  
21:00 46.1 252 2  
7 Apr 2023        
21:00 51.4 411 4  
21:10 50.3 402 4  
21:30 50.2 406 4  
21:45 50.3 218 4  
22:00 49.7 209 3  
22:15 46.7 208 2  
22:30 45.7 149 2  
22:45 45.6 144 2  
23:00 45.5 142 2  
11 Apr 2023        
18:30 50.3 261 4  
19:00 50.5 228 4  
19:30 50.3 212 4  
20:00 46.6 208 2  
20:30 45.1 250 2  
21:00 45 248 2  
21:10 44.9 252 1  
21:30 44.8 202 1  
22:00 44.5 202 1  
22:45 44 196 1  
23:00 43.8 194 1  
23:10       Electricity back
23:15 43.8 287 1 Electricity off
18 Apr 2023        
18:00 50.55 142 4  
19:00 47.5 212 3  
19:01 46 219 2  
19:05 46.7 212   Charging
22 Apr 2023        
21:00 51.6 180 4 Electricity goes out
21:15 50.9 180 4  
21:30 50.9 184 4  
21:45 50.7 197 4  
22:00 50.7 194 4  
22:15 50.6 191 4  
22:30 50.4 233 4  
22:45 49.8 232 3  
23:00 45.8 235 2  
23:10 46.3 236 2 Electricity back
23 Apr 2023        
05:00 51.4 410 4  
05:30 49.8 520 3  
06:00 45.6 294 2  
06:15 44.6 320 1  
06:30 43.5 191 1  
06:45 43.2 189 1  
06:50 42.8 333 0 Warning beeping started
06:55 43.5 103 1 Solar started but showed 0 W - still beeping
07:00 43.5 107 1 Solar watts = 6 W
07:15 43.4 107 1  
07:30 43.5 107 2 Beeping off
07:45 45 102   Charging

 

The electrician made some changes to the settings and it seems like it is performing even worse now. Unfortunately I'm not sure of exactly all the parameters he changed and what to. Feels like he's grasping at straws at this point to try make the system work.

 

We cannot afford Lithium batteries at this time, and considering our old system pulled through easily on the Deep Cycle batteries it's hard to understand why the current ones aren't holding out the way they should.

 

Attached are some graphs for a visual comparison of the above charts.

 

We are at a loss. Has anyone experienced anything similar? 

Can someone suggest any useful advice?

Battery (V) vs Load (W) Comparison-4 Batteries.png

Battery (V) vs Load (W) Comparison-8 Batteries.png

For starters provide if you are in Pretoria and perhaps a suburb. 

2nd point as you are discharging to below 44V this would shorten the life of those lead acids. 

Do you use a battery balancer between the 4x12V series connections? Ha01/02 type. 

I can understand your frustration with the system not working well. Using 50% of the capacity of the 8 batteries should give you an easy 12hrs at 400W load. 

Can you perhaps show a graph of the time period 15h-22h for the battery voltage just to confirm they are fully charged during the day. 

We can then take it from there. 

Edited by Scorp007
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Load shedding now is multiple times a day, and often with not long between sheds. Tomorrow, at my home, at Stage 6, we will have 3.5 hours between sheds at midday and early evening.

So, can you system recharge those batteries in 3.5 hours? WIth lithiums this a no-brainer, but with your SLAs you will need to check the charge rate.

Generally, SLAs are taking a beating right now. There are two problems that occur in our current situation

1) They get discharged below 50% during a single shed. With SLAs, once you go past 50% you are doing the batteries damage.
2) Because they can't recharge in the time between sheds, they go into a shed at less than 100%, and so their chances of hitting 50% increase.

OK... the real problem is (1), with (2) aggravating that problem.

Some of the figures you post, especially for the 4 battery setup, suggest that you don't always recover the full charge before the load shed starts.

OK... this started when you changed inverters. It might be worth checking the settings on the Axpert. Too high or too low a charge current could cause problems (unless the batteries have a way of reducing a too high current). I am guessing that the 8 battery setup is only as good as the weakest battery. IE if you have one weakened battery in there, it brings the whole lot down.

What are you backing up?

All the sites selling these batteries claim 200 to 250 cycles at 50% DOD, so you won't expect to get much life out of these anyway. If you can, bite the bullet and buy lithium. They are expensive up front, but you can expect much longer life from them, so they will pay off in the long run. Plus with a 5kw inverter and 5kWh of lithium you could back up more, and recharge more quickly between sheds.

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@Bobster. is 100% correct with all his comments, but everyone overlooks inverter no-load consumption and overall efficiency. These are normally very closely linked, but you can get exceptions.  @Scorp007 will roll his eyes skyward at my comment....   perhaps we should ask him to share the secret of his 20Watt no-load inverter consumption.

A number of newbies on this very forum have reported their electricity costs to notably rise after having an inverter installed.  The losses are substantial.  For low power consumers like yourself, the no-load power consumption will be the important figure.  For high power uses, those wanting to run kettles, microwaves and washing machines, the overall efficiency is the more important criteria.

I tried to find technical specifications on your old Schneider inverter but couldn't find anything.

You say you got 8 hours when keeping your loads under 300W.  So I read that as 300W peak.  Your nominal consumption might have been only about half of this.  Your new inverter will likely have 60W no-load consumption.  Yes, @Scorp007 .  Possibly more.  As long as there is utility power or you have large solar panels with sunshine, you don't need to worry too much about efficiency.  But the moment the batteries kick in, I am hyper vigilant on any power wastage.  So much so that I recommend people to rather replace certain consumers such as older TVs then purchasing expensive lithium batteries to be needlessly drained by inefficient old-tech.

BTW, inverters are not the only inefficient device.  Nothing is 100% efficient.  Lead acid batteries are known to also waste a huge amount of power.
Also, please do not look at your inverter's maximum efficiency of, say 93%, and then assume that a 100W load will draw 100/0.93 from the batteries.  That figure is the MAXIMUM efficiency, the sweet spot, normally attained at about 80% of rated power.  Running a 30W load on a 5.5KVA the efficiency is near zero.  Think of it like a car idling at a red robot, it's fuel efficiency at that stage is infinite liters /100km.

I have spend many hours thinking about the ideal system.  I personally like the idea of using low voltage DC as the always on supply and then have an inverter only kick-in on demand.  This is problematic for many people as this requires DIY and customized solutions. However, there is hope.  The high power USB-C standard provides up to 48V 5A - that is 240W.  I expect more and more devices to make use of this standard in future.

The alternative would be a low power always-on inverter and a high power on-demand only, inverter.

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54 minutes ago, Modina said:

@Bobster. is 100% correct with all his comments, but everyone overlooks inverter no-load consumption and overall efficiency. These are normally very closely linked, but you can get exceptions.  @Scorp007 will roll his eyes skyward at my comment....   perhaps we should ask him to share the secret of his 20Watt no-load inverter consumption.

A number of newbies on this very forum have reported their electricity costs to notably rise after having an inverter installed.  The losses are substantial.  For low power consumers like yourself, the no-load power consumption will be the important figure.  For high power uses, those wanting to run kettles, microwaves and washing machines, the overall efficiency is the more important criteria.

I tried to find technical specifications on your old Schneider inverter but couldn't find anything.

You say you got 8 hours when keeping your loads under 300W.  So I read that as 300W peak.  Your nominal consumption might have been only about half of this.  Your new inverter will likely have 60W no-load consumption.  Yes, @Scorp007 .  Possibly more.  As long as there is utility power or you have large solar panels with sunshine, you don't need to worry too much about efficiency.  But the moment the batteries kick in, I am hyper vigilant on any power wastage.  So much so that I recommend people to rather replace certain consumers such as older TVs then purchasing expensive lithium batteries to be needlessly drained by inefficient old-tech.

BTW, inverters are not the only inefficient device.  Nothing is 100% efficient.  Lead acid batteries are known to also waste a huge amount of power.
Also, please do not look at your inverter's maximum efficiency of, say 93%, and then assume that a 100W load will draw 100/0.93 from the batteries.  That figure is the MAXIMUM efficiency, the sweet spot, normally attained at about 80% of rated power.  Running a 30W load on a 5.5KVA the efficiency is near zero.  Think of it like a car idling at a red robot, it's fuel efficiency at that stage is infinite liters /100km.

I have spend many hours thinking about the ideal system.  I personally like the idea of using low voltage DC as the always on supply and then have an inverter only kick-in on demand.  This is problematic for many people as this requires DIY and customized solutions. However, there is hope.  The high power USB-C standard provides up to 48V 5A - that is 240W.  I expect more and more devices to make use of this standard in future.

The alternative would be a low power always-on inverter and a high power on-demand only, inverter.

I just switch the unit on. Also after 2 years I have not stripped my inverter. 

The self use does vary a bit. Right now it's 29W if my calculator is right. I never indicated 20W as you seem to remember. Your figure is a 25% difference. 

I am starting to wonder why everything you buy does not perform as designed. 

@Bobster.

I fully agree on your reply as far as not fully charged. That is the reason why I asked the OP to supply battery volts during the afternoon whilst they were charged when there is PV. 

Also we need to know if the 300W is drawn during the day with no grid being used. If that is the case the 4x455W can never even replace 75% of the power the batteries provided. Then we get to what you alerted. Lead acid can take over 12hrs to fully charged. Also the charge current of the inverter needs to be known. Here is just too many unknown factors to start guessing what the problem is. 

One bad battery could affect the series bank badly and the 2nd bank to a lesser extend. I am not always in agreement with battery test results if not done with a full charge and discharge. This takes a very long time. I might be wrong but I have an idea the quick battery test devices work on measuring internal resistance. If so the capacity could be way out. 

I prefer to work with measurements taken and testing than all the factors that can have an effect. Excuse me for following this route but this is only due to my training and job for a number of years. 

Picture taken now. Voltmeters do over read by 0.2V and 0.3V.

IMG_20230423_131446.thumb.jpg.c7e50f2e10ebaead1220066560598d26.jpg

Edited by Scorp007
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1 minute ago, Scorp007 said:

I am starting to wonder why everything you buy does not perform as designed. 

Fat fingers.  😆

For the record, my 2.5KW MCE is specified for <35W idle power.
I measured self-consumption by removing all loads, then switching off inverter, switching off the grid, switching of Hubble, connecting my Fluke in line with the battery cable and then switching back on.  Once the LCD backlight switched off and no fans running I then measured the actual DC current and multiplied this by the battery voltage.  This gave 40W.

So I got higher consumption than manufacturer specification.  Must be the GSR/SCL (Skin Conductance Level) of my fat fingers in an excited state.😁

I would not trust the inverter's own internal measurements for low power levels.  There is likely to be quantization error, measurement noise and DC offsets that could lead to measurement error.
 

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5 hours ago, GeorgeP said:

Our electrician who did the installation has tested the batteries and said that they're all 100% fine.

No, they are not. The batteries are shot. Lead acid batteries are not designed for solar applications, even if they are called "Deep Cycle" batteries. In my experience, lead acid batteries need at least 24 hours to be fully charged. Once they achieve their float voltage, they need to trickle charge for many hours in order to reach full capacity. If you load shed more than once per day, you are dead. Then the batteries will discharge at a faster rate the second and third time round you load shed in 24 hours, as the batteries had no chance to recover. Your system will go below 50% SOC very quickly and you damage them even more. I give your system another 3-4 months and you will be down to 30 minutes before the system switches off due to low voltage. 

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23 minutes ago, Don said:

No, they are not. The batteries are shot. Lead acid batteries are not designed for solar applications, even if they are called "Deep Cycle" batteries. In my experience, lead acid batteries need at least 24 hours to be fully charged. Once they achieve their float voltage, they need to trickle charge for many hours in order to reach full capacity. If you load shed more than once per day, you are dead. Then the batteries will discharge at a faster rate the second and third time round you load shed in 24 hours, as the batteries had no chance to recover. Your system will go below 50% SOC very quickly and you damage them even more. I give your system another 3-4 months and you will be down to 30 minutes before the system switches off due to low voltage. 

Very well explained. This bad cycle is why small UPSes and gate motor lead acid only lasts 4-6 months. When connecting 3 x and each discharges 33% they last 4 or more times longer. They also do much less work each. 

Edited by Scorp007
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@Bobster.and @Scorp007make good points, I also think the batteries are not charging fully. You have added panels to the setup which exposes you to the premature float bug which causes the batteries to only charge to float voltage and not bulk and capacity drops a lot.

Do your batteries have any sticker on them referring to charge voltages?

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