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BANGKOK 12 December 2018 06:42
Arjen

And then are the batteries gone....

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A graph from the monthly performance from my solar system. It is not very accurate, because production from inverter can never be higher then supply from batteries to the inverter.

 

There are two, or three interesting things. 

 

  • In april is a peak in production
  • Around August 2018 the device what measures amps from batteries to inverter stopped working.
  • Since June 2018 the batteries perform very bad.

 

At places where there is a peak in supply from inverter I have used the inverter to charge the batteries. (It is a bidirectional inverter) 

 

It looks like I must buy new batteries.....

 

Arjen.

Growth Kwh.xlsx

Edited by Arjen

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Have you tested them with a hydrometer? Have you charged them with a smart charger?

 

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They are closed, Deep Cycle batteries. The solar charger is according supplier a smart charger. Do not think an other charge will make a difference.

 

I have four batteries already disconected as they look like they will explode soon.

 

Arjen.

 

 

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6 hours ago, Arjen said:

They are closed, Deep Cycle batteries.

Most batteries can be forced open check YouTube. Have the plastic cases expanded?

Edit: maybe look for replacements that can be opened for maintenance.

Edited by stubuzz
Addition

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Thank you very much for this good idea! Now is only one complication, these are Gel batteries, I can find how to open them (by destroying them) but not if it is possible to revover these again?

 

Below pictures from the expanded cases. Four batteries are like this now. I have 20 pieces. I hope you can see it on these pictures.

 

Arjen.20181202_083936.thumb.jpg.948d7fdc551318895edf87c69ce31faa.jpg

20181202_083949.jpg

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They are dead. You do know that gel batteries take a lower charge and float charge. What voltages have you been charging/floating them to?

 

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The gel batteries seem to have the shortest life span in deep cycle installations 

 

Quote

An AGM class battery will last anywhere from four to seven years, while a deep cycle gel cell battery can last from two to five years. Flooded lead acid types have the greatest life expectancy, as these batteries can last from four to eight years.

All of them do best if kept cool and kept above 20% of capacity.

 

Unfortunately it looks as if Arjen's battery bank is not kept as cool as it is possible (excluding A/C) so quite possibly the batteries will be at the shorter end of the range.

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1 hour ago, stubuzz said:

They are dead. You do know that gel batteries take a lower charge and float charge. What voltages have you been charging/floating them to?

 

Usual charging stops at 26.9V, because then the inverter switches on. But there are several occasions this does not happen, mainly, because the load from the grid is to high. Then charging stops at 28.6V. The inverter is powered off at 25.0V

 

34 minutes ago, sometimewoodworker said:

The gel batteries seem to have the shortest life span in deep cycle installations 

 

All of them do best if kept cool and kept above 20% of capacity.

 

Unfortunately it looks as if Arjen's battery bank is not kept as cool as it is possible (excluding A/C) so quite possibly the batteries will be at the shorter end of the range.

They are kept as cool as possible in my house, on a shaded balcony, in nearly always some windy conditions. We do not have AC

 

I bought batteries, charger, and inverter from the same supplier. I suppose charging conditions should be OK then? Powering on and off from inverter is PLC controlled.

 

Thanks for reply!

 

Arjen.

 

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3 hours ago, Arjen said:

I bought batteries, charger, and inverter from the same supplier. I suppose charging conditions should be OK then? 

They could be, but not necessarily.

 

if your batteries need replacement after 2 years rather than 8 years then the supplier makes 4 times the profit, if a gel battery costs more than a flooded cell then the supplier makes more profit.

 

the aims of your supplier are probably not the same as yours.

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3 hours ago, Arjen said:

Usual charging stops at 26.9V, because then the inverter switches on. But there are several occasions this does not happen, mainly, because the load from the grid is to high. Then charging stops at 28.6V. The inverter is powered off at 25.0V

The charge per cell is important information as well as the speed of charge and the number of cells in parallel or series, personally I can't interpret the data but I'm sure others can

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Maxium charge current is something like 60A. I have 20 12V batteries, connected as 24V. So charge load is far below allowed. The charge per cell is nearly impossible to check for me.

 

The data is quite easy to read. 

 

PV is production from PV modules (to charger)

CH is production from charger (to batteries)

Batt is production from batterie (to inverter)

Inv is production from inverter ( to my house)

 

 

You can see that PV and charger still produce, while batt, and inv stay far beyond.

 

Arjen.

 

 

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Maxium charge current is something like 60A. I have 20 12V batteries, connected as 24V. So charge load is far below allowed. The charge per cell is nearly impossible to check for me.

 

The data is quite easy to read. 

 

PV is production from PV modules (to charger)

CH is production from charger (to batteries)

Batt is production from batterie (to inverter)

Inv is production from inverter ( to my house)

Humm I don't know if there is enough information, and we may have miscomunicated.  Have you checked the voltage of each battery both before and after changing? Any big difference would suggest that the battery is dying and will probably stress the other of the pair.

 

you say "You can see that PV and charger still produce, while batt, and inv stay far beyond." I don't understand what you mean.

 

Also are you able to measure the power input and draw (Amps) not just the voltage?

It's quite possible that your battery bank is  smaller than optimal and so is being drawn down lower than is good fo it.

 

The charge rate for a low charge battery should not be higher than 20% of its rated capacity, so a 100 AH battery should not charge at more than 20Ah initially then it should drop once 80% charge is reached.

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The charge rate for a low charge battery should not be higher than 20% of its rated capacity, so a 100 AH battery should not charge at more than 20Ah initially then it should drop once 80% charge is reached.

This is just manufacturers covering themselves. There is actually some research into this (sorry it's too late and I'm too tired to Google it, I'm just enjoying a beer after work and reading through ThaiVisa). An SLA will take as much current as you can supply it during charge. It won't take more than it can handle. Giving it as much current as it wants to charge with might actually do it good. WATCH THE VOLTS THOUGH. . . I never supply any of my SLAs with more than 13.5 volts (or 27 volts for my 24 volt systems) but give them as much current as they want when charging. There's a big difference between forcing the current in with volts, or allowing the battery to take to what it wants. . .

 

About the OP, one of those pictures above appears to be in direct sunlight, maybe the light on your camera, I don't know, but those batteries sure look older than 2 years. Regardless, it sure looks like you've allowed your bank to overheat. It's dead, forget about repair, just bite the bullet and replace. I deploy a LOT of SLA batteries in the field for my line of work (networking and telephony equipment in outdoor cases in direct sunlight). I generally use forced air to maintain case temps at ambient. Occasionally I will use peltiers to keep the temp lower than ambient but only when there are routers and switches involved. The higher the battery temp the lower the float charge. It looks like this is where you're blown it. My cases generally hit 38 degrees most of the year where I'm using forced air and if my batteries last less than 3 years something is VERY WRONG. Generally I get 5 years +.

 

Another thing to watch out for is the manufacturing date on SLAs. If they've been sitting on a shelf for two years and the open circuit charge allowed to drop too far there's a good chance the batteries are permanently damaged, even if you just bought them. My limit is 12.7 volts. If it's below that, I don't buy. Don't be shy to test the voltage in the shop, and check the manufacturing date.

 

"Deep cycle" doesn't give you carte blanche to deep cycle. I never let my batteries go below 11.4 volts when discharging and that's when they'll disconnect automatically. They have a very long life as a result. If I need a system to run for 8 hours without mains power, I'll spec it for 16.

 

 

 

 

 

Edited by NilSS
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To clarify. swelling like that is like stage 4 cancer for batteries. It's invariably overheating due to either an overcharge (read: over-voltage) or a short circuit.

Edited by NilSS
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