Gel battery monitoring??

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Gel battery monitoring??

Postby gpigeon » Sat Jun 03, 2017 6:49 am

I have just had a new PV system installed with 24x 2RPG1410 Energystore cells. I am wanting a procedure for monitoring the health of the battery system. The maunufacturerers instructions just say to measure the voltage across each cell every 3 months. I have done this already but what should I be looking for? What is an acceptable V difference/change?
What do all you old hands do?
Thanks.
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Re: Gel battery monitoring??

Postby davidg » Sat Jun 03, 2017 9:23 am

gpigeon wrote:I have done this already but what should I be looking for? What is an acceptable V difference/change?
What do all you old hands do?
Thanks.

Was there and difference? Did you record the voltage in a "logbook"

Ideally there should NO difference at all. Using a multi-meter with 3 decimal places is a good.

I over the year I have installed, having much heavier inter-connects between the cells or batteries is preferable it drastically reduces the chances of voltage differences between cells or batteries, if they are not heavy enough, there will be point where the cells towards the centre of a 48V pack/bank will shows of "being lazy" the only way to stopp early cells failure then is the go a huge effort and rotate the cells around so the most centre are at the outside ends and the most outside ones are at the centre. That's a real pain to do and hard work.

My own banks use 600mm2 or bigger links between the cells and equal length 70mm2 cable to the inverter for instance, the difference in voltage between cells is not really measurable under any conditions, this is the way I try and do all banks/packs for others as well. Takes more time worth it.
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Re: Gel battery monitoring??

Postby SandyP » Sat Jun 03, 2017 10:52 am

gpigeon wrote:I have just had a new PV system installed with 24x 2RPG1410 Energystore cells. I am wanting a procedure for monitoring the health of the battery system. The maunufacturerers instructions just say to measure the voltage across each cell every 3 months. I have done this already but what should I be looking for? What is an acceptable V difference/change?
What do all you old hands do?
Thanks.


The manual for my Hoppecke GEL batteries shows the following for the acceptable cell voltages when at Float voltage over the "first" 5 years of battery life.
We saw the cell float voltage range decrease over time as per the graph.

Hoppecke_OPzV solar FloatChargeVoltage.jpg
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Re: Gel battery monitoring??

Postby SandyP » Sat Jun 03, 2017 11:57 am

gpigeon wrote:I have just had a new PV system installed with 24x 2RPG1410 Energystore cells.....


I would also get a torque wrench to undertake regular (?6 monthly?) checks of the battery terminal bolts to ensure they are tightened as per the manufacturers specs (being 23Nm for your batteries).
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Re: Gel battery monitoring??

Postby gpigeon » Sun Jun 04, 2017 5:56 am

Thanks for your replies gents.
The Min. reading is 2.287 and the max. is 2.392 with an Avg. of 3.239 and a total V of 55.9. I think the inverter gave a voltage of 56.1 at that time...but not sure.
So, will the "low" one remain the low one and the one to watch or will one of the others deteriorate quicker?
I gather that if one cell goes bad it can "pull" the rest of the others down. Correct?
SandyP, I will study that graph of yours and see what I can make of it. Thanks.
Cheers.
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Re: Gel battery monitoring??

Postby Helipos » Sun Jun 04, 2017 11:57 am

gpigeon wrote:I have just had a new PV system installed with 24x 2RPG1410 Energystore cells. I am wanting a procedure for monitoring the health of the battery system. The maunufacturerers instructions just say to measure the voltage across each cell every 3 months. I have done this already but what should I be looking for? What is an acceptable V difference/change?
What do all you old hands do?
Thanks.


A trustworthy multimeter, check cell volts once a month and cell to cell volt drop every three months would seem good. . Clean the top of the cells with a damp cloth as dictated by how dirty the battery room is.

If you can get a hold of one, do battery impedance readings every 12 months. Gel cells typically do take one to two years to pull all the impedances together so if you do some readings don't panic too much at some variability.
As for voltage reading it might take a few decent cycles to get all the voltages together but I'd expect less than say 50mV pretty quickly and after a month or three less than 30mV.

The main thing for keeping them looked after is keeping the charge up over winter, keeping the overall average temperature down in summer, using the temperature compensation of the float voltage properly.
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Re: Gel battery monitoring??

Postby LeighC » Sun Jun 04, 2017 12:04 pm

Hi all,
Can anyone explain to me how a cell can go high or low in a series connected battery pack?
Wouldn't that be related to the battery chemistry or condition as the load or charge is only as strong as the weakest link?
Cheers - Leigh
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Re: Gel battery monitoring??

Postby Gordon-Loomberah » Sun Jun 04, 2017 4:38 pm

Lower actual capacity of a cell will cause it to go to higher voltage on charge and lower on discharge, in a series pack, of any chemistry.

Also, too high a SG in a Lead-acid cell will cause its voltage to be high all the time, leading to the eventual failure of the lowest cell, as happened with my last Lead-acid Trojans. Ridiculously high SGs in a couple of cells from new.
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Re: Gel battery monitoring??

Postby Helipos » Sun Jun 04, 2017 11:34 pm

Helipos wrote:The main thing for keeping them looked after is ...


I should also add that the manufacturing quality will have the biggest bearing. Seen plenty of supposedly "good " batteries dead at 4 years. Seen some normally fairly reliable batteries have some slight manufacturing defects and do the same too. Hope you did your research.
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Re: Gel battery monitoring??

Postby LeighC » Mon Jun 05, 2017 6:41 am

Helipos wrote
( If you can get a hold of one, do battery impedance readings every 12 months)

What is the best impedance meter to buy please?

Thanks - Leigh
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