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lorenzo-accaroli avatar image
lorenzo-accaroli asked

48V 775Ah battery... Bulk

I wish to try explaining the system and its behavior. Two strings (18 panels 9kW), two SS MPPTs 150\85 and 250/100, 48 V lead acid floaded 775Ah(C5), QUATTRO inverter, controller CCGX. Installed in November so bad weather and first weeks since it is installed during day time never reached absorbtion volt. Then inverter was switched off and MPPTs charges to float three or for days. Then inverter was switched on and the situation now is that during day only bulk and during evening batteries give power for a little bit time (20 min with 3kW loads)... Sorry for this fload of words but I need to know what is happening...

MPPT Controllers
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michelg answered ·

Hi Lorenzo, it seems that your batteries are not fully loaded, if you have the opportunity to run a charger either through a generator or a power line 230VAC. The batteries are probably sulfated and will need :

0) buy a refractometer in order to know what is the real state of each cell

1) charge the batteries till they get into fload mode

2) use the solar power to run an equalization up to get the batteries cells having the same SG

3) check every hour the density of each cell

4) have a journal (excel file) where you write every week / month the status of each cell

Currently, they are new AFAIK, so they need to go through a "break-in" process, but you don't have enough sun, so wait to have sunny days to make them work hard, and always try to get them reloaded on the same day.

Let me know how the things are going.

Michel.

PS: you have very good videos on YT done by ROLLS batteries, in order to understand how they perform, what issues can happen, etc.

Also, what kind of battery are using ? Model, manufacturer, etc. it will be easier to tell you.

This is a refractometer :

refractometre-antigel-concentration-uree-pour-glyc.jpg



refractometre-antigel-concentration-uree-pour-glyc.jpg (35.1 KiB)
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lorenzo-accaroli answered ·

Thank you michelg, i don't have opportunity to run an external charger but here in northern Italy this week is very sunny so yesterday I switched off QUATTRO and Victrob Connect today told me that batteries performs all three phases.

I have a TAB battery 5EPZS775 48V 775Ah(C5). They are not really new. They were ready one year ago but do to some delays in house building the stay under charge for few months, then in October they were send to perform a reconditioning and then were installed in November.

I'm going to watch YT videos you suggest thanks!

So it is a good thing to keep batteries only charging by sun this week and perform the equalization this weekend if it is sunny? What risks and waring I have to consider during the equalization? I bought the reflectimeter meanwhile...

Attached you can find the battery label20210126-173830.jpg




20210126-173830.jpg (1.8 MiB)
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michelg avatar image michelg commented ·

Hello Lorenzo, here is the link to understand the process of equalization (ROLLS, but more or less the same for every lead acid battery) :

https://youtu.be/J8DmZulWnus

Risks ? Basically they are going to make much more gas (Hydrogen), and you need to have a good ventilation. Also consider checking the SG every hour, till all cells have the same gravity (OPsZ are usually around 1,24, check your manual or ask the provider).

Have also a reserve of distilled water to refill the batteries, usually check the levels every month, when you check the SG (check them before adding the water).

Let me know if I can help on other subjects.

Michel

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lorenzo-accaroli avatar image lorenzo-accaroli michelg commented ·

Thank you again!! I'll check the sg first once the reflectomete arrives.

Can you give me a consideration about the VictronConnect graph attached? As you can see today battery performed all phases after days in only bulk (but with battery attached to inverter). What I cannot understand is if battery today really reached its maximum capacity and if it is worth to let battery work normally... Sorry for my poor technical language about the system!

screenshot-20210126-211036.jpg

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michelg avatar image michelg lorenzo-accaroli commented ·

As long as the battery bank don't reach "Float" mode it is not charged. Take a look at my setup you will see that the batteries goes from bulk to absorption the float.

https://vrm.victronenergy.com/installation/68341/share/e08c79bc

If they don't reach Float, this means they are getting depleted everyday, so the risk of sulfating them is present. If you don't have a Cerbo GX + Display, at least using Victron connect will show you how much you produce on a daily basis. Try to switch the view of Victron Connect, to display the values from the MPPT for the entire month, and please post a print screen here. So we can see how the PV system interacts with the battery bank

Michel

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michelg avatar image michelg michelg commented ·

This is how the MPPT in the victron connect section should look like:

screenshot-20200908-121736.png

The white is Bulk, the "grey section" is absorption, and the dark one, is the float section. even in winter the available power is smaller, you should have a graphic like that, almost reaching float on sunny days.


Michel

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screenshot-20200908-121736.png (68.6 KiB)
lorenzo-accaroli avatar image lorenzo-accaroli michelg commented ·

This is mine, quite different uhm, the days at the beginning of January was when inverter was off but very bad weatherscreenshot-20210126-220832.jpg

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screenshot-20210126-220832.jpg (227.3 KiB)
michelg avatar image michelg lorenzo-accaroli commented ·

The picture is clear ! The system is providing enough power to reach the float condition, when the inverter is OFF, but according to the data, yesterday the float condition was achieved, which is a good point ! 12 days without entering absorption and float, means you have been sucking juice from the battery bank. I will suggest to perform an equalization when you have enough sun, for 2h. It won't do any damage to the batteries, and if there is some sulfation, it will revert it.

When you will have the refractometer, it will be much more easy. Also, in March we should have much more sun, so you can consider discharging the battery bank 70-80% and reload it (break-in of the batteries). Look first at the meteo in order to have several sunny days (4-5).

You might also look if there is an option to have some PVs west orientated (not sure if possible in your configuration), in order to get sun from the afternoon, and using an angle adapted to winter conditions. (If you look at my setup, you will seee that I have optimized the angle for winter, as in summer, there is enough power all the day).

Have fun with your RE system !

Michel

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ewalderasmus avatar image ewalderasmus michelg commented ·

@MichelG

I am sorry to jump into this post, but I am absolutely intrigued by your system. Would it be possible for me to email you some questions regarding your solar panel setup, it will be some basic questions like tilt angle and array size ect... My email address is EwaldErasmusjnr@gmail.com


Regards Ewald

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lorenzo-accaroli avatar image
lorenzo-accaroli answered ·

@MichelG


Ciao Michel, sorry for asking again. I have my reflectometer and I want to check SG of cells this weekend. Battery is still with inverter OFF. TAB datasheet tells that nominal SG @30°C and with fully charged batteries is 1.29 with corrector factor of -0.0007 /°C. So:


1) I have to wait evening when batteries are fully charged to perform measurement?

2) My battery are in external place. Do I need to correct the read data or I can put drops inside the refractometer and then enter in house, wait 1-2 minutes and read the SG?

3) If I will find that SG is OK, could I switch ON my inverter? (This would help with my power bill ;) )


Thanks again

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michelg avatar image michelg commented ·

Hi lorenzo ! You have to take the SG of your batteries at the same place, but need to calibrate first the refractometer, using distilled water, and putting the level at 0 using the screwdriver.

Then, you can check and note every SG cell and write it. At 30C you have 1,29, I presume around 10C you will get a 1.295 / 1.305 SG.

You can check the SG whenever you want, and will get a picture of the current status, then when "fully charged", you perform another reading so you will know if the batteries are sulfated (discharged) and which ones. So you can perform the equalization next day, after having the batteries fully loaded (according to the MPPT).

You can switch on the inverter, but when you perform and equalization, it is recommended to switch off everything to avoid false measurements by the MPPT.

A good video : https://youtu.be/Zfw64KKGs6M

Have fun ! Michel


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lorenzo-accaroli avatar image lorenzo-accaroli michelg commented ·

Ok, I performed SG readings. Here the results... They seems to be good, aren't they?

The video tells that a delta of 0.01-0.015 is normal. I have a maximum of 0.021 delta.

Now I want to switch ON inverter and perform EQ tomorrow or during the week, what do you think?


EDIT: I have two MPPTs, so how do I start equalization simoultaneously? I can start EQ entering in one MPPT then in the other...


Thanks as usual!sg-31-01-21.jpg

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