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Lead acid tubular batteries status checking

abdallah.91

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Joined
Sep 11, 2021
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45
Hello everybody,

6 weeks ago I installed my solar system 12 panels 405w from Trinasolar with Must hybrid inverter 5000W 48V (PH18-5048 Plus) , I used it for around 4 weeks without batteries, actually with 4 damaged car battery that give voltage without amperage just because the inverter could not work without batteries so I was using it during the day light until I bought 4 batteries 200Ah C20 tall tubular from Maxma (TAF C20 200Ah) which is very known and famous in our country. during the 2 weeks هt didn't cross my mind to test their capacity under big load so normally during the night my average power is around 250w with no more 500w on maximum therefore my consumption during the night never exceed 1.5 KWh.
Recently I was turned water tank heater during the sunset when the grid was available before the grid goes out and become off-grid, 20 minutes the inverter beeped and the battery voltage down under 45.5V I don't remember exactly. yesterday I hoped to check the batteries capacity status so I fully charged them and tried them under 1500W resistive load, the bad surprise that inverter started beeping 25 minutes after I started my test. attached are some screenshots declaring my test status since 9.00AM when the charging current was 20A which is the limit that I put, until the night when I started the test.
now what I am thinking about is to test each battery capacity after fully charging them during the sunny day and use an 1200W inverter with resistive load 400W and write each 20 min the battery voltage and current. do you see it a good way to test them? is it ok to re-use in series after that discharge? no need to balance them?

I appreciate you help.

Regards
 

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You need to start charging your batteries properly.

Based on the configuration screens, it appears your inverter is like a Growatt. The grid charging does NOT conduct a full bulk/absorption/float charge of the battery. It's just on/off based on voltage. With a "battery stop charging" of 54.7V, you aren't getting the batteries anywhere near full.

First, learn your batteries:


You need to limit the charge current to 20.2A and terminate the charging at 57.6-60V per the battery's cyclic specification. Charging in that fashion will still likely only get you to about 80-90% charge.

Your poor performance is likely due to you rarely getting the batteries charged above 60%. Heavy loads at a lower state of charge will produce a large voltage drop.

You need to check ALL of your connections between batteries and inverter. Thin cables or loose connections will contribute to large voltage drop. Furthermore, heavy loads may force you to lower your inverter cut-off voltage to prevent premature alarms/cut-off.
 
thanks a lot @sunshine_eggo for your reply. I am with you about the inverter. are you available for a discussion here about to tell you what I did and what happened?
 
welcome and thanks in advance.

I freed up the all system (4860w panels) and the sunny days last week 3 days even if I saw the charging current before noon is 20A and after noon is limited to zero also even if utility is available which indicates that charging has been almost finished due to low consumption due day and night(average power less than 300w). yesterday I decided to test the capacity of each battery individually so load it with a non small load (350w heater) 220v with a small inverter 1200w.the first battery emptied in 2 hours 10 min (voc =13.17v befor test) inverter loaded with 350w heater consumes 30A and voltage with load drops from 12.05V at time zero to 10.24V with 20A at the test end. so the total energy consumed is arrout 800wh wich around third the battery 100% capacity.
After that I decided to test 2 batteries in parallel, the same thing around 5 hours for the same load so each battery is arout 2.5 hours so also too much less than rated. after I saw that 3 batteries seems has the same performance I ignored the forth and today morning I connected them in series again and connected to the inverter and charged them, 2 hours after charging start I started the equalization because 3 batteries were empty and 1 should be full. I left them charging and went to buy a hydrometer to check the acidity the surprise that after 5 or 6 hours I returned and found that charging has completed, I disconnected the again and measure the gravity of each and I discovered that the battery that I didn't tested it has almost 1.250 gravity but the 3 tested batteries are 1.15 or less. Now I connected the four in parallel and charging them with two 15 ampers charger in parallels. but unfortunately the gravity of all serms fix or still in red region. ?
 
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Based on the specs, it looks like a 350W load would last about 5.5 hours.

Charging batteries in series when they are at a known different state of charge is a very bad idea. When charging in series, you should check all 4 12V voltages to confirm they are close. If not, they need to be individually charged to full.

1.250 battery was fully charged when you started series charging.
1.150 batteries were discharged when you started series charging.

30A of charging into 800Ah is a low rate. Recommend you charge each battery individually @ 30A and check SG 2 hours after float.

1.250 is a decent number. The hope is that after you fully charge all 4 batteries, you can conduct an equalization charge to get SG to increase to 1.250+
 
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I knew that connect the 4 batteries in series when they are in different states of charge is a bad idea but is it such dagerous or destructive?
i charged a single battery with 15A old tranformator based charged, it was already 13.07V just after disconnect the inverter so during the charging with 12V charger i was hearing bowling or bobbles in the the battery, i charged it alone for 3 hours it was consuming around 8A in average, so started at 12A and end by 6A after that the gravity tended to 1.2 but the bubbles sound worried me. after that I connected them in parallel and put 2 old chargers on them, all that happened I heart bubbles sound, maybe gravity still same or increased a bit.
do you think I need to complete charging even if their voltage if 13.07V each?
 
Yes. Destructive. If one or more batteries are subjected to well over 15.0V because the others are at lower voltage, battery may be damaged.

Example: 58.8V charging (14.7V/battery).

Batteries 1-3 are at 14.2V. That's 42.6. If charging to 58.8, 4th battery is at 16.2V.

Proper charge of each individual battery per datasheet:

Charge at 20.2A until 14.4-15.0V (I would pick 14.7)
Hold 14.4-15.0V until charge current drops to 10.1A
Float at 13.6V for 2 hours.
Check specific gravity to confirm full charge.
 
hello,

thanks for the fruitful information. ok but in my case the one the hasn't been discharged gives a voltage of 13.07V and gravity of 1.250 and that is after after connecting and charging them together in series. but the 3 others batteries are in the red region even if their voltage is exactly 13.07V like the forth battery and that value is after 2 hours of disconnection.
now what is happened during the last 15 hours, I charged one batteries under 12V-12A for 3 hours and then I connected them in parallel all the four batteries. this battery has entered the white region of the hydrometer and the gravities of 2 others (subjected to the capacity test) is very slowly increasing.
now I still connect the 4 batteries in parallel 2 are in the white region and 2 in the red region with gravity values 1.175 and 1.150.
the charging current of the 4 four now is 12A but there is a bubbling sound. is there any good hope?

regards
 
Charge each battery one at a time as follows:

Charge at 20.2A until 14.4-15.0V (I would pick 14.7V)
Hold 14.4-15.0V (14.7V) until charge current drops to 10.1A
Float at 13.6V for 2 hours.
Check specific gravity.

By paralleling them you can't know what is going on with each battery individually.
 
hello

I charged the 3 batteries sometimes each one individual and sometimes 2 in parallel, currently lowest gravity is around 1.200 sometimes I read 1.175 if I flip and turn the hydrometer I see some variation in float glass position. but your are saying charge each until current drops under 10A. :(. 80% of the charging time of a single battery is less than 8 or 7A, 2 batteries may consume 14A and this is reducing with time. during the time that I an typing now the lowest 2 batteries are connected together and charging with 3 old chargers connected in parallel each can charge 15A max but the current enters to the batteries from these 3 chargers is 11A not more. why the charging current of a single battery is always less than 8A? maybe they are fully charged and I am over-charging them? but if this is the situation why the gravity is increasing an tend to its normal value?
I saw it is something complicated the ideally understand lead acid batteries technic.
 
The datasheet indicates what it takes to fully charge your batteries. You need to conduct a full charge in accordance with the datasheet and measure specific gravity.

Once you have done that, you can determine a course of action.

What is your absorption voltage measured AT the battery with a voltmeter?
 
hello,

the charger gives 15 point something at open and when I connected it to the battery it drops to 14.2 or 3 I think, and increase with time to limits 14.8 or 9 also I think. I called the middle east agent today and yhey asked me to carry them to the local dealer I don't know what they will do, I am putting them in the car.

Regards,
 
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