Low specific gravity of new batteries..

saltas84 · October 2016

Hi!I have a problem with my new baterries 6 x 2V Opzs batteries 500AH c120.
My offgrid solar system is: 2 x solar panels 240watt ---total 480watt, 1x charge controller tracer 4210 RN 40A,1 inverter victron energy 1200w/12v. I use maximum 1 kwh per day.My charger shows that the battery is full ,flash battey led indicator,voltage of battery shows 12,7 V but specific gravity is only 1,21 kg/l .I make equallization but nothing change the next days.

mcgivor · October 2016

Personally I would get another hydrometer and verify the one you have, if you have not done so, especially if everything else looks good.

softdown · October 2016

95% chance it is the meter.

Mangas · October 2016

After using mine, I flush with distilled water.

I keep two on hand.

mcgivor · October 2016

With regards to hydrometers, the plastic flag/float things are not accurate like the glass tube type and the better the quality....well you know the rest.

saltas84 · October 2016

Thanks for your answers.I checked the specific gravity of batteries with two deferrent hydrometers with same results.I suppose that my batteries charges only at 75%.Someone tell me that new batteries have full capacity after 50-60 cycles.

mcgivor · October 2016

What are your voltage readings, with an accurate digital volt meter, no load, no charging after 2 hours? This will give an indication of state of charge, if you are 12.7V.you are at or near 100%

saltas84 · October 2016

My voltage readings are 12.7V,no load, no charging after 2 hours, but specific gravity stays at 1.21kg/l. I disconnect solar panels for one day and i spent 1kwh.when i checked voltage readings were 12.1V and specific gravity 1.175kg/l. So battery bank can't full charge..Why charger stop charging at 65-70%?

saltas84 · October 2016

Charging voltage is 13.8 -14.6V and current maximum 26A. I suppose tha low voltage and low current is the problem....

BB. · October 2016

You can charge st 10% or more rate of charge. You are at 5% right now (we use 20 Hour rate, so your capacity will be lower, and your rate of charge higher (using our rules of thumbs).

When charging, do the cells bubble/fizz at the end of charging (good thing).

Have the plates ever been exposed to air (bad thing). Using distilled or similar water to fill the cells (water with minerals or organics can kill cells).

-Bill

westbranch · October 2016

As far as I can see they are standard FLA batteries, that being so It looks like you need to do an equalizing or 'so called "Commissioning EQ Charge" but first try a charge at the recommended maximum Voltage and tell us what you observe.... there should be some bubbling in all cells if they are only getting to 12.7V.
Also you should be seeing the voltage as 13.8 or what ever if you measure it while the charge is proceeding. if it is not that high or higher your charger is not working.

Vic · October 2016

saltas84 said:

Charging voltage is 13.8 -14.6V and current maximum 26A. I suppose tha low voltage and low current is the problem....

Hi saltas84,

Does your Charge Controller (CC) have a Remote Temperature Sensor mounted on one of the batteries? This is very important for almost all systems.

When measuring voltages, it is often important to know the temperature of the battery, as temperature had a fairly large effect on measured battery voltage. Therefore, measuring Resting voltage to try to determine State Of Charge (SOC) really needs to be compensated for the temperature of the batteries.

For Flooded batteries with electrolyte SGs in the normal 1.265-ish range, Gassing Voltage for a 12 volt battery bank at about 25 C should be about 14.4-ish volts. There can be some minimal bubbling below this voltage, but this is usually very minor.

Does your CC have the ability to do an Equalization charge?

Thanks for any answers that you can provide. Vic

westbranch · October 2016

According to page23 of the manual you should be charging at 14.6V for Boost (Absorb) and 14.8 in an EQ
https://pageshot.net/l5cx8qm8AFhyHSTd/www.epsolarpv.com

and the unit has Temp Compensation capabilities too, Do you have a Temp sensor?

westbranch · October 2016

table of specs
https://pageshot.net/tgrc4SO1X2n6vmFQ/www.epsolarpv.com

Vic · October 2016

Wb, in searching for the Tracer 4210 RN manual, get different specs for Boost and EQ -- Boost at 14.8 V, and EQ at 15.5 V for Flooded batteries. The OP must have Flooded batteries, as there are statements of measured SGs.

saltas84, what are the exact model number of your OPZS batteries?

It appears that there may be a Temperature Sensor, but it is implied that it is inside the CC.

It might be time for a new, and even more capable CC, which has adjustable Absorb voltage and time, and allows a manual EQ, with adjustable EQ voltage and time, and has the ability to measure the actual battery temperature, IMO.

FWIW, Vic

mcgivor · October 2016

Seems strange how different controllers have such variations in their charging algorithms, the Morningstar TS 60 PWM for example has 3 settings for FLA batteries, (1) absorbtion 14.4V EQ 15.1V (2) absorbtion 14.6V EQ 15.3V
(3) absorbtion 14.8V EQ 15.3V, all 3 have the same float at 13.4V. Custom settings can also be programmed but these are the default algorithms.

Based on the above algorithms would 14.8V in EQ seem a little on the low side as many battery manufacturers recommend somewhere in the low 15V range especially for lead antimony which need 14.4 to15.0V charge and a 120% equalization overcharge.

Perhaps as a standby a lower setting is preferable but cyclical ? Been reading a lot ang learning every day and it seems there is still more to learn.

mcgivor · October 2016

Been thinking, as always, when charging, what are the voltages at the CC and the battery and dose your CC have battery sense wires to the battery to compensate for volt drop between the two? The reason I ask is, if the CC voltage is at the setpoint but lower at the battery, it may think it has reached full charge when in fact it has not and terminates the cycle early, hence never reaches full charge.

mcgivor · October 2016

The previous comment should read, what are the voltages at the CC and the battery whilst charging.

BB. · October 2016

Some (but not many) have "sense leads". Sense leads are very common in computer systems where you are working with very low voltages (5 volts and below) with tight tolerances (5% or better).

Most charge controllers do not take controller to battery voltage drop into account (would be very easy V=I*R -- program the wire resistance into the controller and it would work about as well as remote sense leads). That is why I suggest that you have no more than 0.10 to 0.05 volt drop (for 12 volt battery bank) between the controller and the battery bank (short/heavy gauge wiring).

As for low EQ voltage--If you are putting the system way for winter (such as a cabin)--You do not want high EQ voltage "boiling" water away while you are not there to monitor the cells/add distilled water.

Others believe that EQ, rather than done for an hour or two every month, should be only done when the cell to cell SG varies (high to low) by more than 0.015 to 0.030 SG units. So setting low EQ voltage would be a way to "turn off" the manual EQ--Or at least not boil the battery dry while you are away.

Solar batteries seen to have a larger electrolyte storage/capacity above the plates vs something like forklift and other batteries). So, the amount of "auto EQ" vs a person there to monitor electrolyte levels can vary based on battery brand/model.

-Bill

mcgivor · October 2016

My point is that the volt drop with no current flow between the controller is not a constant, as current increases the volt drop increases and not knowing the conductor size used, could potentially be an issue. Without such details, it is a matter of leaving no stones unturned as I have no idea as to the electrical experience saltas84 has and it appears he/she has fallen silent, perhaps the problem has been solved. The battery sense input to the controller was simply an offering of help as my controller has one and recommends using it.

BB. · October 2016

And, if you know the maximum current and length, you can use a simple voltage drop calculator.

For example, say 60 amps, one way length 4 feet (some calcs use two way distance), and a maximum of 0.10 volt drop (for a 12 volt bank, 2x for 24 volt, and 4x drop allowed for 48 volt bank). Try a few values of AWG until you get one that works:

http://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=0.8152&voltage=14.5&phase=dc&noofconductor=1&distance=4&distanceunit=feet&amperes=60&x=58&y=23

4 AWG:
Voltage drop: 0.12
Voltage drop percentage: 0.83%
Voltage at the end: 14.38

Many controllers, the largest wire (without splicing or cutting off a few strands) is around 4 AWG...

This shows how 12 volt systems with there low voltage drop margins, high currents, and any longer wire runs are difficult to work around.

-Bill

Low specific gravity of new batteries..

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