WBjr SOC% and voltage failsafe

[cybermaus]

Hi.

I have a Classic 200 rev 4 with WBjr, about 3 years old now.
It's battery bank is now also 3 years old, at a nominal 440Ah 24V, but I had already set the capacity at 300Ah to account for their age.

So, last night the Power invertor attached to the setup went into error mode. It seemed the battery voltage had dropped to a scary low 21.4V.
(It took a while to wake up and hear the beeping, so the invertor was disconnected already a while. So the 21.4 may have been after some voltage recovery already, making it even more scary...)


Reasoning back, I came to the conclusion the batteries now actually only hold 150~170Ah.
The reasoning is below for those that want to play along, but that is not my question.
Nor is the point that I obviously am in need of some new batteries.


My point is: It is nice that the AUX1 is set to SOC%-HIGH (50% I believe), but if the WBjr is counting down from float to 50%, ergo counts down 150Ah, it should really have some sort of safety net, and if the battery drops to below 22V for a significant time (a minutes or so) it should turn off AUX1, and not go back high until it hits float again. This regardless of the fact it thinks it is still only at SOC 50%


Possibly it is already supposed to work like that, but please let me know if so, and also, if functionality is already like this, what went wrong?
BTW: firmware is about 1.5 years old 1795 (yes, I will update soon)

Thanks



The way I came up with the 150~170Ah current capacity is this:

Last evening SOC% was at 100% float. In the middle of the night the inverter went into error at 21.5V. Unfortunately I did not see the what the Classic though the SOC% was (sorry). But today end of day again it was at 100% float.

According to the logs, both yesterday and today it picked up 4.1KW from the sun, and as I was grid connected all day, all of the 4.1KW must have gone to the battery. So, it takes 4.1KWh to go from dead-flat into float. That is about 4100Wh/24V = 170Ah.

[dgd]

So what are the batteries that make up your 440aH 24volt bank?
Have you measured the voltage of each cell after they have finished charging and after a while when they are discharging. Perhaps there is just one cell/battery that is going bad.
Are they FLA types and are you able to measure the SG of each?
I would NOT be trying to estimate battery capacity rather identify to reason for 21 volts.
Also are you sure the grid feed is not an issue and the bank is really getting a full charge?

Dgd

[cybermaus]

As stated, not the topic :

To restate:

The AUX1 SOC% 50% HIGH setting should switch low as a safety-net when the  voltage drops that low.
That should be so *regardless* of the *reason* of the low voltage.
I would like to know if that is how it already is programmed in the Classic, or what could be any arguments against it.



That is what I'd like this thread to be about. It should not matter *why* the voltage is low, the AUX1 should switch off.
But to answer your remarks, which are not bad in itself: While I did not measure all the cells individually, when full and no charge the battery always shows a good 25.5 or so volts. I will measure the cells for good measure, but that should distract this thread.

[tecnodave]

cybermaus,

Your voltages are too low for a 24 volt bank, first off lead acid batteries are 2.1 volts per cell, not 2.0 as is commonly assumed.......that leaves a dead voltage of 25.2.........so you are not charging your batteries up to 100%..........any "SOC" reading is only an estimate of battery capacity!  The only true indication of "State of charge" is the specific gravity of the acid as measured with a hydrometer!


So......get your battery manufacturers specifications for the exact batteries that you are using......set your controllers to the battery manufacturers specifications!

Then .....if you have removable cell caps on your batteries get a good hydrometer and measure "specific gravity" of each cell and log it......

Then come back to the forum and post your results, including battery manufacturer data....make & model and type of battery.

Just pointing out what you are missing...........

dave

[Halfcrazy]

Aux1 SOC does not have a safety net. I could see a LVD added also but for the most part the SOC should be pretty accurate. You would typically get it adjusted in the beginning and tweak as needed. I have never seen a battery go from 300AH to 150AH in a day or two so that should have shown signs of failure long before?

I will see if a LVD can be added