Growatt SPF 3000TL LVM-ES: System working last night--tonight battery measures .6 volts??!

[rsi77]

My system has been running flawlessly (as far as I could tell) since April of this year. Yesterday I was in the garage and noticed the normal charge on the battery. This evening I went in the garage and the system was completely dead, and my refrigerator and freezer were not being powered. They were still cold so they lost power a relatively short time ago. I briefly checked my panels and they are not shorted--they are reading a very low voltage (it's nighttime). I shut off the panels and read the battery power--it's only reading .6 volts. What could kill the battery in less than 24 hours. Even with no charging I'm certain my battery should be able to power the load for a couple days. I guess I will know more tomorrow when I can check my array with the sun shining. Could there be a short inside the Growatt? The panels run through a combiner box with breakers. And my panels are fused.
I'll have more data tomorrow.

 

[rsi77]

The panels are generating the expected voltage, but the system will not turn on. According to the manual the Growatt won't turn on if the batteries have insufficient voltage. They recommend charging the battery, or replacing the battery. The only way I have to charge the battery is through the Growatt, but at this point I'm not even sure it's working. My batteries definitely have "insufficient voltage", but I'm don't know how that happened. They went from 51volts to 0.6 volts in less than 24 hours. The system should shut off once the battery voltage drops too low (I believe the setting is 46 volts or there about).
Do batteries simply "break", even when not being subject to some remarkable event? The batteries I'm using are 2 x 24V (100Ah) Ampere Time in series for 48V service.
Thanks,
Ron

 

[Mattb4]

Are your batteries LiFePO4? If so and your BMS tripped on low voltage they will need to be charged with a dumb charger or jump started to get them operating again. You are correct that your Growatt will not be able to charge until it sees sufficient battery voltage.

 

[rsi77]

Are your batteries LiFePO4? If so and your BMS tripped on low voltage they will need to be charged with a dumb charger or jump started to get them operating again. You are correct that your Growatt will not be able to charge until it sees sufficient battery voltage.

Thanks! Could you explain "dumb charger"? (Yes, they are LiFePO4.)
But how can the batteries read 0.6V if they should have disconnected at 46V?

 

[Mattb4]

A lot of smart chargers require a battery voltage before they will start to operate. Dumb chargers are basically a DC power supply.

 

[Mattb4]

Although it is written about Battle Born 12v batteries this Blog might be of help. https://battlebornbatteries.com/low-voltage-disconnect/

 

[rsi77]

Thanks! That was very helpful. So it seems likely my batteries are cut off internally by the BMS, and only need a "jump" to get back above the critical shut-off point. If so, it means I may need to give them more charge during the daylight hours so they can last the night now that we are encountering shorter days.

 

[rsi77]

I also found the following on the Solacity Inc. website:

Jump-Starting The BMS​

To make the BMS switch on again after a low-Voltage disconnect event the battery needs to see a charging Voltage. How much exactly varies from brand-to-brand, but generally this means 14.0 Volt or up (for a 12V battery). Keep in mind that inverter-chargers won’t work without a battery, nor will solar charge controllers. They need to see regular battery Voltage to function. That means you cannot switch the battery BMS back on by charging from a generator (via your inverter-charger) or your solar panels. To make the BMS switch on again you either need a 120V AC charger that can do “dead battery charging” as it is usually called in the brochure, meaning it puts out a charging Voltage even if it does not sense a battery. Alternatively you can “jump start” the switched-off battery by taking another battery of the same nominal Voltage, even a lead-acid battery, and connect it in parallel with the dead battery, and then charge via solar or your inverter-charger. As soon as the Voltage reaches high enough the BMS will sense it and switch the battery back on again. At that point you can disconnect the extra battery, but please keep charging so the empty battery does not immediately switch off again with the slightest load.

 

[acdoctor]

I am not telling you this is what you should do,I am saying it is what I would do. As a option you could use a solar panel connected directly to the battery it may take 2 in series to get the required voltage to wake it up. I would use a volt meter on the battery connections to ensure I am producing the correct voltage. Higher than the BMS low voltage disconnect and lower than the high voltage disconnect.

 

[Mattb4]

You may want to check your Growatt low voltage cut off setting and tweak it up a bit if you manage to wake up your batteries. It should be high enough to prevent a BMS low voltage cut off.

 

[JWLV]

Once you get it all working again, you may want to analyze how much power your refrigerator/freezer uses, what your LiFePo4 battery capacity is, and average solar power generation.

A lot of people tend to underestimate how much power a refrigerator/freezer uses (me included). Previously I had a 1500W solar array that's was powering a 7 cu ft chest freezer and a side-by-side refrigerator/freezer. I have two 12v 300AH LiFePo4 batteries. The entire system shut down around 4am after a cloudy day. I ended up adding another 750W of solar panels and it's been running ok since then, even after some rainy days.

 

[rsi77]

You may want to check your Growatt low voltage cut off setting and tweak it up a bit if you manage to wake up your batteries. It should be high enough to prevent a BMS low voltage cut off.

I was thinking the same thing--I'd rather lose power just for the evening, and then have it turn on automatically once the sun started shining, rather than lose power and be forced to intervene with a manual recharge. But I will also want to add some kind of alarm so that I'm aware if/when that happens.

 

[SYKSolar]

Question: Did you guy have a AC input connected to your inverter or you just have PV array input? I have the same 3000K ES Inverter with 48V100AH and 6x320W PV array.

 

[rsi77]

Once you get it all working again, you may want to analyze how much power your refrigerator/freezer uses, what your LiFePo4 battery capacity is, and average solar power generation.

A lot of people tend to underestimate how much power a refrigerator/freezer uses (me included). Previously I had a 1500W solar array that's was powering a 7 cu ft chest freezer and a side-by-side refrigerator/freezer. I have two 12v 300AH LiFePo4 batteries. The entire system shut down around 4am after a cloudy day. I ended up adding another 750W of solar panels and it's been running ok since then, even after some rainy days.

Yes, especially with Fall/Winter on the way. I was good all summer, but now there is less sunlight, and apparently I hit the limits of my current system. I already measured my refrigerator and freezer power usage using a Kill-a-watt, but I need to access the actual power of my solar system.

 

[rsi77]

Question: Did you guy have a AC input connected to your inverter or you just have PV array input? I have the same 3000K ES Inverter with 48V100AH and 6x320W PV array.

I have not yet connected it to AC power--but I have all but made the connection.
My current array is 6 x 250 W (nominal). I only have about half of my panels set up, so I will likely set up another array and add it to the combiner box in the coming weeks.

 

[rsi77]

I am not telling you this is what you should do,I am saying it is what I would do. As a option you could use a solar panel connected directly to the battery it may take 2 in series to get the required voltage to wake it up. I would use a volt meter on the battery connections to ensure I am producing the correct voltage. Higher than the BMS low voltage disconnect and lower than the high voltage disconnect.

That's actually a really good idea, and would save me some money. Without even modifying the panel wiring, I could cover some of my panels with a tarp and see if I can achieve an appropriate voltage for manual recharge of the batteries. (My panels are mounted on the ground.)

 

[SYKSolar]

I have not yet connected it to AC power--but I have all but made the connection.
My current array is 6 x 250 W (nominal). I only have about half of my panels set up, so I will likely set up another array and add it to the combiner box in the coming weeks.

Since you didn't have AC input on your system, your load must have drained the battery. But how could Growatt not shutting in down when the battery hit 46V that I don't understand? If you have AC input and set it to SBU, Grid power would safeguard/support your load when PV and Battery power are not available

 

[acdoctor]

Since you didn't have AC input on your system, your load must have drained the battery. But how could Growatt not shutting in down when the battery hit 46V that I don't understand? If you have AC input and set it to SBU, Grid power would safeguard/support your load when PV and Battery power are not available

His LFP battery likely disconnected from low cell voltage rather than low pack voltage. Once he gets it going he will need to look into that.

 

[rsi77]

His LFP battery likely disconnected from low cell voltage rather than low pack voltage. Once he gets it going he will need to look into that.

So what you're saying is that my total voltage likely read higher than the BMS cutoff point, but that the BMS detected a low voltage in one of the cells which initiated the cutoff. Thus I might have one or more bad cells in my batteries? Am I understanding your post correctly?

 

[rsi77]

Back up and running?. Thanks for the help. I did use my panels to briefly charge the batteries and once they started reading a voltage again I connected my full array to the Growatt and everything turned on.
I found that my low voltage shutoff was set to 42V which is the default. I've never seen the reading dip below 50V, and I'm not sure at what voltage the internal BMS will shut down the batteries. I changed the shutoff voltage to 47V for the time being.
I'll check the system tomorrow morning before he sun comes up and see what the voltage is. If the issue is a single cell in the battery, I'll have to learn more about how to troubleshoot that.
Ron