Sok 100ah 48v batteries draining fast?

[Dieharddan]

Hello, ive been running my system for 2 years without issue, i recently installed an additional battery and seems like the two batteries drain faster than with only one... im currently only using it to power a fridge, freezer, tv and some smaller devices associated with the tv. Before adding a battery i could normally get through the night with 50-60% charge left, but the past few days i wake up to both batteries drained to 0. Im no expert in this and am always learning, is there anything obvious i could be doing wrong?

3.5kwh solar panels.
Sigineer power m3048bp inverter.
2awg battery cables.
110A T Class fuse on + battery cable.
Positive battery cable is about 14" longer than negative due to addition of t class fuse.
two sok 100ah 48v server rack batteries.
Communication cable so bms controls inverters battery settings.
New battery set as master with dip switch 1 set to up and old battery dip switch 2 set to up.


Thanks

 

[BentleyJ]

Is it possible that with 2 batteries the capacity has doubled and they are both not reaching full charge therefore the BMS has partially lost SoC calibration? Screen shots don't show anything obvious other than the Voltage is still 3.3V+ per cell so they are not severely discharged and may be at a higher SoC. Its difficult to determine based on voltage in the middle of the range.
Also, thinking just in terms of Amp Hours. Two batteries at 25% to 30% SoC is the same amount of remaining Ah as one battery with 50% to 60% remaining. In other words if the same total amount of daily charge is now divided up between 2 batteries and they both only get to 50% SoC then over night they are going to drain down to the 25 to 30% shown on the display.

I would charge them up to 100% at 56V. Then check next morning, they both should be at about 75% if your loads are the same as usual.

 

[Solar Guppy]

3.5kw of solar isn't allot, maybe 10kWh / day this time of year?

Start with watts in vs watts out, even if the batteries are not equal sharing loads, that wouldn't explain them going dead.

Either loads increased or generation to charge decreased or both

 

[Dieharddan]

Is it possible that with 2 batteries the capacity has doubled and they are both not reaching full charge therefore the BMS has partially lost SoC calibration? Screen shots don't show anything obvious other than the Voltage is still 3.3V+ per cell so they are not severely discharged and may be at a higher SoC. Its difficult to determine based on voltage in the middle of the range.
Also, thinking just in terms of Amp Hours. Two batteries at 25% to 30% SoC is the same amount of remaining Ah as one battery with 50% to 60% remaining. In other words if the same total amount of daily charge is now divided up between 2 batteries and they both only get to 50% SoC then over night they are going to drain down to the 25 to 30% shown on the display.

I would charge them up to 100% at 56V. Then check next morning, they both should be at about 75% if your loads are the same as usual.

Heres after the batteries fully charged. They show 100% full but are you saying they might not be actually full?

 

[Q-Dog]

Is that 3.3 volts per cell? That isn't anywhere close to fully charged.

Also, I only see 1 battery (lower one) with a communication cable. How does the upper battery communicate?

 

[Dieharddan]

3.5kw of solar isn't allot, maybe 10kWh / day this time of year?

Start with watts in vs watts out, even if the batteries are not equal sharing loads, that wouldn't explain them going dead.

Either loads increased or generation to charge decreased or both

The batteries fill up pretty quick in the morning, just need more batteries to carry me through the cloudy days which is why i added a battery, the load hasn't increased to the 2 years ive had it

 

[Dieharddan]

Is that 3.3 volts per cell? That isn't anywhere close to fully charged.

Also, I only see 1 battery (lower one) with a communication cable. How does the upper battery communicate?

Unless i read it wrong there was only one cable to the can port from the inverter, i questioned whether there should be a cable between the two batteries but didnt see that

 

[Q-Dog]

Unless i read it wrong there was only one cable to the can port from the inverter, i questioned whether there should be a cable between the two batteries but didnt see that

How does the upper battery communicate with the lower battery?

 

[Dieharddan]

How does the upper battery communicate with the lower battery?

My understanding was the master battery gets the communication and the other batteries get addressed as "slaves" via dip switches

https://www.currentconnected.com/manual-4-6/

 

[Q-Dog]

My understanding was the master battery gets the communication and the other batteries get addressed as "slaves" via dip switches

https://www.currentconnected.com/manual-4-6/

Yes, but there should also be a communication cable connecting the batteries to each other so they can talk to each other.

 

[Dieharddan]

Yes, but there should also be a communication cable connecting the batteries to each other so they can talk to each other.

Dk you know if that includes the growatt inverters which uses can port?

 

[Q-Dog]

Dk you know if that includes the growatt inverters which uses can port?

Yes. If you are using battery to inverter communications, the inverter talks to the master battery. Then the master talks to all other batteries ... but it can't talk to the other battery if there is no communication cable connecting them together.

 

[Dieharddan]

Yes. If you are using battery to inverter communications, the inverter talks to the master battery. Then the master talks to all other batteries ... but it can't talk to the other battery if there is no communication cable connecting them together.

Ok, i will try connecting a patcb cable from RS485B and RS485C ports. Do you know how i can fix the batteries showing 100% even though theyre not?

 

[Q-Dog]

Ok, i will try connecting a patcb cable from RS485B and RS485C ports. Do you know how i can fix the batteries showing 100% even though theyre not?

Charge them up fully. 3.3 volts per cell is not fully charged. It should be closer to 3.6 volts per cell.

Do you have a manual that explains the communications connections?

 

[Dieharddan]

Charge them up fully. 3.3 volts per cell is not fully charged. It should be closer to 3.6 volts per cell.

Do you have a manual that explains the communications connections?

Sorry, what do you mean by fully charge them other than having the system on and allowing the panels and inverter to charge them. I have the sok manual but, its not real clear to me regarding growatt

 

[Q-Dog]

Your second set of photos shows your batteries are at 53.2 volts. The fully charged voltage should be 56 to 57 volts. You need to go through your inverter/charger settings and figure out why you are not charging the batteries to full.