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Help! Two U27-12XP parallel connected shutting down 2000W inverter?

ChasRob

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Dec 28, 2019
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Attached is the read out of the two batteries . When fully charged attached to 2000W 12V( Sungoldpower, inverter/charger ), using 1/0 copper welding cables, the inverter shuts down within mins from a load of 130amps(shunt reading) (13watt rated microwave). The voltage starts out at 14.2 volts and drops about 1mV/sec until reaching 12V on shunt meter(about 1min), inverter starts low voltage alarm <12volts and system shuts down load with 3 mins of the start of the load (microwave). Inverter is new and under warranty, Sungoldpower says it my batteries. Batteries charge up well and stay balanced, what do you think is going on? I have tried many different scenarios to fix this problem, but nothing seems to help.Valence #1.pngValence #2.png
 
Based on the WH discharge parameter, that's equivalent to about 400 full depth cycles.

Both batteries, especially the second have high max cell volt and max cell volt time counts. This suggests they were operated without a BMS and overcharged significantly. The 4.1V suggests 16.2V peak, which is a common equalization voltage.

Both batteries have been subjected to about -10°C. If either were charged at that temperature, massive damage will occur.

Both batteries appear to have been subjected to very high charge and discharge currents. That can damage cells.

Based on my limited understanding of the battery data, I would expect that your batteries are heavily used and abused. You are either the perpetrator of said abuse, or you were the victim of either an a-hole or an ignorant seller on ebay.
 
Thanks for the reply, if the cells were damaged you would think that the individual cells would stop taking an charge or be out of the voltage range. The batteries have been in the cold (in the RV) but they were not being charged, or at least by me. Maybe I few others familiar with the valence battery data will reply.
 
Thanks for the reply, if the cells were damaged you would think that the individual cells would stop taking an charge or be out of the voltage range? The batteries have been in the cold (in the RV) but they were not being charged, or at least by me. Maybe I few others familiar with the valence battery data will reply.

Not usually. LFP degradation is either:

1) catastrophic cell failure where the cell drops to near 0V and won't ever take/hold a charge.
2) progressive capacity loss with each damaging event.

#2 is far more common.

The behavior you describe is very consistent with #2.

While I said I have "limited understanding" of that output specifically that's in the context of me accurately assigning meaning to what's being reported. It seems very straightforward, but I'm allowing that I may be misinterpreting something. I would be very surprised if I'm wrong as the units are clearly indicated, and I'm very familiar with what spending 17+ hours over voltage limits may do to a battery as well as charge/discharge currents on the order of 2C will do if they are not rated for it.

Additionally, buying used batteries is a complete crapshoot and requires luck.

I assumed that you've:
  1. Confirmed all of your connections are tight
  2. No fuse or breaker in the line is producing excessive resistance.
  3. You are not seeing a large discrepancy between battery voltage at the battery terminals and battery voltage at the inverter terminals while under load.
If the above are not true, they should be addressed.
 
Yes I have check all connections, ANL fuse/ holder does get hot, should be using a high end T type fuse. I am trying to rule out the inverter if it the problem I need to send it back , (1 year warranty )so I was thinking of hooking up my two wet cell batteries and see if the over load still occurs. Yes buying used batteries is gamble, for the same money I could have built my own lithium pack.
 
Under the heavy load, what is the:

1) voltage at the battery terminals
2) voltage at the inverter terminals.
3) voltage across the ANL fuse/holder.
 
I will check all 3, I have had the voltmeter connected to the inverter terminals, and the voltage starts at 14 volts and drops very rapidly under a 130amp load, dropping to below 12 volts with in 2-3 mins under 82% load via inverter readout. The voltage via the battery software never goes below 12V.
 
Comparing those two voltages establishes if there is excessive drop between them.

If you're seeing a 1600W draw pull your batteries to 12V in a few minutes, your batteries may be in very bad shape.
 
Inverter on: Battery (B)=14V/Fuse(F) 13.99V/Inverter lugs(In)=14V
33% load 52amps B=12.82V/F=12.67/In=12.58
62%load 109amps B=12.2V/F=11.92v/In=11.72v
Inverter shut down (~5mins) B=13.17v/F=13.22v/In=13.21v
 
You've got two batteries so each battery is only putting out 54.5A. Your battery's voltage is starting out at just the right voltage to prove they are as full as they can be. And they fall flat on their face so fast there is no other answer for you then they are bad.
Now the geek in me wants you to do a slow drain capacity test for the purpose of gaining a greater understanding of the characteristics of a bad battery.

 
Thanks Travis, think I will still place the lead acid batteries in the set up just to make sure the inverter is preforming as it should. Guess that is the gamble you take in buying used batteries off eBay, $850 lesson. Do you see anything on the read out that alerts you to the batteries being bad? If so what? I have been looking at you tubes of people building LiFePo2 seems you can build one for a $500.00. Thoughts?
Not usually. LFP degradation is either:

1) catastrophic cell failure where the cell drops to near 0V and won't ever take/hold a charge.
2) progressive capacity loss with each damaging event.

#2 is far more common.

The behavior you describe is very consistent with #2.

While I said I have "limited understanding" of that output specifically that's in the context of me accurately assigning meaning to what's being reported. It seems very straightforward, but I'm allowing that I may be misinterpreting something. I would be very surprised if I'm wrong as the units are clearly indicated, and I'm very familiar with what spending 17+ hours over voltage limits may do to a battery as well as charge/discharge currents on the order of 2C will do if they are not rated for it.

Additionally, buying used batteries is a complete crapshoot and requires luck.

I assumed that you've:
  1. Confirmed all of your connections are tight
  2. No fuse or breaker in the line is producing excessive resistance.
  3. You are not seeing a large discrepancy between battery voltage at the battery terminals and battery voltage at the inverter terminals while under load.
If the above are not true, they should be addressed.
Snoobler, Reading back over what you said and looking at the read out of these two batteries, battery #2 was over charged to 4.1 volts/cell (max 3.8V?) x 4 cells = 16.4 volts for over 17 hrs, battery #1 was 3.842volts x 4cells=15.36V for 1.5 hrs, so this was likely the reason for the battery capacity lose/damage? And perhaps the charging also occurred at 14F. The inverter charger I have should cut off at 14.4, so not sure how it could have gotten to 16.4V. I also have been running heat in the RV to protect the batteries. If indeed the inverter overcharged the two batteries, would the readout not be the same? Just trying to figure out if I damaged the batteries or did I buy them already damaged. Really does not change anything ,I am still out $850 and I still need two more batteries!
Not usually. LFP degradation is either:

1) catastrophic cell failure where the cell drops to near 0V and won't ever take/hold a charge.
2) progressive capacity loss with each damaging event.

#2 is far more common.

The behavior you describe is very consistent with #2.

While I said I have "limited understanding" of that output specifically that's in the context of me accurately assigning meaning to what's being reported. It seems very straightforward, but I'm allowing that I may be misinterpreting something. I would be very surprised if I'm wrong as the units are clearly indicated, and I'm very familiar with what spending 17+ hours over voltage limits may do to a battery as well as charge/discharge currents on the order of 2C will do if they are not rated for it.

Additionally, buying used batteries is a complete crapshoot and requires luck.

I assumed that you've:
  1. Confirmed all of your connections are tight
  2. No fuse or breaker in the line is producing excessive resistance.
  3. You are not seeing a large discrepancy between battery voltage at the battery terminals and battery voltage at the inverter terminals while under load.
If the above are not true, they should be addressed.
 
And Travis battery #1 show "1 error" and "1 under temp count," and "under temp for 128sec" can enlighten me to what this means? Is it related to charging?
 
The battery data is its entire history. Likely those were done by the previous owner(s).

I'm assuming you've reported voltages based on the use of a voltmeter, and not voltages reported by equipment.

109A @ 12.2V through 1/0 3 feet long (I'm guessing) should only see a 0.06V drop

You're showing nearly a 0.5V drop. If this is a 20' long run, you should see about 042V drop.

#3 was "voltage across the fuse," i.e., check voltage from one end of the fuse to the other. Also worth checking the resistance through the fuse with an ohmmeter.

Given that your fuse gets hot, I suspect the fuse is causing excessive voltage drop causing the inverter to crap out. Again, a poor quality or loose connection can do the same.
 
The battery data is its entire history. Likely those were done by the previous owner(s).

I'm assuming you've reported voltages based on the use of a voltmeter, and not voltages reported by equipment.

109A @ 12.2V through 1/0 3 feet long (I'm guessing) should only see a 0.06V drop

You're showing nearly a 0.5V drop. If this is a 20' long run, you should see about 042V drop.

#3 was "voltage across the fuse," i.e., check voltage from one end of the fuse to the other. Also worth checking the resistance through the fuse with an ohmmeter.

Given that your fuse gets hot, I suspect the fuse is causing excessive voltage drop causing the inverter to crap out. Again, a poor quality or loose connection can do the same.
Yes I used a voltmeter at battery terminals, and inverter terminals , but the fuse only getting reading probe too fuse and probe too ground, this is a gold plated fuse with lugs torqued to 15ftlb (suggested) but its not what should be used, will replace with a high end T type fuse, since this is a catastrophic fuse use to protect system. Hope you saw my comment about the over voltage ,I just got what you were communicating. However you comment on the Max discharge 28.5amps(28527) and Max charge 25.5 amps(25493), the specs on batteries say 65A Max cont. current charging, and 150amp cont. current discharge. I know the inverter charger shows about 60amp starting charge but quickly starts dropping.
 
And Travis battery #1 show "1 error" and "1 under temp count," and "under temp for 128sec" can enlighten me to what this means? Is it related to charging?
The battery was under temperature for 128 seconds. The lowest temperature it was ever at was 14゚F. I'm in Hawaii and there's no cold temperature here so I haven't played around with the under temperature stuff. And not sure if it means that it was actually used while it was under temperature or not but I have a feeling that no. I'm in Hawaii and there's no cold temperature here so I haven't played around with the under temperature stuff. And not sure if it means that it was actually used while it was under temperature or not but I have a feeling that no. I have plenty of batteries with under temperature counts In their history and the batteries perform just fine today.

Another thing to consider is that these batteries are not able to record this kind of information unless there connected to a laptop or BMS. If the last owner used them without these things in place there could have been all kinds of abuse that wouldn't have been recorded.
 
Another thing to consider is that these batteries are not able to record this kind of information unless there connected to a laptop or BMS. If the last owner used them without these things in place there could have been all kinds of abuse that wouldn't have been recorded.

Do you know this for certain? That seems very counterintuitive for a battery capable of reporting in this manner. While logging charges and discharges and detailed voltage behavior may require a laptop, the event log is only keeping counts and min/max values.

Have you verified that if you discharge the battery some Wh value, that the count doesn't increase unless a computer is connected?
 
Do you know this for certain? That seems very counterintuitive for a battery capable of reporting in this manner. While logging charges and discharges and detailed voltage behavior may require a laptop, the event log is only keeping counts and min/max values.

Have you verified that if you discharge the battery some Wh value, that the count doesn't increase unless a computer is connected?
yes & yes
 
Thanks. That's an argument to NEVER purchase these used. Disturbing the BMS permits operation outside those limits to the extent visible on those batteries.
There all used but the trick is to Purchase them directly from their original installation. Because in the original installation they have a uBMS so they were protected in every way.
 
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