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lv6548 will not charge batteries more than 54.2 volts

Justmee

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Joined
Nov 29, 2021
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I recently purchased (2) lv6548 units and (3) big battery 48 volt hsky's. I currently am only running 1 lv6548 and 1 battery as I am testing my setup.
I ran one battery (A) with the lv6548 and it will not charge the battery past 53.7 volts. I tried to charge battery (A) with a separate 58.8 volt 15 amp charger and it won't charge past 53.7 volts.
I charged battery (B) with the same charger and it charged to 56.2 volts.
I connected battery (B) to the lv6548 and ran it for a week and it will not charge the battery past 54.2 volts. The amperage is charging around 20 amps and at 54.2 volts it drops to around 10 amps and voltage drops to 53.9 volts. This continues throughout the day.
I cannot figure out what I am doing wrong. I have messed with the settings. and there are no changes. I finally just lowered setting 26 to 54 volts and setting 27 to 53.7 as I do not know what continuing to trying to charge this battery past 54.2 volts will do.
Settings:
1. sbu
5. use
12. 48v
13. 50
16.oso
26.58v
27 57v
PV array 6 panels 3s2p 171 volts. At peak I get about 1.2 kw.
Thank you for any help
 
I recently purchased (2) lv6548 units and (3) big battery 48 volt hsky's. I currently am only running 1 lv6548 and 1 battery as I am testing my setup.
I ran one battery (A) with the lv6548 and it will not charge the battery past 53.7 volts. I tried to charge battery (A) with a separate 58.8 volt 15 amp charger and it won't charge past 53.7 volts.

Have you confirmed voltage readings with a separate meter?

Are all wires of suitable gauge?

Are all connections properly torqued?

If yes to all of the above, suspect imbalanced battery with BMS cutting them off.
 
We get these problems often with any inverter model, but they all have one thing in common. Lithium batteries.
If one of your lithium cells is fully charged, and the others are not (even in a fully assembled battery), it will stop absorbing power while charging , this shuts off the charging process.
Yes, you can connect your batteries to a 58V power supply, your batteries will get there in just a few minutes, further indicating that they are just flat out not taking any more charge. when you remove the power supply, they usually drop to the voltage they stopped charging at.

Lithium batteries are not without their problems, in fact they are very far from being trouble free.
 
I recently purchased (2) lv6548 units and (3) big battery 48 volt hsky's. I currently am only running 1 lv6548 and 1 battery as I am testing my setup.
I ran one battery (A) with the lv6548 and it will not charge the battery past 53.7 volts. I tried to charge battery (A) with a separate 58.8 volt 15 amp charger and it won't charge past 53.7 volts.
I charged battery (B) with the same charger and it charged to 56.2 volts.
I connected battery (B) to the lv6548 and ran it for a week and it will not charge the battery past 54.2 volts. The amperage is charging around 20 amps and at 54.2 volts it drops to around 10 amps and voltage drops to 53.9 volts. This continues throughout the day.
I cannot figure out what I am doing wrong. I have messed with the settings. and there are no changes. I finally just lowered setting 26 to 54 volts and setting 27 to 53.7 as I do not know what continuing to trying to charge this battery past 54.2 volts will do.

Do those packs have managed BMSs on them? If not, then you almost have to know what the BMS specs are (get the model number on them and try to find a spec sheet), and check cell voltages to try and figure out what the BMS is doing based on behavior seen...

Some BMS without bluetooth could have a UART serial port on them that one could tap in to and log into it that way somehow, if you know how to interface with it...

Or you might be able to pursue it from another angle and contact Big Battery and tell them that one of the 2 packs is behaving differently, and see if they can send another pack for you to test.

I agree with sunshine_eggo that there could be a problem with the one pack, as you see same behavior when trying to charge it using a different charger and see same problem, the BMS could likely be cutting off.
 
Thank you all for your response,
I have contacted BB and they said to fully discharge the battery and recharge a few times. All of my connections are tight and I am using 2/0 wire. The BB BMS is not accessible. The battery parameters are printed on the battery. The only info I can get from the battery is the digital LED voltage and amp display which never agrees with my meter or inverter display. For instance the inverter and my meter will show 20 amps and the battery displays 8 amps.
I have finally just shut the system down as bad weather and my lack of panels won't keep up with my demand so the inverter would just run in bypass mode.
Over the weekend we had good weather so I fired it up again. The battery charged to 54.7 volts at a charge rate of 28 amps . The charge would not go any higher after a few hours even though I was still charging at 28 amps.
When I turned off the battery at the battery's switch the battery display read 58 volts. so I know the inverter/charger is working.
This battery at one point would shut off at 55.7 volts. The battery display would then read 58.1 indicating that the BMS has shut down the charge. This seemed normal except for it shut down at 55.7 not 58 which is what the battery is rated for and the the inverter is set to charge to.

Am I doing harm to anything by continuing to try to charger the battery at 28 amps when the voltage is not rising?
I am also afraid to connect battery (C) for fear of it not working properly in case it is me that is doing something wrong.
BTW... Ian I do not suspect your products that I purchased to be the problem. And I would recommend to anyone to purchase from you.
 
Last edited:
Since you mention battery (C), this implies that you have A & B powering the unit?

These units have 103Ah each, thus your A+B battery has 206Ah?

Are you saying that the battery is at 54.7V and there is 28A flowing into it, and that you are absolutely certain that this current is going into the battery and not being used by loads?

54.7V / 16 = 3.419V/cell average.

This may be NORMAL. LFP charges at lower voltages than lead-acid with a huge amount of charging below 3.45V/cell. The curve is so flat, the voltage may creep up agonizingly slowly until the very end.

206Ah / 28A = 7.4 hours of charging to charge from empty, so I wouldn't be worried about charging them for just a few hours.

The cut off at 55.7V is at 3.48V/cell average - this is indicative of a high voltage disconnect due to imbalance.

Recommend you continue to cycle the batteries; however, change to:

26: 57.6
27: 55.2
 
Thank you sunsine_eggo for your help,
Yes. My last attempt to charge was with no loads
I am currently only running one battery at a time. Battery (A) or Battery (B) Battery (C) has not been tested yet.
I will eventually connect (A and B) in parallel powering both lv6548's for a split phase setup.
I am concerned about one battery accepting a higher charge over the other since either will charge to 58 volts.
Each battery will quickly charge from 46 volts to 54.6 volts (3 hours or so) then either do not seem to accept a charge even after a couple of hours, but still accepting up to 28 amps. At this point neither battery cuts out.
So I will continue to cycle a battery with 26: at 57.6 and 27: at 55.2 until I see a change .
My next question is how long can I try to charge a battery to full charge ? I don't feel safe leaving for work and letting the battery just sit there with 20+ amps going into it.
Thank You
 
I am concerned about one battery accepting a higher charge over the other since either will charge to 58 volts.

Generally not a concern, but its best to stick with one battery at a time since you're having issues. Once they balance, there should be no issues with paralleling them.

Each battery will quickly charge from 46 volts to 54.6 volts (3 hours or so) then either do not seem to accept a charge even after a couple of hours, but still accepting up to 28 amps. At this point neither battery cuts out.

46V is an incredibly low state of charge - very nearly empty, so you're going to need near 100Ah input. That's 4 hours at 25A.

While this chart isn't exact, it's representative and is useful to illustrated the concept. Note the yellow line:

1640681577926.png
Look how much of the red line is under that level - about 80% of it, and it pops above 3.4V only after about 20-30% charge. At 54.6, you're at 3.41V, so there's more to charge.

When current is flowing into the battery, the rise in voltage is VERY slow. You've already demonstrated that the BMS will trip high voltage protection, so it will protect itself.

So I will continue to cycle a battery with 26: at 57.6 and 27: at 55.2 until I see a change .

Good.

My next question is how long can I try to charge a battery to full charge ? I don't feel safe leaving for work and letting the battery just sit there with 20+ amps going into it.

Since this is a new system, I too would be hesitant to leave it running unattended. It's more so for being able to see what goes wrong when it goes wrong rather than safety.

It's important to understand if you're charging while using loads and what the current value means, i.e., if you're getting 28A, are you sure that 28A is going into the battery, or is it also being consumed by loads?
 
Another thing to note is Big Battery is known for providing less then quality cells that may not be properly top balanced. It only takes one cell to hit high voltage for the BMS to go into safety mode.

The conflicting voltage readings of your meter and display lead me to believe you are another lucky owner of Big Battery box of crap cells & BMS. You are not the first nor the last.

Time to reach out to Big Battery and start the RMA, good luck, they fight tooth and nail taking back one of the failed batteries blaming customer errors.
 
Another thing to note is Big Battery is known for providing less then quality cells that may not be properly top balanced. It only takes one cell to hit high voltage for the BMS to go into safety mode.

The conflicting voltage readings of your meter and display lead me to believe you are another lucky owner of Big Battery box of crap cells & BMS. You are not the first nor the last.

Time to reach out to Big Battery and start the RMA, good luck, they fight tooth and nail taking back one of the failed batteries blaming customer errors.

That's likely why BB told him to discharge and charge a few times first, as they think the BMS balancing will eventually get them balanced out or something, that's all I can figure there...
 
Each battery will quickly charge from 46 volts to 54.6 volts (3 hours or so) then either do not seem to accept a charge even after a couple of hours, but still accepting up to 28 amps. At this point neither battery cuts out.
How can it both be charging at 28A AND not accept a charge? This makes no sense.
 
Thank You sunshine_eggo,
That is what I meant. Being new to these batteries I am not sure what they are doing. I guess I'm not letting them charge long enough. After 4 hours of charging I see the amperage reading at 20 amps or more and voltage rise to 54.7 volts and then the voltage just seems to not increase. even after a 5th hour of charging then I get scared thinking that something is wrong and shut everything down.
My conclusion is that I need to let them charge until the BMS shuts them down no matter how long it takes and I should do this with no other load on the system.
Thanks everyone for the help
 
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