Where is my power going?

[jimf909]

What has happened to this thread? Is anyone trying to assist the OP with these posts?

 

[zanydroid]

What has happened to this thread? Is anyone trying to assist the OP with these posts?View attachment 185644

It went a little off, sure. Though I wouldn't characterize that as "not trying to assist" -- multiple decent to very good answers was already given, and it's up to OP to synthesize.

(Also I don't really understand the wording of the banner, this is still somewhat on track compared to the threads that really went off. An alternate solution would be to have an easier way to branch discussions without hard-creating a new thread).

 

[Zwy]

Which part do you mean? " Those are not LFP cells, those are LiIon" Which must mean everything I said isn't LEP, so the seller of the BigBattery Lifepo4 battery is not LFP/Lifepo4? comments like that are how the OP and others will lose track of this thread, and clearly shows you may post a lot but have little understanding of what you are talking about,

I quoted your post and responded to the part about the Samsung cells which are LiIon. The reason for quoting your post is to direct the response to what you had posted. That is how those reading can understand the response.

And If you are talking about the Samsung 25R cells, yes it is not Lifepo4 but ether Lithium chemistries can do their balancing in the same way, the only reason I used the 25R cell + BMS for an example was it was resent in my mind, but I like plenty of others have had the same findings with Lifepo4 BMS balancing just the same, and as I build and often repair battery packs using both chemistries you get to see it all first hand.

Referring to LiIon in this thread will just confuse the OP even more.

 

[Mattb4]

Yeah, me too. From day one i have been curious as to why they don't drain equally, it seems like every other day my system decides to deplete one battery for a day or two, then the other. Never made sense to me.

As your curiosity is telling you such behavior is not normal for two paralleled batteries. There would have to be some kind of circuit that apportioned that to happen, a bad battery or a connection problem. As someone else in this Thread mentioned (might have been lost in the Static) in regards to isolating the problem area you would want to try charging up and running from just 1 of your Big Battery units. Then try running from the other. Note your loading and how the batteries carry it to determine if capacity seems less than rating. You may be into Warranty area if Big Battery has such.

 

[New England Rhinoceros]

Please post your charging settings.
The more detailed info you can provide about your equipment the better.
Provide the specific link to your Battery Packs.

LFP is a fairly simple charge profile. It is two-stage, meaning it uses (Constant Current - Constant Voltage) for Bulk & Absorb cycles and then switches to (Constant Voltage - Variable Current) for Float to finish off the last 5% +/- and top-off / balance the cells.
* Absorb can be set to 1 hour, but would likely never reach that period as Endamps will be triggered and switched to float by that time usually..

The Transition from Absorb to Float occurs when the EndAmps/Tailcurrent is reached. This is when the internal resistance of the batteries increases to a point where they are 95% Full (real world) and can only accept a lower charge. EndAmps/Tailcurrent is calculated as follows:
100AH X 0.05 = 5A or 280AH X 0.05 = 14A

For a STANDARD 48V - 16S (16 Cell Pack) the voltages should be as follows.
54.400V (3.400 Volts per cell) = 100% full.
51.200V (3.200 Vpc) = 50% SOC and is also the Nominal Cell Voltage.
48.000V (3.000 Vpc) = 0% SOC technically *1
*1 Many people will allow it to go down as far as 2.700Vpc 43.200V and set Low Volt disconnect thee to prevent bricking the BMS if it gets too low.

Take Note: There is some general confusion & misunderstandings with regards to LFP voltage ranges. ALL Batteries have Two Ranges, the Allowable & Working voltage ranges..
LFP Allowable (which does not harm cells) is from 2.500 to 3.650 Volts. This is NOT working range.
LFP Working Voltage Range is from 3.000-3.400 which is what range delivers the specified AH rating of the cells @ Nominal Temp of 25C/77F.
LSF will ALWAYS Settle post charge, this is normal & expected. Generally we suggest charging to 3.450-3.500 MAX which will then settle to around 3.400 after about an hour post charging.

A NASTY GOTCHA !!!
When charging a battery pack, is one cell races ahead and triggers a High Volt Disconnect because it reached 3.650+ Volts, that will make the BMS report 100% Full, even if all the other cells are below 3.400. This kind of behaviour can be managed to a point by careful adjustments to teh charging profile.

Last Note on Voltage Readings.
The Battery Pack(s) voltage readings are what matters most. 99% of the time an AIO / Inverter / SCC will see 1 voltage but through line losses and wire resistance, this will not match the voltage at the battery terminals. This requires adjustments on the charger side to ensure you are not sending more power, even a 0.1 Volt difference can cause issues. Also the Low Volt Disconnect for teh Inverter Side has to be right, otherwise it could cut off too early or worse too late resulting in a bricked BMS.

Please download these resources, they will be helpful to have handy when your looking at the voltages etc.
Also grab the UPDATE graphic as well...
General LiFePO4 (LFP) Voltage to SOC charts/tables 12/24/48V

Good Luck, Hope it helps.

Good morning. Thank for all the input yesterday, I apreciate it. I stopped trying to charge last night, my batteries wouldn't get above 98% charge. Back at it this morning. Most of my cells are at 3400mv, some at 3500mv. Both of my batteries indicate full charge in less than three minutes at the rate they're charging but one is at 98% and the other is at 96%. neither one have budged from that point for over 20 minutes.

 

[Quattrohead]

Can you see if there is balancing taking place on the cells at this point?

 

[New England Rhinoceros]

Can you see if there is balancing taking place on the cells at this point?

I can't tell. The majority of my cells during charge are reading 3400mv, some at 3500mv. After 40 minutes I shut my generator off cuz I felt like al I was doing was wasting fuel. If you think I should just let it go I'll fire it back up. I'm beyond frustrated.

 

[smr.ruby]

Good morning. Thank for all the input yesterday, I apreciate it. I stopped trying to charge last night, my batteries wouldn't get above 98% charge. Back at it this morning. Most of my cells are at 3400mv, some at 3500mv. Both of my batteries indicate full charge in less than three minutes at the rate they're charging but one is at 98% and the other is at 96%. neither one have budged from that point for over 20 minutes.

Rhino: this is why suggested to you set float to a bit over 56V or to at least the 55.6V spec in the manual. As I showed in the graph many BMSs won't show full charge until they have no current flowing at their specified charge voltage. Your batteries are "mostly" full and they are probably both at 98% in reality . But the SOC indicator is based on counting amp hours in and out of the battery and it isn't perfect. To reset to 100% it needs some clue (varies by BMS) such as no current at stated charge voltage or one cell going to over volt. I know with 100% certainty that if I only float my batteries at 54V the BMS will never make it past about 96-97% SOC but they are probably really closer to 99.5%.

While I don't disagree entirely with those that took this thread down the merits of not fully charging for battery life etc etc that isn't going to help reset your SOC and is a bit off topic to you solving your problem, to do that you need to satisfy whatever the BMS expects to check off as 100% - probably a 55.6V charge with no current flowing for a minute or two and then BANG, it will trip to 100%. and after that if you feel better you can set float down to below the manufacturer recommended voltage to satisfy those that feel you should not follow the recommendation. Which again I don't completely disagree with, but whomever made the BMS has some threshold they are waiting for to hit full charge. If you don't make it back to 100% SOC once a month or so your %SOC will always be off - which frankly isn't a big deal but I personally believe for the sake of your further diagnosis you should get it to 100%.

I run a similar RV setup to you and in the winter I run a float at 56.4V and get to 100% charge every week or so. In the summer when I have no shortage of sunshine and don't need the heater fan I run float at 54V. So there, happy compromise.

 

[New England Rhinoceros]

Rhino: this is why suggested to you set float to a bit over 56V or to at least the 55.6V spec in the manual. As I showed in the graph many BMSs won't show full charge until they have no current flowing at their specified charge voltage. Your batteries are "mostly" full and they are probably both at 98% in reality . But the SOC indicator is based on counting amp hours in and out of the battery and it isn't perfect. To reset to 100% it needs some clue (varies by BMS) such as no current at stated charge voltage or one cell going to over volt. I know with 100% certainty that if I only float my batteries at 54V the BMS will never make it past about 96-97% SOC but they are probably really closer to 99.5%.

While I don't disagree entirely with those that took this thread down the merits of not fully charging for battery life etc etc that isn't going to help reset your SOC and is a bit off topic to you solving your problem, to do that you need to satisfy whatever the BMS expects to check off as 100% - probably a 55.6V charge with no current flowing for a minute or two and then BANG, it will trip to 100%. and after that if you feel better you can set float down to below the manufacturer recommended voltage to satisfy those that feel you should not follow the recommendation. Which again I don't completely disagree with, but whomever made the BMS has some threshold they are waiting for to hit full charge. If you don't make it back to 100% SOC once a month or so your %SOC will always be off - which frankly isn't a big deal but I personally believe for the sake of your further diagnosis you should get it to 100%.

I run a similar RV setup to you and in the winter I run a float at 56.4V and get to 100% charge every week or so. In the summer when I have no shortage of sunshine and don't need the heater fan I run float at 54V. So there, happy compromise.

Thank you, I appreciate all the feedback. This thread definitely created a lot of back and forth with other users that was a bit confusing for me.