Senbury LiFepo4 cells 280ah

[Luthj]

Do you have especially long or low gauge cell sensing wires? If so the voltage drop from the BMS power consumption would create an offset on whatever wires see the current.

 

[shavermcspud]

Do you have especially long or low gauge cell sensing wires? If so the voltage drop from the BMS power consumption would create an offset on whatever wires see the current.

Theyre the standard balance cables that were provided, about 25cm

 

[Bob B]

@shavermcspud Have you tested to see if there any change if you unplug the relay outputs from the Chargery ... using internal power?

 

[cinergi]

Revelation time

I just had a thought, as i'm powering the BMS from the battery pack itself, it also has the option to use an external DC power supply with a little toggle switch. although completely impractical for my use, ive run an extension cord outside to my battery box, pluged in a 12v wall adapter and changed the switch from internal power to external on the BMS. Instantly all voltages now read correctly within 5mv of each other on the BMS display

No idea why or how or what but its working.


Again I cant use this setup full time as my battery box is outside with no easy mains power access, so I think based on that alone they will have to go back to chargery, this is either a massive oversight on their part hence why some people don't see any issues and some do.

Anyone else confirm this for me?

Fascinating. I'm currently externally powered as I'm in a 4s configuration. This makes me want to create an 8s configuration (I can temporarily do that) and see what happens.

To the point of other comments, I too am curious what happens if you disconnect or turn off the relay (or DCC or whatever you have) ... If there's truly a design issue, I'm hoping you can help us all debug it so we can get chargery to fix the problem ... if you have time & energy (no pun intended). I'll create an 8s config and report back. Might be several days (I'm away this weekend).

 

[cinergi]

How hard would it be for you to create an 8s configuration and let it sit, self-powered? Sorta wondering if this is a problem with >8s ...

 

[Bob B]

The cell voltage accuracy on my 4S pack seem to be fine whether powered externally or externally ... but right now I am using relays with a low current draw.
It seems pretty odd that the larger pack would be the one to have problems when internally powered ... I sure would have predicted the opposite.

Really glad you thought to troubleshoot with an external power supply. Sometimes the process of elimination works in spite of the fact it doesn't seem likely.

 

[shavermcspud]

@shavermcspud Have you tested to see if there any change if you unplug the relay outputs from the Chargery ... using internal power?

I will take those out of the loop today and report back..

 

[shavermcspud]

The cell voltage accuracy on my 4S pack seem to be fine whether powered externally or externally ... but right now I am using relays with a low current draw.
It seems pretty odd that the larger pack would be the one to have problems when internally powered ... I sure would have predicted the opposite.

Really glad you thought to troubleshoot with an external power supply. Sometimes the process of elimination works in spite of the fact it doesn't seem likely.

What BMS are you using? is it the smaller chargery version?

 

[Bob B]

What BMS are you using? is it the smaller chargery version?

It is the BMS8T.

 

[shavermcspud]

Well it all turned to utter sh1t last night.

Got up this morning, neither the BMs cut off or the inverter low voltage disconnect at 48v two cells down to 2.1v. I give up.

 

[Dzl]

Well it all turned to utter sh1t last night.

Got up this morning, neither the BMs cut off or the inverter low voltage disconnect at 48v two cells down to 2.1v. I give up.

Jesus, you are having a run of really poor luck, I'm sorry your having such a poor experience.

Have you
(1) Made sure this is actually the case with a multimeter
(2) Charged the cells back up to a normal levels (I vaguely recall you want to charge slowly to recover from undervoltage, but I may be mistaken)

 

[shavermcspud]

Jesus, you are having a run of really poor luck, I'm sorry your having such a poor experience.

Have you
(1) Made sure this is actually the case with a multimeter
(2) Charged the cells back up to a normal levels (I vaguely recall you want to charge slowly to recover from under voltage, but I may be mistaken)

Yep both read exactly the same as the BMS for a change, ive put the two cells on my Lifepo active model balancer and bringing them to 3.2v at 2amp they seem to have recovered but what damage has been done i dont know.

 

[Dzl]

Yep both read exactly the same as the BMS for a change, ive put the two cells on my Lifepo active model balancer and bringing them to 3.2v at 2amp they seem to have recovered but what damage has been done i dont know.

Since the BMS is suspected to be defective, Its not too hard to imagine the LVD on the BMS failing, but the inverter too? Any idea what went wrong there, what is the inverter LVD voltage?

 

[shavermcspud]

I was kind of hoping the LFP cells were going to be my holy grail with almost a set and forget
I knew there was some pre setup involved in top balancing etc but this is now a daily chore of monitoring adjusting.

I'm scared to leave the sodding things unattended as none of the safety cut outs seem to work
I get why the inverter didn't cut out as the pack voltage was still over 48v which is my lvd, but why the BMS didn't disconnect the relay ive no idea, i checked the BMS disconnect manually, several times and it works, the cell disconnect is set to 2.50v.

Out of the 32 cells i Purchased, I've got one massively ballooned, two now run down bellow their absolute minimum spec and two Chargery BMS units which on the face of it look good but seem to have a mind of their own.

I would like to say ive done something wrong, but at the time of purchase I bought two lots of everything one for me and one for a friend, so we have two identical AC coupled inverters, the same cells, the same BMS, his is working absolutely fine since day one with identical settings.

Ive either been extremely unlucky or ive borked something badly.

I've kept my charge ranges to maximum 54v and Low voltage of 48v to stay within 15-80% charge range.

I honestly give up now

 

[shavermcspud]

@Chargery

So another small revelation after reading the translated manual from the resources on here vs the manual I had

2. Cell voltage display is not accordance with actual cell voltage ---Check
a) Check 9 pin balance wire connections are good and secure. --- Check
b) Measure actual cell voltage on the BMS balance port. ---Check
c) Disconnect battery, measure resistance on balance port. Such as, if cell 5 voltage is not correct, hadn't done this, but just chekd and my unit measures 19 kOhm or there abouts on port 9 and 10 and the rest are 102 kOhm , think here in lay my problem
measure resistance between cell 5- and 5+ on balance port. Generally it is very large (100K ohm or so).
d) Or send back to us and calibrate the cell voltage again.

I have now binned off all the cells that went bellow 2.5v and the bloated cell and used fresh cells from my reaming set for a new 16s fully balanced to 3.65v, each one individually checked with a Volt meter, at exactly 3.65v, attached the BMS and again 9 and 10 show 4.1v and 3.8v.

Looks like i need to do option D, send back to us to calibrate cell voltage, wish I could do that at home.

to think I've f**cked three new cells trying to get to the bottom of this, wasted hours of time and money.

Also found this thread, which sums up exactly what I am seeing
https://secondlifestorage.com/showthread.php?tid=9632 see post eight about others saying using the internal power causes odd readings.

 

[Luthj]

Are you sure the low voltage disconnect was enabled? Are all the cells enabled in the settings?

I would capacity check the low cells. If they have good capacity, I would consider reusing them.

Might be worth trying one of the simpler BMS, and use its output to drive your relays.

 

[nebster]

2.1V one time only is not a problem for LFP cells. Those cells will probably be okay, if you want to use them.

You do need to figure out the source(s) of your errors so you can get back to a stable setup and start to gain confidence. You are learning the semi-stressful way, but hang in there... you will get on top of it soon, and then you will be wiser, too. :D

 

[cinergi]

those 2.1 cells are probably OK indeed.
For what it's worth I've tested HVD and LVD in my 4s setup and it works fine. Also tested temperature disconnect. I'll retest evertyhing in a 16s config and pay very close attention after everything you just went through. Ugh. In your shoes I would give up, too.

 

[The New JC777]

I honestly give up now

I have some top balanced Senberry LF280 cells here in Florida. If you decide you need some right away I can send you some of mine. My project is moving at a snails pace and I have more coming.

 

[shavermcspud]

I have some top balanced Senberry LF280 cells here in Florida. If you decide you need some right away I can send you some of mine. My project is moving at a snails pace and I have more coming.

Thats very kind of you. thank you.