JK BMS won't turn off DISCHARGE via APP ?

[carpetpaul]

Forgive me if you've seen my other couple of posts discussing an issue with my JK BMS (both of them) where after correctly cutting off at UVP level (when a small charger is connected during discharge) the BMS turns back on without waiting for the pack to reach UVPR using the charger. I've tried all sorts and cannot get this to work. Tonight I discovered that although both BMS can turn the load off at UVP, when I turn off the discharge setting on the APP, the BMS still allows discharging. I'm confused and wonder if I've done something wrong in the wiring, so here it is :

the positive wire from my pack comes from my fuse, straight to a terminal block
the negative wire from my pack goes through the BMS and to the terminal block

to this terminal block, my inverter is directly connected, also is my charger*

does this sound correct ?


* I can turn the charger on and off via the APP, but not the discharge
I'm presuming that BMS should have some kind of diodes or similar that can allow power from the charger in, whilst not allowing power to flow out to the load ? even when I turn the charger off from the APP, I still cannot turn the load / discharge off from the APP

 

[Frank in Thailand]

I think you already gave your own answer.

If you have S16, all 17 "spaghetti" wires are to be connected to the terminals of the battery.

Each cell has 2 terminals, one positive, one negative.

All 16 red ones go to each cell positive terminal.
The black one to the last cell negative terminal.

The B- to the battery array negative terminal
The P- to your power (usually inverter/ charger)

Connecting any "spaghetti" wire on any different spot, is going outside specification.

A picture will help to understand how you connected things!

Then there is the wide range of JK BMS.
While the most used, 200A 1 or 2A active balancing is fantastic

The 30-50A with 0.6A active balancing..
They are known to have their challenges.
(Like non responsive to settings)

What model do you have?

 

[carpetpaul]

Hi, thanks for your reply, I have two JK BMS, a BD6A17S8P, and B2A20S20P

All balance wires and power to the BMS wiring is correct, both checked and verified on the app and by lack of any error messages, balancing works fine, as does Undervoltage Protection

what I wrote previously is pretty much accurate I think :

the positive wire from my pack comes from my fuse, straight to a terminal block
the negative wire from my pack goes through the BMS and to the terminal block

to this terminal block, my inverter is directly connected, also is my charger.


I will attempt to put a couple of photos below, bear in mind that I'm in the middle of reinstating my original BMS, so you can clearly see the lack of balance wires connected, but it's obvious where they go, likewise the B- is not currently connected, P- exits under the BMS on the photo and goes straight to the negative terminal. you can see where the charger socket is, and it goes straight to those terminals. When finally finished, input from the Charge Controller will go to these same terminals

 

[Frank in Thailand]

It's a bit hard to see, what I can see 15 connection for the BMS "spaghetti wires".

So you have either S14 battery,
Or S16 and don't connect those 1 leads to the battery terminal.


To avoid all confusion, those are the battery terminals.

A "terminal block" is not a terminal
I'm sure yours is different, and wired nicely.
I'm sure you are sure that an extended cable from the terminal to the terminal block, and attach there is "almost the same".
And you are right, it's almost the same.

Call me old fashioned, call me stupid.

If things doesn't work the way it should, dumb it down to a setup that you are sure the seller will accept as "indicated per manual", and this setup doesn't follow those guidelines.

I totally understand the how and why, and understand why it "should not matter".

You don't have to convince me(!!)
Both BMS behave in the same way in a setup that is not according to specification.

Obviously this can be a production error.

It seems like while it does enforce the under voltage protection at your preference, it doesn't listen to the recovery voltage to start discharge again.

But... It does stop, it does gives the cells time to recover.
Say for example you want then to stop at 2.7 and recover at 3.0

It does stop at 2.7, but starts discharge again at 2.8v

I don't know the white paper by head, and usually JK bMS doesn't allow settings beyond its standard specification.

So if you are able to set it to 3.0v, it should block discharge untill all cells reached +3.0v, correct?

I'm thinking outside the box here.
What it this is one of the many many possible settings they forgot to block "wrong input"?

What is your required setting?

And perhaps more...
Is that worth making this much hassle about?
It works!!
Does protect!
It does have "shut down voltage" (that is lower then the protection voltage)

If you have it protect at 2.6 and shut down at 2.4..
Recovery at 2.8

That works.
Even the shut down. I did test.

I've seen "wierd" behavior at my installations and many forum members.
9 out of 10 times, redo the balance leads will fix the problems.

They are all sure it's OK, untill they refitted the lugs, be extra careful and suddenly.... No wierd behavior!

The 0.6a active balance versions, my friend had a few and send them all back.
So many wierd problems, unusable.

His experience:
The cheaper ones, like the BD6A17S8P
"Useless". The black "expensive" ones, good

There were some funny resistance notifications on the lines, but....
New lug, problem fixed.

If your only problem is that the BMS doesn't protect up to your set voltage, but everything else works perfect..
And the reconnect voltage is "reasonable" (stop at 2.5 start at 2.6 or so) ... I would call that a win.

Is it perfect?
Nope.
Far from.
If you want perfect you buy batrium
(+$1000)
There are lots of other good brands in the $500-$1500 range.

Everything cheaper, there will be some consessions.

This looks to me like a minor one.

You are refitting your old BMS, what apparently wasn't up to your standard or demands, otherwise it would not have been replaced.

If the problem is unworkable, it's a warranty request.
Warranty request will require standard installation. Don't fight with me, try to explain the unwilling to refund Chinese seller that your setup is "better" or at least as good....
Or just follow the manual exactly, so there is no wiggle room to deny warranty.

If the problem is absolutely workable (at it seems to me now)..
Be happy this is the biggest of your worries!!

 

[carpetpaul]

thanks for your reply Frank, you're right, it's a 14S battery, as far as I know, the install is per the manual and wiring diagram for the JK

indeed, I have Both the silver coloured cheaper BMS, and the Black 'expensive' type, both behave the same

sure, it's not the end of the world, and the issue only happens when a charger is active at the point of low voltage cut-off, you are correct though, the BMS doesn't listen to the instruction to stay off until LVPR, issue is that it turns right back on and connects my load to the depleted battery, which cuts out as per LVP, and the cycle continues, I can't use this in this way, I will damage the load for sure. however :

if you use this BMS in an application where no charger is connected during your discharge, when the battery is depleted, you manually disconnect / turn off your load, then you can recharge and repeat, fine.

I think I (hopefully have a solution) when finally installed, I can use the load terminal of my Solar Charge Controller to control the power switch on my inverter via a relay (and keep the load turned off) at whatever voltage levels I choose, I can therefore avoid the BMS protection mechanisms completely.... until theres a real problem !

if it works