JK BMS pack not working with another pack with JBD

[kuranaga]

Hi

I have a strange problem: I have 2 DIY packs, both 280ah 24V. One uses JBD BMS (xiaoxiang app) and the other one JK BMS B2A8S20P.
The JBD pack is older it was working like 6 months here and I added the JK pack 2 days ago. Both go onto same 24V busbar.

So far all looked good, however this night I run into this problem:

- initially (around 10pm) both packs showed to discharge (power, current different from 0 in their app). I went to sleep then around 6am inverter lost power the JBD pack went down to programmed zero (about 15% SoC 25.5V), however the JK pack was apparently at 26.8V and the JK app showed discharge state off, charge state off - BUT the controls were set to ON (so discharge on, charge on), l mean these in this screen (example picture not mine):

https://user-images.githubusercontent.com/7570415/97902977-639b7680-1d64-11eb-8a3b-71437c543a82.PNG

( so the top screen indicators were shown as charge: off, discharge: off, balance: on, DESPITE the knobs under "control" set to ON for charge, discharge).

NO errors logged in system log on the JK BMS. It was also not powered down or so.

Now the question is what is wrong with that? Why would the JK BMS suddenly disable discharge when discharge control is set to ON and log no error?

Any thoughts?

 

[kuranaga]

Ah and then I pressed the emergency mode knob to ON and it started discharging (and apparently charging the JBD pack at 2kW, sucks).
Really no errors logged, is the BMS faulty?

 

[kuranaga]

Now again same situation, but banks behaving swapped! It is night time now, so nothing comes in into the packs:

JBD bank stopped to discharge (current 0A), bat voltage hoovering at around 26.9V, BMS shows "charge ON discharge ON"

JK bank discharging, battery voltage at around 26.4V, discharging.... BMS shows "charge ON discharge ON"

WTF is going on here?

I measure around 0.52V across the JBD BMS (bat- to P-), so means the discharge MOS is NOT open, despite BMS showing it open.

Any explanation for this phenomenon?

 

[Steve_S]

OK, well you State that you are using a 24V Config (8S) and two battery packs connected to a Common DC Bus (Busbars).
YET the image you posted (copied & inserted below) shows a 48V/16S on the JKbms with a fairly high Cell Wire resistance which should be around 0.050-0.060 at most. The Cell Wire Resistance is a Big RED Flag of issues as well.

So WHAT's up with that ?
You cannot have a 24V & 48V battery on the same BUS !
I would not be surprised at all if you fried the JBD 24V battery if you dropped a 48V battery on the same bus.

Provide Screen Shots from the JBD Battery Pack & the JK Battery Pack, and also provide a Photo of teh batteries connected to the common dc bus.

 

[kuranaga]

OK, well you State that you are using a 24V Config (8S) and two battery packs connected to a Common DC Bus (Busbars).
YET the image you posted (copied & inserted below) shows a 48V/16S on the JKbms with a fairly high Cell Wire resistance which should be around 0.050-0.060 at most. The Cell Wire Resistance is a Big RED Flag of issues as well.

If you read my post correctly, it was saying "EXAMPLE picture, NOT mine) - to demonstrate how the screen looks like.

IN my case, this morning the problem happened again and the two BMS apps show:

Album — Postimages

postimg.cc

Now it happened the other way around! JBD BMS did not discharge, JK BMS went down to 26% SOC

 

[Steve_S]

One BMS will not override another, they do not interact. There are folks here using different brands of BMS' together in a paralleled bank of batteries without issues. Of course each BMS has to be properly configured both with their Software Settings and their connection to the Common DC Bus.

There is clearly a mismatch / misconfiguration and the 1st step is to make sure that both BMS' have similar configurations with regards to cutoff voltages etc... I assume you wired both Battery Packs with identical gauge wire with matching (or very close) lengths of wire to the (+) & (-) busbars. If not that could also introduce issues if there is too much difference.

 

[kuranaga]

There is clearly a mismatch / misconfiguration and the 1st step is to make sure that both BMS' have similar configurations with regards to cutoff voltages etc... I assume you wired both Battery Packs with identical gauge wire with matching (or very close) lengths of wire to the (+) & (-) busbars. If not that could also introduce issues if there is too much difference.

you seem to not understand... the BMS that does not discharge does NOT go into any cutoff. No errors logged (cutoff would be logged), discharge is shown as ON but MOS gets not polarized - 0.63V drop over P- and B- !

 

[42OhmsPA]

Post photos of your wiring and set up.