TechDirect BYD BMS in pre-built units: Can anyone read this Chinese label?

[GVSolar]

These are the pre-built units - no way to access the individual cells without tearing the whole unit apart - or finding a way to access BMS readings or use the built-in adapter connections. It's a quandary.

 

[GVSolar]

FYI:

 

[Darkstar]

Yes. I did - and I considered that to be the low battery cut-off - and shut down the discharge test on my three TechDirect units. From my point of view, actual usable capacity of these units is from right before the BMS high voltage disconnect (HVD) and right above the BMS low voltage warning (LVD). The lack of cell level monitoring is from the user's point of view (we have no way to access the BMS readings). The BMS settings published by TechDirect indicate that the BMS is monitoring the individual cells (see attached, Chinese version included) - user's simply can't access those readings. If any of the smarter folks on this forum can figure out a way to access those BMS readings I'd surely appreciate any advice...

Why does the english version of that chart have columns "Min, Standard, MAX" if you can't change any of the settings?

 

[GVSolar]

Beats me... perhaps it is a tolerance issue - or there is some way to communicate with the BMS that I'm not aware of - hence the question/thread.

 

[Darkstar]

Jus

Wow

I saw low voltage cut off is 2.2V, high voltage cut off is 3.75V

balance starts 3.6V but only 40mA

and of course no low temp cut off

I emailed Techdirectclub this morning asking about cell balancing and recieved this as a reply:

"The do on charge 200 ma"

So it balances when charging at 200ma apparently???

 

[Darkstar]

How does one reset the Techdirect BMS after High or Low cuttoff?

 

[ytwytw]

Why does the english version of that chart have columns "Min, Standard, MAX" if you can't change any of the settings?

According to that chinese manual, the standard is referred to 25C degree, value may change depended on temperature.

Personally, I dont think max/std/min make sense to me

 

[BiduleOhm]

These are the pre-built units - no way to access the individual cells without tearing the whole unit apart - or finding a way to access BMS readings or use the built-in adapter connections. It's a quandary.

At least you can easily access the cells voltages at the BMS connector to measure them with a DMM.

 

[GVSolar]

I reset the circuit breaker on mine... but it does list a delay and a release voltage on the BMS specs.
Question: "The do on charge 200 ma"
What the heck does that mean? When does it start? And how would you know?

 

[GVSolar]

Bidule: I have to plead ignorance - could you explain that process to me? (DMM measurement at connector - please refer to photo) Thx.

 

[ytwytw]

"The do (cell balance when its) on charge (but the max balance current is) 200 ma"

 

[Darkstar]

I reset the circuit breaker on mine... but it does list a delay and a release voltage on the BMS specs.
Question: "The do on charge 200 ma"
What the heck does that mean? When does it start? And how would you know?

The question I asked him was "Does it do cell balancing and what is the balance current?"

That was the response, which seems to be what ytwytw stated above. Max balance current 200 ma during charging.

200 ma contradicts with what the "single cell balance current" row in the english table states? Or is it 200ma max balance current for all cells at the same time?

 

[BiduleOhm]

Bidule: I have to plead ignorance - could you explain that process to me? (DMM measurement at connector - please refer to photo) Thx.

This connector:



It has one wire per cell positive plus the main negative. If you take a DMM or voltmeter you can measure between each wire (from 1 to 2, then 2 to 3, 3 to 4, etc...) and you'll have each cell voltage

 

[ytwytw]

make sure turn off the pack via circuit breaker before unplugging the balance leaf.

 

[GVSolar]

Thanks... so turn off circuit breaker - unplug "balance leaf" - apply pos DM lead to connector #1 position and neg DM lead to main neg (at BMS?). Correct? Any significance to red lead (Cell #1? perhaps).
Do you think theres anyway to get a y-connection to that setup for monitoring?

 

[GVSolar]

"The do (cell balance when its) on charge (but the max balance current is) 200 ma"

Does that mean the balancing starts on "any" charge - or that it only starts at a particular voltage? Thx.

 

[ytwytw]

Does that mean the balancing starts on "any" charge - or that it only starts at a particular voltage? Thx.

Does that mean the balancing starts on "any" charge - or that it only starts at a particular voltage? Thx.

according to the label
3.6V+

I assume it does top balance.

 

[GVSolar]

Since my three units are cutting out at 28.0v it would seem that they will never get a chance to balance. Argh.

 

[ytwytw]

Since my three units are cutting out at 28.0v it would seem that they will never get a chance to balance. Argh.

200mA is not enough to balance it.

If you really really really need to monitor, consider buy a new BMS

 

[BiduleOhm]

Thanks... so turn off circuit breaker - unplug "balance leaf" - apply pos DM lead to connector #1 position and neg DM lead to main neg (at BMS?). Correct? Any significance to red lead (Cell #1? perhaps).

That's not correct.

The correct procedure:

- turn off circuit breaker
- unplug balance leads connector
- measure cell 1 voltage between pin 1 and pin 2 of the connector
- measure cell 2 voltage between pin 2 and pin 3 of the connector
- measure cell 3 voltage between pin 3 and pin 4 of the connector
...
- measure cell 8 voltage between pin 8 and pin 9 of the connector
- replug the connector
- turn on the circuit breaker

It doesn't matter which way around you put the voltmeter leads, the only difference will be a sign "-" on the screen but we don't care, we just want the voltages

Previously I didn't say to turn off the circuit breaker and to unplug the connector because you can do the measurement without unplugging the connector but it's a bit more complicated if you're not familiar and there is greater risk to make a short-circuit between the connector pins with the voltmeter leads, so yeah, don't go this route.

Do you think theres anyway to get a y-connection to that setup for monitoring?

Yes, but you need to find the same connector which is used here and do the Y yourself.