JBD BMS 60-80A - Can overcurrent be set by app ?

[meetyg]

Hi.
I'm planning a 24v 40Ah Lifepo4 pack.
The cells I plan to get state maximum discharge current of 3C.

I am considering getting the 80A JBD 8S BMS. my question is can the overcurrent (discharge) protection be set by the app?
For example, can I set the 80A to protect at 60A ?

Is it common to oversize the BMS and use lower protection parameters?

Thanks

 

[MisterSandals]

my question is can the overcurrent (discharge) protection be set by the app?

If you are talking about the Xiaoxiang app, yes you can set both charge and discharge over current separately at the millivolt level.

Is it common to oversize the BMS and use lower protection parameters?

Oh yea.

 

[meetyg]

Thanks.
Another question: Can these BMSs handle a short-timed current surge larger than their rating?
If so, how much?

 

[MisterSandals]

Thanks.
Another question: Can these BMSs handle a short-timed current surge larger than their rating?
If so, how much?

“Handle” is the key word.

They can be configured with a delay but how/if the BMS survives is the question.

 

[meetyg]

So what your saying is that I should size my BMS by the maximum current surge I'm expecting?

 

[MisterSandals]

So what your saying is that I should size my BMS by the maximum current surge I'm expecting?

My understanding is that momentary surge is not used for BMS sizing.
The sizing guideline I believe are the consensus is to size the cheap BMSs about 100% over and quality BMSs at or 25% over their rating.

 

[meetyg]

Cool.
Would you consider the JBD BMSs to be quality or cheap?

 

[MisterSandals]

Cool.
Would you consider the JBD BMSs to be quality or cheap?

I have 2x Overkill which are rebranded JBD with some additions like wiring options and Bluetooth.
I think they are very good quality. Not great but head and shoulders above most.

 

[kshopper2084]

Thanks.
Another question: Can these BMSs handle a short-timed current surge larger than their rating?
If so, how much?

Here's the spec sheet re: the tolerances that the 200A JBD can handle: Link

 

[Just John]

Just buy the 100 or 120 amp BMS. I suspect then the weak link would be the cells.
The JBD are substantially better built and tested than the Daly line, and are accurately rated. Yes you can set charge and discharge limits, and for about 2 seconds they can easily handle a much greater surge current.

 

[meetyg]

Great! Thanks for all the info.
After measuring maximum current of the DC motor (at complete stall) which this Lifepo4 pack is for (AGM swap for Lifepo4 in a small mobility scooter), I ordered the 80A JBD.
The DC motor is rated at 20A max, but at complete stall I saw 30A. So I think the 80A will suffice.
The current setup uses 40A breakers, so an 80A is well over this. I will still be using 40A breakers to protect the wiring.
Can't wait to receive the Lifepo4 cells and the BMS and start playing around

This will be my first DIY Lifepo4 pack build, but since I discovered @Will Prowse and his YouTube channel and of course thus forum I have learned alot and feel more confident in do so.

 

[JoeHam]

Spend a half hour here to learn more about the JBD. :

 

[meetyg]

Yeah, I love Andy's channel too!
I have seen his videos about the JBD.
Overall I got the understanding that he is for it, although those double temperature sensors can be confusing. I think mine come only with one temp sensor.
I don't care much for low temps, as it rarely gets below freezing where I live. The mobility wheelchair won't be use at such low temps.

The software might also be confusing...
I think that in my case I couldn't have got something better than the JBD for its price (under $60).
I think Will and alot of others also favor the Overkill BMS. They have nice documentation for the JBD, but I just can't justify paying twice as much for a calibrated JBD from overkill (they don't have the 80A anyways).
I am hoping that mone will be fairly calibrated by the factory. If not, I might either try to calibrate it myself (using the PC software) or just live it as it is.