Finally found a LiFePO4 BMS with Low-temp Charging Protection

[OverkillSolar]

Has anyone successfully mapped out what the other connections are on this JBD BMS? Apart from the comm and balance lead connections?

Looking from left to right on mine, I see:

• CANBUS?
  • CANH
  • CANL
  • GND
• Mystery
  • B
  • A
• Mystery
  • "SW" with 2 terminals
• Comm port - TTL? what baud?
  • VDD
  • TX
  • RX
  • GND
• Mystery
  • Bat+
  • NC
  • Bat-
• Balance lead 4S
  • BC4
  • BC3
  • BC2
  • BC1
  • BC0

On the one I sell, The only header that’s populated is SW, it can be enabled from the apps and it functions as a discharge cut off switch. Could be useful to prevent discharging in storage or prevent unauthorized use, in the case of electric vehicles. I ordered the next batch with the 2 pin connector installed.

The comm port is TTL 9600 baud. The protocol datasheet is on my github page.

 

[Sgt Raven]

After my first discharge test of my XUBA 280AH battery a couple of things.
1) the BMS had it at 0% for days when the battery got down to 13.1V
2) ran it down to 12.8V and the BMS changed it to a 308AH battery and said it had 3 cycles on it.
3) the 1st test ended at 12.8V with an Error code on the fridge, voltage too low to start compressor.

Doing my 2nd big long term slow draw test and it has already run 4 more days this time. I changed the fridge from half fridge, half freezer this time, to fridge/fridge and only charged my tablet from 0% to 100% once. Right now it says 34% left and that it has 5 cycles on the battery.
Not sure how the BMS counts the number of cycles, it doesn't make sense to me.
It does seem the BMS has adjusted the percentage left for this test, compared to the 1st test.
It does seem the BMS is Smart as it adjusts some of the stuff after being run thru a charge/discharge cycle.

 

[Sgt Raven]

It looks like this 120A Smart BMS w/Bluetooth really is smart and learns.
I had it set for 280AH on my 12V battery.
The first big slow test, it was sitting on 0% left for days at 13.1V. and it lasted 6.5 days.
Last test the fridge cut it off at 12.8V with compressor failed to start Error.
After the first test, it changed the battry capacity to 308AH.
Running the 2nd test like that and now 12 days in. BMS says 12.8V and 19% 59AH left.
BMS is set to cut off at 11.5V or 2.875V cell.
12V fridge is set to the lowest of 3 battery voltage cutoffs.
Waiting to see if the fridge or BMS cuts it off this time.

Only thing that doesn't make sense, is the cycle count. The first time around it said 3 cycles and it says 6 cycles now.

 

[Tball]

It looks like this 120A Smart BMS w/Bluetooth really is smart and learns.
I had it set for 280AH on my 12V battery.
The first big slow test, it was sitting on 0% left for days at 13.1V. and it lasted 6.5 days.
Last test the fridge cut it off at 12.8V with compressor failed to start Error.
After the first test, it changed the battry capacity to 308AH.
Running the 2nd test like that and now 12 days in. BMS says 12.8V and 19% 59AH left.
BMS is set to cut off at 11.5V or 2.875V cell.
12V fridge is set to the lowest of 3 battery voltage cutoffs.
Waiting to see if the fridge or BMS cuts it off this time.

Only thing that doesn't make sense, is the cycle count. The first time around it said 3 cycles and it says 6 cycles now.

Anxiously waiting to see how this turns out Sgt Raven!

 

[Sgt Raven]

Anxiously waiting to see how this turns out Sgt Raven!

At this point it works great and so does the XUBA 280AH cells.
Sure it would cycle a bit more if I was pulling food out of it. But by then I'll have the solar hooked up too.
Even if for some reason it went down to 10V, that's still 2.5V per cell and they should be OK.

 

[Sgt Raven]

I haven't seen this before, like this. On the Cell voltage readout page.
1) 3.176 _______ 2) 3.154
3) 3.165 _______ 4) 3.149

Cells 1 and 4 are flashing and it's like it is trying to take power from #1 and move it to #4....
Weird....

Any time before, it would balance either even numbered cells or odd numbered cells together
It normally looks like it is balancing when those even/odd # cells are flashing.

 

[NEWYORKHILLBILLY]

I haven't seen this before, like this. On the Cell voltage readout page.
1) 3.176 _______ 2) 3.154
3) 3.165 _______ 4) 3.149

Cells 1 and 4 are flashing and it's like it is trying to take power from #1 and move it to #4....
Weird....

Any time before, it would balance either even numbered cells or odd numbered cells together
It normally looks like it is balancing when those even/odd # cells are flashing.

From what i understand the flashing is the high and low cell.

 

[Sgt Raven]

From what i understand the flashing is the high and low cell.

Yeah, the BMS shut down around 7:30am and the battery was completely off when I woke up this afternoon.
Hooked up to my PS and it turned back on real quick and was close to 0% and zero AH left.
Now the lowest and highest cells are flashing, so I think we can confirm that.
But it didn't do that, before. Maybe it needs to be below a certain voltage or voltage spread?
I'll see what happens as it charges back up.
Strange thing, after my first long test, which ended at 12.8V my AHs jumped to 308AH.
Now it is back down to my preset 280AH.

 

[Sgt Raven]

From what i understand the flashing is the high and low cell.

Just checked it again and my cells are all 3.28xV and the flashing stopped.
SWAG the high/low flashing is when it is around 3.1xxV.
It should start flashing either both even or odd cells, when they're above 3.4xxV, when it goes into balancing mode.

 

[NEWYORKHILLBILLY]

Just checked it again and my cells are all 3.28xV and the flashing stopped.
SWAG the high/low flashing is when it is around 3.1xxV.
It should start flashing either both even or odd cells, when they're above 3.4xxV, when it goes into balancing mode.

honestly i new to all this stuff.I just had seen in one of the videos reviews of the meter it was flashing high and low cells .

 

[HRTKD]

My current plan is to create a 2p4s battery with the 280 ah cells from Xuba. Will this be a good use case for the @OverkillSolar BMS? I don't need the battery bank for high current draws. I camp in cold weather and need a battery set that will last all night running the furnace and still have enough juice to run the coffee maker in the morning.

 

[Sgt Raven]

My current plan is to create a 2p4s battery with the 280 ah cells from Xuba. Will this be a good use case for the @OverkillSolar BMS? I don't need the battery bank for high current draws. I camp in cold weather and need a battery set that will last all night running the furnace and still have enough juice to run the coffee maker in the morning.

What is the max amperage you think it will draw? I'm using a 120A with a 4S XUBA 280AH battery, but I haven't pulled out more than 10A at a time. I did try a 300W inverter I bought a couple of years ago, but never used and it blew up on the first try.

 

[HRTKD]

What is the max amperage you think it will draw? I'm using a 120A with a 4S XUBA 280AH battery, but I haven't pulled out more than 10A at a time. I did try a 300W inverter I bought a couple of years ago, but never used and it blew up on the first try.

My spreadsheet says the max draw is 129 amps. But that would be turning on just about everything in my trailer at once, which is very unlikely. I included the four tank heaters in my calculation, but I rarely run them and most likely would only run the two on the 120 gallon fresh water tank if I had enough spare power. In a day, I calculated that the total draw would be 3302 watts and that is figuring an expected runtime for each item.

I have a 1000 watt MSW Xantrex inverter that is usually used only for the coffee pot. I didn't factor in the standby draw for that, just the known draw when it is active.

 

[Sgt Raven]

My spreadsheet says the max draw is 129 amps. But that would be turning on just about everything in my trailer at once, which is very unlikely. I included the four tank heaters in my calculation, but I rarely run them and most likely would only run the two on the 120 gallon fresh water tank if I had enough spare power. In a day, I calculated that the total draw would be 3302 watts and that is figuring an expected runtime for each item.

I have a 1000 watt MSW Xantrex inverter that is usually used only for the coffee pot. I didn't factor in the standby draw for that, just the known draw when it is active.

Max on your inverter looks like 145A, but that's a real short pull when it peaks. I think you might want to get Overkillsolar's 8AWG wire upgrade for the 120A version. That would give a little more fudge factor in it. IIRC, mdare pulled 147A on his 120A with the 8AWG upgrade he did. But that wasn't a long term test, either. Again, IIRC it was around post 400 or so in this thread.

 

[OverkillSolar]

Max on your inverter looks like 145A, but that's a real short pull when it peaks. I think you might want to get Overkillsolar's 8AWG wire upgrade for the 120A version. That would give a little more fudge factor in it. IIRC, mdare pulled 147A on his 120A with the 8AWG upgrade he did. But that wasn't a long term test, either. Again, IIRC it was around post 400 or so in this thread.

A 150a surge is no problem for the BMS. Long term at that level heat builds up regardless of what size wires are on it.

 

[NEWYORKHILLBILLY]

A 150a surge is no problem for the BMS. Long term at that level heat builds up regardless of what size wires are on it.

What would be the recommended long term draw of this BMS . I know its rated for 120 amps but many say to be conservative in that draw. what would you recommend?

 

[OverkillSolar]

I am comfortable with 120a at 100% duty cycle as long as it gets some air to stay cool.

The BMSs that I ran for extended load testing at 125 amps all got up to around 50 Celsius just sitting flat on the table. In a tight enclosure they got up to 90c and started melting the plastic box.

No need for a fan, just some free air for convection is enough.

 

[Sgt Raven]

I am comfortable with 120a at 100% duty cycle as long as it gets some air to stay cool.

The BMSs that I ran for extended load testing at 125 amps all got up to around 50 Celsius just sitting flat on the table. In a tight enclosure they got up to 90c and started melting the plastic box.

No need for a fan, just some free air for convection is enough.

I guess if the battery and BMS is in a closed box, a vent and a small computer case fan might be of some help. Really the fan part could be a pusher or puller, just as long as the air is exchanged enough.

 

[HRTKD]

A method of air flow is in the works for my project. The location where the batteries will be placed is currently enclosed, but I plan to add a method of inflow and outflow. Supplementing the passive air flow with an active fan, based on temperature, is something I'll have in Phase II of the project.

Can the BMS sent a high temp signal to a relay? That would be an easy way to trigger the fan.

 

[NEWYORKHILLBILLY]

I am comfortable with 120a at 100% duty cycle as long as it gets some air to stay cool.

The BMSs that I ran for extended load testing at 125 amps all got up to around 50 Celsius just sitting flat on the table. In a tight enclosure they got up to 90c and started melting the plastic box.

No need for a fan, just some free air for convection is enough.

Did you do any testing at 1/2 duty cycle 60amps? I wondering if at 60 amps this would stay cool enough to be in a battery case with the cell's

 

[Sgt Raven]

I think mine got to around 30C pushing 35A charging. My Alinco PS's heat sink body was around 72C at the same time.

 

[OverkillSolar]

A method of air flow is in the works for my project. The location where the batteries will be placed is currently enclosed, but I plan to add a method of inflow and outflow. Supplementing the passive air flow with an active fan, based on temperature, is something I'll have in Phase II of the project.

Can the BMS sent a high temp signal to a relay? That would be an easy way to trigger the fan.

This is in the works. I’m reversing engineering the comm protocol so we can run arduino type stuff. A relay module will be no problem.

Did you do any testing at 1/2 duty cycle 60amps? I wondering if at 60 amps this would stay cool enough to be in a battery case with the cell's

I can do that today. I’ll wrap one up in bubble wrap and run it for a while.

 

[OverkillSolar]

I can do that today. I’ll wrap one up in bubble wrap and run it for a while.

Test begins:


Running at 69 amps (nice) for at least 20 minutes unless my battery goes dead first

 

[Sgt Raven]

This is in the works. I’m reversing engineering the comm protocol so we can run arduino type stuff. A relay module will be no problem.


I can do that today. I’ll wrap one up in bubble wrap and run it for a while.

That could be a sticky mess and smelly, too.

 

[HRTKD]

This is in the works. I’m reversing engineering the comm protocol so we can run arduino type stuff. A relay module will be no problem.

Blue Sky thought here: How about a low temp signal too? That way I could turn on a pad heater - or other suitable heater - to keep the batteries from getting too cold.