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JK BMS Current Consumption (JK-B2A8S20P-H)

drlucid

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I am trying to get some data on what the power consumption of the JK-B2A8s20P-H (I didn't order the heating version, but apparently they gave it to me anyways heh). I plan to leave this connected to ~560 Ah batteries for extended periods of time, and I want to know how concerned I should be that this will drain the batteries. The batteries are for my RV which sits unattended, sometimes months at time. I apologize for all the questions, but after spending an hour googling I wasn't coming up with anything !

I did buy the LCD display, but also noted that it came with a push button switch (note on aliexpress says they just started shipping these as of 5/1/2022). What is the push button switch for? If that can be used to turn it on/off I just wasted 30 dollars on the LCD ? Good to know for others ... Can the push button switch power it completely off and on ? Also, what about the LCD display, I read from another post that it can only be used to turn it on -- not turn it off even with a long hold, which I find very odd. I used the LCD display to turn it on today, but that is about it. I imagine the push button could have done the same thing??

I read from another post that normal power consumption without the screen attached is 560 mW. That is kind of high, over a long period of time that will create a drain on my batteries, ~ 8 Ah per week which could add up, although I should be good for just a couple weeks at a time.

Ok, so if it is 560 mW, does that include the unit going into standby mode ? The aliexpress site (https://www.aliexpress.com/item/325...st.0.0.21d51802wjEkYf&gatewayAdapt=4itemAdapt) list the modes shown in the image at the bottom of the post. If the unit goes into standby, will it consume less. Also, will I need to do something to use it from there, it appears I will need to apply a charger to it ? That may not always be possible, so should I have the switch and/or LCD handy and connected to it should this happen? I did not see anywhere to configure the 1-30 days standby period listed in the image below.

1654464955662.png
 
Does anyone have any idea on any of the questions I asked ? Sorry, just curious !
 
And yes the LCD screen is superfluous if you are going to use the mobile app the connect to it via Bluetooth or use some other means of accessing the data of the BMS if you want. I think the screen was more for using the BMS for electric bikes. I also see no way to configure "standby" mode". @Nami or @upnorthandpersonal may know some of these answers to questions you asked.
 
Ok thanks rhino, appreciate any info that is out there. That is what I thought, oh well it was $18 dollars for the screen that really serves me no other purpose than activating it which i could have done with the button. I may mount the button if I can figure out a good way of doing that. It is outside in the elements, so I would probably add a thin sheet of rubber to protect it from moisture ingress.

I have it set up so that the battery C- is disconnected so the RV won't draw any current, but the BMS idling will do so. It sounds like it will go into standby mode (somewhere between 1 to 99 hrs, haha), which I am guessing draws less current. It doesn't show directly, but I am also led to believe the unit will still respond to bluetooth and not need to be activated when it is in standby? If the standby current draw is small enough I would just assume not mess with figuring out how to mount the button and not worry about it at all...
 
And yes the LCD screen is superfluous if you are going to use the mobile app the connect to it via Bluetooth or use some other means of accessing the data of the BMS if you want. I think the screen was more for using the BMS for electric bikes. I also see no way to configure "standby" mode". @Nami or @upnorthandpersonal may know some of these answers to questions you asked.

@Nami sent me a new version of the screen that is larger, and has a separate button, and has touch. Unfortunately it appears to have another connector type (on the 'open design' version I guess compared to the black version) so I can't use it with my BMS:

20220609_113329.jpg
20220609_113403.jpg
20220609_113458.jpg

Why they keep changing connectors, I have no idea... @Nami ?

A screen like this would probably be nice if you don't want to have a mobile phone anytime you want to see the battery status. I could see some application for this - it looks better than the small one that was shipped with before, has an SD card slot which I guess could allows for graphics/firmware changes, but don't quote me on that.

I briefly powered it up with a power supply. It consumes 250mA at 5V and doesn't appear to have a standby mode. That's 1.25W - which in my opinion is not insignificant, but also not excessive for a pretty large, bright display.

20220609_114929.jpg
20220609_114936.jpg
 
I see that your BMS is an earlier version. After January 2022, we agreed to replace all BMS interfaces with those in the picture,
I will contact the engineer to arrange a link cable of the previous interface for you,

IMG_7320.jpg
 
That LCD looks nice, I can definitely see the applications for it. I would advise the display should have a way of being turned off when not needed (but keeping the bms active), and then easily tapped or a button so that it can be seen and left on for long periods of time if desired. Battery power is a precious commodity in most applications, so it should be treated as such. Just a potential suggestion, maybe it works that way already.

Could either of you entertain any of these three questions. 1) how long does it take for the JK BMS to go into standby mode, which happens when there is no charging or discharging action for a period of time. 2) once in standby mode, is the unit still active, or does it need to be activated again with a charging action / button press / etc. ? 3) What is the power draw (or equivalent current at 13.3V) once the BMS does go into standby mode?
 
It doesn't go into stand-by mode; it doesn't have that. It's active at all times, as it should be in case something goes wrong with a cell. I don't remember the current draw exactly, but it's somewhere around 10mA. For all intents and purposes negligible.
 
Hi everyone!
I think I have a faulty unit. I left my 12V 100Ah LiFePo4 Battery a few weeks "alone" and the BMS shut itself off. After waking it up, one cell showed 2.54V thats why it shut down the output and later it self as well (Stand-By, Turn Off Voltage was set to 2.4V). So this seems to be working. However just sitting there, even with the "Start-Button" (with red LED built in) detached and without any phone connected via Bluetooth I measure round about 150mA of idle current! (running out of the Battery through B-, P- open (attached to nothing). Switching off Charing, Dischraging, or Balancing does not reduce the used power.
Can anybody confirm his/her BMS a high standby current like this?
I hooked up my previous Jiabada BMS which consumes around 8-10mA (on B-, it could also draw power on the balance connector, couldn't check that easily), which seems ok to me.

Any values from your BMSes welcome!

Cheers sergios
 
it shut down the output and later it self as well (Stand-By, Turn Off Voltage was set to 2.4V). So this seems to be working. However just sitting there, even with the "Start-Button" (with red LED built in) detached and without any phone connected via Bluetooth I measure round about 150mA of idle current! (running out of the Battery through B-, P- open (attached to nothing). Switching off Charing, Dischraging, or Balancing does not reduce the used power.
Can anybody confirm his/her BMS a high standby current like this?
I hooked up my previous Jiabada BMS which consumes around 8-10mA (on B-, it could also draw power on the balance connector, couldn't check that easily), which seems ok to me.

Any values from your BMSes welcome!

Cheers sergios
I haven't made any measurements myself, but, according to the threads the standby power is 560 mW. If the batt voltage is 13V, then P = I*V; 0.56/13 = 0.043 A = 43mA. So, that does appear high, assuming you are running a 12V system. Note, if your voltage is lower than that the corresponding current will be proportionally higher.
 
Hi Guys,

Seems indeed my BMS has a very high Power Consumption. As drlucid stated my power is 13.2V * 0.120A = 1.5W, a vast 1.5Watts!!
So I took the unit a part and had a look at it with my thermal camera, and sure enough, I found where all the energy seems to go:
IMG_5178.JPG
20220710T144616.jpg

It's that resistor which I believe belongs to some sort of DC-DC Converter circuit which provides the different needed Voltages (3.3V, 5V?) for the µC etc. Just out of curiosity I unsoldered the part and of course the BMS didn't start up. I measured the unsoldered part on my bench with my multimeter it showed no capacitance but a very low resistance (about 0.3 Ohms), that's why I guess it must be a resistor. I think it's not the resistor itself that is at fault, it's just the poor guy through which all the energy flows and thus gets hot.

I tried to get in contact with JKBMS but their support form just throws an error, and tells me to try it later again, and to an E-mail which I sent at info[at]jkbms.com they did not replay. And for an aliexpress dispute it's too late, that works only 15days after arrival of the product.

Seems I have to try my luck and get another one ☹️
I love the 2A balancer because my "Grade B" cells go easily out of balance.

Cheers sergios
 
Hi Guys,

Seems indeed my BMS has a very high Power Consumption. As drlucid stated my power is 13.2V * 0.120A = 1.5W, a vast 1.5Watts!!
So I took the unit a part and had a look at it with my thermal camera, and sure enough, I found where all the energy seems to go:
View attachment 102034
View attachment 102035

It's that resistor which I believe belongs to some sort of DC-DC Converter circuit which provides the different needed Voltages (3.3V, 5V?) for the µC etc. Just out of curiosity I unsoldered the part and of course the BMS didn't start up. I measured the unsoldered part on my bench with my multimeter it showed no capacitance but a very low resistance (about 0.3 Ohms), that's why I guess it must be a resistor. I think it's not the resistor itself that is at fault, it's just the poor guy through which all the energy flows and thus gets hot.

I tried to get in contact with JKBMS but their support form just throws an error, and tells me to try it later again, and to an E-mail which I sent at info[at]jkbms.com they did not replay. And for an aliexpress dispute it's too late, that works only 15days after arrival of the product.

Seems I have to try my luck and get another one ☹️
I love the 2A balancer because my "Grade B" cells go easily out of balance.

Cheers sergios
The first batch of products is about 20, as the first product. The chip does have such a problem. Too high load leads to overheating of the chip. When receiving this feedback, the design scheme is changed in time. Please contact the store to reissue the chip for you. I think you should have enough technology to replace this chip. If you can't replace it, please also contact the store to deal with it. Sorry for the inconvenience
 
I connected using my Victron Shunt. The BMS uses 2W continuously. If I connect the LCD screen instead of the stand-alone button, it consumes 4W.
 
I have 10 various bms's. All between 0.003-0.040A at 53.3V. My JK 150A with 2A balance consumes between 0.005-0.010A. My JBD with the contactor consumes 0.040A. Overkill= 0.017A. Ant= 0.003A. QUCC= 0.019A. Daly= 0.015A.

Edit: My 6 new JK200A 8S-20S (Wired as 16S) BMS's consume 14mA and the LCD consumes 29mA. All you need is a toggle switch on the red wire from gps connector to turn off LCD.
 
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The first batch of products is about 20, as the first product. The chip does have such a problem. Too high load leads to overheating of the chip. When receiving this feedback, the design scheme is changed in time. Please contact the store to reissue the chip for you. I think you should have enough technology to replace this chip. If you can't replace it, please also contact the store to deal with it. Sorry for the inconvenience
Can you provide the serial number where this change was made so that we will know if our BMS is affected?
 
Believe they are buck DC-DC converters. The three 100uF 16v aluminum caps are Vin to pin 5 of buck switchers. Probably source from the large DC-DC converter above the three smaller switchers. The black part you squared out is the multi-layer buck chip inductor. Output of buck converter is bottom of chip inductor with the two small output filter caps below it.

Part is similar to LM2734 but I don't see the buck diode so maybe this part is synchronous buck converter or has diode on backside of PCB.

On 6 pin SOT device, Pin 1 is bootstrap cap, pin 2 is ground, pin 3 is feedback, pin 4 is enable, pin 5 is Vin, pin 6 is switcher to inductor.

You can measure their output DC voltages from bottom of inductor to ground.
 
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