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Bms power consumption

gates59

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Jan 3, 2025
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Ontario canada
Ok so I purchased 3 aolithium 12v 100ah batteries and are working just fine. I decided that I wanted to upgrade the bms in one of my batteries to have active balancing. I purchased the new version of the 100ah 8s bms. It's the new smaller version that just came out. Installation went just fine and fully charged my batteries and fully balanced my batteries with no issues. Next morning I noticed that my battery had dropped voltage to 13.3v. Found that to be quite low so charged again and left it overnight again with same results. I then fully charged my other two batteries with the factory jbd bms and next morning those were well over 14v by morning. I then decided the check how many mA the jk draws. With everything off and cells fully balanced, it draws 62mA. Checked my jbd with same settings and it's at 8mA.
So my question is, can this new jk bms really use this much power or do I have a defective bms.
Model number jk-b1a8s10p
 
Seems to be in line with what others have measured in the past:


Most of that is related to Bluetooth as far as I remember. Which JBD do you have?
 
This one. 8s 100ah. Jk-b1a8s10p.
My jbd with bluetooth off uses 8mA and bluetooth on is 10mA
 

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This one. 8s 100ah. Jk-b1a8s10p.
My jbd with bluetooth off uses 8mA and bluetooth on is 10mA
The JK BMSs can be forced via the control button into a sleep mode (Power MOS-FETs off), with an internal Power consumption of close to nothing. However If you apply an external voltage to the BMS output (some 1.7 V above the battery voltage), it will turn on again. The external voltage may be generated unintentionally by your PV system.
Some may consider this to be a feature, others call it bad design.......The real Problem with JK is, that they may change their design but never tell you........
 
The JK BMSs can be forced via the control button into a sleep mode (Power MOS-FETs off), with an internal Power consumption of close to nothing . . .
Interesting. Our JBD 200a BMS doesn't have a sleep mode, but we did notice a significant drop in parasitic current when we turned off the charge/discharge mosfets. Turning off the mosfets is probably a good idea if you're taking the battery off-line for any length of time (and don't have a sleep mode).

Correction, it does have a sleep mode. See post #9 below.
 
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I suppose I can get it to go to sleep automatically when not in use but it's still a big difference in power consumption from my old one. No real reason for it as far as I can see. After testing jk for a while, it's really nice to have the passive balance.
 
Ok so I finally figured out why my bms is using so many milliamps. So after all my testing and purchasing a new multimeter, my bms is using 80 milliamps on a 4s 12v configuration. Just for fun I hooked it up to a 24v power source and it is only using 20mA. Ok so does this mean it's not really designed to be used in a 4s configuration. Seems to be starving of power at 12v and is drawing more amps?
 
As far as I remember it needs an additional DC/DC converter internally to work at 12V. Also remember that P = V x I so if you increase the voltage, current draw will drop. But in this case, there is still a big difference even taking that into account...
 
My jbd with bluetooth off uses 8mA and bluetooth on is 10mA

Your measurements got me curious so I just took the time to measure the draw (parasitic) on one of our 4s JBD 200a BMS's a second time.

We use a switch to turn power to the bluetooth (BT) modules off and on. When the BT module is powered on, the BMS pulls 10.40ma while the BT module is being accessed via an app. After access stops, current momentarily drops to 7.50ma. This is close to the 10ma and 8ma you measured. If you wait another minute or two, you should see the 8ma fall to less than 1ma.

With the BT module powered on, BMS parasitic dropped to 650ua (micro-amps).

With the BT module powered off, BMS parasitic dropped to 82.4ua (micro-amps).

I mentioned earlier that our JBD didn't have a "sleep" mode. Based on these measurements I was incorrect. During my first test (a year or so ago), I probably didn't wait the minute or two for the current to drop into sleep mode.

Another observation. While the BMS was (asleep) drawing either 650ua or 82.4ua, noticed a distinct voltage spike every 7-8 sec. Unable to measure it accurately with the ammeter (wish I had a scope). I'm guessing this voltage spike every 7-8 seconds may be the BMS doing a periodic sweep of all voltages, current and temperatures. If true, this probably explains how the BMS is still able to protect/function with the very low parasitic. If the BMS was active and not asleep, I'm guessing this same sweep would probably be occurring every X number of micro-seconds.

For what it's worth, I used to think our 500a Victron shunt's 1.88ma parasitic was miniscule. The Victron's 1.88ma is almost 23 times higher than the JBD's 82.4ua.
 
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The JK BMSs can be forced via the control button into a sleep mode (Power MOS-FETs off), with an internal Power consumption of close to nothing. However If you apply an external voltage to the BMS output (some 1.7 V above the battery voltage), it will turn on again. The external voltage may be generated unintentionally by your PV system.
Some may consider this to be a feature, others call it bad design.......The real Problem with JK is, that they may change their design but never tell you........

If this is indeed how most/all JK's operate, I see this need to be manually placed in sleep-mode as a design flaw. If the JK's also have a propensity to drop-out of sleep mode (requiring manual reactivation of the sleep-mode), this makes things even worse. I believe the JBD's automatic sleep-mode activation after 1-2 minutes of inactivity (that we witnessed on our JBD 200a BMS) provides much more efficient use of ah resources, plus zero need for user intervention.

Was considering a JK for our next build. Especially like their on-board, 2a active balancers. Not sure how this going to play out for us---not fond of baby-sitting or high parasitics.
 
If this is indeed how most/all JK's operate, I see this need to be manually placed in sleep-mode as a design flaw. If the JK's also have a propensity to drop-out of sleep mode (requiring manual reactivation of the sleep-mode), this makes things even worse. I believe the JBD's automatic sleep-mode activation after 1-2 minutes of inactivity (that we witnessed on our JBD 200a BMS) provides much more efficient use of ah resources, plus zero need for user intervention.

Was considering a JK for our next build. Especially like their on-board, 2a active balancers. Not sure how this going to play out for us---not fond of baby-sitting or high parasitics.
The actual version of the JK BMS modules can be set to go to sleep mode after a preset time of inactivity.....I have not used this feature......
For details see Andy's video
 
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Interesting. Our JBD 200a BMS doesn't have a sleep mode, but we did notice a significant drop in parasitic current when we turned off the charge/discharge mosfets. Turning off the mosfets is probably a good idea if you're taking the battery off-line for any length of time (and don't have a sleep mode).
Yes it does have a sleep mode. If it decides that it hasn't seen charge/discharge current for longer than the timeout you set (max of 65,535 seconds), it will first drop the contactor and then the processor will sleep about ten seconds later. It will not wake up until the measurement chip sees sufficient current.

This is a big problem for some of us using JBD contactor models in parallel with other batteries. Once they sleep, they won't wake up because the other batteries handle the load. I have a solution that I am ready to test. Getting a new software load from JBD would be best, e.g. maybe setting the delay to zero seconds disables the sleep mode. No such luck yet....
 
Yes it does have a sleep mode. If it decides that it hasn't seen charge/discharge current for longer than the timeout you set (max of 65,535 seconds), it will first drop the contactor and then the processor will sleep about ten seconds later. It will not wake up until the measurement chip sees sufficient current . . . .
My bad. You're right, it does. I posted all the details in post #9. Forgot to annotate the correction in post #5 (since annotated). For what it's worth, the JBD 4s 200a BMS sleep mode appears to operate differently from your JBD contactor model. It goes into sleep mode (82.4ua draw) automatically after 1-2 min of inactivity. Not that I'd want to change it (IMO works great as-is), but as far as I know there's no way to adjust the timing for the sleep mode (for the 4s JBD 200a BMS) using the Overkill Solar/JBD Windows apps and/or Overkill Solar/Xiaoxiang/JBD iOS apps.
 
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