Smart Energy Management for Marine and Off Grid

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REC Q BMS Startup problems

I'm having some trouble firing up my REC BMS.  I have it to control a 4P14S Kokam battery pack, and to control a Victron Easysolar 2 GX when it comes to charging.   I have wired up the BMS, checked all voltages and all seems OK.

But, i can not get connected to the BMS with my laptop, i have tried to install the USB driver several times but with no luck. I have set the settings according to the Master program manual.

I can not find any settings in the USB-Serial device to set it to 485 and not rs232, is it a hardwired rs485 converter that cant be used at rs232?

I did try a Moxa  uport 1150 rs485 converter as well, but no luck there.

Do you have any input to get me connected to the BMS?

Adding some screenshots of faultcode and setup.

Regards, Stig


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Yes, the software has a few details it is very picky about, and I have some ideas.

The error you see I am able to reproduce, it seems related to a comms error with the REC BMS its self – not the hardware/driver/RS485 level, but the software App -to- BMS level.   Some ideas to try:

  1. Make sure the REC BMS is on and active (ala, showing the LEDs on the REC BMS itself.  Hopefully GREEN and not beeping out a fault.)
  2. On my setup here I needed to change the “MAIN address” from 1 to 2 to make things work. (Attached screen from user).   Bump up that value and look for the ‘Present?’ button to change to Green when he hits the right combination.

FYI:  I have attached a screen shot:

  1. Another hint, when entering the Serial Number to ‘Unlock’ the BMS  (Ala, after pressing the ‘Unlock’ bar on the top right) it needs to be entered in a VERY specific way.  On my test setup the ‘SN label’ is like this:  SN: 1-A-1228   To have this accepted by the software to unlock, it needs to be entered like this:  1A-1228    Anything else will not work.

Let me know if the above get the customer moving forward, we should make up a kind of ‘Hint Sheet’ with the above detail as it is not well published in the REC manuals.  If the customer is still having issues let me know and we will loop in REC to get it resolved.


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I got it going, not sure what was the trick, did juggle a bit back and forth with the settings again and suddenly i got the green light.

Did get the setup as i would like it, but I got a 500/50 shunt from you, do you know the correct voltage-to-current coefficient to put in the REC with this? As it is now out of the box, i do think its measuring a bit low, maybe its set for a 300/50 shunt?

If you got a screendump the REC Master page of a "normal" setup for a lithium ion batterypack it would be great, just to double check my settings.

Regards, Stig


Good news on progress!  Tks for the feedback.

I have attached an overall screen-shot of the setup on my bench:

Frankly, all I did was select the Winston cell items and adjust way down the Ah capacity  (Using small motorcycle battery in the office).  All else was pre-populated.  The user will want to review these settings, ala, the start, max temps, etc. as those are what will be the basis for the BMS to direct the WS500 via CAN.  Figuring you all would have a better idea how to guide the detail for the battery set points if not using the build in values.

Shunt:  500A/50mV is the default the REC BMS is pre-configured for and he should be good to go; should be no need to resend a new value to the BMS.  As to accuracy, the shunt value should be printed on its side; note that resistive measurement in the field are very inaccurate.  If he is comparing current to other know sources, I would say give it some additional time to gain experience and if things still see sideways can dig into it.  One idea:  Though doing resistive readings on a shunt are all but impossible in the field, if there is a know steady current through the shunt, most DVMs will be able to give somewhat useful voltage measurements on the shunt.  Have him maybe set up an inverter with a space heater drawing around 1,000W.  Make sure ALL other loads and charging sources are off and then take current readings with what he has available, including the BMS and a DVM across the shunt its self.  Formula then becomes:

  • Amps = (DVM mV reading)  * 10   (for a 500A/50mV shunt)

So, if the DMV reads 8.4mV, that would translate into 84A of current.

Should give +/- 10% accuracy without too much difficulty.


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