Smart BMS 14s

daromer

daromer

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Thought I had a thread but apperantly not so I create this one.

I have digged into and used this Bluetooth/RS232 BMS that works decent. The software is rather crappy but it seem to work as cheap alternativt. Great for smaller 50Ah and less battery banks. The balancing current is like 60mA so not much at all.
More work done with the Smart 14s BMS alternativt
 
Fixed ur video link :p

I thought you had one too. not sure where it vanished to.
 
I've love to see this work for a 4S battery pack. A lot of lifepo4 guys in the RV space want to go lithium but there isn't a lot of options for cheaper BMS protection units (the balance is almost worthless on this unit for larger 4S packs).
 
Is it possible to use this smart bms system to limit overcharge/over-discharge conditions while using another mechanism to actually balance? I was looking at those 1s active balancers that have 1amp of balance current for a small battery pack I'm building. I do like that the smart bms can limit the charge per cell as well as the discharge per cell. Limiting the range of charge seems to help pack longevity.

What would be REALLY neat is if grafana could read the usb smart bms data and display it. I can calibrate and edit configurations with the issued pc software but it would be awesome to have a little raspi just doing some monitoring and data display.

Oh, and thanks for the video! Really awesome that you put those together. I really appreciate it!

EDIT:
I should add that I am accumulating INR18650-25R cells for a portable battery build. I'm currently planning on a 7s30p pack with mppt solar charger and 1000w pure sine output capability. So that is what I would be using these 1s active balancers for.
 
Can you link the 1s balancer you mentioned? I've never seen such a device, especially with 1A balance current.

I just got one of these smart BMS boards, hopefully I can have a PC read the data over Bluetooth, seems they are just using the Bluetooth adapter as a virtual UART connection. Still reading through info on the Endless Sphere thread on this board. I also cheaped out and bought the 30A version even though my application needs 40A, was hoping to figure out what the difference in FETs or shunt resistors is and add the extra/different parts later to upgrade mine. Official website for the software gave a malicious software warning on Chrome... not encouraging. Guess I'll start with the Android app anyways: https://www.lithiumbatterypcb.com/smart-bms-software-download/
 
I bought a 7s smart bms in the 60amp variety. Just started playing with it. I setup a 7s1p pack to do some testing with it and see how it works. My new plan is to use node-red to read the serial data and spit out something that grafana can display.

the other thing that I wanted to see was how much it could really balance. I will probably end up with the 1s smart balancers on my 7s battery. Those seem to be about $21usd/ea x7 for a total of about $200 for a BMS with good balancing. The best part of the "smart bms" is the ability to change ovp and uvp settings for the cells.
 
rev0 said:
Can you link the 1s balancer you mentioned? I've never seen such a device, especially with 1A balance current.

I just got one of these smart BMS boards, hopefully I can have a PC read the data over Bluetooth, seems they are just using the Bluetooth adapter as a virtual UART connection. Still reading through info on the Endless Sphere thread on this board. I also cheaped out and bought the 30A version even though my application needs 40A, was hoping to figure out what the difference in FETs or shunt resistors is and add the extra/different parts later to upgrade mine. Official website for the software gave a malicious software warning on Chrome... not encouraging. Guess I'll start with the Android app anyways: https://www.lithiumbatterypcb.com/smart-bms-software-download/
Click to expand...

Does your smart bms have the charge and discharge on the same port? How does the charge and discharge FET disable these independently if they are on the same port?
 
gpn said:
rev0 said:
Can you link the 1s balancer you mentioned? I've never seen such a device, especially with 1A balance current.

I just got one of these smart BMS boards, hopefully I can have a PC read the data over Bluetooth, seems they are just using the Bluetooth adapter as a virtual UART connection. Still reading through info on the Endless Sphere thread on this board. I also cheaped out and bought the 30A version even though my application needs 40A, was hoping to figure out what the difference in FETs or shunt resistors is and add the extra/different parts later to upgrade mine. Official website for the software gave a malicious software warning on Chrome... not encouraging. Guess I'll start with the Android app anyways: https://www.lithiumbatterypcb.com/smart-bms-software-download/
Click to expand...

Does your smart bms have the charge and discharge on the same port? How does the charge and discharge FET disable these independently if they are on the same port?
Click to expand...

I believe it has a bi directional current shunt and disables the charge and discharge FETs that are wired together with voltages on the gates, like how simple 1s battery protection ICs work.
 
Woould love to test it. Dont have the money to buy it right now though :( But as soon as I get some dimes to spare I will for sure. That looks interesting!
 
I think I might buy the one that that I highlighted to test it out in a 7s32p pack I am building. It will be a week or two to purchase and then a month to get it here. But I'll keep you updated!
 
On the topic of the original "Smart BMS" that Daromer reviewed, what is the difference between "charge balance" and "balance"? I assume having "charge balance" checked means it will only balance cells when there is a current into the battery (charging is detected)? I think I made this mistake while leaving it plugged in to charge over the weekend so now it's in limbo, unable to charge because one of the cells exceeds 4.2V while charging, yet unable to balance because it only does so while charging...

In other news I shuffled around some shunt resistors to make a roughly 7.5mOhm effective resistance so I could use it as the shunt for my 50A current/voltage/watt meter (came with a 75mV per 50A shunt, but is also compatible with a 75mA/100A version):

image_inqflo.jpg
 
Charge balance is the most common where it only balance during charge. It should still balance when going above 4.2 but cannot answer how this is programmed.

You can always change to normal balancing to get it down again.
 
It seems it is still not balancing with "balance" only checked. Charge balance is working, but if any cell exceeds the overvoltage threshold, it disconnects the charge FET (as it should), but also stops balancing, since it is no longer detecting a charging state (not as it should; in this case the pack will just be disconnected and the cell still stay out of balance and over voltage). Will try more debugging, maybe there's something weird going on with the balancing "windows" setting or balancing voltage setting I have set...

Edit: Think I cracked the (not so smart) code... Balance only works when *not* charging (and above the threshold you set I believe). Charge balance only works when charging. I hope they make a firmware update to fix this, I'm going to try contacting them.

Edit 2: Ok, best setting to use is balance (not charge balance). If while charging one cell exceeds 4.2V, it will cut off the charge FET and stop charging, and then balance. Otherwise it will only balance while not charging. Not ideal, but better than the situation before.
 
Here's some pictures of the 14s Smart BMS:


image_yyvges.jpg

image_qpohed.jpg


image_kgqfuf.jpg

image_bhlplq.jpg


image_hvityz.jpg


It uses International Rectifier IRFB3607 MOSFETs, which are each rated at 75V, 80A, 9.0mOhm (at 46A). I forgot to check whether the charger side has the same FETs, but I think so. If that is the case, each FET should dissipate around 2.9W at 40A discharge which I plan to use my pack at. We'll see whether this is too much since the BMS is rated for 30A. There's space on the other side to populate an additional 5 FETs each for the charge/discharge protection.
 
I wrote some code for an arduino to read this smart BMS ,..... when I am able to I will put a link to show the one I mean ,...... I've loaded it to github, ...... when I am able to I will put a link to it, on github, search bres55, you might find it ,........
It appears to use a variation of ModBus.
 
I wrote some code for an arduino to read this smart BMS ,..... https://www.aliexpress.com/item/8S-...rd-for-8-Packs-18650-Battery/32844170262.html ,...... I've loaded it to github, ...... https://github.com/bres55/Smart-BMS-arduino-Reader ,........

It appears to use a variation of ModBus.

UPDATE:-
I have uploaded a new file, for arduino mega, but it can be edited for uno.
And from the serial monitor, one can now change the mosfet settings.
I know this can be done with the software that came with it, but I need to be able to change these settings and get the cell voltages, so that it will tie in with my other project.
 
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