(off topic) what job do you have?
Aerospace Engineer at a small UAV company called Area-I but since weâre so small (15 engineers) we are pretty well versed in several other areas.
PM for more info. Dont want to drag the thread too far off topic.
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So a couple questions from this:
Would this mean that even though the BMS can do 12s (with its built in converter) it can only do up to 9s with CV?
will there be a chance of using up to a 12s supply? A LOT of people have 10s chargers, they wouldnât work with this BMS, correct?
lastly, if using CV direct, will the circuit still balance the battery?
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The built in converter is what allows it to do CV at any battery voltage. The limit I was referring to was the voltage limit of the charger input, which is now 50V, so there is no problem.
Yes, I have changed the design to allow for 50V power supplies.[quote=âWrinklyWink, post:184, topic:8952â] lastly, if using CV direct, will the circuit still balance the battery? [/quote]
The BMS will balance the cells regardless of the charging method. It tries to balance them before the CV stage begins.
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Is a software feature possible to set up the âcell balancing intervalâ?
e.g. i wanna say that the bms should only balance cells if the drift between them is higher than 0,5V or 0,05V
That feature would be awesome 
Why would that be awesoms? What do you need that for?
Yes, that value is software configurable. Itâs not really useful to change it dynamically, but different people may have different requirements for their batteries.
@raphaelchang Great work I´m searching for an BMS for my project. I´m undecided if your BMS or the DieBieMs from JTAG is the right one for me.
I´m working on an self balancing scooter and plan to use either one 10s2p 5000mAh or two 10s1p 5000mAh battery packs (power both ESCs with one battery pack or power the left and right hub motor/wheel independent). The scooter uses brushless hub motors with 36V 60A max rating and I drive the motors with an VESC each. My dream is to have an BMS which could send the following data back to my MCU over SPI/UART/CAN:
- state of charge
- individual cell voltage
- actual discharge current
- actual charge current
- temperature of the hot spots on the PCB
- temperature of the battery
Could you please give an short feedback of what should be possible with the beta testing BMS? I know your BMS could do some of the feautures (I think except the temperatures).
I have a few more questions to you. Is it possible to use your BMS with only a 10s LiPo pack? Is it possible to use WS2812 to indicate charge status and an digital interface to an MCU (SPI, UART, CAN) at the same time? Your BMS could charge and balance your 12S pack does the software automatically recognize a 10s pack and could this be charged also?
Thank you very much. Best regards, Garfield
All of your listed features are possible on the current hardware (including both temperatures). Some features arenât implemented in software yet, but it should be easy to update the firmware on the beta testing version.
It is possible to use it with any cell configuration (4S-12S), including charging and balancing. Everything is configurable through a dashboard (like the VESC). If you want to connect it to WS2812s, you will have to use CAN to communicate with your MCU. The I2C/UART/WS2812 pins are designed to be used for display peripherals (LCD, LEDs, etc.) so they are mutually exclusive. The CAN bus is designed for inter-PCB communication.
Sign me up for Beta testing on both BMS and ESC. I also have all the tools to do my own assembly if it helps.
I would love to do some beta testing on the ESC
The ESC isnât quite ready for beta testing yet, but Iâll let you know!
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Normally your new 18650 cells wont drift very much! Especially if you have them in parallel. @whitepony is riding without bms and he does not have battery voltage cell drift at allâŚ
The problem is that a normal BMS would balance the cells every charge cycle. And i mean every cycle⌠You just have 1500 charge cycles and waste some on unnecessary balancing. I want to avoid that and extend the life time of my batteries. So I want to set up that the BMS should only balance the cells if it is really required (more than 0,5 or 0,05).
Sorry but AFAIK:
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Is it possible to use two LiPos each with one BMS connected in parallel? I mean one 10s1p LiPo with BMS and an second LiPo 10s1p with BMS and those two packs then paralleled. I didnât see any reason against it. So if Iâm not mistaken count me in for two beta test BMS.
@DeathCookies The balancing is working in the way that the energy which initially should charge the full (highest voltage) cell is dissipated in heat in the balancer. So the full cell doesnât see any charge/discharge while the balancing is on. The cells which have a little lower voltage are charged until these are also full (and then balanced) and if all cells are full the charging is stopped. So the balancing only ensures that every cell is individually charged to the max cell voltage and the balancing doesnât add any charge/discharge cycle to your cells. So if you prefer to charge unbalanced you gain no charge/discharge cycle. So it doesnât matter if the balancer is starting at 0.5V or 0.005V or even 0.0V difference of the cells. I hope you could understand my explanation.
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why do you see balancing as wasting energy? if the cells are balanced every time when charging you will have more energy as each cell will be filled to whatever voltage you decide. for longest cell life a bms makes sense also. for convenience and simplicity going without works but you will likely have to add a bit of buffer into the max charge voltage to be safe. Or donât and have cells not being charged to the optimum voltage for greatest energy holding and longest life.
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Well, The description on @raphaelchang website says " This video shows the BMS balancing cells while charging. When one cell reaches a voltage close to the fully charged voltage, it discharges all the higher cells that are a threshold above the lowest cell and continues charging."
That means that the higher voltage cells get discharged to get balanced to the other cells. @Garfield you have said that the Full cell does Not get energy, it gets dissipated by heatâŚ
This does Not Match raphaels description. Could you tell me what this BMS actually do?
Thatâs how all BMS with balancing function works 
If this was a truth, we would not need a over-charge protection. It will charge even further until it fails ( catastrophically ).
Okay it was a bit unclear. With âit gets dissipated by heatâ I mean an resistor (in the BMS) parallel to the cell is switched on and discharges the full cell (which generates heat) OR these discharge resistor is a sink for the charge current and the charge current is heating up these resistor.
@DeathCookies If these resistor and MOSFET/TRANSISTOR is powerful enough the charger doesnât have to stop charging while balancing and if the resistor isnât powerful enough the charger hast to stop/slow down charging until balancing is finished. I didnât know whether of this is used in raphaelâs BMS but from the description in the video I assume that charging is stopped while balancing.
It is not meant that the full cell heats up itself which would be catastrophically here you are right. Sorry for the not fully clear description.
I hope it is clear now if not please feel free to ask.
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