Adam, just keep in mind that once you go over certain voltage levels all new manner of risks and issues will start to crop up - such as the spacing between PCB tracks and the potential for arcing on contacts etc which don’t really exist at 40-50V packs - keep safe!
Today i ordered the PCBs and the Parts.
At the moment i am going to use a 2ohm resistor and only use M1. If it should be necessary in the future i can always exchange R1 and maybe put M2 in.
Concerning the “Ground” term, while i was changing the “Ground” to “Bat -” in KiCAD, i tought about, that Battery is not much better. A single PCB is measuring a single Cell. So “Cell +” and “Cell -” would be correct.
But then i threw everything out of the window and just put a “+” and “-” symbol on it, problem solved 
This is my latest Version
I’m especially interested in how the small text of the open hardware logo will turn out.
Here is the latest Version
Now lets wait and play around with the Wemos mini.
Cheers, Chris
Thanks stuart
Got my pcbs today one week turn around that is awesome of JLCPCB here all think of a credit card see V3 size what an awesome you guys have done now have to wait for all the componants to come to build the boards.
thing im thinking will all 1206,1210 components fit or be better to get 0806 components ?
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This newer board is designed for the smaller 08 parts - although it is setup for handsoldering so the pads are a little larger - so the 12 range may fit in some places.
thats going to suck have all 12 serious components coming who know when resisters and caps have to contact my supplier and see if i can get my order changed to 08’s as there on holidays at the moment
Hi,
is PCB V3 O.K. to handle my 24V 600Ah battery?
are the tracks, around the balancing circuit from D1 to Q1, beefy enough to handle this size of battery?
espacialy around the load resistor R1 for eventually higher balancing currents?
Would it be wise to recalculate also Diode D1 and MOSFET Q1?
should I change the load resistor to a lower value and higher power rating for more current?
greetings Oliver
Hi,
so I may answer some of my questions by myself…
- It looks like the balancing current is high enough also for larger battery banks (in my case 24V 600Ah) according to the following document:
White Paper - How much balancing current do you need?
Li-Ion BMS - White Paper - How much balancing current do you need?
any way I did not like to take a chance and beefed up the powertracks of the V3 board and placed through hole connectors in parallel beside the SMD parts, before I ordered my boards. Now I got the option to use throuhg hole parts as well for D1 and Q1.
If anybody has a clue how to balance 3.2V 600Ah cells in a DIY way let me know. If I am lucky my Alibaba friends do what they are according to my order supposed to and balance the cells before shipping 
- Only the large cells should be balanced before the batterie is assembled, otherwise the value of balancing current is a bit low. Am I am right for LiFePo?
3.2 cell voltage(nominal) / 3.3 Ohms = ~0.96 A
or
3.65 cell voltage (chargeing) / 3.3 Ohms = ~1.10 A
Limited by PPTC Resettable Fuse to max.1.5A
If anybody likes to comment please do so.
- I transfered the code for the ESP8266 Wimos to an clone
ESP8266 12-E NodeMCU Kit. It needed some minor changes to the code to make WiFi work. It works now, only I could not test the I2C because I need to wait for boards and parts now.
greetings Oliver
Hi Vela_Nautica
I’m now to the making of the BMS V3 from what i understand these modules are top balance circuits 1.8v to 4.35v @2A
each little circuit does 1.8v to 4.35v blocks of balancing per module say if you have 24v bank 7 cells you would need 7 moduals to balance each cell iv put in a 2amp fuse. not all information has been update for the new v3 boards as of yet only been out 2 weeks this thursday.
I currently have the boards and the components are on there way only part i could get localy in australia for a good price was the thermistors. rest of the components like attiny85, ADUM1250ARZ, REG710NA-3.3 caps and resisters all from a seller on alibaba [email protected] supply ICs, Diodes, Transistors, Resistors, Capacitors, Connectors, LEDs, Fuses & more
If you want to chat with me direct Discord
Hi,
my system will be LiFePo4 24V 600Ah 6parallel 8 in series 6P8S
As I learned, if there is no misunderstanding, a well balanced system does not need so high currents to keep it balanced. It´s more an issue when the factory balancing is insufficent?
I ordered for now R1 as 2.2 Ohms 10 Watts?
Voltage 3.2 → 1,45 A
Voltage 3.6 → 1.69 A
balancing current.
I took a 2.6 A fuse.
hope that will work
Oliver
have a V3 question U2 & U3 which item goes where cant get schmatic to load?
U2 is the ADUM1250 chip - top right of PCB
U3 is the ATTINY - middle bottom of board next to the 2x i2c connectors
NOTE THE ORIENTATION OF THE CHIPS USING THE DOT TO INDICATE PIN 1
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thank you so much Stuart got my first lot of parts in attiny, SE30AFG-M3/6A Standard Recovery Diode a and SI2312BDS-T1-E3 MOSFET Transistors, still waiting for a lot of parts takes so long
Those are a nightmare to solder - they are TINY!!
thinking of getting some solder paste and us my heat gun or solder iron with my 1mm tip
so far 6 attiny and 12 SE30AFG-M3/6A Standard Recovery Diode soldered on the moduals.
hard to find connector and 4 pin cables in 2 mm only have 2 s2-s5 cables from a pack i brought for my first battery bank s6. Australia suck for finding supply’s for modual building not even jaycar sell smd smt any more
wire wound resisters 10w 2ohm are $1.80 each
Hi,
congrats! its going forward I am still waiting for boards and parts. but its on its way…
do you use a tiny smd solder iron? like these 12V sticks.
But SMD is still tiny anyway!
hope you make good progress!
Oliver
i used my normal iron with a 1mm tip attachment 0.7mm tin/copper solder and no-clean flux pen
will get 80% of the parts on monday via alibaba dhl. next time i will buy all from my supplier in china at a better price. than what i did pay for most of my items.
- ATTINY85V-10SUSOIC-8 6 $1.00 $6.00
- REG710NA-3.3 12 $0.65 $7.80
- ADUM1250ARZ 12 $1.70 $20.40
- 0.1uF 0805 100 V, ± 10%,X7R 36 $0.20 $7.20
- 2.2uF 0805 100 V, ± 10%,X7R 24 $0.60 $14.40
- 0.22uF0805 100 V, ± 10%,X7R 24 $0.40 $9.60
- 47R Resistor0805 SMT 12 $0.05 $0.60
- 20K Resistor 0805 SMT 12 $0.05 $0.60
- 10K Resistor0805 SMT 12 $0.05 $0.60
- 47K Resistor 0805 SMT 24 $0.05 $1.20
- 470K Resistor0805 SMT 12 $0.05 $0.60
- 680K Resistor 0805 SMT 12 $0.05 $0.60
- 4.7k Resistor 0805 SMT 36 $0.05 $1.80
shipping cost $35.00
6% paypal fee $6.38
Total $112.78 usd
Total $166.28 aud
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That is a lot of money! i have 20 boards+ components for about 60 bucks! A few people did mention to you to lookup our wishlists on aliexpress though!!
Yes it is cheaper when you know what prices you can get items for !
Those capacitor prices are very high - but still, you got the parts!
I’m working with the designer of the new board to simplify the parts list, but don’t worry what you have ordered will be fine and work!
yes they are little high but even higher if i had to buy them from RSonline