DIY Lithium Battery Balancer and monitoring (BMS)

Hardware
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467

For those who have sat through my YouTube video (and stayed awake!) I’ve released the smaller PCB design over to GITHUB - its in a separate branch for now.

A couple of the resistors have been changed to 4.7K simply to reduce the number of different components required - this will also make the LED not as bright as some people have reported issues with this.

1 Like
468

I like smaller design much better. First of all boards will be cheaper. With panelizing hints from Colin you can get around 30 of them at about $12 dollars shipped. Also 0805 SMD is not much harder to hand solder compared to 1206 but the board is way more compact. Still have to try Stuart’s frying pan trick :slight_smile:

Great to see such progress.

469

what size is the new board

470

65mm x 28mm (approx) - (2.5" x 1.35")

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471

thanks for that stuart
Just one last question is the file ready to download and also board requiremants like myself is the first time ordering a pcb make like copper weight, finish pcb thickness

472

I just used the defaults for the pcb tickness and weight etc. Use the GERBER.ZIP file - I ordered some boards using that last night.

473

found it all good orderd 30units now to find all the parts
so if i was to get 2 amp 8v Resettable fuse as 1.5 are hard to find ?
would it make much of a difference

474

I thought people might like to see some photos of my v3 PCB “in action” ? Since v2.1 of Stuart’s diyBMS board (March 2018), this v3.0 is my complete redesign with the following improvements:

  • Smaller 0805-size SMD components instead of 1206-size (slightly cheaper and more readily available)
  • Far more documentation on the board silkscreen, including labelling all inputs/outputs, consistent orientation of components & labels for easier hand assembly, and marking pin 1 on all ICs
  • Thermistor labelled as fitting to front of board (for measuring power resistor) or back of board (for measuring battery pack)
  • BOM optimised with fewer components, and re-uses standard resistor values where possible
  • Supports a choice of data & power socket sizes: JST PH 2.0mm, JST XH 2.5mm, or generic DuPont 2.54mm
  • More reliable I2C communication with reversed ADUM I2C chip
  • 2-pin power socket is now the standard way around (positive on right), so commercial red/black cables work without modification
  • Much smaller board, just over half the size of v2.1 at exactly 65x28mm
  • Via-stitched copper ground planes for better heat-dissipation
  • Standardised M2.5-size NPTH mounting holes (non-conductive pads)
  • Shorter PCB traces, especially for high current signals
  • Does not support the larger/more expensive aluminium-housed power resistors (e.g. Arcol HS50)

the photos below show my prototype board, which only supported JST PH 2.0mm sockets. The v3 files that Stuart uploaded work with all 3 socket sizes.

IMG18_7334_web
IMG18_7334_web1000×574 162 KB

IMG18_7335_web
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IMG18_7237_web
IMG18_7237_web800×600 150 KB

1 Like
475

Technically you don’t need the fuses (although for safety its recommended) - you could just use a piece of wire!

476

need more information on components values, not prices
1206 1/4W
[1206 5% SMD Chip Resistors SMT Resistance ( 0R to 91R ) Ohm](
[1206 5% SMD Chip Resistors SMT Resistance ( 100R to 9.1KR ) Ohm]
[1206 5% SMD Chip Resistors SMT Resistance ( 10KR to 910KR ) Ohm]
[1206 5% SMD Chip Resistors SMT Resistance ( 1MR to 10M ) Ohm]
[1206 1% SMD Chip Resistors SMT Resistance ( 0R to 91R ) Ohm]
[1206 1% SMD Chip Resistors SMT Resistance ( 100R to 9.1KR ) Ohm](
[1206 1% SMD Chip Resistors SMT Resistance ( 10KR to 910KR ) Ohm]
[1206 1% SMD Chip Resistors SMT Resistance ( 1MR to 10M ) Ohm]
These are examples of some of the items im trying to find even at my local jaycar electronics store

477

Another diyBMS in the wild, thanks everyone who contributed to this project so far!

Couldn’t wait for new solderpaste to arrive and had to hand solder the first board :slight_smile:

IMG_20180928_123848
IMG_20180928_1238482862×2146 2.02 MB

1 Like
478

The 1% or 5% tolerance isn’t critical to this project, but go with the 1% if you can.

480

that does answer my question but more information on components more so like ohms. the more information the better would have to get parts in there local area.
as i look for some other the items like resisters under the info given but lacking key info like ohms and watts stuff like that. sorry if im a pain but not every one is a circuit guru
i’m aussie and info her is a major key to finding required part other wise our sale people look at u stupidly no former circuit degree
so i take it a 47R is 47ohms resister .1% threshhold

481

GitHub - stuartpittaway/diyBMS: Do it yourself battery management system for Lithium ion battery packs/cells has all the info you need if we talk about version 2.1 boards.

482

Pound cost here in australia is 3 to 5 times the australian dollar. if you understand where im coming from

483

I often use AliExpress to order components like these - hopefully they ship to Australia.

Take a look at this

Its a book full of the various resistor values so useful for all sorts of projects without needing to specify exactly which one you want.

484

thanks stuart is mostle my source ebay, lcsc.com alibaba RSonline.com.au there valuse not everything is there may sites but all show diffrent valuse more than just ohms, or resistance. say is a part is out seeded out of stock need to look for next best closest value to items as in list in Pars build list

20180928_232126
20180928_2321261527×1527 898 KB

485

I handsoldered all my boards, its not hard or anything?? Whole mess with solder paste n stuff, i think i’m twice as fast with hand soldering… A good soldering iron/station does help though, i use a Metcal sp200. Its a gem.

486

Is it normal a cell module is pulling 12mA in normal operation? (no led or bypass on). thought it would be more in 3mA range, and actually was hoping for uA. Wonder if its worth implementing some sleep modes and lower reading intervals.

487

I’m going to be working on that shortly, as I’m keen to get the power consumption down as low as possible.