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DiyBMS PartsList / Bill of Materials

Parts list and additonal info for a 7S build of the Stuart Pittaway DiyBMS project. Prices and links are in Australian dollars.

Project links & useful resources



I ordered the PCBs from by just zipping and uploading the gerber files from the main project.

ESP 8266 controller

I purchased a handfull from Australian and Chinese based ebay sellers with no issues. I bought ones based on/clones of the NodeMCU design. It's important to note that the square USB chip chip is a CP210x chip and this needs drivers. On macOS you need to make sure you give the installer permissions to install the kernel extensions.

Alternatives to ADUM1250ARZ I2C isolator

The Adum1250ARZ chip is quite expensive ($8.59 AUD), rather than buy 7 or more of them upfront I tried two alternatives that are both working well for me as drop in replacements.

R2 Value

There has been some discusison on the correct value of R2. Adam Welch has used 510 ohms (so have I) but Stuart has used 47 ohms. Ultimately it depends on how bright you want the LED and how much power draw you want it to add to the main resistor when discharging a cell.

An alternative to the 510R resistor below is 47R - Yageo RC1206FR-0747RL.

R1 Value

Similar with R1, it depends a bit on how quickly you want the BMS to discharge a cell. I have picked 2.2 Ohms, you can also go with the value marked in the schematic with 3R3 - HS50 3R3 J 50W Axial Wire Wound.

These resistors are also far cheaper on ebay for under $2 a piece. A range of values are at this listing: 50W Aluminum Clad High Power Wirewound Resistor 0.5/1/2/2.2/4/6/8/10/20 R Ohm.

Wire Lengths

It's best to keep the wire lengths between the boards as small as possible.


Hot air/rework station

To do the smd soldering I purchased a ATTEN AT 858D clone from ebay named "Yihua 858D" for $59.89 AUD delivered. These devices are known to arrive with bad electrical defects, prior to using it I checked it's internals by following this guide.

So far I have had no issues with my model, it works very well, but I keep it unplugged when I'm not using it.

Solder sencil / Solder paste

I plan to 3D print a stencil based on Colin Hickey's sencil generated at, however purchasing solder paste that came with a very fine nozzel/tip has been fine for placing solder on the pads of the boards.

Three module test build

I've put together three boards to test the different isolator chips and was able to get it all working and reporting to emoncms without any modifications to Stuart's code, just by making sure I soldered things properly and sanity checking things by following along with Adam Welch's videos.

Test Build


Component Board marking Mfr No. Store Price (AUD) Qty Total Size/Notes Link Datasheet
ATTINY Microcontroller ATTINY85V-10SU SOIC-8 ATtiny85V-10SU Mouser 1.82 7 12.74
Voltage Regulator REG710NA-3.3 REG710NA-3.3/250 Mouser 1.93 7 13.51
I2C Isolator IC ADUM1250ARZ SOIC-8 Analog Devices ADUM1250ARZ Element14 8.59 7 60.13
Mosfet "M1 SI2312BDS-T1-E3 MOSFET Transistor, N Channel, 3.9 A, 20 V, 0.025 ohm, 4.5 V, 850 mV" VISHAY SI2312BDS-T1-E3 Element14 0.588 10 5.88
Diode "D1 SE30AFG-M3/6A Standard Recovery Diode, 400 V, 3 A, Single, 1.1 V, 1.5 µs, 40 A" VISHAY SE30AFGHM3/6A Mouser 0.486 10 4.86
Fuse "F1 MC36228 PPTC Resettable Fuse, 1.5A 8V" 0ZCG0150FF2C Mouser 0.192 10 1.92 1812
Thermistor "B57891M0103K000 Thermistor, NTC, 10 kohm, B57891M Series, 3950 K, Through Hole" EPCOS B57891M0103K000 Mouser 0.793 10 7.93
Blue LED BLUE LED 1206 SMT 150120BS75000 Mouser 0.269 10 2.69 "1206, 3.2Vf"
Green LED GREEN LED 1206 SMT APTR3216SGC Mouser 0.127 10 1.27 "1206, 2.2Vf"
0.1uF Cap * 3 1206 Size C3/C4/C5 AVX 12065C104KAT4A Mouser 0.133 25 3.325 "1206, 50V, X7R"
0.22uF Cap * 1 1206 Size C6 AVX 12065C224KAT2A Element14 0.092 10 0.92 "1206, 50V, X7R"
2.2uF Cap * 2 1206 Size C1/C2 Yageo CC1206KKX7R8BB225 Mouser 0.155 20 3.1 "1206, 25V, X7R"
JST 2mm right angle 2 pin J1 JST S2B-PH-K-S (LF)(SN) Element14 0.097 10 0.97
JST 2mm right angle 4 pin J2/J3 JST S4B-PH-K-S (LF)(SN) Element14 0.062 20 1.24
2R2 50W R1 HS50 2R2 J Element 14 4.45 7 31.15 50W 5%
510R R2 (Adam Welch) Yageo RC1206FR-07510RL Mouser 0.012 100 1.2 "1206, 1%"
20k R3 20K Yageo AC1206FR-0720KL Mouser 0.019 100 1.2 "1206, 1%"
10k R4 10K Yageo RC1206FR-0710KL Mouser 0.012 100 1.2 "1206, 1%"
47k R5/R9 47K Yageo RC1206FR-0747KL Mouser 0.012 100 1.2 "1206, 1%"
470k R6 470K Yageo RC1206FR-07470KL Mouser 0.012 100 1.2 "1206, 1%"
680k R7 680K Yageo RC1206FR-07680KL Mouser 0.012 100 1.2 "1206, 1%"
2.2k R8/10/12 2.2kR Yageo RC1206FR-072K2L Mouser 0.012 100 1.2 "1206, 1%"

JST Cables

I have not included any JST wires (only the PCB connectors) in the list. These are easy to find on eBay.

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