# Wireless Monitoring



## zaxxon (Jul 11, 2009)

Would like to determine interest for a wireless “cross check” type battery voltage and temperature monitor. The present prototype unit operates from 9 to 390 volts with an accuracy/resolution of 0.3 volts. Higher accuracy/resolution can be achieved for lower voltage ranges. 
The unit communicates measured voltage and local area temperature information via BLE advertisement packets which can be read by any BLE enabled device running a compatible data structured app. 
The device runs off the power source it is monitoring. The unit’s current draw is dependent on the applied voltage and update rate. At 100 volts and 5 second update rate, its average current draw is less than 100 uA. 
Attached figures shows first prototype board connected to 9 volt battery, and example Nuxus 7 display showing its measurement and two other prototype units measuring different voltages at different location in my house. More devices are automatically added to display list when powered up and detected. 
This type device can be easily installed by using double stick tape and two small connection wires for power and return. Use to temporarily monitor voltage and temperatures at various locations for troubleshooting or for permanent installations where running long monitor wires is risky and or difficult. 
This device can be used for measuring banks of batteries and comparing values for catching larger cell imbalances. For example, I plan to use three units, one on each of my three 28s3p modules. If I had had this in place, I would have seen that one of the 3P group had sorted in one of the three modules before I started charging. A smaller unit for individual cell monitoring with built-in passive cell balancing could also be made, but the total costs for higher voltage systems using 100 cells is likely more than anyone would be willing to pay. 
Let me know what you think. Any suggestions? What would be an attractive cost number? Desired voltage range and “reasonable” accuracy needs?


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## madderscience (Jun 28, 2008)

My first BMS design was wireless; each sender was powered by, and monitored two 6V golf cart batteries for voltage. They used garage door transcievers to transmit the voltage data at semi random intervals (to avoid collisions, as there was no synchronization protocol. (Note: The "M" in BMS in this case was "Monitoring", there was no per-battery management, e.g. shunt resistors)

There were two receiver units (front and back of car) and 12 senders total. 

This design did have some nice advantages, mainly reduced wiring, reduced risk of short circuits, and no isolation issues. However due to the baud rate (2400) and long power-up time for the transmitter units the overall sample rate worked out to about 1 sample every 10-20s per battery. Not useless, but not great.

A similar design using better wireless technology like BLE or such might actually work quite well. 

If its a BMS however and monitoring each cell it would need much better voltage resolution, ideally about 0.01V and a useful sampling range about 2V through 5V.

If trying to sample the entire pack voltage then yes resolution around 1V would probably be OK.


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## zaxxon (Jul 11, 2009)

Thanks for your feedback. BLE parts do open up a number of possibilities with their integrated arm processor, RF and communication stacks, low power management and built-in A/D converters. The A/D ranges without going to a two chip approach so far seem to limited to 10 to 12 bits. To meet operating temperature requirements and to keep cost and size down, I am trying to stick to and determine if a single integrated chip design would meet most needs.
With the present single chip design, I can get 11 bit resolution over voltage measurement ranges (Vmax/2 to Vmax) like: 200 to 400, 150 to 300, 100 to 200, 50 to 100 ….. 2.5 to 5. For the 2.5 to 5 voltage range, the resolution would be .00122 volts.
For a single cell measurement of just 2 to 5 volts, the size of the device could be around the size of a US first-class postage stamp. Don't need regulator and larger divider networks. But the cost per unit at DIY volumes would likely need to be in the range of $25 to $35.


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## tommypress (Jul 20, 2016)

Great to read this! Will be watching this space for more.


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## jumpjack (Sep 9, 2012)

Do you know ESP8266 breakouts?


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## zaxxon (Jul 11, 2009)

jumpjack said:


> Do you know ESP8266 breakouts?


I am not familiar with this module. But the pin out for the 5-pin module variant pictured in the link you provided can be found at this link near the bottom of the page: http://l0l.org.uk/2014/12/esp8266-modules-hardware-guide-gotta-catch-em-all/


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## jumpjack (Sep 9, 2012)

zaxxon said:


> I am not familiar with this module.


What is cool in them is that they're very cheap (2 to 5$ depending on model) and all-in-one (controller + wifi), and you can easily program them directly as if they were Arduino boards. And they can operate simultaneously as Access Point and client.
The only "defect" I found is that they have just one analog input.


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## zaxxon (Jul 11, 2009)

jumpjack said:


> What is cool in them is that they're very cheap (2 to 5$ depending on model) and all-in-one (controller + wifi), and you can easily program them directly as if they were Arduino boards. And they can operate simultaneously as Access Point and client.
> The only "defect" I found is that they have just one analog input.


This is an interesting chip set. Your right about the one Analog input is a limiting factor. I had originally wanted to go WiFi, but it looked like there were more low energy options, with higher levels of I/O integration and options available for BLE along with the promise of IPv6 capability and mesh networks in the future. So I decided to learn about BLE/Apps.


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## zaxxon (Jul 11, 2009)

Assembled and tested first PCB unit shown in attached Photo. 

This is my first DIY surface mount PCB design and build. Had some difficulties soldering the BLE Module’s blind pads under the part without shorts. May have cooked the part removing and resoldering enough to cause some measurement error. I followed the recommended pad size when making the foot print, but based on results, I think I need to extend the pads outside the part more for hand soldering or use a stenciled solder paste process.


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## jumpjack (Sep 9, 2012)

zaxxon said:


> I had originally wanted to go WiFi, but it looked like there were more low energy options, with higher levels of I/O integration and options available for BLE


It just came to the market ESP3212, with embedded WiFi+BLE.


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## zaxxon (Jul 11, 2009)

jumpjack said:


> It just came to the market ESP3212, with embedded WiFi+BLE.


I did see reference to and looked at when checking out the ESP8266 you mentioned. The ESP32 looks like it has the right types of hardware and configurability for many applications. Not so sure about the tool set and ease of setup and use for a low level software/programmer like me. The level of tool set integration, vendor support, and ease of use is why I went with the Cypress part. It also was the only part with a 12 bit multi-channel ADC and operating temperature at the time. It seems many of the ESP32 interface peripherals mimic the Cypress part.


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## zaxxon (Jul 11, 2009)

Made 3S cell pack BLE battery monitor and Android Apps demonstrator with data logging and graphing features: total pack voltage, temperature, and over and under voltage and cell imbalance faults versus real time minutes and date. 

Connected unit across my 12 volt truck battery to log some data. Pictures shows the stored voltage and temperature (C) versus the real time clock’s time in minutes for a typical drive to bank and two other stores, and graph of voltages captured March 2 (302) through March 9 (309). 

The attached PDF document has additional information and pictures.


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## PStechPaul (May 1, 2012)

Looks somewhat similar to some of the designs I've been working on. I just made a 12V SLA battery monitor that has options for Bluetooth as well as I2C connectivity for an LCD display and a serial EEPROM for datalogging. Elements of the design could be adapted to monitor cells in packs up to 60 volts. My concept for Bluetooth uses the cheap Chinese modules that are less than $5 each and would be activated manually for short periods of time. I have found some buck regulators that work up to 76 volts with efficiencies over 90% at low power levels. I look forward to following your progress, and perhaps we may benefit from each other's ideas. Good work.


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## zaxxon (Jul 11, 2009)

PStechPaul said:


> Looks somewhat similar to some of the designs I've been working on. I just made a 12V SLA battery monitor that has options for Bluetooth as well as I2C connectivity for an LCD display and a serial EEPROM for datalogging. Elements of the design could be adapted to monitor cells in packs up to 60 volts. My concept for Bluetooth uses the cheap Chinese modules that are less than $5 each and would be activated manually for short periods of time. I have found some buck regulators that work up to 76 volts with efficiencies over 90% at low power levels. I look forward to following your progress, and perhaps we may benefit from each other's ideas. Good work.


 Thanks. Now that automotive is transitioning toward 48 volt systems, low quiescent current 60 volt buck regulators are starting to appear. For the 300 voltage BLE measurement unit, I could not find a regulator with a low quiescent current, so I made a linear regulator from a low bias Zener and MOSFET. Given the BLE unit’s small transmit duty cycle and sleep operation, the resulting dissipation is reasonable, and the circuitry is less complex with no RFI concerns. 

The lower voltage 3S unit uses an ultralow quiescent current linear LDO regulator and op-amp buffers to prevent measurement cell imbalance. The 3S unit draws an average of 250 micro amps of current with a 5 second broadcast rate and running real-time clock. 

The Broadcast Monitor App lets you view data as it happens. The logged data is stored within the BLE SOC part not external. The Datalogging App lets you download the stored data and displays it graphically.


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