|02-19-2017, 10:08 AM||#1|
Join Date: Jul 2014
NEW: Bluetooth for Segway-Batteries
After I had presented the mobile diagnostic device for Segway batteries here in the forum, I would like to deprive the worthy forum community of my current innovation no longer: Full diagnostic adapter for Segway batteries with bidirectional Bluetooth functionality.
BT1 - Im Vordergrund der BT-Adapter - P1100152.JPG
After completion of the development work on the project "mobile diagnostic device" presented here - the luxury variant with a high-quality color TFT display - I had searched for a possibility to measure the values of a Segway battery which are important for a user and to display them on a tablet / smartphone. In addition, there was the desire for a measuring device which is as small as possible and more cost-effective without having to dispense with the functionality known from the mobile diagnostic device or aspects of device and operational safety.
The result is a highly innovative "Bluetooth measuring device for Segway batteries", which I will briefly call "BT adapter" in the following (BT = Bluetooth).
It is known that the Segway battery communicates with the Segway Base via a system bus and various data are exchanged. After attaching the BT adapter to the Segway battery to be tested, the BT adapter connects to the battery via the system bus, reads out the relevant data from the battery and holds it for forwarding via Bluetooth. After a tablet / smartphone is connected to the BT adapter (BT connected), the data is sent and output to the tablet / smartphone.
The recording of the individual measured values is largely carried out by the Segway battery (BMS) itself and transmitted via the system bus to the BT adapter - the procedure corresponds to that of the TFT diagnostic device. For checking, the BT adapter has a measuring circuit independent of it, with which important voltages are cross-checked again (redundancy).
This concept also has a great value on security and network independence, the device is directly supplied by the Segway battery: unlike other devices, the advantage of the network independence is that the BT adapter requires no 120V power supply or internal batteries. The current consumption through the BT adapter is relatively low: 6 mA flow after plugging the adapter on the battery (BT inactive), approx. 15 mA during operation (BT active).
Furthermore, various commands have been implemented, which can be entered via the tablet / smartphone and sent to the BT adapter, whereby the flow and display mode can be influenced by the user. The user thus has the possibility to arrange the individual values according to relevance and best possible legibility, to omit individual values, to insert additional blank lines, etc.
Of course, the changes made by the user are stored internally and are retained for the next session in the event of a power failure (ie after the BT adapter has been removed).
The battery values are output either on demand by the user (= On Demand) or continuously updated (= Free Run) and in one of three selectable display modes:
- MINI = minimum output of the relevant battery values
- MAXI = maximum output of the battery values including the 23 individual cell voltages
- USER = user defined; The user can define values and output order themselves
The status transmitted by the battery (normally to the Segway Base) can be permanently visualized, which can be used in advance to determine whether the base accepts a battery as fault-free or not. In addition, an acoustic alarm device warns the user of a critical operating condition or indicates a possible fault situation.
The following values are transmitted by the BT adapter via Bluetooth:
- Status bytes (corresponds exactly to the data stream battery <-> Base)
- Battery status (OK / FAIL)
- Display the battery error code at status = FAIL
- 23 cell voltages, accuracy +/- 0.5 %
- Maximum cell difference in mV (Cell-drift)
- Average cell voltage in mV (AVG)
- Lithium cell with the highest voltage, with the cell no. (MAX)
- Lithium cell with lowest voltage, with the cell no. (MIN)
- Total voltage in V (measurement by battery BMS), accuracy +/- 0.5 %
- Total voltage, measured by BT adapter internal ADC, accuracy +/- 0.5 %
- pos. Current in mA (unloading), accuracy +/- 1 %
- Total battery temperature in °C
- Charge state SOC (State Of Charge) in %
Other features or functions of the BT adapter:
- Acoustic alarm function for under- / overvoltage
- Acoustic alarm function for status = FAIL (with error code display)
- Data transfer to tablet / smartphone via Bluetooth (On Demand / Free Run)
- User programmable sequence control
- Changes made by the user remain permanently (EEPROM)
- The last selection remains permanently (EEPROM)
- Self test function
- Device function in the range 48 ... 88 V
- Genuine Segway connectors (gold-plated)
- BT adapter installed in the impact-resistant ABS small housing (9 x 5 x 3 cm)
3.0) Redundant voltage measurement
As with the TFT diagnostic device, several protection mechanisms have been provided to protect both the BT adapter and a contacted battery as best as possible.
An additional plus of security is ensured by the integrated redundancy by double-voltage measuring circuits: The BT adapter performs internal voltage measurements through internal AD converters. That means that the battery terminal voltage is permanently measured with an accuracy of +/- 0.5 % and checked for critical limits (U_ADC).
This allows a reliable comparison to the total battery voltage determined by the battery BMS and transferred via the system bus (U_I/O). This means that not only the voltage values can be checked for plausibility, even if the system bus is faulty, the BT adapter is always aware of the actual battery voltage.
The BT adapter sends the battery values in the display mode MINI (MIN / MAX / AVG):
BT2 - MINI-Darstellung - P1100139 (1).JPG
The BT adapter sends the battery values in the MAXI display mode (including the 23 individual cells):
BT3 - MAXI-Darstellung mit 23 Einzelzellen (1).JPG
The BT adapter sends the battery values in the display type USER (example with blank & copyright):
BT4 - USER-Darstellung - P1100160 (1).JPG
Example for the measurement accuracy of the BT adapter and the plausibility of the individual voltage values: With an actual battery terminal voltage of 76.0 V (FLUKE, unloaded measurement), the BT adapter has a value of U (ADC) = 76.05 V . The measurement error is 50 mV, the accuracy is better than + 0.1 % (FLUKE = reference with a basic accuracy of +/- 0.05 %):
BT5 - 50mV Messgenauigkeit - Fluke wurde kalibriert mit 0,05% BT (1).jpg
The entire knowledge from the development of the TFT diagnostic device could be successfully implemented with the BT adapter. The BT adapter is simply plugged onto the Segway battery to be tested, the data from the battery are read out and sent via Bluetooth - Well done.
At this point, the question arises whether the BT adapter could be installed directly into the battery. Thus all relevant values from the battery could be checked, without the necessity to dismantle the battery from the Segway. It is technically actually possible (and I have already been implemented by myself) to install the PCB with the BT transmitter module DIRECTLY IN THE BATTERY! This means that all the relevant data of the two batteries can be visualized during the ride - here, in particular, the load-dependent current level should be interesting. For this, it is necessary to use the system bus from / to the battery together with the base in a time-delayed manner - quasi a multi-master system. Studies in running Segway operation have shown that the internal system bus to the battery is actually not used for the greatest time, so it is possible to communicate with the battery during the breaks between the base activity itself. The procedure used for this is somewhat tricky, a continuous parallel operation is still possible in my experience, without the additional communication overloading the accumulator μC (more inquiries) or the Base with a fault in the emergency shutdown (unexpected bus activity).
For this I am sure there will be further developments.
6.0) Further documentation
A video about the functionality of the BT adapter can be found in my international YT channel :
(Tip: There can be an additional description activated by clicking on the below Button "SEE MORE")
Last edited by AccuXperT; 02-19-2017 at 10:59 AM..
|02-19-2017, 11:51 AM||#2|
Join Date: Jul 2007
Location: Columbia, MD
Sounds great, pending review by Jason at MTO Battery. Where can I buy one and how much would it cost? I suspect that I'd prefer that it NOT be internal to the battery since I own more than 70 batterie$...
SegTours of Gettysburg, PA
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|02-19-2017, 06:48 PM||#3|
Join Date: Jul 2014
Oh, thank you, I'm in touch with Jason Abel, we occasionally exchange technical details. However, I had a long absence, I am unfortunately not so often in the SegwayChat.
But I do not want to keep technical news, of course ...
The installation of the BT adapter directly in the battery requires the opening of the battery. This is not, of course, a matter for everyone and requires a lot of technical knowledge. Of course, the future closing of the battery (gluing) will never be as the weld from the battery manufacturer.
The installation could be useful if the battery has to be opened for a repair (for example a cell exchange).
In order to increase the potential benefit for the user, I am currently working on an improvement of the BT adapter. For this I will provide a relay as well as a professional OEM power supply with CCCV charging methods especially for lithium cells. It will be a "safe" charging process as the important data such as battery temperature, charging voltage, fault status, charging current, etc. are permanently monitored during the charging process. When the battery is full or an irregularity occurs, the charger is galvanically separated from the battery by the relay in a safe way.
I have successfully used this fast-loading method for 2 years on 2 Segways. A shortening of the battery life due to the higher charging current can neither be determined nor expected.
To recharge a Segway-battery in only 2 hours and to make the next tour should be quite interesting for some users ...
|02-20-2017, 03:41 PM||#4|
Join Date: Jun 2016
Location: Ocean Springs MS
Question - If this Bluetooth 'monitor' were permanently installed within the battery, would it be drawing current from the battery 24/7? It would seem to me that's the last thing we would need - One more way for a Seg battery to run itself flat and shorten battery life. While it would be nice I guess to see the battery condition without having to remove it from the machine, I'm not sure that would be a good trade-off. I think I would rather have the external version
Isn't there an existing computer program which gives most of this information direct to a laptop? It's not Bluetooth and the laptop must be wired to the battery, but if you're not interested in putting the technology inside the battery, it seems almost as practical as using Bluetooth
What does that program cost? How much does your standalone Bluetooth box shown in the pictures sell for . . . . or are you selling them?
Last edited by Don M; 02-20-2017 at 05:13 PM..
|02-20-2017, 06:40 PM||#5|
Join Date: Jul 2014
your concerns are justified and I have considered this very well.
It would be really a bad solution if the (built-in) BT adapter would discharge the battery slowly ... No, I'm not doing so, of course, because I attach great importance to safety and longevity!
Down to business: when installed in the battery, the BT adapter is only supplied with power when the base activates the battery when the Segway is switched on. It is no secret, I use a switching voltage which is only present when the Segway is activated.
To talk again about the installation of the BT adapter in the battery brief: This is not intended for everyone, probably find the most users not helpful. I have been studying the Segway technique for many years. For me, the vital data of the battery during the trip is very important and revealing.
The battery power is also extremely interesting for me, not just for a battery power test, but especially during the ride. Currently I am technically able to determine the height of the battery current every 10ms. The accuracy achievable is +/- 1 %. This allows precise load characteristics to be recorded during the journey.
But this does not detract from the functionality and the usefulness of the BT adapter which is externally plugged into the battery.
The BT adapter is currently being revised, I can not comment on a final price yet. The price is also dependent on how many users will find the BT adapter useful and want to buy. In any case, I will make my contribution to a good product.
Greetings from Germany,
|02-20-2017, 09:42 PM||#6|
Join Date: Jul 2014
In fact, I wrote a program that outputs the interesting data of a Segway battery pack on a PC / laptop. In this case, the data is not transmitted via Bluetooth, but via a data cable.
With a sample photo I would like to demonstrate how the data is displayed on the screen.
The following photo shows the values of a perfectly balanced Rev.AF battery.
Important: A fast charging method was used, recognizable by the maximum charging current of 2926 mA. Nevertheless, the cells are perfectly balanced! This shows very clearly that fast charging a Segway battery and balancing the cells do not have to be a contradiction!
The program "Seg_Term" has been developed by me and shows all data of the Segway battery clearly on a PC / laptop:
Voller Akku mit 0mV Zellendrift offenbar perfekt balanciert - klein.JPG
|02-22-2017, 08:32 PM||#9|
Join Date: Jul 2014
This is a device in a 19"-housing, which is intended for stationary workbench use.
The Worstation has a built-in electronic load (2 kW), to be able to discharge a battery with 2,5 A defined. In this way, the capacity of a battery can be determined very precisely.
The functionality of the Workstation is much more extensive than with the BT adapter presented here:
- Measurement of the internal resistance of all 23 cells (= Cell-Ri)
- Measurement of the internal resistance of the entire battery pack (at the connection terminals, = Pack-Ri)
- complete galvanic decoupling of the battery by power relay
- precise voltage measurement in 4-wire technology (loss-free under load)
- built-in electronic load with 2 kW and MOSFET load control
- built-in quick charger with 3 A and CCCV-charging procedure (fully automatic loading control)
The program "Seg_Term" shows all the important values of a rechargeable battery, but I intentionally did not use graphics. It is proprietary software running on a laptop.
The Seg_Term-screenshot I had inserted above, since the question was asked for a representation on the PC / laptop.
Example photo of the Workstation (prototype) with adapted Segway battery:
Workstation mit einem Segway-Akku - klein.JPG
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