Weber & Coulomb's LyteFyba BMS

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Weber & Coulomb's LyteFyba BMS

Post by offgridQLD » Sun, 18 Oct 2015, 02:18

The moment I spotted the battery in the thumbnail pic of the video. I thought to myself...he's not going to make a fuse out of that track is he Image


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Weber & Coulomb's LyteFyba BMS

Post by Adverse Effects » Sun, 18 Oct 2015, 04:06

like i always say

" get a bigger hammer :-) "

well done

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Weber & Coulomb's LyteFyba BMS

Post by weber » Tue, 20 Oct 2015, 03:37

Coulomb and I recently had two days all-expenses-paid at Cabarita Beach. There was a catch. We had to work on installing and testing a Demand Charge Management system based on lithium-ion cells, protected by a LyteFyba BMS, at a location nearby. Wot fun.

Image

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Weber & Coulomb's LyteFyba BMS

Post by coulomb » Fri, 25 Mar 2016, 03:34

[Edit: You can skip to a new version of this low-cost RS232-to-CMU interface, that has the ability to use wired comms as well as fibre.]

When working with the Industrial Fibre Optic (IFO) used in the LyteFyba Battery Management System, we usually use a Novus USB i485 device with a custom fibre interface. We've published the design for this interface elsewhere. It allows for either Fibre Optic or electrical connections to the LyteFyba BMS. And it allows for sniffing and injecting signals into existing fibre comms paths.

But the Novus i485 device is somewhat expensive. We've had reason to knock up a simpler cheaper interface recently, and now we've had to make a second one. So we thought we'd publish the schematic and layout. This inexpensive interface doesn't have the ability to talk to the LyteFyba BMS electrically, so you need to add the optional IFO connectors at the start and end of the chain of CMUs (Cell Management Units). It's RS232 to optic fibre, so you'll probably need a USB to RS232 adapter, such as the Prolific model available from Jaycar.

Here is the schematic:

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It can be made up on a small piece of Veroboard with this layout:

Image

The female D9 connector (technically, a DE9 connector, but it's often misnamed as a DB9 connector) must have pins 1-5 under the board, since connections are required to pins 2-5 (pin 1 is unused, as are pins 6-9 in the second row of pins). The solder bucket type is best, since the Veroboard fits tightly between the two rows of pins. So the PCB should look similar to this, when the D9 connector is soldered, the holes drilled, and the appropriate tracks are cut:

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The tracks can be cut using about a 4 mm drill.

The final board, from above:

Image

The IFO connector pigtails have to be spread out a little to accommodate the 2.54 mm pitch of the Veroboard holes. This seems to be by far the best way to fit these connectors to Veroboard.

Note that I tried to use a film capacitor for C2, of value 0.27 uF, since I had a bag of these on hand. But I found that file transfer was not reliable; it really needs a 1 uF capacitor. These can be bought as tiny "sky caps" (monolithic, ofen blue in colour) with 5.08 mm (0.2") spacing, or you can solder an 0805 surface mount capacitor under the board, between the GND trace on pin 5 of the D9 connector, and the track next to it (away from the D9 connector) labelled -8V. I did that, and left the 0.27 uF capacitor in place.


[ Edit: blue caps -> sky caps (monolithic) ]
[ C1 and C2 were swapped in diagram; added needed cut tracks; added C1 and C2 alternate positions under the PCB; no need for 1 mm holes ]
[ Added IFO part numbers to schematic; redrew slightly for neatness ]
[ Added note re spreading IFO connector pigtails ]
[ Added links to Prolific USB to RS232 adapter, Novus interface post. ]
Last edited by weber on Mon, 26 Jun 2017, 11:22, edited 1 time in total.
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Weber & Coulomb's LyteFyba BMS

Post by weber » Sat, 26 Mar 2016, 19:06

Here's a slightly more compact version of Coulomb's simple RS232 to IFO interface design. This one omits C2, which has been proven unnecessary, and swaps the order of R1 and D2 on the schematic. It also allows the IFO mounting screw heads to contact tracks which are in use, but one of these is GND, and the other is DTR which we are using as a +9 V supply. If the two are accidentally shorted, only 30 mA flows.

Image

Edit: I note that the DE-9 female connector is of the solder-bucket type, not the PCB-pin type, because this provides mechanical support, as it lets the board wedge tightly between the two rows of pins.
Last edited by weber on Sat, 26 Mar 2016, 08:21, edited 1 time in total.
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Post by weber » Sat, 26 Mar 2016, 20:13

Darn. After posting the above, I realised it could be reduced a little more in size, but only by increasingly "cheating", by putting more parts on a diagonal.

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Post by coulomb » Mon, 27 Mar 2017, 22:52

The other piece of hardware that is needed with these Celltop Management Units (CMUs) and Battery Management Units (BMUs) is a JTAG (Joint Test Action Group) programmer. This is needed for initial programming of the processors, and for debugging if needed.

We use an inexpensive TI Launchpad Development board, available from RS-Online, element14, Digi-Key, direct from TI, and others. It just needs a small cable (250 mm maximum) added to it, and the jumpers moved to one side of their headers as shown:

Image

The header is industry standard 2.54 mm spacing. The wires are soldered to pads 2, 3 and 4, counting from the end near the single-row header. These are GND, JD_RST and JC_TEST respectively. This will allow you to program both BMUs and CMUs.

The development software we use is called IAR Embedded Workbench. It's free to use for assembly language projects, and C projects up to 8 KiB. Download here (use the "Download a free trial" button, and select the Kickstart, size-limited evaluation license when prompted after installing.

[ Edit: had IAR size limits incorrect. ]
Last edited by coulomb on Mon, 27 Mar 2017, 14:30, edited 1 time in total.
Learning how to patch and repair PIP-4048 inverter-chargers and Elcon chargers.

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Post by weber » Mon, 08 May 2017, 19:24

We haven't posted about LyteFyba BMS development for quite some time. But that doesn't mean it hasn't been happening. In fact there have been two major innovations:
• wireless infrared comms (optional) between adjacent CMUs (Cell-top Management Units), and
• the elimination of 16 bypass resistors in favour of a single zero-cost "printed resistor" covering most of the underside of the CMU.

And I'm pleased to announce that after 8 years (including building an electric MX-5 and several solar Monoliths to test it on Image ), we've finally stopped fiddling with the design and have gone to production. Hoorah!

We've licensed production to Lithium Battery Systems here in Brisbane, and here's the first panel of 12, hot off the production line on Friday, tested over the weekend, and its CMUs are going into the first customer's system as we speak.

Image

Other recent innovations are:
• increased voltage measurement range to 4.35 V for use with Lithium chemistries other than LFP,
• a low-cost watch crystal for comms frequency precision,
• a yellow-green LED for receive comms, in addition to the existing blue for transmit, amber for bypass and red for cell stress (an LED in each corner),
• a 3-pin comms header so orientation doesn't matter when you plug them in, and ready-made leads are available in various lengths at ridiculously low cost from the radio-controlled hobby industry,
• a 4-pin expansion port that allows a tiny daughter board to be added to the first CMU for monitoring a current shunt, and to the last CMU for controlling two contactors,
• a break-out that allows them to be fitted to the cells that use M10 studs at 73 mm spacing, in addition to all the common M6 and M8 spacings,
• width reduced to 30.4 mm to allow them to be fitted to cells as narrow as the CALB 72 Ah cells in the blue aluminium cases, and Nissan Leaf cell modules.

The reduction in width has meant reducing the bypass current from 800 mA to 650 mA, but we've added holes that allow the fitting of a 5 watt resistor if more bypass current is required.
Last edited by weber on Mon, 08 May 2017, 14:02, edited 1 time in total.
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Post by weber » Mon, 26 Jun 2017, 21:08

We've added a new feature to our low-cost RS232-to-optic-fibre adapter -- the ability to use wired comms as well as fibre. This makes it useful in more situations, for changing CMU parameters, data-logging, and reflashing to update firmware.

This required the addition of an optocoupler, two 3-pin headers and a new layout on a slightly larger piece of veroboard. All the parts are readily available (e.g. from Jaycar), except for the optic fibre connectors which are only available from Digikey. It is intended for use with a USB-to-RS232 converter cable such as this one. https://www.jaycar.com.au/usb-to-db9m-r ... m/p/XC4834

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Here's the schematic.

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And here's the veroboard layout.

Image


The TX header could be moved further away from the blue fibre connector, by swapping rows with the wire link above it.

If you only need wired comms, you can omit the fibre connectors. You can also shorten the board from 13 to 9 spaces.

If you only need fibre comms, you can omit the optocoupler and the headers.

The track cuts and mounting holes:

Image

The wire links: These can be made from resistor and diode lead offcuts.

Image

The finished underside:

Image

[Edit: I realised that the TX header did not require a fourth pin and a jumper. So I edited all the images and the text accordingly.]
Last edited by weber on Tue, 27 Jun 2017, 05:31, edited 1 time in total.
One of the fathers of MeXy the electric MX-5, along with Coulomb and Newton (Jeff Owen).

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