DIYBMS for Lithium Iron Phosphate battery cells (LiFePo4) 280aH

Albert · 2022-06-25T20:51:16.586Z

Don’t forget to clamp in your cells to prevent them from swelling.

JoshyJS · 2022-06-25T21:45:16.503Z

The battery is in test stadium.
Did not jet find the time to put it in a cupboard, cut the Data cables
and produce a pressing stand.

First I have to produce a vacuum table for my CNC mill.
Then I cut the boards for stand.
And then I move the complete battery.

Come time comes improvement!

Stijn · 2022-06-29T17:07:28.733Z

I can’t flash my cell monitor
What flasher do u guys use? i have a USBASP.

platformio.ini - Untitled (Workspace) - Visual Studio Code (gyazo.com)

moscito · 2022-07-02T19:16:35.759Z

Hi
I wanted to have 32 modules made at JLCPCB but unfortunately the component for D1 C10204 (https://datasheet.lcsc.com/lcsc/1810181740_RUILON-Shenzhen-Ruilongyuan-Elec-SMBJ5-0A_C10204.pdf) is not available and I have in seen the search function that C473804 (https://datasheet.lcsc.com/lcsc/1912241104_Slkor-SLKORMICRO-Elec--SMBJ5-0A_C473804.pdf) is very similar or the same. Can I use this ?

I am using the EVE file from April 3rd. 22, is that current? I want to use the modules for my BASEN cells, they also have 123mm

JoshyJS · 2022-07-08T15:15:33.374Z

Now I took my time to change all PCBs.
Unfortunately one has an issue with instable voltage setting.
I try to find out whats going wrong. Attiny is not the problem.
All resistors seem to be OK. But I have to set around 4.5 to get the right voltage.
And during change of voltage its to high when higher and to low when lower.
Maybe one has an idea which component is kidding.

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jetronic · 2022-07-08T20:18:45.814Z

Maybe it is this topic?

Issues with TL432 (voltage drift) diyBMS

Building a lot of battery. 3kWh Building Blocks. Up to now … puh a lot. more than 30 I think. From Offgrid to Solar energy storage. But nothing commercial. Plus the Modules that were wrong ordered, wrong built, wrong redrawn for panelizing, wrong D1, defect Attiny …

JoshyJS · 2022-07-09T11:05:43.900Z

I expect now the D1 Zenerdiode is the cause of the problem.
Maybe got to hot during soldering the Attiny.

VAS, is there any difference in resistors connected to the Attiny for reference voltage?
I measure differend values to the schematic of Stewards 4.40.

Nico1 · 2022-07-26T06:43:09.441Z

As much as i love the project, (kudos) i have to choose for an commercial BMS. Its impossible (or very complicated and expensive) to source all the components. I will look back on it in a years time (when i expand my battery) and hope this chip problem ends.

JoshyJS · 2022-07-26T12:47:51.593Z

At JLC in the moment all parts are available.
Except one RGB LED.
It works without.
And for the cell boards you only need the Attiny. Available at Alibaba or Express…
Or some by me…

Smurfix · 2022-07-26T14:04:59.877Z

vas:

the idea is that once you have everything plugged in and running, doing a s/w upgrade means you have to disconnect from the cell (at least that’s the theory!)

My solution is to not disconnect from the cell; instead I simply disconnect the programmer’s 3V wire.

Warning: this only works if the programmer is not otherwise grounded. In my case it’s a Raspberry Pi with a battery power supply from LiFePo4wered.com.

moscito · 2022-07-31T09:56:06.013Z

I saw the lifepo4 design and fell in love immediately, especially since I’m just changing from 18650 cells to 280AH lifepo4.
I like your lifepo4 design but there are a few things that have always annoyed me about the modules. It’s the small JST sockets, they’re just not for my sausage fingers And the arrangement of the resistors bothers me a bit.

I would like to have the resistors in a large group in order to use a larger heat sink and possibly cool it with a fan and of course a connector for the power supply.
The motherboard can easily be 60 or 65mm wide so that a 60x60mm heatsink and a 50x50 fan fits on it. The cells are 70mm wide.

I read in the data sheets that most 5V fans work in the voltage range from 3.5 to 5.5v. A simple fan control that allows the fan to only run from 40 degrees would be really great.

Since twisted pair and shielded cables are recommended for RX/TX, I would like to use RJ45 sockets and cables. Short Cat5 cables can be bought for little money and the design of the circuit board can certainly be adapted. Without the hole in the middle there would be enough space for 2 standing network sockets. The circuit board for the sensor will certainly find a different position if it were smaller.

I expect better handling and error-free data transmission.
When I think that I need 96 modules and should therefore use 192 of these little JST things, I get scared

Unfortunately, I lack the skills to adapt all of this to my needs. If someone bothers to change this I would in return make a donation to Stuart’s project or whatever is requested.

I was able to make a few changes. It wasn’t easy for me
I would be very grateful if someone would look at the result, I’m not sure if everything is error-free.

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PCB_DIYBMS_123mm_test.zip (278.4 KB)

jetronic · 2022-08-01T15:01:26.840Z

What kind of firmware do you actually flash onto the EVE_v1.9F boards from vas?

These are available in the ESP32 controller:
V440 (be82379d)
V440_COMMS_5K (be82379d)
V440_COMMS_9K6 (be82379d)

Andrew_Congdon · 2022-08-02T07:07:50.876Z

Any of those work for me. I suggest you start with just the V440.

Andrew_Congdon · 2022-08-02T07:35:35.566Z

moscito:

I would like to have the resistors in a large group in order to use a larger heat sink and possibly cool it with a fan and of course a connector for the power supply.
The motherboard can easily be 60 or 65mm wide so that a 60x60mm heatsink and a 50x50 fan fits on it. The cells are 70mm wide.

Vas has already stated that he tested these at 100% PWM and with his latest resistor layout no heatsinks were required. I can’t think why you’d need so much cooling? The balance resistors are only used at the top
of the charging cycle. Even if the cells are poorly matched the balance current required should be related to your charging rate, ie you drop the charging current as the cells are top balancing. I’ve seen my cells at well over 30 degrees ambient and still no need for additional cooling. After the cells have been balanced once you shouldn’t get a large drift between cell SOC so you only need large balance currents when the cells are new and you can get around that by charging more slowly for longer at high SOC then change your BMS and MPPT settings when the cells have completed a balance cycle a couple of times. With LifePO4
there is only a very small change in SOC where you would be balancing so charging with more current is fairly pointless, ie you’ll find at the top of the charge curve there is a rapid change in voltage for little change in SOC, that’s where you’ll be balancing the cells.

Also in his design you can see the cell vent which may be quite useful.

One of the original design goals of these modules was to reduce the twisted cable lengths so communication shouldn’t be an issue even in large packs. Perhaps you could use a tool for the JST connectors? I agree they are a fiddle.

Andrew_Congdon · 2022-08-02T07:43:33.907Z

… and you can purchase JST cables in custom lengths quite cheaply on Aliexpress.

moscito · 2022-08-02T19:00:07.109Z

Thanks for your detailed answer.

I think where heat is generated, it should be dissipated well. In any case, I will mount 4 small heat sinks. Let’s just call the reason “German Angst”
I’m a craftsman, my motto is “having is better than needing”
As for those lousy little JSTs…I HATE THEM. I find the JST as useful as a fly in a meal.
I definitely want to use the Futaba RC servo cables. I’ll see if I can change the design so I can see the lid.
The Futaba cables are available on aliexpress for little money

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JoshyJS · 2022-08-03T20:09:49.845Z

/

Um es mal auf klar Deutsch zu sagen: total verrückt.
Das Futaba Zeugs nimmt mehr Platz auf der Platine weg. Die Kabel sind nebenbei zu lang.
Die JST Kabel tun was sie sollen.
Ich habe mir auch erstmal Kühlkörper gekauft.
Die liegen immer noch Inder Tüte weil ich nie mehr als 40 Grad beim balancen sehe.
Die VAS Boards haben schon mehr Widerstände als das normale 4.40 Board.
Die Wärmeabfuhr ist daher deutlich besser. Auch vom Design her.
Was Lüfter angeht: hatte ich auch drüber nachgedacht.
Wenn man das Design versteht: da abgreifen wo die Widerstände angesteuert werden.
Schon läuft auch ein Lüfter wenn sie Widerstände warm werden
Aber all das braucht man nicht.
Auch ich bin Handwerker. Aber andere Philosophie. Je einfacher desdo besser.
Aber der gute Deutsche braucht für alles ne Versicherung.
Eine Stoppmutter mit Sicherungslack, Splint durch, Sealer drauf und verschweißen.

/

moscito · 2022-08-05T18:46:12.445Z

Ich habe die Kabel in 5,10 und 15cm länge liegen und kann sie auch selbst krimpen. Die Schirmung ist gut und sie sind fertig verdrillt. Platz ist auf der Platine genug für die 1x3p 2.54mm Header. Mit ein bisschen Geschiebe geht das.

Glaube mir wenn ich sage das meine riesigen Pranken nicht für JST geeignet sind
In meinen Händen wirkt ein Fussball wie ein Tennisball.

Ich ging von der Wärmeentwicklung der 4.21 Module aus die ich in Benutzung habe. 60grad sehe ich da oft.
Es ist gut zu wissen das es mit den LFP Modulen nicht so ist. Somit “brauche” ich für mich nur die 1x3p Header damit ich glücklich bin.

JoshyJS · 2022-08-05T19:03:22.661Z

Du schiebst die Kabel doch nur einmal drauf.
Dann fasst Du da nie wieder an…

moscito · 2022-08-07T19:32:12.517Z

Ich mag die trotzdem nicht