Idiot's guide to a self build battery

[Kenny000666]

Here’s a link. It’s the official JK BMS store.

https://a.aliexpress.com/_mqRTLHo

[Caesium]

Question for you Caesium, what info did you use to connect the JK BMS to an ESP32? Did you have to buy a special version of the BMS to do that? I’m thinking once things have been hooked up, I’d like to connect the BMS up to my raspberry pi and read the BMS info into HomeAssistant.

There's a port on mine that is advertised as being "RS485" but in reality its actually just a TTL serial port. I think they all have this, its a 4pin connector near the display connector. So you have direct access to a set of RX/TX that can be directly hooked up to an ESP32. The hardest part honestly is finding a plug that fits! For now I've very messily soldered some wires onto the pins but I've ordered a set of cables to make this neater. I daren't move anything near the BMS for now

Then its a case of parsing the data with the ESP32, for example with something like this https://github.com/syssi/esphome-jk-bms

[Kenny000666]

There’s 2 ports on mine
The first one is labelled can/rs485.
The 2nd one is labelled gps (strangely) this is the 4 in port for RS485 comms according to this.



I think it’s one of these connectors https://amzn.eu/d/6K4qPVr, I might have some spares from some stepper motors I have lying around, might try it at some point. I’ve got a rs485 USB adaptor thing I used to get Rs485 from the pylons, so will try it out with this.

[Caesium]

Ah you have a slightly different model to mine - I think mine might be older, the silver case style. I think the newer ones are black case. Should be pretty similar though once you find the right port. Did you pay for the canbus extra option?

[Kenny000666]

Ah you have a slightly different model to mine - I think mine might be older, the silver case style. I think the newer ones are black case. Should be pretty similar though once you find the right port. Did you pay for the canbus extra option?

Um, no I don’t think so. I just selected the first and cheapest option . But there is a can port so I don’t know if it is just a dummy port. They didn’t send any cables that could go in it.

[ALAN/ALAN D]

Thanks Kenny.


Here’s a link. It’s the official JK BMS store.

https://a.aliexpress.com/_mqRTLHo


What device would people suggest is the best for

16 x 3.2V 320Ah LifePO4 batteries.

[Tinbum]

What device would people suggest is the best for

16 x 3.2V 320Ah LifePO4 batteries.

Seplos

[ALAN/ALAN D]

LifePO4
16 230Ah
Not got them delivered yet.


Not seen any information on best way to mount / use them.

Some people are.

Using threaded rod to compress the battery.
Side to Side.
To stop the battery expanding when it warms up.
But not end to end / Top to bottom. ?
Some are mounting them vertical. Some horizontal.
I am thinking horizontal. If metal things get dropped on them, possibly better of ?
But horizontal. Is there chance of leakage around the terminals . ?
Not seen any information on web sites about how to position them.
Use foil backed insulation on all sides / bottom.?

[Joeboy]

LifePO4
16 230Ah
Not got them delivered yet.


Not seen any information on best way to mount / use them.

Some people are.

Using threaded rod to compress the battery.
Side to Side.
To stop the battery expanding when it warms up.
But not end to end / Top to bottom. ?
Some are mounting them vertical. Some horizontal.
I am thinking horizontal. If metal things get dropped on them, possibly better of ?
But horizontal. Is there chance of leakage around the terminals . ?
Not seen any information on web sites about how to position them.
Use foil backed insulation on all sides / bottom.?

So many choices, all are valid apart from upside down I suppose. I went vertical stud face in a vertical orientation with 3 sets laying horizontal. No leaks seen. Went this way as logic dictated for the space I was aiming for. Minimise potential to arc is No1 priority, all the rest is window dressing. I used no insulation but I see the point, 9.5 degs is the coldest my pylontechs have reported in -11 so I expect the LF280's to be about the same.

[Colin Deng]

Ok so here’s mine, I put mine under the work bench, it’s close enough to the inverter and the pylon and put insulation around the sides and the front when I finish. Figured the concrete floor would serve as a heat sink if it ever gets too hot, but I doubt it would be necessary.

Very well packaged, thanks Deriy (Colin)







JK BMS (0.6a active balancing, up to 20s, 100amps charge discharge, brought from AliExpress for something like £50 - the supplier seems to have accidentally sent me 2 )



Levelled out the floor



Stacked the 15s and surrounded the pack with wooden boards and PIR. Cut up the Padding/insulation inside the box to protect the spare EVE cell.


All cells checked, my multimeter shows as between 3.303v - 3.304v, albeit slightly higher than the test values Deriy included (they had the cells at around 3.268v).

So tomorrow, to hack up one of the bus bars to join the 2nd row with the 1st row. Make an Eve cell sided enclosure to store the BMS and to act as a filler to complete the 2nd row. Once finished, I may screw in some 3x2s over the top to prevent any expansion upwards (and as a preparation to a 2nd stack if I ever go that way, or just storage)

Connect up all the cells to the JK BMS, and give it a whirl. I chose the welded stubs and had the bolts and nuts provided. In hindsight probably would have been better to have welded bolts, means one less set of tasks.

Side note: as I have a spare Eve, I’m going to do some reading on nowtys thread to try and understand why making a 16s pack to go in parallel to the Pylon isn’t going to work.

Thank you Kenny
Glad that we can help you with the battery needs