Idiot's guide to a self build battery

[Kenny000666]

So I let it charge last night at max amps (80a set on the inverter) between 00:30 - 04:30

From 30% SOC (5kwh), it went to 90% (15kWh) in about 2 1/2 hours (approx 3am), which according to my inverters battery charge metric is 10 kWh charged. After that it charged very slowly as normal but SOC didnt reach 100%.

here are my charts


looks like it peaks at 51v when it hits 90%, at 15% its around 48v.

I wonder if we can do anything to the pylontech BMS to reduce the percentage when it slows down? Im going to try dropping the minimum SOC to 15% and see if its worth doing anything about not reaching 100% overnight

[Stinsy]

So I let it charge last night at max amps (80a set on the inverter) between 00:30 - 04:30

From 30% SOC (5kwh), it went to 90% (15kWh) in about 2 1/2 hours (approx 3am), which according to my inverters battery charge metric is 10 kWh charged. After that it charged very slowly as normal but SOC didnt reach 100%.

here are my charts


looks like it peaks at 51v when it hits 90%, at 15% its around 48v.

I wonder if we can do anything to the pylontech BMS to reduce the percentage when it slows down? Im going to try dropping the minimum SOC to 15% and see if its worth doing anything about not reaching 100% overnight

Relax! Don't mess with anything based on one cycle!

It'll take a few cycles for everything to settle down.

[Swwils]

Looks good to me, amazing that we have access to such good cells. If the majority above 280ah what a winner.

[Kenny000666]

So i finally got the JK BMS data, without having to do any additional wiring.

I found a repo, and made some modifications, but largely it works out of the box to retrieve the JK BMS data from bluetooth, and sends it to MQTT which i can read using Home assistant.

if anyone is interested, repo is - https://github.com/schweizp/jkbms_ble.git

[MrPablo]

It looks like the DIY battery club will be getting another member...
I've just pulled the trigger on an order of 17 x EVE LF304 cells, plus a 200A (2A active balancing) JK BMS from Colin at Deriy.

I'm going to go with a slightly different setup than the ones I've seen on this thread so far, building a 17s battery instead of the usual 16s.
My inverter is limited to 65A discharge (67A charge) on the battery side, so the Pylontech stack has always maxed out at about 3100w discharge.
Fine for most situations, but sometimes I'd like a little more headroom to eradicate that last grid import for the kettle, etc.

The inverter can charge at 58v, so a 17s setup will see about 3.41v per cell when charging. My research suggests this won't be an issue, it just might take longer to hit near 100% in the CV stage of charging.
The real benefit will be the higher nominal voltage of the battery (54.4v), unlocking an extra 400w or so of discharge when needed. That plus the 16.5kWh of capacity!

Just got to start ordering cables, crimps, etc now.

[Joeboy]

It looks like the DIY battery club will be getting another member...
I've just pulled the trigger on an order of 17 x EVE LF304 cells, plus a 200A (2A active balancing) JK BMS from Colin at Deriy.

I'm going to go with a slightly different setup than the ones I've seen on this thread so far, building a 17s battery instead of the usual 16s.
My inverter is limited to 65A discharge (67A charge) on the battery side, so the Pylontech stack has always maxed out at about 3100w discharge.
Fine for most situations, but sometimes I'd like a little more headroom to eradicate that last grid import for the kettle, etc.

The inverter can charge at 58v, so a 17s setup will see about 3.41v per cell when charging. My research suggests this won't be an issue, it just might take longer to hit near 100% in the CV stage of charging.
The real benefit will be the higher nominal voltage of the battery (54.4v), unlocking an extra 400w or so of discharge when needed. That plus the 16.5kWh of capacity!

Just got to start ordering cables, crimps, etc now.

Congratulations, its a great way to expand storage and we all learn as well.

[nowty]

It looks like the DIY battery club will be getting another member...
I've just pulled the trigger on an order of 17 x EVE LF304 cells, plus a 200A (2A active balancing) JK BMS from Colin at Deriy.

I'm going to go with a slightly different setup than the ones I've seen on this thread so far, building a 17s battery instead of the usual 16s.
My inverter is limited to 65A discharge (67A charge) on the battery side, so the Pylontech stack has always maxed out at about 3100w discharge.
Fine for most situations, but sometimes I'd like a little more headroom to eradicate that last grid import for the kettle, etc.

The inverter can charge at 58v, so a 17s setup will see about 3.41v per cell when charging. My research suggests this won't be an issue, it just might take longer to hit near 100% in the CV stage of charging.
The real benefit will be the higher nominal voltage of the battery (54.4v), unlocking an extra 400w or so of discharge when needed. That plus the 16.5kWh of capacity!

Just got to start ordering cables, crimps, etc now.

Congratulations, its a great way to expand storage and we all learn as well.

@ MrPablo, what are you going to do with your existing Pylontechs ?

[MrPablo]

I have a friend with 2 x US3000s already, he'll be taking my three once I'm all setup on the DIY stack.

[sw25481]

I just wanted to report another success thanks to all your help and encouragement (and the services of Colin)

[Colin Deng]

It looks like the DIY battery club will be getting another member...
I've just pulled the trigger on an order of 17 x EVE LF304 cells, plus a 200A (2A active balancing) JK BMS from Colin at Deriy.

I'm going to go with a slightly different setup than the ones I've seen on this thread so far, building a 17s battery instead of the usual 16s.
My inverter is limited to 65A discharge (67A charge) on the battery side, so the Pylontech stack has always maxed out at about 3100w discharge.
Fine for most situations, but sometimes I'd like a little more headroom to eradicate that last grid import for the kettle, etc.

The inverter can charge at 58v, so a 17s setup will see about 3.41v per cell when charging. My research suggests this won't be an issue, it just might take longer to hit near 100% in the CV stage of charging.
The real benefit will be the higher nominal voltage of the battery (54.4v), unlocking an extra 400w or so of discharge when needed. That plus the 16.5kWh of capacity!

Just got to start ordering cables, crimps, etc now.

Thank you Paul for the support
Most customer would go for 15s or 16s
17s is kind of new to us , waiting for the system share when battery arrived