I reworked the charger a bit and made a few changes with 7 AWG wires:
Removed the trimpot and extended it with a simple three-pin/two-wire JST connector:
I was able to measure out a few values for adjusting the output voltage:
166 Ω | 3.65 V |
569 Ω | 3.40 V |
963 Ω | 3.20 V |
1.45 KΩ | 3.00 V |
I'll probably use a 5-way rotary switch to switch between the different voltages since this isn't a CC power supply and OCP trips in if the voltage is not gradually increased during charging.
The cables are now crimped with Anderson SB50 connectors:
And the PZEM-015 module is now powered through a USB Type-C power adapter that's connected a USB-PD "decoy" module that outputs 12V:
This solution was actually more cost-effective than a dedicated 12V+5V power supply (the power adapter is a dual port one, I might want to add a ESP8266 module to this in the future).
Link for the module:
https://quartzcomponents.com/produc...book-9v-12v-15v-20v-pdc004-pd-board-12v-model
The load tester also got new cables, I repurposed the 12 AWG wires I used previously for the charger:
Looks nice and tidy now:
I didn't have smaller gauge wire for the voltage sense wires, so I just ended up using the 20 AWG I had for another project. These are all silicon insulated wires.
Then I made probably the largest non-EMI purchase in recent years, four brand-new 105Ah LiFePO4 cells from MDS Enterprises:
That's because they had a minimum order quantity of 4. These are Narada FE105 cells, and are almost the same size (they're not as tall). I'll be taking out three of the weakest cells from the MuscleGrid pack and adding in these four to make my own 16S pack.
They come pretested, which is nice. The black terminal is positive, while the white terminal is negative.
All four added up to Rs 17540 with shipping, I'm still coming to terms with that. My family tells me there's more to life than LiFePO4 cells (ha) while the internet tells me it's okay if hobbies get expensive every now and then. I'm just hoping it all works out in the end and this'll end up serving as a long term battery backup solution, a few months of daal-chawal in exchange for a few years of service from this pack should be worth it.
Next is to top up these cells and do capacity testing. It'll be interesting to see how much charge and/or capacity was lost since these were last tested in September 2022 before being imported.