ricky_shaw

Wish sourcing headaches like this were our biggest problem here.

Cells are still landing at $58–65 equivalent in Pakistan after customs and shipping, but even at that price they outperform everything locally for stationary storage. The floor is moving fast and it matters everywhere, not just the US market.

Pakistan is informal like Arizona — no dedicated EV conversion category yet. I get a certification letter from an approved inspector and a note on the title. It works for registration but creates complications at resale because buyers don't know what to make of it. Formal state processes like Arizona's are genuinely better even if they seem onerous.

The thermal management problem looks different when your total build budget is $800 USD and you're working in Karachi where ambient summer temperatures run 40–44°C on a normal afternoon. The solutions this thread describes — aluminum plate between cells, mineral oil immersion, Peltier cooling — all involve cost or complexity that doesn't fit what I can actually source or afford locally. What I've settled on after three commercial 3-wheeler builds: passive airflow through the pack using vehicle motion, with cell spacing generous enough to allow it, and a BMS temperature cutoff set conservatively at 42°C that reduces discharge current before the cells get into trouble. Not elegant, but it works for my duty cycle — city stops and starts, rarely more than 45 continuous minutes of operation. The point I want to flag from this thread: cell spacing is free. Every builder I work with here packs cells as tightly as possible to save enclosure material, and every builder eventually deals with the consequences. Spreading cells 3–4mm farther apart adds maybe ₹800 to a 16S build and makes a measurable difference in peak cell temperature. I've made it non-negotiable on every new design. The specific failure mode I've seen twice: overtemperature triggering BMS cutoff at an intersection in peak summer traffic. No shade, stopped, pack baking with no airflow. First time I thought it was a cell problem. It was a thermal design problem — the pack had no path for convection when the vehicle was stationary. A 12V fan wired to a thermal switch at 38°C fixed it completely. Twelve dollars of parts.

Most of these packs don't reach Pakistan without costs that double the price, so I work with locally-sourced motorbike and 3-wheeler NMC packs instead. The principle is identical — grade and load test everything. What I've found useful is the Carfax-equivalent you mention for US cars: I check the vehicle inspection record from the transport authority before buying any pack from a crashed vehicle.