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At Munro & Associates, teardown leads to insight—and few battery evaluations have made us stop and say “this changes everything.” In a bold series of experiments, we tested a revolutionary new battery cell from Sakku, designed with a polymeric current collector. Our safe battery test results include hammering a nail through the cell and even firing a bullet into it. The cell survived both without bursting into flames.
These safe battery test results go beyond expectations. They redefine how we think about energy storage in electric vehicles, especially in high-risk or crash-prone environments.
What Makes Sakku’s Battery Different?
Sakku’s innovation lies not in the chemistry of its lithium-based cells, but in the architecture—especially its polymeric current collector. Unlike traditional copper or aluminum collectors, which are highly conductive and prone to violent thermal runaway when shorted, Sakku’s polymer-based collector introduces a deliberate resistance.
This higher resistance:
- Limits short-circuit current
- Reduces fire risk
- Adds mechanical robustness
- Enables new, lower-cost manufacturing methods like printing
The core advantage isn’t just material substitution. It’s a manufacturing shift—Sakku’s production process resembles laser or 3D printing rather than traditional battery construction. The result is a lighter, thinner, and safer energy storage unit with intriguing potential for modular EV applications.
Testing Method: Nail and Ballistic Impact
Munro engineers subjected Sakku’s sample cells to rigorous abuse:
- Standard Nail Penetration Test: A nail was driven directly through the cell. With typical lithium-ion cells, this causes a thermal event, often leading to fire or smoke. But Sakku’s cell shorted momentarily (evidenced by an LED going dark) and then recovered. It did not combust or overheat.
- Ballistic Test: Taking the experiment a step further, the team fired a round directly into the cell. The LED blinked—but did not go out—and the battery continued to function. There were two entry holes in the cell, yet it remained operational.
Takeaway: No other lithium-ion battery we’ve tested has survived both nail and bullet penetration while remaining electrically functional. The inherent safety built into the polymeric current collector is unprecedented.
Key Metrics and Tradeoffs
While the safety performance is impressive, the Sakku cell is not without tradeoffs:
- Higher Internal Resistance (DCIR): This limits peak power output.
- Small Cell Format: The tested cells were around 40 mAh, equating to about 92 mWh. Not enough to power a vehicle alone.
- Power Delivery Constraints: Due to the resistive current collector, large outputs (e.g., C20–C100) aren’t feasible without significant redesign.
However, the cell demonstrated stable delivery in the C2 to C5 range, which is within practical limits for many electric vehicle applications—especially those that prioritize safety over ultra-high performance, such as:
- Urban delivery vehicles
- E-bikes or micromobility
- Residential battery backup
- Defense or aerospace systems
Scalability: A Matter of Design
The modular potential of Sakku’s approach is vast. The printed layers can be arranged into stacks, then configured for voltage (series) or current (parallel). Engineers noted:
- Series stacking benefits: No need for inner facing metal layers, reducing copper and aluminum usage.
- Parallel stacking drawback: More copper must be reintroduced to manage increased current paths, slightly negating weight and cost savings.
Still, with thoughtful architecture, Sakku’s technology could be competitive even against established formats like the Tesla 4680.
Adjustable Conductivity: The Game-Changer
Another key breakthrough? Tunable conductivity.
Sakku can manufacture polymeric current collectors at different resistance levels. In future iterations, the resistance could be 100x lower, allowing for higher power delivery without sacrificing safety.
This flexibility wasn’t possible with traditional copper or aluminum. Battery designers are no longer stuck with static conductive properties—they can now adjust them based on use-case, whether for:
- Maximum safety (high resistance)
- Balanced power (medium resistance)
- High performance (low resistance)
What the Industry Should Take Away
If you care about battery volume, weight, and cost—and you’re designing for systems that demand absolute safety—Sakku’s technology offers a rare trifecta:
- Lower manufacturing cost through print-based methods
- Lighter weight due to removal of heavy metals
- Superior safety even under extreme abuse
These are the metrics that investors, OEMs, and fleet integrators care about. And Munro’s early analysis confirms that Sakku’s claims aren’t just marketing—they’re backed by test data and real-world resilience.
Final Thoughts: Safety That Performs
The safe battery test results we observed with Sakku’s polymer collector cells go beyond incremental improvement—they point toward a paradigm shift. A battery that can survive gunshots and still power an LED? That’s not evolution. That’s revolution.
It’s worth noting: these tests were conducted with early prototypes. Sakku claims their next-gen versions feature even better energy density and lower resistance. If those specs prove out, this battery might not just be safer—it might also be the most competitive on the market.
Looking for More Safe Battery Test Results?
For a closer look at the footage from these destructive tests, including the nail and bullet demonstrations, check out the full video on Munro Live. And for deeper insights into battery testing, lean engineering, and disruptive EV technology, explore the rest of our content at Munro & Associates.