The test that actually measured it
A mini grid is a small power system that serves a village or a cluster of businesses without connecting to the national grid. CrossBoundary Advisory, a firm that finances and researches mini grids, tested reused electric vehicle batteries against new batteries at mini grid sites in South Africa, Nigeria and Democratic Republic of Congo. Buying a reused battery cost 11 to 28% less upfront than buying a new one.
Second life batteries represent smart resource optimization.
Tombo Banda, Managing Director and Innovation Lab Lead at CrossBoundary Advisory. Source 3.
Over the full life of a mini grid, CrossBoundary found the saving can reach 18%, but only if the reused pack lasts 7 years or more. A pack that instead needs replacing after 6 years erases much of that advantage, cutting the lifetime saving by 15 to 18% over 15 years.
Economics hinge entirely on how well batteries are managed in the field.
Charles Sweetland, Data Analytics Lead at CrossBoundary Advisory. Source 3.
Why the 7 year mark is not guaranteed
Whether a reused pack reaches 7 years depends on how much life was left in it when it left the car. A United States project tore down and tested more than 1,000 retired Nissan Leaf battery modules before building a working microgrid from them, and found their average health at retirement was 71% of original capacity. The team says 71% is likely close to the best a buyer should expect, not the middle, since much published work assumes packs retire around 80% health.
These are modeled averages from 1 study, not measured lifespans. CrossBoundary Advisory treats 7 years as the point a reused pack must clear to keep its cost advantage over a new one.
Show the numbers
| Second life lithium pack | 6 to 8 years |
| Lead acid battery | 3 to 5 years |
A separate 2014 modeling paper put a reused lithium pack at 6 to 8 years of second life, meaning years of use after leaving the car, against 3 to 5 years for a lead acid battery doing the same job. Those are modeled averages, not measurements, and both sit above the 7 year mark CrossBoundary treats as the line a pack must clear to keep its cost advantage.
Whether one pack fits one mill
No source in this set has built and measured a mill running on a reused car battery, so sizing the job means comparing 2 models rather than reading 1 measurement. A 2025 engineering study modeled a grain mill, a machine that grinds cereal into flour, for 2,000 people, milling about 932 kilograms of grain a day over 7 hours, and found the best matched storage size to be about 46 kilowatt hours. The 2014 paper puts a reused electric car pack at 24 to 75 kilowatt hours when it leaves the vehicle. The mill need sits inside that range, supporting the idea that 1 reused pack could cover it, but nobody has actually built and measured that combination.
The pack range comes from a 2014 modeling paper, source 1. The mill figure comes from a separate 2025 modeling paper, source 2. This chart compares the 2 studies, it is not a measurement of 1 pack running 1 mill.
Show the numbers
| Reused pack, low end | 24 |
| Mill, storage needed | 46 |
| Reused pack, high end | 75 |
What the power actually costs
The same mill study compared 4 ways to power it. Solar power backed by a battery cost 0.25 dollars a kilowatt hour, and a grid connection cost 0.19 dollars, both cheaper than a diesel generator at 0.56 dollars or a diesel engine driving the mill directly at 0.50 dollars. Solar and battery power also produced the least carbon dioxide of the 4, 3,191 kilograms a year against 14,484 kilograms for the diesel generator.
Modeled costs for a hammer mill serving 2,000 people. The study does not model a reused battery, only a lithium ion battery generally.
Show the numbers
| Diesel generator | 0.56 |
| Diesel engine, direct drive | 0.50 |
| Solar power and battery | 0.25 |
| Grid connection | 0.19 |
A new pack is also cheaper than it looks
The reused pack case is measured against a moving target. BloombergNEF measured the global average price of a new lithium ion battery pack at 108 dollars per kilowatt hour in 2025, down 8% from 2024 and down 93% in real terms since 2010. As new packs keep getting cheaper, a reused pack has to keep clearing that lower bar, and the unknown 7 years, to stay worth the risk.