Why the cells die first
An industrial battery is not made up of cells alone. The enclosure, battery management system (BMS), connectors and wiring account for a substantial share of the value and the development effort — and they age differently from the cells. The cell loses capacity with every cycle; its State of Health (SoH) falls. A practical limit is often an SoH around 70–80 %: below that the usable capacity is no longer enough for shift operation.
The BMS and the enclosure do not undergo this chemical ageing. So when the runtime collapses, it is usually exactly one component that is worn out — the cell. Everything else is still what it was once designed to be.
The process: measure first, then replace
Refurbishment is not a cell swap by gut feeling, but a diagnostics-driven process:
- 1
Diagnostics
SoH measurement of the pack and the individual cell strings, reading out the BMS history (cycle count, fault events, balancing state), mechanical inspection of the enclosure, connectors and wiring. This diagnosis decides whether refurbishment even makes sense.
- 2
Cell replacement
Replacement of the spent cells with new cells of the same chemistry and form factor, matched electrically and mechanically to the existing pack. No mixing of old and new cells — otherwise the weakest one drags the whole string down.
- 3
BMS re-parametrisation
The capacity value, protection limits and balancing parameters are set to the new cells. A BMS that still calculates with the old capacity values reports wrong SoC figures and does not protect correctly.
- 4
Final test
Capacity verification under load, functional test of the BMS protection functions, documentation. Only then is it released for redeployment.
Why it pays off — and what it saves the environment
The economic lever is simple: when buying new, you pay for cells, enclosure, BMS, connectors and wiring. With refurbishment you essentially pay for the cells and the rework — the expensive electronics and the enclosure stay. For a pack whose value lies substantially in the BMS and enclosure, the saving is correspondingly large.
The second effect is electronic waste: scrapping a complete pack when only the cells are defective throws away intact electronics. Refurbishment keeps the enclosure and BMS in circulation and reduces the amount of waste to what is actually at end of life.
From practice: a mobile battery fleet
For the mobile battery boxes we have built for proLogistik since 2016, packs come back after a few years of shift operation whose runtime no longer lasts through the week. The diagnosis regularly shows the same picture: the cells' SoH below the usable limit, the BMS and Peli-Case enclosure flawless. These boxes get new cells, a re-parametrised BMS and go back into the fleet at full capacity — at a fraction of the cost of a complete replacement and without a working enclosure ending up in the scrap.
When refurbishment makes sense — and when it doesn't
In favour
- ✓Cells at end of life (SoH below the usable limit), BMS and enclosure intact
- ✓Cell format still available on the market
- ✓Design allows a clean cell swap (disassemblable, contactable)
Against — then a new build is the better route
- ✗Enclosure mechanically damaged or corroded
- ✗BMS defective or technically obsolete
- ✗Cell format discontinued, no suitable replacement obtainable
- ✗Potted/bonded design where the cell swap costs more than a new build
The decision is made in the diagnostics, not in the sales pitch: if the measurement shows that more than the cells would have to be renewed, a new build is more honest and cheaper in the end. For returns from your fleet we first check the SoH and the condition of the electronics — and tell you which route works for the specific pack, technically and economically.