Battery discharging is the mandatory first step in EV battery recycling - yet it remains one of the industry's least mature processes. While recyclers have scaled shredding and material recovery, most still rely on manual teardowns and multi-day salt baths to remove charge from end-of-life batteries. As volumes increase and packs arrive with unknown state-of-charge and hidden damage, this bottleneck threatens the entire recycling supply chain.

One Spotlight: Battery Discharging - The Recycling Industry's Least Favourite Topic?

Current Battery Discharging Methods: Manual and Ad-Hoc

Before a battery can be safely shredded or reused, the energy has to be removed. In theory, that means isolating the pack, verifying its condition, and discharging it in a controlled, measurable way. In reality, today’s workflow looks more like this: batteries arrive with unknown SoC and hidden faults → operators assess, photograph, and store them.

For large modules / packs → Operators manually remove the casing to access discharge points behind the contactors—internal switches that close when batteries leave vehicles, blocking external-connector access and preventing discharge through the HV connector.

For cells / smaller batteries → Usually end up in sodium-solution baths. The industry standard is immersing batteries in salt baths (typically NaCl solutions) for several days. The salt water conducts electricity, allowing the battery to discharge through an electrochemical process.

What operators say:

“Most recyclers still rely on ad-hoc resistive setups or sodium baths — slow, hard to control, and unsafe as voltages rise. In practice it remains one of the least mature stages of the recycling chain” — RecoVolt

“Testing individual batteries after a sodium bath is problematic and time consuming and poses risks with safety if any batteries aren't discharged correctly” — Ecoshred

“Manually unscrewing the top takes 1-2 hours of highly trained personnel's time. One alternative, carefully grinding through the cover, exposes employees to fire and electrocution hazard” — Wattloop

Why Battery Discharging Is Getting More Dangerous?

Today's recycling stream is still dominated by production scrap and warranty recalls - relatively predictable. As true end-of-life packs enter the system at volume, recyclers will face batteries with hidden faults, water ingress, uneven SoC, corroded busbars, swollen pouches, and unpredictable BMS behaviour. A paradox with the BMS makes it worse: these systems prevent dangerous rapid discharge and thermal runaway, but recyclers must bypass them to achieve deep discharge with cycler - introducing new hazard.

What operators say:

“For mechanical recyclers, discharged modules mean less shredder wear and drier black mass. Some recyclers are even finding that depth of discharge affects black mass quality” — Wattloop

"Huge variability between packs, even from the same model or manufacturer, makes each discharge event unique and difficult to automate without tighter process control"— RecoVolt

Source: France24's video

The Future: Regenerative Discharge Systems That Assess and Recover Value

The solution isn't just better equipment - it's rethinking what can be done during the discharge step. Rather than just treating it as a safety checkbox before shredding, it could be the first diagnostic touchpoint where recyclers assess capacity, identify reuse candidates, and recover energy... instead of burning it off as heat..

The technology exists. Bosch Rexroth, REGATRON, and No Canary already offer regenerative discharge systems up to 1000V that feed energy back to the grid. Bosch's system discharges batteries in 5-15 minutes versus the traditional 24 hours. Wattloop is working on discharge using the outside high-voltage connector before or during disassembly, "that operation becomes less dangerous and quicker - discharge and automated dismantling can happen concurrently."

The players that figure out diagnostic discharge - systems that simultaneously deactivate, assess, and recover value - will have a real advantage in the market. Everyone else will still be dunking batteries in salt water.

"Discharge should be the first diagnostic step rather than a safety afterthought" — RecoVolt

"In an ideal world, we'd have a single discharging system capable of handling every format — cells, pouches, modules, and full packs — at industrial scale. That alone would remove the bottleneck." — Ecoshred

Many thanks to Ecoshred , Wattloop and RecoVolt for your insights.