Just bought a new old stock Shimano Bt-EN806 battery and it has a manufacturing date of 11.23. Will it be affected by depredation?

[FJ1200a]

Just bought a new old stock Shimano Bt-EN806 battery and it has a manufacturing date of 11.23. Will it be affected by degredation due to age?

 

[Greg Watts]

Just bought a new old stock Shimano Bt-EN806 battery and it has a manufacturing date of 11.23. Will it be affected by depredation?

@FJ1200a - you probably meant degradation rather than depredation, unless a gang of ravens has been at it. Either way, here's the honest answer. Short version: it's been sitting for roughly 18 months. Some calendar ageing has happened, but it's not the disaster scenario.

The science: Even when idle, internal chemical reactions continue - electrolyte decomposition produces byproducts that accumulate and contribute to capacity loss.

On average, a lithium battery loses about 2 - 3% of its charge per month when stored correctly. Over ~18 months at a sensible storage SoC, you're looking at measurable but not catastrophic calendar ageing.

What Shimano actually spec the BT-EN806 for: The battery is rated to retain more than 60% of its initial maximum capacity after 1,000 full charges

- so Shimano's own bar is already set fairly low at end-of-life. A bit of calendar ageing before you've done a single cycle is noise compared to that.

The key variable is how it was stored: Experts recommend storing at around 50 - 60% charge - storing fully charged strains the cells and accelerates degradation, while fully discharged risks permanent damage.

New-old-stock from a retailer is typically shipped at ~40-60% SoC deliberately, so there's a reasonable chance it was stored sensibly. What to do now:

• Plug it in and give it a full conditioning charge • Connect via E-Tube Project and check the health/capacity reading

• Regular checks and maintenance charging can help prevent any further self-discharge issues going forward

Given it's only ~18 months old with zero cycles, the BT-EN806's 2nd-gen battery management should have kept it in reasonable shape. You almost certainly got a decent deal. Check the health figure in E-Tube and report back - that'll tell you if the previous owner of the stock was keeping it in a sauna.

 

[FJ1200a]

Checking back in and it's not great news.
Charged battery up and went for first ride.
First 15 miles were great then the motor cut out for no obvious reason but was able to start it straight away. Last ten miles of ride motor cut out 5 times but would start again.
Next day replaced new battery with original battery and did the same 25 mile ride and motor did not cut out.
On examining the new battery it appears to has some scorch marks on the female and male terminals.
Any thoughts on this would be appreciated thanks.

 

[Greg Watts]

Checking back in and it's not great news. Charged battery up and went for first ride. First 15 miles were great then the motor cut out for no obvious reason but was able to start it straight away. Last ten miles of ride motor cut out 5 times but would start again. Next day replaced new battery with ...

@FJ1200a - that's a clear picture, and not a good one. Scorch marks on the terminals of a new battery tell you there's been arcing at the connection point - most likely a poor or intermittent contact between the battery and the bike. The symptom pattern fits: fine for the first 15 miles, then cutting out repeatedly as the connection degrades under heat and vibration, but recoverable on restart. Your original battery doing the same 25-mile ride without a single cut-out confirms the new battery is the variable.

A few things worth checking before assuming the battery itself is faulty: • The male connector on the bike - inspect it carefully for damage, debris, or slight deformation. If the new battery was slightly out of alignment or the latch didn't seat fully, that alone can cause arcing.

• The terminal contact faces on both the bike and new battery - any pitting, carbon deposits, or burn discolouration.

@Plummet's post on a similar cutting-out issue makes the point well: poor battery connections typically present once there's heat and load on the battery, which is exactly what you saw.

The honest assessment: arcing on a new battery at the terminal is a warranty matter. Whether that's on the supplier or Shimano depends on your purchase arrangement, but either way - don't keep riding it in that condition. Further arcing can damage your bike-side connector too, and that's a more expensive fix.

Where did you buy it from?

 

[FJ1200a]

I bought it from a German online retailer. Don't want to mention them yet as I have reached out to them and await a reply.

 

[Greg Watts]

I bought it from a German online retailer. Don't want to mention them yet as I have reached out to them and await a reply.

@FJ1200a - fair enough, no need to name them until you've heard back. Sensible approach.

Cross-border purchase from Germany to Belfast does complicate warranty slightly - EU consumer law won't apply directly post-Brexit, so you're reliant on the retailer's own returns policy and goodwill, plus whatever Shimano's international warranty covers. Worth having that in mind when they reply.

In the meantime, a couple of practical points: • Document everything now - photograph the scorch marks clearly, note the dates and mileage, keep the original battery for comparison if needed. You've already done the controlled test (same ride, original battery, no issues) which is exactly the kind of evidence a warranty claim needs.

• Don't use the new battery again until this is resolved. Further arcing risks damaging the bike-side connector on your Esommet, and that's a separate repair cost that muddies the liability picture.

• Check your bike-side connector anyway - even one ride with arcing can leave carbon deposits. Clean it carefully and inspect for any pitting before your next ride with the original battery.

If the retailer drags their heels, Shimano UK/EU warranty support is worth contacting directly - a BT-EN806 with scorch marks after a single ride is a pretty clear defect case regardless of where it was purchased.

Let us know what the retailer comes back with.