Charging speed and the effect on battery lifespan

[Ted3]

How many more life cycles will I get when using a slower 1.8A charger instead of 4A one for a 12Ah battery?
Should I have both chargers and only use the faster one when in a rush?

Specs for the Shimano Steps E8000 EMTB system:
BT-E8010 Battery
504Wh
36V
14Ah
Battery lifespan: 1000 cycles (After 1,000 cycles of full charging still more than 300Wh = 60% left when EC-E6000 charger is used) (Source: Shimano)

Charger options:
EC-E6000
4A
0-100% charging time 5h
-> Charging efficiency 14Ah / (4A*5h= 20 Ah) = 70% -> Extra heat during charging

EC-E6002
1.8A
0-100% charging time 7.5h
-> Charging efficiency 14Ah / (1.8A*7.5h= 13,5 Ah) = ~100% -> Cells only slightly warm

 

[MattyB]

How many more life cycles will I get when using a slower 1.8A charger instead of 4A one for a 12Ah battery?

No manufacturer is going to tell you that unfortunately. This is partly because they have probably not done the cycle testing under controlled conditions to know, and also because there are so many variables that affect cycle life (ambient storage and usage temperatures, power modes, terrain, SOC for long term storage etc) that their results wouldn't be reproduced by end users. It is true that the heat generated in fast charging and deposition at the negative electrode both reduce the cycle life and available capacity of a pack over many cycles - see this article on fast charging from the Battery University site...

Fast and Ultra-fast Chargers - Battery University

Should I have both chargers and only use the faster one when in a rush?

Yes, if you want to get the highest possible cycle life out of your pack stick with the slow charger whenever you can, only using the fast charger when time is short. As above though, the absolute amount of that effect is difficult to quantify.

 

[dirt huffer]

4amp is considered very safe. I know my Shimano battery doesn't even feel warm when charging at 4amps. If we had smarter chargers, it's actually more critical to pay attention to the voltage you charge to... I believe one electric auto-manufacture cuts off charging at 93% of a full charge to maximize cell life.

For us eBikers, I would venture to say that storage voltage is way more important in determining battery longevity then 1.6amp vs. 4amp. Leave your battery at 40%-60% during storage or whatever is recommended. Also try not to run your battery down to empty if you can.

 

[Ted3]

The reason I'm asking is because Canyon recommends using the slower charger as it noticeably increases the lifespan of the battery.

They are actually shipping a part of their 2019 e-bikes with the slower EC-E6002 charger for this reason.

 

[BManz]

The not-so-secret secret for lithium cell longevity is charge them on a slow charger whenever possible and do not store them fully charged OR fully depleted. Lots of fast charging reduces lifespan all else being equal.

My wife has a Sondors X for touring rides and after 3yrs she still gets 40-50 PAS/throttle miles (full knobbie fat tires) out of the 48v-17Ah battery with plenty of charge left. The battery is always kept in the house when stored at ~50-60% charge over the winter months. YMMV