Infinion
Well-known member
A couple of weeks ago, there was this Engineering Explained YouTube video that took some excerpts from a couple of sources to discuss some of the worst things you could do to an EV battery.
Eng Exp vid:
source 1: https://pubs.rsc.org/en/content/articlehtml/2021/cp/d1cp00359c (Lithium-ion battery degradation: what you need to know)
source 2: https://www.sciencedirect.com/science/article/abs/pii/S0378775313016510 (Calendar and cycle life study of Li(NiMnCo)O2-based 18650 lithium-ion batteries)
source 2 [webinar] EV Battery Health with Dr Jeff Dahn Dalhousie U:
I preferred the webinar and paper because the whiteboard engineer is condensing the info to cover the essentials, but the gist was that
Despite the data presented, I have a big problem with the depth of discharge interpretation and believe the conclusion is faulty and lacks rigor, so I can only vouch for the recommendation to store cars in cooler areas at low SOC.
Oh I should also point out that 100% = 4.2V traditionally, but in the Spark EV 100% is 4.08-4.1V depending on cell balance and temperature, at least from my own OBD II readings. By comparison, Tesla usually sets their EVs' 100% SOC = 4.15V and only recommends it for non-daily trip use. So the Spark does offer a slight reduction in wear when you use the whole battery, but it's still fairly high, obviously because the cells require higher energy density to compensate for their small size.
Eng Exp vid:
source 1: https://pubs.rsc.org/en/content/articlehtml/2021/cp/d1cp00359c (Lithium-ion battery degradation: what you need to know)
source 2: https://www.sciencedirect.com/science/article/abs/pii/S0378775313016510 (Calendar and cycle life study of Li(NiMnCo)O2-based 18650 lithium-ion batteries)
source 2 [webinar] EV Battery Health with Dr Jeff Dahn Dalhousie U:
I preferred the webinar and paper because the whiteboard engineer is condensing the info to cover the essentials, but the gist was that
- Calendar aging: Parking in Higher Temperatures and 100% SOC Degrades the battery more quickly, but at 30% SOC this is cut by an order of magnitude. And like you would expect, cold temperatures slow aging even moreso, to the point where even storing at 100% would be comparable to storing at a lower SOC in the heat.
- Author Madeleine Ecker and the professor from the webinar argue that small Depth of Discharge cycle use between 40% and 60% presents the least amount of battery volume change which would otherwise cause microcracking in the electrode material and generation of more SEI/CEI electrolyte solvation in those cracks, leading to capacity degradation and performance loss too.
Oh I should also point out that 100% = 4.2V traditionally, but in the Spark EV 100% is 4.08-4.1V depending on cell balance and temperature, at least from my own OBD II readings. By comparison, Tesla usually sets their EVs' 100% SOC = 4.15V and only recommends it for non-daily trip use. So the Spark does offer a slight reduction in wear when you use the whole battery, but it's still fairly high, obviously because the cells require higher energy density to compensate for their small size.
