Before we get into any heated argument, let me mention that this has been discussed on the forum many times before. The article linked below was written by a forum contributor and it sums up what our collective understanding of the topic was couple of years ago. Considering the faster than expected capacity loss in warm climates, I would reprioritize the list of recommendations and put the average temperature of the pack as the largest concern. If you can park away from the sun and pick a cooler spot, that could potentially be more more helpful than worrying about charging to 60% or 80%.
There are several processes that degrade LMO batteries. One of the more important ones is the dissolution of the cathode material (manganese) into electrolyte. It's been shown in academic research that these losses peak near the top and bottom SOC. The loss is higher at high SOC than low SOC too. That said, there appear to be some crystalline processes that distort the cathode spinel structure when the battery is left sitting at low charge (below 20%). Fortunately, these processes are slower than the other ones, and take some time. Nissan blocks off several percentage points at the top of the charge and about a couple at the bottom. This means that the amount of damage a consumer can do to the battery through overcharging or overdischarging is limited.
When you look at the accelerated aging experiments performed in various labs, it appears that one can slow down degradation by keeping a lower average SOC. So when deciding if charging between 30% and 60% or 50% and 80%, the average SOC will be higher in the latter and the dissolution of manganese into electrolyte will be higher too. When you look at the Prius, Toyota keeps the battery between 40% and 60% SOC. Although it's a different chemistry, this protocol is intended to minimize cycling losses. Their batteries are NiMH, which have been shown to be more temperature resistant.
Unfortunately, maintaining low SOC is not very practical for most owners, and we have not seen much measurable benefit. Stoaty, who seems to be doing exceedingly well, created most of the documentation on the
Wiki. He drives very gently and efficiently. Additionally, he ensures that his LEAF is parked at about 30% or 40% SOC for the most part of the day. Conservative approaches won't hurt the battery, they can only help. Pack temperature seems to be by far the most important factor, but it's difficult to control.
Eight Tips to Extend Battery Life of Your Electric Car
