I called Nissan LEAF customer service and asked them some questions about battery life and charging. According to this agent they recommend charging at LEVEL 2. Level 1 is for convenience when you don't have 220V. Will trickle hurt it? Don't think so, and I did not press the agent on if it would reduce life. The did offer that fast DC charging is not something you want to do often (if at all). Is there data to back that up or is this their opinion? Did you read the manual. Sometimes there are pearls of wisdom in there.