It's summed up nicely here: > http://www.powertechsystems.eu/en/technics/lithium-ion-vs-lead-acid-cost-analysis/ http://www.powertechsystems.eu/en/technics/lit

It's summed up nicely here: > http://www.powertechsystems.eu/en/technics/lithium-ion-vs-lead-acid-cost-analysis/ http://www.powertechsystems.eu/en/technics/lithium-ion-vs-le... Basically, lead acid have much lower lifespans, and also degrade very quickly if discharged below 50%. So straight off you have to double the size of your battery to not massively shorten the lifespan, so his costs are already closer to $0.30/Wh. Also, lead acid batteries are larger/heavier per Wh, and even if you never discharge below 50% last less than half the time of Lithium batteries