Hacker News new | comments | show | ask | jobs | submit login

For lead acid batteries, figure 70% of the energy you put in will come back out. Wikipedia tells me that lithium ion batteries are 99.8% efficient, but has no citation and the temperature of my phone charging heavily make me suspicious of that number. Perhaps that is a theoretical maximum.

Motor efficiency is proving elusive on the web. But let's say 90%-95% for brushless DC motors. (square that for in and out)

The trick about batteries is that if you only want to use them for intense bursts you will need a huge energy capacity. You don't normally want to charge at a rate faster than say, 1 hour to get full. If you need to store a 3 second brake stomp and give it back 5 seconds later then you are going to have about 1200 times more batteries than you needed just to store the energy (to support the current).

Applications are open for YC Summer 2016

Guidelines | FAQ | Support | API | Security | Lists | Bookmarklet | DMCA | Apply to YC | Contact