posted 9 years ago
I suggest two fans for redundancy. If one fails, you'll still have air flow to prevent hydrogen build up. Be sure to use brushless fans; the last thing you want is a spark or electrical arc in the exhaust channel.
The plan seems solid enough to me, allowing for the fact you have to vent upwards as Eric pointed out.
You might want to inquire about how this might affect your insurance. In the case of a fire *by any cause* you want protection. The batteries wouldn't be something you could hide after the fact, so check to ensure they don't invalidate your coverage.