Battery box vent size?

[S_Davis]

I am installing an inverter system on my truck, it has two separate battery boxes that will hold three Lifeline GPL-30HT each for a total of six, one box will vent to the other and then that box vents to the outside of the cab, What size vent should I run?

[enblethen]

Here is an example of what you need.battery vent kit
AGM batteries are normally sealed and do not require venting.
I would use two separate venting system and not connect together for vented lead acid batteries.