If you live in a location with a cool climate, You should use a venting system similar to the one pictured below. This type of venting system helps keep the flood of cold air from rushing in at the bottom as the warmer air rushes out the top. Large and fast temperature changes are not good for a battery.
The idea is to NOT use power or fans, You should only vent the hydrogen while not changing the temperature of the inside of the battery box.
Hydrogen is lighter then air so it rises and exits the top tube while creating a vacuum forcing outside air in through the bottom tube.
With both tubes kept at the same height and level all the way from the outside of the building to the back of the inside of the battery box, There is less change of temperature from the in coming tube to the out going tube. There is no cold air circulating in the box like if one tube came in at the bottom and the other at the top of the box. It stops the circulation when there is no Hydrogen left to force it's way out.
As with any project you find on this website, There is no promise it will work for you and you are building / installing at your own risk. OY Not nor anyone working for OY Not will be responsible good or bad for your project. Hydrogen is an explosive gas, if handled incorrectly could kill.
This image shows a long run of 1 inch PVC thin wall. This allows time for the air to come up or down to room temp.
Yes that was a doggy door, The puppy dog, and fat cat, both died of old age a couple of years before. And the door was no longer in use. It does need a little finishing work and a little paint.
There could have been more elbows used to form a closer fit to the front of the battery box. However, This way allows the PVC to be moved up or down a little without the need to cut anything. This was in case you wanted to remove the cover on the wiring box. Just the way it worked out on this one, While still getting a long heat exchanger run between the battery box and the doggy door.
Just a second view to show the electrical box entering the battery box.
Here you can see the PVC pipe running along the inside of the battery box near the top.
The long run inside the top of the box brings the air temperature a little closer to the battery temperature If you look deep enough to the end of the box you can see the air inlet tube heading down at the back.
The air inlet tube is about 1 inch from the bottom. This is so the hydrogen will not exit this tube unless the top PVC pipe is clogged or too small of PVC is used. Or not correctly installed or even too long of a run.
In this image you can see the top tube
(PVC pipe) is open and is about 1 to 1.5
inches from the top to allow the hydrogen
Sorry about the fuzzy picture.
On the outside of the home you can see
the hydrogen outlet tube is about an inch
or two higher then the air inlet. This is to
keep the hydrogen from going back in
with the fresh air.
The caps on the ends are just that. They are aimed down to keep water out. And have 1/16 inch holes drilled all over the ends to let the air and hydrogen pass and keeps the bugs out.
There were steps and a doggy door that had to be removed and new siding installed.