Hi Brian. Sounds like you're making progress. Have you picked a
particular battery model/manuf. yet ?
I pondered battery location early on in the design process and using the
K boat design as a starting point first planned on external battery
pods.
Now I have them located inside to reduce drag and make it easier to
access them. There are some dangers though.
As you know, fire/smoke is one of the worst things in a confined
space like a sub. Precautions should be made to eliminate any
possible ignition of the gases produced by charging and operating. Wire
connections should all be sealed against corrosion and sparks with heat shrink
covers. Good ventilation when charging or maybe even removing the batteries
when charging them.
I am putting the 4 main battery banks in sets of three each,
inside 12 gage stainless boxes with hinged lids and rubber seals on the lids.
Rubber grommets are used where the battery cables exit the boxes, with a
coating of silicone applied over the grommets. They won't be "water tight" but
are sealed pretty good.
The boxes are strong enough so if the gas builds up and ignites the boxes
will contain the explosion.
When charging the hatch will be open, lids open of course, and a box fan
and flexible duct work to vent the sub and keep the fan motor away from the
interior.
The boxes have only a small amount of extra space in them to reduce the
volume of area where gas can accumulate when the lids are closed. I'm
considering a hydrogen gas sensor in each box to alert me to any gas
build-up.
The AGM batteries can be had with valve regulated caps so gas doesn't
escape. Not all batteries have these.
The switches and other electrical components should be investigated for
possible ignition points. You can get "explosion proof" devices like switches,
lights, etc. but they're pricey. A little thought and innovation can
be used to seal up many standard components but removing any
ignition sources will help. Components that can't be sealed should be switched
out for ones that can or replaced with explosion proof ones.
It's risky to have the batteries inside but the advantages can
be worth the risk if the right steps are taken to minimize the threat.
I've thought a little about a "fire control system" but haven't
decided just how and what to use. Like I said, there's extra risks in having
the batteries inside so solutions to alleviate the risk must be
considered.
Have you taken any new pictures lately ? Your design is a lot different
than the standard K boat design and many innovations are being used. Sure
would like to see some pics. Maybe you can bring your model to the
convention.
Keep working, it sounds good.
Frank D.