Re: [PSUBS-MAILIST] Battery pod. (question for Dan H.)

Hi Bill,

Sorry to take so long to respond. I had to make a decision before i reply. I have choose to go with all steel pod. One of my friend have access where he work to a rolling machine. So we will roll the tube and I will use 5/8" steel plate as end caps. I will also place plates inside the pods and fill the empty places around the battery with lead so the pod will also serve as weight. To reduce over-all weight of the sub. Which i want to keep at around 1000 pounds. the removable end-caps will be similar to what Dan explain except that i will have 2 bolts and they will thread directly on each side of the battery in a permanent side plate.

As for the battery, I presume that since my battery have about 3/4" of air on the top, the plastic case will be under pressure. And it may crack. I'm by no mean an expert but I'm still not convinced about air-compensation the battery pod. I'll built a pod that can bear the total pressure.

Yes i will compensate the motors. I'm using 2 minn-kota endura 30 motors. The only reason to compensate them is because of the seal. The rest of the motor is capable, I think, to resist much pressure! I will compensate them from the carbon tube directly. this tube will stay open inside the cabine of the sub.

Thank you again for your much appreciated input!

Pierre Poulin

Québec Canada

----- Original Message -----

From: Akins

To: personal_submersibles@psubs.org

Sent: Friday, January 14, 2005 4:02 PM

Subject: Re: [PSUBS-MAILIST] Battery pod. (question for Dan H.)

Dear Pierre.

You said....."My design is mainly to be used in scuba deepth. I'm currently certified to
dive at 60 feet max. And I doesn't plan to go deeper in the near futur with
or without the sub. Battery pods: I think using PVC is a cheap and easy substrats to work with.
I like that! But I prefer the liability of the openning end made from steel.
I might do a hybrid of both pods... I'll let you know guys.
I don't think i will pressure compensate the pod. There is some air inside
the battery (lead-acid) and I'm affraid that if put under pressure they will
crack. If I had AGM battery, I wouldn't even build a pod. I would place the
battery inside and that's it. Like Alec do."

Actually PVC 12 inch pipe and it's fitting are not that cheap Pierre, (I paid $12.00 per foot for the

pvc pipe and about $225.00 for the permanent end cap, female end and male plug)

but it is cheaper than having steel frabricated.

Why would you want to mix pvc pipe with an expensive to frabricate

steel end cap? Just use the already threaded pvc female fitting with it's already threaded

end plug. Much cheaper and easier than frabricating steel for the depths of 60 ft where you don't

really need the strength of steel. The 12 inch pvc pipes and its end cap, female fitting and

end plug are already made and all you have to do is have the pipe cut to the length you want

and glue it all together. Why hassle with making a steel end cap or plug? Note, depending on the

size of the batteries you are using, you might even be able to use 10 inch pvc pipe. Depends

on the size of your batteries. I use the 12 inch myself.

What makes you think that the small amount of air inside the batteries would

make the batteries crack if you air equalized the battery pod? By you air

equalizing the interior of the battery pod which would also seep into the batteries

thru their vents, I don't see the air pressing against the water/acid mixture

enough to crack the batteries at your 60 feet max depth which is about 6 feet

under 2 atmospheres.

I don't know what kind of motor you are going to use, but if it is a trolling motor

I would recommend pressure equalizing it if you go beyond 33 feet, and if you

pressure equalize the motor, you might as well

also pressure equalize the battery pod to preclude any leaks.We are not talking

about that much pressure here at under 2 atmospheres.

Kindest Regards,

Bill Akins.