[PSUBS-MAILIST] battery compensation

[hank pronk via Personal_Submersibles]

Tom,I think the relay will be okay, I think I have done it in the past, just can't remember where ;-)    Hank 

    On Thursday, January 14, 2016 11:36 AM, TOM WHENT via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
 

 #yiv9361479466 p {margin:0;}I think that your lead acid battery weight in water question would be a simple matter, but you likely would have to calculate it individually for each size of cell. I would think the density could vary with the composition of each size. Most battery manufacturers provide a spec sheet for their batteries so it would be simple from the weight and dimensions provided to calculate the density and the specific gravity of the cell.

I have no ideas on the relays being in an oil bath. Would that lead to coking on the contacts?

From: "hank pronk via Personal_Submersibles" <personal_submersibles at psubs.org>
To: "Personal Submersibles General Discussion" <personal_submersibles at psubs.org>
Sent: Thursday, January 14, 2016 11:48:28 AM
Subject: [PSUBS-MAILIST] battery compensation

Thinking ahead, I need to reduce the weight of my deep diver.  I am now planning external batteries- lead acid in oil.  This reduces the amount of syntactic foam needed.  My deal on CNG  tanks fell apart.  The ebay seller would not honour the sale, can't blame him.   I may go with store bought syntactic foam if business looks good with 30 dollar per barrel oil, Yikes.  
I am not sure how to go about the oil filled battery set up.  I assume the batteries are filled as high as possible with water then topped up with oil, then the compartment filled with oil and a rubber lid on that.  I assume you take a syringe with distilled water to top the batteries up from time to time.  This way you wouldn't have to drain the oil.Does anyone know how heavy a battery weighs under water compared to in air?
I also am thinking about having the reversing relays for the motors in the oil tank to reduce the amount and size of wires penetrating the hull.  I will just send small wires for messaging to the relays.Hank
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