[PSUBS-MAILIST] battery compensation

[TOM WHENT via Personal_Submersibles]

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? 

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

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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