[PSUBS-MAILIST] battery compensation

[Alan via Personal_Submersibles]

Hi Brian,
the AGM batteries need to be kept at an internal pressure
of between 1-6 psi to reabsorb gasses. They have little one
way valves on each cell & are difficult to compensate.
Can go in to detail if you like.
Alan

Sent from my iPad

> On 16/01/2016, at 6:01 am, Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> Hank,
>                  Using AGM batteries you may have less issues with topping off the cells.
>  
> Brian
> 
> --- personal_submersibles at psubs.org wrote:
> 
> From: hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
> To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
> Subject: Re: [PSUBS-MAILIST] battery compensation
> Date: Thu, 14 Jan 2016 18:47:38 +0000 (UTC)
> 
> 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:
> 
> 
> 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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