<html><head><style type='text/css'>p { margin: 0; }</style></head><body><div style='font-family: arial,helvetica,sans-serif; font-size: 10pt; color: #000000'>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.<br><br>I have no ideas on the relays being in an oil bath. Would that lead to coking on the contacts?<br><br><hr id="zwchr"><div style="color:#000;font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt;"><b>From: </b>"hank pronk via Personal_Submersibles" <personal_submersibles@psubs.org><br><b>To: </b>"Personal Submersibles General Discussion" <personal_submersibles@psubs.org><br><b>Sent: </b>Thursday, January 14, 2016 11:48:28 AM<br><b>Subject: </b>[PSUBS-MAILIST] battery compensation<br><br><div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:12px"><div id="yui_3_16_0_1_1452789352970_2427" dir="ltr">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. </div><div id="yui_3_16_0_1_1452789352970_2427" dir="ltr"><br></div><div id="yui_3_16_0_1_1452789352970_2427" dir="ltr">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.</div><div id="yui_3_16_0_1_1452789352970_2427" dir="ltr">Does anyone know how heavy a battery weighs under water compared to in air?</div><div id="yui_3_16_0_1_1452789352970_2427" dir="ltr"><br></div><div id="yui_3_16_0_1_1452789352970_2427" dir="ltr">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.</div><div id="yui_3_16_0_1_1452789352970_2427" dir="ltr">Hank</div></div><br>_______________________________________________<br>Personal_Submersibles mailing list<br>Personal_Submersibles@psubs.org<br>http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles<br></div><br></div></body></html>