This company is advertised in “Silicon Chip” Magazine… which I subscribe to.. www.siliconchip.com.au it is an Australian magazine but for anyone interested in electronics and is a bit of a do it yourselfer it is an invaluable knowledge base of everything electronics J they make custom battery packs, lithium or otherwise… and build custom charging circuits etc etc They have ROUND lithium ion cells! Square cells… rectangular… pretty much every shape you could want! The round cells might be a goer… they could be made to fit into a cylindrical battery pod with air gaps for cooling between them…. Transferring the heat from the air to the water is the job of the heat pipe/heatsink/heat exchanger… Also the only time you need to really worry about cooling with lithium cells is when your charge/discharge rate is above 1C or 1x the amp hour rating of the cell/cells… another plus with lithium battery technology is charging… you can charge it at 1x the amp hour cell rate… or greater depending on the battery and cooling!!!! So you can re-charge your batteries off shore power much much quicker than a lead acid battery bank… From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of Stewart Gardiner Im going to start some experiments with some smaller lipo packs… to see what sort of cooling I can achieve with a few small cells.. The only problem I foresee is expansion… Lipo cells like to change in size… ALL battery’s give off gases while charging etc… So ventilation is a must… Modern PC’s use “Heat Pipes” http://en.wikipedia.org/wiki/Heat_pipe At the hot interface within a heat pipe, which is typically at a very low pressure, a liquid in contact with a thermally conductive solid surface turns into a vapor by absorbing the heat of that surface. The vapor condenses back into a liquid at the cold interface, releasing the latent heat. The liquid then returns to the hot interface through either capillary action or gravity action where it evaporates once more and repeats the cycle. In addition, the internal pressure of the heat pipe can be set or adjusted to facilitate the phase change depending on the demands of the working conditions of the thermally managed system. An aluminium or stainless steel plate… with a lipo cell on each side… connected to a central heat pipe! J think a stack of those placed side by side… in a stack of cells and plates.. with the central tube running up the middle of the cells… From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of Cliff Redus Carsten A four fold increase in range for your application is a strong motivation for following the lithium battery technology. My hope is that with the resurgence of the electric car and the R&D that is being funded in battery technology, the Psub world will get some next generation batteries that are affordable with the bugs worked out. Sgt.Peppers would make a nice test bed for Lipos. Cliff |