Prevent explosion, battery compartments, Lipo batteries
Posted: Dec 23rd, 2015, 4:14 am
Again I have been thinking about the potential danger of keeping lipos in a closed off aluminum tube, I don't want it to explode on me. I have been reading a lot on the subject and life batteries seems to be a good alternative, for my requirements however I have to pay a bit more for a bit less capacity.
Faulty life batteries will also most likely puff (expand) but I guess it's the reaction with air that make lipos less safe. The life batteries most likely won't catch fire but that is not my main concern. I already got all the lipos so I am using those for now and perhaps when they are depleted I get something else.
I wrote about a pressure release valve I found in another post, the low pressure is around 55$ which I believe is resonable price but it is rated for a depth of 100m and I am aiming for a bit more so everything else is designed for a depth of 300m. The high pressure ones are ridiculously expensive so they are not an option. So here are my options as I see it.
1. Remove the endcaps of the battery compartments when out of water. Potential fire hazard but at least there will be no explosion with flying endcaps as a result. As long as the endcaps are on there is a potential of an explosion however. I do believe most accidents happen when the cell(s) are discharged to much or when charging so it might be resonable safe. 2. Buy the 55$ pressure release valves or make a weak spot on the battery compartments and make them in to silicon oil filled pressure compensating compartments. I've read people claim that Lipos handle pressure very well but I haven't seen any figures on how well. I have no idea if a lipo can handle 450 psi. 3. Buy a ball valve or similar that can handle 450 psi and manually open it when out of water. A concern could be that I forget to open it. A advantage is that there will be a hole straight into the compartment so pressure building up would escape immediately. No tools required and no flying projectiles, might get a bit bulky and perhaps cause a jet of flames shooting out if the batteries ignite. 4. Make my own pressure release system that can handle the pressure. I was thinking a bit how the design would look and thought about the base principle. It need to brake easily when force is applied from the inside and withstand force from the outside. I made a simple design to get the thoughts going realizing that it could turn into a bullet if an explosion would to occur. 5. Fill the compartments with silicone oil (it's non-flammable) to remove the air to decrease the risk of an explosion. The expansion of the battery cells would still build up a pressure but without the fierce reaction when in contact with air it might not cause a problem.
6. The danger of lipos is overrated, just put the batteries in the compartments. Monitor the voltage carefully when charging, discharging and operating and there won't be any issues. I mean poring the floor full of gasoline and lighting a match will also burn down your house, I wonder on how many occasions "the batteries just exploded" without the user doing something wrong. Alternatively: The force of the batteries expanding won't be enough to make the compartment explode.
So that's my current thoughts on the matter, all ideas seems potentially dangerous. Any comments or other ideas?
Faulty life batteries will also most likely puff (expand) but I guess it's the reaction with air that make lipos less safe. The life batteries most likely won't catch fire but that is not my main concern. I already got all the lipos so I am using those for now and perhaps when they are depleted I get something else.
I wrote about a pressure release valve I found in another post, the low pressure is around 55$ which I believe is resonable price but it is rated for a depth of 100m and I am aiming for a bit more so everything else is designed for a depth of 300m. The high pressure ones are ridiculously expensive so they are not an option. So here are my options as I see it.
1. Remove the endcaps of the battery compartments when out of water. Potential fire hazard but at least there will be no explosion with flying endcaps as a result. As long as the endcaps are on there is a potential of an explosion however. I do believe most accidents happen when the cell(s) are discharged to much or when charging so it might be resonable safe. 2. Buy the 55$ pressure release valves or make a weak spot on the battery compartments and make them in to silicon oil filled pressure compensating compartments. I've read people claim that Lipos handle pressure very well but I haven't seen any figures on how well. I have no idea if a lipo can handle 450 psi. 3. Buy a ball valve or similar that can handle 450 psi and manually open it when out of water. A concern could be that I forget to open it. A advantage is that there will be a hole straight into the compartment so pressure building up would escape immediately. No tools required and no flying projectiles, might get a bit bulky and perhaps cause a jet of flames shooting out if the batteries ignite. 4. Make my own pressure release system that can handle the pressure. I was thinking a bit how the design would look and thought about the base principle. It need to brake easily when force is applied from the inside and withstand force from the outside. I made a simple design to get the thoughts going realizing that it could turn into a bullet if an explosion would to occur. 5. Fill the compartments with silicone oil (it's non-flammable) to remove the air to decrease the risk of an explosion. The expansion of the battery cells would still build up a pressure but without the fierce reaction when in contact with air it might not cause a problem.
6. The danger of lipos is overrated, just put the batteries in the compartments. Monitor the voltage carefully when charging, discharging and operating and there won't be any issues. I mean poring the floor full of gasoline and lighting a match will also burn down your house, I wonder on how many occasions "the batteries just exploded" without the user doing something wrong. Alternatively: The force of the batteries expanding won't be enough to make the compartment explode.
So that's my current thoughts on the matter, all ideas seems potentially dangerous. Any comments or other ideas?