DIY Molten salt battery - Page 1
Forum section: electronics / projects

author: Artlav
author_rank: Frequent Contributor
timestamp: July 30, 2015, 06:13:21 pm
content: Molten salt cells are mostly used by the military for their near-infinite shelf life.They can be sitting in a warehouse for decades as a solid brick with with no self-discharge, then be plugged into the weapon system, heated up by the included pyrotechnic charge, and provide full power and capacity.I found the concept rather curious, but couldn't find much details or any previous DIY attempts, so i decided to make my own.Didn't get the supposed high power density, but that might just be a question of engineering the thing carefully.In any case, it is a battery that works at 400-500*C, which curiously enough is the kind of temperature you can find on the surface of Venus.If that's where we happened to live, that might have been the chemistry in our everyday AA cells, while the alkaline batteries were just some obscure cryogenic cell a few scientists heard about.A fun what-if to consider.Project details:http://orbides.org/page.php?id=1005Nothing really practical, but it does satisfy the philosophical hunger.Hope someone found that interesting.

author: richard.cs
author_rank: Super Contributor
timestamp: July 30, 2015, 06:31:45 pm
content: That looks really interesting, thanks for sharing.

author: MagicSmoker
author_rank: Super Contributor
timestamp: July 30, 2015, 08:05:55 pm
content: Look up the ZEBRA battery. It runs at a much more manageable 250C, IIRC. Uses molten sodium, though, which can be very "exciting" if mishandled.

author: Artlav
author_rank: Frequent Contributor
timestamp: July 30, 2015, 08:35:09 pm
content: Quote from: MagicSmoker on July 30, 2015, 08:05:55 pmIndeed, and then some.I was aiming for something safe to make at home and something that can be made out of obtainable components. ZEBRA is a complete opposite of that on every count.The design i used is based on the power supply of a Soviet Igla anti-air missile, and even that used a hard to get calcium which i had to replace with much more common magnesium.

author: MagicSmoker
author_rank: Super Contributor
timestamp: July 30, 2015, 09:49:26 pm
content: Quote from: Artlav on July 30, 2015, 08:35:09 pmWell, I suppose molten magnesium or calcium is safer than molten sodium, but, well... kind of splitting hairs here, aren't we?

author: Artlav
author_rank: Frequent Contributor
timestamp: July 30, 2015, 10:19:46 pm
content: Quote from: MagicSmoker on July 30, 2015, 09:49:26 pmAh, but the magnesium is not molten in my case.It would have gone boom spectacularly if it was.That's the whole point of using a low temperature eutectic mixture of two salts instead of a single salt at 600-700*C and molten metals.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: July 31, 2015, 12:56:52 am
content: Pretty cool. You may also be interested in the kind of battery they came up with in WWII for the electronic proximity fuze...https://en.wikipedia.org/wiki/Proximity_fuze100000G acceleration (or worse, "jerk", or setback), 20000RPM, glass ampoule broke open and started the battery. And yet, the vacuum tubes in the fuze didn't break... Awesome stuff.

author: Artlav
author_rank: Frequent Contributor
timestamp: July 31, 2015, 11:13:12 am
content: Quote from: Alex Eisenhut on July 31, 2015, 12:56:52 amThat's a neat bit of engineering for sure.Can't quite find the info on the battery, however.

author: Fungus
author_rank: Super Contributor
timestamp: July 31, 2015, 01:20:40 pm
content: Quote from: Artlav on July 31, 2015, 11:13:12 amWould be better with a batteriser.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: July 31, 2015, 11:13:43 pm
content: Quote from: Artlav on July 31, 2015, 11:13:12 am

author: DaveW
author_rank: Frequent Contributor
timestamp: August 01, 2015, 09:26:01 pm
content: These are fantastic batteries, they're what I use at work for almost all our stuff. Interesting going through some of our previous suppliers when they go through their company background, they always talk about how they've managed to reduce the number of fires that occur on the production line; never eliminating them!The safety procedures they have to make these things in bulk are also seriously impressive, lots of fume hoods and remote manipulation equipment.The big versions of these are used to power entire aircraft briefly if they lose power from the generators in the engines, large batteries that can supply kWs of power.As you've already found keeping the temperature up is key, along with the tricky parts of ensuring that all the cells initiate at around the same time. Good luck; would love to see DIY versions of these!