Making Lead-Acid Style Batteries (With Alum / Epsom Salt)

[LukeDupont]

Hi guys!

I've been experimenting with making rechargeable Lead Acid style batteries using Alum Crystals and/or Epsom Salt as an electrolyte. I'm curious about how batteries work and thought it would be really cool to make my own.

After making a simple voltaic pile, I came across lots of videos of people making these Lead / Alum batteries on youtube and getting a decent current and voltage! So, I gave it a try. I mixed Epsom Salt with hot water, and submerged two lead plates separated by a sponge / cloth. I made several of these, and also some using Alum instead of Epsom Salt as the electrolyte.

However, my performance is a bit underwhelming. My batteries lose their charge very quickly, in a matter of hours or a few days (depending on how saturated the electrolyte is), and the voltage is quite a bit lower than the 2 volts that I see other people getting. Mine come in at only about 1.7 - 1.6V fully charged, and slowly drop to 1.5.

The Epsom Salt seems to be better about holding its charge when the electrolyte is saturated. I had a battery that held its charge for a full 24 hours, but was nearly depleted by the next morning.

The Alum I'm using is perhaps not the right type. I've got some crystals, and some powder. The crystals don't seem to form a strong electrolyte and allow a lot of current to flow through discharging the battery in idleness, and the powder is heavy and seperates from the water. Neither seem to work as well as the Epsom, but I think this chemistry should be capable of higher voltage and better performance, and seems to be what everyone is defaulting to. I just have to figure out what exactly they're buying, and what a good concentration is.

Perhaps my water is impacting the performance. I'm using regular tap water as I can't for the life of me find Distilled water for sale here in Japan.

So, is there anyone with experience doing this sort of thing? How might I go about troubleshooting and potentially improving the voltage and charge retention of my cells using these ingredients?

 

[(*steve*)]

A chemistry forum would probably be able to give you the sort of advice you need.

 

[Hopup]

You must use distilled water for it if you want best results. You can buy cheap distiller which can produce the water at very cheap cost.

 

[kellys_eye]

I admire those that wish to experiment with battery construction but the subject is very, very well covered, especially recently with the increase in EV's and battery technology is improving all the time.

As a DIYer it is unlikely that you will ever achieve a performance to match, let alone exceed, current battery manufacturing methods and the costs of DIYing will also exceed that of purchasing a mass-produced unit.

I don't want to discourage you so please don't take this post as such but if you have a particular aim for using your batteries perhaps you'd like to inform us and we could make a more reasoned judgement?

 

[duke37]

Distilled water may be difficult to find but de-ionised water which is used in lead-acid batteries should be readily available at any garage.

Have you determined the chemical reactions in the battery. Epsom salt is magnesium sulphate, how is this used to produce lead sulphate?

Alum is a broad term for complex aluminum sulphate, there are many different types and all contain aluminium except for those that do not.

 

[LukeDupont]

Hey guys! A bit of an update:

I think I figured out what I'm doing the most wrong, besides the distilled water issue (which I solved by very, very slowly distilling water myself with crude apparatuses).

Apparently, to properly form a lead acid style battery, the polarity needs to be reversed several times in the first few charging sequences to reduce the internal resistance. This, for whatever reason, increases the current and capacity that you can get from the battery. I'm trying this out now and will report my findings with this process and lead / epsom salt / distilled water.

Anyway, replies to your awesome comments!

> *steve*
Yeah, I suppose a chemistry forum might be a better place. This honestly falls inbetween chemistry, electrical engineering, and some sort of practical "I just want to make XYZ" engineering type subject matter, so there might not be any truly suitable forum for it Is battery chemistry a common subject matter for, well, general chemistry?

> kellys_eye
Well, I don't for a second think that I can match the quality, energy density, convenience, or capacity of something like Lithium Ion or even NiMH batteries. But, that isn't my goal. I like to reinvent the wheel, because I like to understand how things work.
But, I also like using the things that I make, even if they might be considered "inferior" by modern standards. And, I get good utility out of them generally, because I make them for my own purposes, and not for the purpose of whatever occupies the narrow interests of industry. The more I learn, discover, and make things on my own, the more I find that I can make products that suit my needs, and not just the narrow needs of the generic consumer / market. This has proven to be the case in every hobby I've pursued thus far, so I doubt this is any different. I'm sure I can eventually make something which is quite useful for me, personally. And, even if that doesn't happen, I'll still gain useful knowledge about batteries and chemistry in general. I've already learned a good bit on that front, in fact.

> duke37
Thanks! That's really useful advice. I should definitely go by an auto shop and search for such things, including perhaps some standard sulfuric acid electrolyte to compare my alternative solutions against.
To be honest, I don't know why Epsom salt works, and don't have enough of an understanding of Chemistry yet to tell you why. But apparently, going by many comments of people who have built such batteries as well as my own findings, there are a large host of salts which work in addition to Sulfuric Acid, Alum, and Epsom. My intuitive guess is that they're "similar enough" that the same reaction takes place, but hopefully I can answer this better at some point as I learn more. All I know is that Epsom salt works from my tests, and is attested to by many others.

 

[Hopup]

Proper acid would certainly work much better than using only Epsom salt. Using both together would probably be most effective, just guess. You could also use glass fiber instead of cloth.

 

[kellys_eye]

Well, I don't for a second think that I can match the quality, energy density, convenience, or capacity of something like Lithium Ion or even NiMH batteries. But, that isn't my goal. I like to reinvent the wheel, because I like to understand how things work.
But, I also like using the things that I make, even if they might be considered "inferior" by modern standards. And, I get good utility out of them generally, because I make them for my own purposes, and not for the purpose of whatever occupies the narrow interests of industry. The more I learn, discover, and make things on my own, the more I find that I can make products that suit my needs, and not just the narrow needs of the generic consumer / market. This has proven to be the case in every hobby I've pursued thus far, so I doubt this is any different. I'm sure I can eventually make something which is quite useful for me, personally. And, even if that doesn't happen, I'll still gain useful knowledge about batteries and chemistry in general. I've already learned a good bit on that front, in fact.

Great reply - and one I can definitely associate with.

Good luck with your experiments!

 

[duke37]

Just a couple of points.
1 I do not think that distilled/deionised water is necessary unless the other components are also pure.
2. Lead acid batteries have grid electrodes stuffed with lead paste. This has a much greater surface area then a flat lead sheet and so a much greater capacity and lower resistance.

You could look up my brother in law's book on galvanic reactions. Gibson and Sudworth. That will make your mind boggle

 

[LukeDupont]

Well, I appear to have properly formed the plates to some extent. The positive plate is brown, and the negative a dark grey. When I reverse the polarity and charge them backwards, the colors switch.

However, I'm still losing charge while the battery sits idle. I'm having a really hard time figuring out why this is.

For fun, I tried making an aluminum copper battery rechargeable with epsom, and that worked initially! The voltage stabilized at around 1V and sat there. But subsequent charge discharge sequences caused it to nolonger hold on to a charge, similar to my lead acid attempts. While this is a different chemistry and perhaps shouldn't work at all (maybe just some kind of capacitive effect going on?) it's interesting to observe the same thing happening.

I think my electrolyte is the problem, or perhaps the current / voltage I'm charging at. This is quite a bit more difficult than I thought it would be, and I'm quickly coming to appreciate just how much work goes into making a battery with any level of respectable performance! Nonetheless, there's plenty of people making respectable DIY batteries, so I'll continue to doggedly pursue this when I find the time.

 

[Fortune]

You could distill your own water... boil water & collect the steam. Easy.