How To Make - 7V Salt Water Battery Out Of Nails & Wire 

Glad it helped. Batteries are great science projects and fun to build.

Glad you enjoyed it!

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You are so welcome

Thanks for watching

You're welcome. Thanks for watching.

Thanks

Thanks and welcome

Thanks, will do

The solar module voltage was too high for the prototype battery. It had about 18V open circuit with around 500ma of current. In order to make that work, the battery has to have more cells in series and in parallel.

So this is just a demonstration battery so it's really small. So tiny that I had hard time trying to measure it's ah capacity. Like any battery, you can add in series and in parallel to make any size and/or voltage that you need

Today is day 5 and the light is still on. So much for time lapse photography - switched to still photos,

@@MyEngineeringProjects How long

The light stayed on for weeks but it was really dim. The current was really small and I did not measure it continuously. I thought it would only last for a few hours when I originally posted the comment.

@@MyEngineeringProjects This is the only test you did on salt battery?

@@MyEngineeringProjects if you replenish salt in the water, will that prolongue electrical generation ? .. or, how can you "recharge" such a battery ?

It would have to be tested. This idea of exchanging electrolytes is currently being researched. If the technology could be perfected, it would change the way re could recharge electric cars.

Here is an interesting article on the subject. www.purdue.edu/newsroom/releases/2017/Q2/instantly-rechargeable-battery-could-change-the-future-of-electric-and-hybrid-automobiles.html

@@MyEngineeringProjects thank you, I subscribed

Thanks

Most likely yes it would. Corrosion in general is a problem with salt water batteries. This was just a test project to demonstrate the concept.

It would increase the performance. The issue with wires and nails is that there is a small surface area available.

To followup: both the cathode and the anode would have to have an increase in surface area. If only one were changed, it's unlikely there would be much difference.

@@MyEngineeringProjects Thanks, that sounds plausible :-) I have seen approaches where they have used metal-foam elektrodes with increased surface area, to maximize the volt output. I wonder if something similar could be achieved without a nanoscience lab, by bending a stripe of sheet metal around some really sharp angles, so that the material rips and tears on a microscopic scale... Sounds stupid enough? Let's give it a try!! :-D

Sure. You can put more in series for higher voltage. Likewise you can put matched pairs in parallel for increased current. This demo project cannot run an inverter due to it's low C rating.

It would be interesting to find out. Each combination of electrodes will produce different results.

you can try different metals..... like zinc and copper?? or zinc and magnesium even? stuff like that.

Hi Raine. Glad to hear you are replicating the battery. You could try an un-galvanized nail and see how it performs. I used a galvanized nail so that the battery would use the zinc from the nail. I have not tested regular steel. Let me know how it goes. You do not need to charge it when it's first built. You will get a voltage and will be able to light a small LED immediately.

The battery had such a small C rating that it took weeks to drain it. I stopped trying to calculate it's capacity and decided to build a better version later and try again.

I have not tried deionized water. It should work. I just used tap water

No, that would not be possible.

@@MyEngineeringProjects oh I see. Corrosion will be the end of it right? Still, this tech will give light whenever there's power outages. Will it be affected by EMP?

Please don't mind my curiosity 🙂 I've never had real physics/chemistry classes.

A battery under a small load like my LED will eventually exhaust the stored energy and will need to be recharged. Corrosion in a salt water environment is something that has to be dealt with.

Due to it's small capacity it can only do a few milliamps. Thin copper would work. I coiled it in order to increase the surface area. You could use straight wires as well.

@@MyEngineeringProjects so how long would you say will it last ? I don’t understand what milliamps are. Could it go on for few month ?

Amps are a measure of the number of electrons that flow per second. It's a huge number of electrons so we use amps to make it easier to work with. A milliamp is 1/1000 of an amp so it's 1000 times smaller than 1 amp. Small batteries like AA, AAAA etc are measured in milliamps since they are smaller. A typical AA rechargable could do something like 1500 miliamp-hours. The hours says that 1500 milliamps could flow for one hour or a a factor of this at a lower flow rate such as 750 milliamps for 2 hours. This is a unit of energy which is current flowing over time. My demonstration battery is very small and it can only max out at about 10 millimaps total. This is not a unit if energy, but a unit of work. To say how long will it last, we need to define the flow of current in amps that the battery could sustain over time, which describes how much stored energy it has. I left that tiny led light hooked up and the battery ran the light very dimly for a couple of weeks. So dimily that I could only see it at night. I would say it was running in micro amps at this point, but nonetheless I was able to see energy flowing out for a while.

@@MyEngineeringProjects thank you very much for your work !!

Desalination in any form requires a great deal of energy. Adding more salt does help, but it would have to be a huge battery in order to desalinate.

@@MyEngineeringProjects true. What if the steam from desalination turned a turbine before becoming freshwater. Maybe that could ease the loss in energy consumption.

With a heat desalination system, it's low pressure and can't easily turn a turbine.

Yes it would. I did just that and maxed out at about 1000 milliamps

@@MyEngineeringProjects how big did you do? I mean, something like 10 amps, 48 volts. Then check The capacity. How big the build do you think it will be to achieve 48v 10amps?

The largest one I made is a single cell but it had a large surface area. This is the same as several cells in parallel. I over charged it on purpose and shorted the terminals to see the absolute maximum current. The size was about 2" x 3/4" - 1 amp max but the life was short so it could only do it for a few seconds. A few years ago I talked with a salt water battery manufacturer. The batteries were designed to store photovoltaic energy. For 10 amps and 48 volts, it would probably be the size of 4 car batteries. For a house, it was on a pallet.

Charging any battery is calculated by knowing it's capacity in amp-hrs and the rate of charge that it can accept. For example say a battery has 1000 mah capacity and we charge at 200 ma, then 1000 mah/ 200 ma would be 5 hours. Since this battery has so little capacity, it charges very quickly. I'm working on a new design to overcome this issue.

Any over voltage charging should increase the electrolysis. The battery would have to be encased in order to prevent the water from evaporating. If it got too dry due to evaporation and/or electrolysis , water would have to be replaced.

@@MyEngineeringProjects okay, thanks for replying :) 1,23V before electrolysis is not much to work with..

Well you have to remember that hydrogen is going up at 45 miles an hour and that there are tiny holes for the hydrogen and oxygen to escape not giving and build up

By closing the bottle, you could prevent evaporation, no ?

Not too many. this is more of a demonstration project the choice of materials used causes a lot of electroplating

Mine ran a small led for a couple of weeks but the current was small, like 1 ma.

It's such a small battery that it only has a few milliamp hours of capacity. It was difficult to measure and get an accurate number.

I was able to pull a load right after placing in the salt water

It's small, just a few milliamps

There is no need to charge it before using. The battery is at full capacity as soon as it's created. The wires were just some hookup wires I had lying around. Probably 22 gauge but anything will work since the current is so small.

@@MyEngineeringProjects Thank you

yes that's right

I've seen charts for various electrolytes but I have not seen urine on the list. You could attempt to match it to the closest published electrolyte. I'm not sure which one is the closest.

I had the same idea.

Well the light stayed on for days but got really dim and the measurable current dropped to below a milli amp. I did not perform an accurate amp our test for this design.

Well the battery performed differently than I was expecting. It continued to light a very small led for weeks and I gave up trying to perform an amp hour test. The current was very low and I didn't have a method to measure continuously over such a long time frame.

@@MyEngineeringProjects Thank you for replying. Weeks, cool! Wonder what increasing the load does! Keep it up dude

I have done a few other salt water type batteries but have not scaled anything up yet. There are some issues that need to be worked out and this is why we don't have large scale salt water batteries available commercially.

It has a low capacity since it's a demonstration project. It trickled current in milliamps for weeks and you could see a low powered LED during that time.

I have not seen any

They're being advertised as an emergency battery kit online. It's a pouch light and on-off switch mounted on the front.All you have to do is add your own table salt to it Runs over 100 hours. Bright little light!

Good point.

dont bother electron plating...just buy some zinc bars.

wonder is stainless steal works? it would withstand the corrosive salt.

Each cell as a potential of about 0.7467V. Batteries in series add the voltage, so 9 in series is 6.72V. If you want 12V you will need 16, for 24V you would need 32. Keep in mind that the voltage varies depending on the metals used for the cathode and anode. I'm only reporting based on Zinc and copper which is what I used for this test.

I thought an electrolyte cell was capable of holding just over 2 volts-that's why we have six cell 12 volt batteries. I didn't know about metal type and all that. I made a small cell with stainless steel bolts and used sulfuric acid one time and baking soda the next and was getting over two volts on that after having it connected to my car's 12 volt system, so I just assumed that all liquid cells were two volts.

Not very long it’s just a demonstration battery. It has fairly low current.

@@MyEngineeringProjects will it work for a few minutes or hours? I want it to work during my school's science exhibition. Btw very nice video.👍

For a school science project, you can run the LED for a while a few hours probably it’ll be enough to show how it works

@@MyEngineeringProjects I have one more question for you. Can I use a thick aluminium wire instead of the galvanized nails?

It will work but bear in mind that each metal has different characteristics and produce different voltages.

I'm not sure what you mean. Can you explain?

ok, but I need some sort of electrical load so light bulb or led are both fine for my purposes

Only one cell but you could have cells in parallel

Of course I haven’t tested this but I think it in a large body of electrolyte it would quickly fail as the distance between electrodes increases

@@MyEngineeringProjects sounds right.

This battery is very small. I just made it for demonstration purposes and it has a small surface area. Therefore, the amp-hour rating is hard to find. I attempted it but the max current is just a few milliamps. It did run for weeks at a very small load but I don't know the rating. The length of time to charge for any battery depends on the current you are charging and the capacity of the battery.

Yeah copper does not last long in an environment like this.

I have not tried that. The ions transport current through the electrolyte so that probably won't work without an aqueous solution in water.