Amplifying the voltage from a homemade battery.... In rural Africa

[Astock]

Hi PF! Though I've lurked here for some time, this is the first time I've created an account.

I'm a volunteer in a country in West Africa. The school I teach at has a tiny library with 4 small dell PC's and a printer that were donated some time ago. A grant was used years ago to buy a battery and solar panel, but after a while the battery died and I've found that they're not economical on such a miniscule budget. I stumbled across a "scrap-metal battery" (https://news.vanderbilt.edu/2016/11/02/making-high-performance-batteries-from-junkyard-scraps/) and found the paper (not available without $.. but I have my ways...). I have found most of the supplies in a larger city near my village, and believe it to be feasible. Maybe I'll make another post about that.

Now for the actual problem... IF it does work, the voltage will be at most 1.something. The power regulator, solar panel, etc etc are all set up to work with a 12v battery.

A) Buying and shipping a commercial amplifier (I'd need two, really..one to drop the solar panel voltage, and one to raise the battery voltage) would be expensive and defeat the point of giving the school an economic solution.

B) I could put several cells in series, but this complicates the battery construction... I'd have to build maybe ~8 identical cells, test and tweak so they have the same capacity (tricky) and assume the cells all age at the same rate. Otherwise, the weaker ones will be damaged after they discharge first.

C) I could pry opamps out of trashed electronics, maybe? And find resistors (maybe?) to make voltage amplifiers. But I have doubts about their efficiency. My education is in Computer Engineering so it'd be awesome to take this route but I have doubts about it's practicality as well.

Option (A) seems to be the cleanest and I might be able to find grant money (sorta defeating the purpose of the project, but if the claims of the researchers hold, they'd at least have a battery that works for 5,000 cycles). If I take option A, what kind of commercial product can I use? Everything I find online is for RF/AC, not DC, applications. Maybe someone could point me in the right direction.

What have I not thought of yet? What do you think, PH?

 

[Borek]

It is not the voltage that is your main problem, but the battery capacity. I doubt you will be able to make a battery from a scrap with enough Ah to run these computers.

 

[Averagesupernova]

Yeah I don't quite follow the objective here. Signals are amplified. Power is not.

 

[Astock]

Thanks for the replies.

It is not the voltage that is your main problem, but the battery capacity. I doubt you will be able to make a battery from a scrap with enough Ah to run these computers.

Yeah I don't quite follow the objective here. Signals are amplified. Power is not.

The feasibility of the battery is another question. Let's assume I have a working battery. Even if the capacity of my battery per cm^3 is 1/5 that of a commercial battery, that's fine. I'll make it big, the supplies are cheap.
I'm not trying to amplify the power. I'm trying to make ~1.5v DC -> 12v DC. My goal is to find a practical way to do a simple amplifier given the unique circumstances.

 

[Borek]

To get your nomenclature right: you are not looking for an amplifier but for a step-up (boost) converter.

 

[Averagesupernova]

Given your input previously, I would say you are biting off more than you can chew. You cannot take an op-amp as you referenced earlier and configure it to output a higher voltage.
-
There circuits that can convert from a lower voltage to a higher voltage but based on what I have seen you post I would not recommend you attempt them just yet.
-
I did not follow the link you provided but it seems awfully far fetched that you can build up batteries from junk and expect to run computers.

 

[Astock]

To get your nomenclature right: you are not looking for an amplifier but for a step-up (boost) converter.

Aha! Thanks, I knew perhaps getting the technical terminology right might help me find stuff online easier. So, do you think it would be easy to implement a step-up converter?

 

[Astock]

Given your input previously, I would say you are biting off more than you can chew. You cannot take an op-amp as you referenced earlier and configure it to output a higher voltage.
-
There circuits that can convert from a lower voltage to a higher voltage but based on what I have seen you post I would not recommend you attempt them just yet.
-
I did not follow the link you provided but it seems awfully far fetched that you can build up batteries from junk and expect to run computers.

Isn't that what opamps are for? Gain = -R1/R2, I am sure you're familiar with that most basic configuration.
Either way, I'm open to buying a commercial product to do this if it comes down to that.

If you read the paper, it involves anodizing (with reasonable voltages and common chemicals) both brass and low-carbon steel to form "nano-rods" and "nano-thorns" on each material respectively, along with a KOH+water electrolyte. The results they published speak for themselves.

I should add, I plan to make a small prototype first.

 

[anorlunda]

I am skeptical of your ability to make a homemade battery plus amplifiers that is as good or as cheap as an auto battery.

Aren't there any junk yards or auto parts salvage there? For simplicity, cost, durability, and equivalence in remote locations an ordinary auto lead acid battery is very hard to beat.

after a while the battery died and I've found that they're not economical on such a miniscule budget.

Can you elaborate on that? What kind of battery was it, and how much did it cost?

 

[CWatters]

Lets say you need 1A at 12V. That equates to at least 12A at 1V of the battery. So essentially you have a choice...

Increase the battery capacity by a factor of 12 or increase the voltage by a factor of 12.

Usually increasing the voltage and eliminating losses in the step up converter is usually more efficient.

 

[CWatters]

Astock - unfortunately you missunderstand what opamps do. Yes they amplify a voltage BUT they need a power supply at least as great as their output voltage and typically 3V more. So for an op-amp to produce +12V at 1A the op-amp needs a power supply of perhaps 15V at 1A.

Think of an op-amp like a water tap. You open the tap a bit and water comes out but the tap doesn't make the water, it just controls how much water comes out up to the limit of the water source.

 

[NascentOxygen]

B) I could put several cells in series, but this complicates the battery construction... I'd have to build maybe ~8 identical cells, test and tweak so they have the same capacity (tricky) and assume the cells all age at the same rate. Otherwise, the weaker ones will be damaged after they discharge first.

This is the only feasible option, with the likely requirement being closer to 800 cells than your 8. You may have misunderstood the generous energy density estimates in the researchers' paper. Their figure of up to 20 Wh/kg involves not the bulk of metal in the jar of electrolyte, but the weight of thin oxide* coating on that metal. Most of the metal in a plate battery is there for mechanical stability and support and takes no part in the battery's electrochemistry. While your scrap metal battery sounds attractive in principle, and the research may lead to commercial production of a new and cheaper cell with its alluring 1.8 volts, there is a lot more involved to making one than merely stuffing pieces of steel and brass into recycled glass jars.

https://pubs.acs.org/doi/suppl/10.1021/acsenergylett.6b00295/suppl_file/nz6b00295_si_001.pdf

You have to ask yourself why do cars require such a big, heavy battery when a dozen little AAA rechargeable cells bunched together with a rubber band is all that's needed to produce a voltage identical to that of the car battery?

But full marks for enterprise in spotting the news release and thinking how it could be of benefit to those you work with.

And if it hasn't already been said, Astock,

 

[CWatters]

Stock - can I ask how much a new battery costs in your part of Africa?

 

[Astock]

Aren't there any junk yards or auto parts salvage there?

Unfortunately no. This feeble economy here out in the brush would never be able to afford to get rid of a vehicle (or parts therein) that have any utility whatsoever. Cars that are abandoned have had everything -- wiring harnesses and all -- repurposed. I'd just as well buy a new auto battery.

Can you elaborate on that? What kind of battery was it, and how much did it cost?

It was a Chinese gel battery. I could give you more specifics once I'm at the school later today.

Usually increasing the voltage and eliminating losses in the step up converter is usually more efficient.

Gotcha.

So for an op-amp to produce +12V at 1A the op-amp needs a power supply of perhaps 15V at 1A.

Shoulda remembered this. Thanks for the info, clearly I haven't applied much of my knowledge in the real-world yet.

Their figure of up to 20 Wh/kg involves not the bulk of metal in the jar of electrolyte, but the weight of thin oxide* coating on that metal

This is both good to know and discouraging. Of course the oxide would be a tiny % of the total battery mass... So I'd have to make a collosal battery... :'(

Stock - can I ask how much a new battery costs in your part of Africa?

I've heard numbers from 600,000F to 1,000,000F. This works out to ~$65-110 but this is a huge number given the economic circumstances. The govmnt won't pay two of our teachers, and we are struggling to collect the $2 per student to pay their already pitiful salaries.

 

[CWatters]

How did you find yourself volunteering in such a remote area? You working for a international charity or?

 

[Astock]

How did you find yourself volunteering in such a remote area? You working for a international charity or?

Peace Corps. I teach math at a school in the Fouta Djallon.

 

[Astock]

This is the only feasible option, with the likely requirement being closer to 800 cells than your 8.

Btw, didn't plan on replicating that puny thing they made in a glass jar. They have these rectangular 10L "bidons" i was thinking of using. Perhaps it'd be possible with 8 cells of that size? Assuming I can find that much brass and steel sheet metal...

 

[anorlunda]

Gel cells are fragile with respect to operating temperature. 50C is the upper limit. Even temperatures above 40C shorten the lifetime. If you had the cell exposed to the hot sun, or in a box exposed to the sun, death of the gel cell is nearly certain.

I still think your best option is an ordinary lead acid auto battery. Ordinary means a flooded battery, not gel, not AGM. The price of a new battery should be less than the price of one panel, or 5% of the price of a laptop.

Cars that are abandoned have had everything -- wiring harnesses and all -- repurposed.

Exactly, and buying a used battery from someone who strips cars is your own participation in the local repurpose economy.

You must also protect any kind of battery from overcharge from the solar panel. Whoever designed your solar panel installation should have provided a controller. If not, you need to add one or you'll continue killing batteries.

You didn't say how many watts of panels or watt-hours of batteries you need. But the smallest simplest charge controllers rated for 7A start at about $20.

Good luck. Solar panels are an excellent way to provide power in remote locations. That's an excellent choice. But success depends on non-trivial design details.

 

[Astock]

Gel cells are fragile with respect to operating temperature. 50C is the upper limit. Even temperatures above 40C shorten the lifetime. If you had the cell exposed to the hot sun, or in a box exposed to the sun, death of the gel cell is nearly certain.

I still think your best option is an ordinary lead acid auto battery. Ordinary means a flooded battery, not gel, not AGM. The price of a new battery should be less than the price of one panel, or 5% of the price of a laptop.


Exactly, and buying a used battery from someone who strips cars is your own participation in the local repurpose economy.

You must also protect any kind of battery from overcharge from the solar panel. Whoever designed your solar panel installation should have provided a controller. If not, you need to add one or you'll continue killing batteries.

You didn't say how many watts of panels or watt-hours of batteries you need. But the smallest simplest charge controllers rated for 7A start at about $20.

Good luck. Solar panels are an excellent way to provide power in remote locations. That's an excellent choice. But success depends on non-trivial design details.

Yeah, it's sounding like auto batteries might be the way to go. There is in fact a controller between the panel (it's probably 50W iirc). The batteries are in fact stored inside in the shade. I'll let y'all know what comes of this...

 

[rbelli1]

The batteries are in fact stored inside

If you use flooded batteries you must vent them outside or you will end up with an explosion hazard.

BoB

 

[Dr_Zinj]

Given your input previously, I would say you are biting off more than you can chew. You cannot take an op-amp as you referenced earlier and configure it to output a higher voltage.
-
There circuits that can convert from a lower voltage to a higher voltage but based on what I have seen you post I would not recommend you attempt them just yet.
-
I did not follow the link you provided but it seems awfully far fetched that you can build up batteries from junk and expect to run computers.

Now that sounds like a Scientific American, Amateur Scientist project challenge. Something a bit more sophisticated than how many potato batteries does it take to run a cell phone?

 

[sophiecentaur]

Even if the capacity of my battery per cm^3 is 1/5 that of a commercial battery, that's fine. I'll make it big, the supplies are cheap.

Please. You really must not pursue this battery making idea. It will cost you a fortune in materials and it is very unlikely to work. Believe me, if it were really feasible then PF would be full of threads from people who had made one and just wanted to improve on its performance a bit. You wouldn't expect to manufacture your own PV arrays, TV cameras or TV displays. Batteries are at least a far beyond the reach of the casual DIY'er as those three items.
If you need new batteries then you will have to buy them and you will have to come up with a money making scheme to fund them with.

 

[jmar9]

How can I get a new battery to you? That seems like the easiest thing to do so you can be creative on something new. «mod note: personal contact details removed» Its obvious you weren't asking for money, but sometimes its the easiest thing to do.
later - - jmr

 

[Mark Harder]

For a fun, let's see if..., kind of project it sounds interesting and worth a try; but I wouldn't want to depend on a homemade device for a 'serious' application. BTW, voltage converters work by storing charge in capacitors and magnetic field in inductors. Depending on whether you want to step-up the voltage or step it down, the current supply is switched on and off, discharging the electric field in the capacitors and magnetic field in the inductors in a feedback-controlled fashion so the output voltage comes out right. An op amp or power amp, as some have said, provide no form of 'bootstrapping' voltage. The switching converter design can be very efficient.

 

[Rive]

SO, if I take it right the OP actually has a whole PV system (PV panel, charge controller and inverter)?

IF it does work, the voltage will be at most 1.something. The power regulator, solar panel, etc etc are all set up to work with a 12v battery.

Since the charge controller will try to charge that battery at 12V, you just can't avoid connecting those homemade batteries in serial. Unless you plan to modify the charge controller too? You mentioned that the charge works around 50W, which means ~ 4A charge (at 12V). At 2V it would be 25A. No way that the controller would be able to supply that and to receive that with a homemade battery - well, just forget it...
If you keep the 4A charge then the power received would be 8W instead of 50W. Quite serious cut I think.
However, my guess is that for such homemade battery to be able to receive half amp charge current would be already a quite good result. So: instead of 50W it would be able to receive 1W power.

Next, the output. If the charge is 50W, then I guess the output would be around 4-500W at most. The lower the voltage on the battery, the higher current it need to provide for the same output. At 2V for 400W output it would be 200A. That's simply insane. Most effective would be to get an used (but still usable) car battery. If you can't get even that, then it is quite unlikely to get the equipment needed to bring and fit in any homemade miracle.

 

[scottdave]

Interesting article. The voltage per cell has to do with the metals involved. So making a bigger cell will have about the same voltage, but the potential for higher capacity (lasting longer before recharge) and potential for higher current. A battery is several cells connected together (usually series to increase voltage).

 

[scottdave]

Most effective would be to get an used (but still usable) car battery. If you can't get even that, then it is quite unlikely to get the equipment needed to bring and fit in any homemade miracle.

I agree. I have seen various YouTube videos with people reusing old car batteries, where maybe 1 or 2 of its cells had gone bad. It's worth a shot. This may be easier to accomplish than harvesting scrap metals to make your own cells.

 

[sophiecentaur]

harvesting scrap metals to make your own cells.

Time for a grumpy reply here. The metals needed for a workable battery are not readily available so the OP will not be able to make his own. Even thinking in terms of drilling through the case of a duff 12V battery to find perhaps a single non-duff cell is pretty unrealistic for someone who has such little knowledge of the topic. The OP should be strongly advised (I have already made this point) against any DIY approach as is is likely to end up costing more money in the long run than getting hold of proper batteries. Also there is the risk of acid splashes in the eye and explosions during charging. A set of dissimilar cells, salvaged from various old batteries and connected in series will not last long. We all know that mixing AA cells of different ages and charge states is not recommended and Lead Acid cells are the same.
Why is no one else making these points more strongly? Even just on the basis of health and safety.

If a sort of solution is really needed then why not suggest that the PV array should be pointed East and West when the Sun is near the horizon and getting as much PV based power as possible. The Cosine function of illumination is very relevant in early morning and late evening. You could get another hour or so of use at each end of the day this way. The rotating mechanism would need some ingenuity but it's all easy, low tech stuff.