Just a thought project for being self-sufficient at home for power.
We’ve got a 5.2 kW solar panel set-up on the roof right now, assuming I put a bunch more up there (I worked out I could fit 80 in total if I wanted, something like 16 kW all up) and have the appropriate inverter, the cost of a suitable battery back-up makes it all quite expensive.
But really, how difficult would be it to just build a large lead-acid battery? Something around 40 kW-h or so …. ?

Should be easy enough.
The material is easily sourced but you’d have to jump through a lot of hoops to get it approved I’d imagine.
However I did read a couple of days ago that the best solar battery is too big to be portably.
I’ll have a look for it later.

And and sibeen (points) said that the price of batteries is going to nosedive early in 2016.

For someone of your nous I wouldn’t think it would be difficult at all.

Peak Warming Man said:

Should be easy enough.
The material is easily sourced but you’d have to jump through a lot of hoops to get it approved I’d imagine.
However I did read a couple of days ago that the best solar battery is too big to be portably.

Given the purpose, I don’t think it needs to be portable.

Were you thinking of using PVC case and separators?

Something off the shelf … or dare I say 3D printed…

dv said:

Peak Warming Man said:

Should be easy enough.
The material is easily sourced but you’d have to jump through a lot of hoops to get it approved I’d imagine.
However I did read a couple of days ago that the best solar battery is too big to be portably.

Given the purpose, I don’t think it needs to be portable.

I imagine it’d easily be up around a tonne or so. Maybe a fair chunk more even.

dv said:

Were you thinking of using PVC case and separators?

Something off the shelf … or dare I say 3D printed…

3D printers are too small. But yes, very simple plastic tanks. Doesn’t need to be flash or complex.

Spiny Norman said:

dv said:

Peak Warming Man said:

Should be easy enough.
The material is easily sourced but you’d have to jump through a lot of hoops to get it approved I’d imagine.
However I did read a couple of days ago that the best solar battery is too big to be portably.

Given the purpose, I don’t think it needs to be portable.

I imagine it’d easily be up around a tonne or so. Maybe a fair chunk more even.

Gunna scavenge the lead from discarded batteries?

dv said:

Spiny Norman said:

dv said:

Given the purpose, I don’t think it needs to be portable.

I imagine it’d easily be up around a tonne or so. Maybe a fair chunk more even.

Gunna scavenge the lead from discarded batteries?

Nah go for new. It’d have to last over a decade to make it worthwhile.

These are also of interest.
Vanadium Redox Battery.

Spiny Norman said:

These are also of interest.
Vanadium Redox Battery.

Yeah, I’ve read a few times that they are the bee’s knees when it comes to allowing tens of thousands of deep cycles and “full life cost” but I’ll be damned if I know where to get vanadium…

Err, depends upon the application, but it’s one of those scenarios where it’s not as simple as it first appears.

Building a lead acid battery for a standby apllication – ie, it sits there and waits for an emergency to come along is completely different to building a battery that is going to be cycled every day. The additions to the lead chemistry are completely different, and beyond a home construction project, IMHO.

get vanadium…

spanners, crome vanadium.

sibeen said:

Err, depends upon the application, but it’s one of those scenarios where it’s not as simple as it first appears.

Building a lead acid battery for a standby apllication – ie, it sits there and waits for an emergency to come along is completely different to building a battery that is going to be cycled every day. The additions to the lead chemistry are completely different, and beyond a home construction project, IMHO.

Okay thanks for that.
What about the vanadium type? A mate of mine on my car forum has built one, on one of the projects he was doing somewhere.

From my car forum, the bloke that’s made the vanadium battery …

Found some old blurb https://www.asme.org/engineering-topics/articles/renewable-energy/flow-batteries-augment-wind-power quick google tells me the tech has come along way in the last 10 years or so…

The one I was involved in was built on King Island in 2003. We supplied all the pipework, valves & instruments. It was build by a start-up which seems to be out of business now. I found some other info on it http://www.kingislandrenewableenergy.com.au/history/kirex

“Following an operational event, the VRB is currently out of service. Hydro Tasmania is currently evaluating rectification or replacement of that energy storage system.” Hmmm, maybe I should give them a call…

Basically they are some big tanks of electrolyte, which has Vanadium suspended in a weak sulfuric acid solution, half of the tanks positively-charged electrolyte, half negative.

Lots of pipework to transfer the electrolyte around, it gets pumped to some cell stacks which are ion-exchange membranes. The AC current coming in is converted to DC through a transformer and fed into the cell stacks. Likewise to get energy out, there is another transformer from DC to AC.

The thing was huge, bigger than your shed mate.

Google tells me there are a number of companies that have commercialised this tech now. At the time this one on King Island was one of the only ones outside of Japan. As I recall anyhow…

Hey Shebs – I’m still not convinced that lead-acid is a bad thing though. Could it be as simple as making the battery big enough so a ~30 kW/h discharge every day doesn’t put much of a dent in it? Some quick searching shows that it shouldn’t be too difficult to make something like a 200 kW/h battery so that’s only a small discharge from it.

Spiny Norman said:

Hey Shebs – I’m still not convinced that lead-acid is a bad thing though. Could it be as simple as making the battery big enough so a ~30 kW/h discharge every day doesn’t put much of a dent in it? Some quick searching shows that it shouldn’t be too difficult to make something like a 200 kW/h battery so that’s only a small discharge from it.

Bill, never stated that lead acid was a bad thing, just that some of the special plate chemistry may be beyond someone who was a glorified truck driver :)

sibeen said:

Spiny Norman said:

Hey Shebs – I’m still not convinced that lead-acid is a bad thing though. Could it be as simple as making the battery big enough so a ~30 kW/h discharge every day doesn’t put much of a dent in it? Some quick searching shows that it shouldn’t be too difficult to make something like a 200 kW/h battery so that’s only a small discharge from it.

Bill, never stated that lead acid was a bad thing, just that some of the special plate chemistry may be beyond someone who was a glorified truck driver :)

You’re stuck in the past, man. I’m doing mechanical engineering at Griffith Uni now.

Spiny Norman said:

sibeen said:

Spiny Norman said:

Hey Shebs – I’m still not convinced that lead-acid is a bad thing though. Could it be as simple as making the battery big enough so a ~30 kW/h discharge every day doesn’t put much of a dent in it? Some quick searching shows that it shouldn’t be too difficult to make something like a 200 kW/h battery so that’s only a small discharge from it.

Bill, never stated that lead acid was a bad thing, just that some of the special plate chemistry may be beyond someone who was a glorified truck driver :)

You’re stuck in the past, man. I’m doing mechanical engineering at Griffith Uni now.

Jaysus, mech engineering spits that’s even worse!

I can see that you’re all well ahead of me. I totally agree with what has been said above. A large lead acid ought to be easy to make. A vanadium redox is the bees knees because it handles a very large number of charge discharge cycles without breaking down. Other types of flow battery are also good, not quite as good as vanadium redox but much better than your average rechargeable. But the redox flow batteries are always big and expensive. So more than you need. The battery should be designed for a predetermined number of charge discharge cycles. So forget about nicad for starters, too much memory effect. Vanadium is marked as VRB on the following figure.

What are the sizes required for a simple lead acid of that magnitude, more cells vs larger plates would be the first obvious trade off. The next obvious tradeoff would be plate thickness. Also consider distances between plates and acid pH.

For some reason as your battery bank goes up they increase the volts by pairing batteries in series.
As the battery bank size goes up the voltage is made to go up from 12 to 24 to 48.
I wonder why they do that?

so the amps go down and so you don’t need fat cables. therefore cheaper.

Hey I can’t help much with this but just to give some idea of the numbers, if nothing else as an exercise for myself…

The reaction is 2HSO4- (aq) + 2H+ (aq) + Pb (s) + PbO2 (s) -> 2H2O (l) + 2PbSO4(s)

From my tables, the enthalpies of formation are:

H2O (l) -286 kJ/mole

PbO2 (s) -277 kJ/mole

HSO4- (aq) -877 kJ/mole

PbSO4 (s) -920 kJ/mole

So I get 381 kJ/mole of this reaction.

40 kWh is 144000 kJ.

So that means 378 moles of this reaction (assuming, for a moment, 100% efficiency).

That makes:

78 kg of lead
90 kg of lead dioxide
37 kg of 98% sulfuric acid ie about 20 litres

However, in reality you would want to only be cycling 50 to 70%. Let’s say 60% for argument’s sake, so multiply those by 1.67

130 kg of lead
150 kg of lead dioxide
62 kg of 98% sulfuric acid ie about 33 litres

I think that a 33% aqueous solution is used commonly so this would mean there is 67 L of water, neatly 100 L of fluid altogether.

JudgeMental said:

so the amps go down and so you don’t need fat cables. therefore cheaper.

Yeah, that’d be right.
Which makes it a bit tricky for the average punter I think.
If you’ve arranged your batteries as a 24 volt system connecting up a solar panel that has a 12 volt regulator is not a good idea I think.

dv said:

Hey I can’t help much with this but just to give some idea of the numbers, if nothing else as an exercise for myself…

The reaction is 2HSO4- (aq) + 2H+ (aq) + Pb (s) + PbO2 (s) -> 2H2O (l) + 2PbSO4(s)

From my tables, the enthalpies of formation are:

H2O (l) -286 kJ/mole

PbO2 (s) -277 kJ/mole

HSO4- (aq) -877 kJ/mole

PbSO4 (s) -920 kJ/mole

So I get 381 kJ/mole of this reaction.

40 kWh is 144000 kJ.

So that means 378 moles of this reaction (assuming, for a moment, 100% efficiency).

That makes:

78 kg of lead
90 kg of lead dioxide
37 kg of 98% sulfuric acid ie about 20 litres

However, in reality you would want to only be cycling 50 to 70%. Let’s say 60% for argument’s sake, so multiply those by 1.67

130 kg of lead
150 kg of lead dioxide
62 kg of 98% sulfuric acid ie about 33 litres

I think that a 33% aqueous solution is used commonly so this would mean there is 67 L of water, neatly 100 L of fluid altogether.

Fanks – That’s smaller than I thought it’d be.
Mr Been’s concerns aside, it wouldn’t be too difficult to build a ~200 kW/h battery that would only get light cycles per day.

connect the panels in series.

Still you should probably put a fence around it to prevent the neighbour’s kids from falling in.

dv said:

Still you should probably put a fence around it to prevent the neighbour’s kids from falling in.

There’s a non-zero chance they might have some lead or sulphuric acid on them.

Spiny Norman said:

dv said:

Still you should probably put a fence around it to prevent the neighbour’s kids from falling in.

There’s a non-zero chance they might have some lead or sulphuric acid on them.

You’ve already got a big mother inground concrete tank that is just crying out for some lead and sulphuric acid, Bill.

Peak Warming Man said:

Spiny Norman said:

dv said:

Still you should probably put a fence around it to prevent the neighbour’s kids from falling in.

There’s a non-zero chance they might have some lead or sulphuric acid on them.

You’ve already got a big mother inground concrete tank that is just crying out for some lead and sulphuric acid, Bill.

I could probably power the entire suburb with that!

Spiny Norman said:

Peak Warming Man said:

Spiny Norman said:

There’s a non-zero chance they might have some lead or sulphuric acid on them.

You’ve already got a big mother inground concrete tank that is just crying out for some lead and sulphuric acid, Bill.

I could probably power the entire suburb with that!

dream big

>I wonder why they do that?

everything has voltage drop, wires, connectors, transformers, switching transistors, batteries too have an internal resistance

as you increase your load (and current) the various voltage drops from battery (power source) to the load increase as a proportion of the ideal battery terminal voltage.range.

so, to reduce this (too as someone said you can use wires with lesser cross sectional area) you can increase the voltage

they do it with powerlines all over the country.

Current(I) x Volts(V) = power(Watts)

1Amp x 1Volt = 1Watt

• 5Amp* x 2V = 1Watt (allows a smaller wire to be used)

Peak Warming Man said:

For some reason as your battery bank goes up they increase the volts by pairing batteries in series.
As the battery bank size goes up the voltage is made to go up from 12 to 24 to 48.
I wonder why they do that?

the battery bank will need to supply lots of amps

eg

1A * 100V = 100W

100A* 1V = 100W

having an electrical circuit pumping out lots of amps warms up cables which translates to losses

it’s why very high voltages are used to shift power around , having small currents and high voltages reduces current related losses

to do the same work you have a higher voltage and lower current and less losses

Japan used to have building that used off peak power to charge a huge lead acid battery that would sell power back to the grid at peak times

lead acid batteries should not be discharged below 80 percent capacity or you’ll damaged them

I don’t like the whole discharge thing they do where they drain the entire battery and then charge it up again – it reduces service life

if anything goes wrong you have lots of capacity to do some damaged in the event of a fault

if you have done your research then by all means build one but you might have ongoing problems

if you need power over night for air con freeze water in a metal water tank with lots of fins and blow air over it of a night

a number of years ago I had the idea of people using unused in ground swimming pools to store electrical power

you’d dunk a large array of plates into the pool full of sulphuric acid

the pool would need to be fibreglassed to resist the acid

you’d put a cover over the entire thing and lock it

wookiemeister said:

a number of years ago I had the idea of people using unused in ground swimming pools to store electrical power

you’d dunk a large array of plates into the pool full of sulphuric acid

the pool would need to be fibreglassed to resist the acid

you’d put a cover over the entire thing and lock it

As much as I love the idea, I think the groundwater coming through the hydrostatic valve would destroy your chemistry.

Then there’s the risk of structural failure and environmental contamination. How would you find a leak, even a tiny leak, in the wall of an in-ground pool filled with acid? Perhaps it would be better to use the pool as a bund for a tank or tanks?

Rule 303 said:

Then there’s the risk of structural failure and environmental contamination. How would you find a leak, even a tiny leak, in the wall of an in-ground pool filled with acid? Perhaps it would be better to use the pool as a bund for a tank or tanks?

Rainwater tank batteries?

How much surface charge would a tank size battery deliver?

Rule 303 said:

Then there’s the risk of structural failure and environmental contamination. How would you find a leak, even a tiny leak, in the wall of an in-ground pool filled with acid? Perhaps it would be better to use the pool as a bund for a tank or tanks?

Memory tells me that inground pools leak for a long time until they are eventually ripped out because the leak/s haven’t yet been found.

roughbarked said:

Memory tells me that inground pools leak for a long time until they are eventually ripped out because the leak/s haven’t yet been found.

Most leaks are pretty easy to find, if you know what you’re doing, but not in acid.

Rubber Band Points are doubled for the bowled/caught combination.

Rule 303 said:

Rubber Band Points are doubled for the bowled/caught combination.

Sorry, wrong fred.

Rule 303 said:

Rule 303 said:

Rubber Band Points are doubled for the bowled/caught combination.

Sorry, wrong fred.

There’s energy involved in rubber band aid.

roughbarked said:

There’s energy involved in rubber band aid.

Someone had better tell Geldof.

roughbarked said:

There’s energy involved in rubber band aid.

Yeah, but the losses to friction are outrageous.

Rule 303 said:

roughbarked said:

There’s energy involved in rubber band aid.

Yeah, but the losses to friction are outrageous.

Better than the losses to fiction.

Postpocelipse said:

How much surface charge would a tank size battery deliver?

Given that a car battery supposedly has about half an amp hour of surface charge, you would reckon that a tank sized battery for reasonable values of tank could have tens of thousands of amp hours if surface charge.

Btw one thing, Bill…

It occurs to me that in a taller battery there will be greater stratification of water and sulfuric acid than there will in a small car battery so that is one thing that won’t “scale up”.

dv said:

Btw one thing, Bill…

It occurs to me that in a taller battery there will be greater stratification of water and sulfuric acid than there will in a small car battery so that is one thing that won’t “scale up”.

Noted, ta.
Circulation of the fluid is easy enough to do, and in any case you could build the battery packs in multiple layers, to keep the individual heights down. Since each unit would have to be connected either in parallel or series it’d actually be an advantage.

Spiny Norman said:

dv said:

Btw one thing, Bill…

It occurs to me that in a taller battery there will be greater stratification of water and sulfuric acid than there will in a small car battery so that is one thing that won’t “scale up”.

Noted, ta.
Circulation of the fluid is easy enough to do, and in any case you could build the battery packs in multiple layers, to keep the individual heights down. Since each unit would have to be connected either in parallel or series it’d actually be an advantage.

If you’re going to do that, though, why not just buy a bank of batteries designed for deep cycles? That’s essentially what you’re describing. It’s probably cheaper to buy mass-produced batteries, too.

btm said:

Spiny Norman said:

dv said:

Btw one thing, Bill…

It occurs to me that in a taller battery there will be greater stratification of water and sulfuric acid than there will in a small car battery so that is one thing that won’t “scale up”.

Noted, ta.
Circulation of the fluid is easy enough to do, and in any case you could build the battery packs in multiple layers, to keep the individual heights down. Since each unit would have to be connected either in parallel or series it’d actually be an advantage.

If you’re going to do that, though, why not just buy a bank of batteries designed for deep cycles? That’s essentially what you’re describing. It’s probably cheaper to buy mass-produced batteries, too.

I’m just trying to make a guesstimate as to the costs. If I could get by with a plain lead-acid battery I could do it a hell of a lot cheaper than something like the Tesla Powerwall. But according to Mr Been a lead-acid won’t work as I’d like it to.
If I get time later I’ll do a bit of research to find out what types of batteries could be built at home, and how good they’d be at this type of application.

dv said:

Hey I can’t help much with this but just to give some idea of the numbers, if nothing else as an exercise for myself…

The reaction is 2H …

However, in reality you would want to only be cycling 50 to 70%. Let’s say 60% for argument’s sake, so multiply those by 1.67

130 kg of lead
150 kg of lead dioxide
62 kg of 98% sulfuric acid ie about 33 litres

I think that a 33% aqueous solution is used commonly so this would mean there is 67 L of water, neatly 100 L of fluid altogether.

That’s great. Very interesting dv.

Spiny Norman said:

btm said:

Spiny Norman said:

Noted, ta.
Circulation of the fluid is easy enough to do, and in any case you could build the battery packs in multiple layers, to keep the individual heights down. Since each unit would have to be connected either in parallel or series it’d actually be an advantage.

If you’re going to do that, though, why not just buy a bank of batteries designed for deep cycles? That’s essentially what you’re describing. It’s probably cheaper to buy mass-produced batteries, too.

I’m just trying to make a guesstimate as to the costs. If I could get by with a plain lead-acid battery I could do it a hell of a lot cheaper than something like the Tesla Powerwall. But according to Mr Been a lead-acid won’t work as I’d like it to.
If I get time later I’ll do a bit of research to find out what types of batteries could be built at home, and how good they’d be at this type of application.

I’m with BTM on this because I can see distinct advantages in buying the batteries in several batches, perhaps as the PV system grows, which would help spread the cost at start-up, give you the opportunity to test the system as its growing (to more accurately match your needs) and then spread the cost at replacement time, too. Also give you some flexibility to re-configure the system if a component fails.

Rule 303 said:

wookiemeister said:

a number of years ago I had the idea of people using unused in ground swimming pools to store electrical power

you’d dunk a large array of plates into the pool full of sulphuric acid

the pool would need to be fibreglassed to resist the acid

you’d put a cover over the entire thing and lock it

As much as I love the idea, I think the groundwater coming through the hydrostatic valve would destroy your chemistry.

you put a pipe from the valve to the top of the pool and over

full the pool to capacity with acid and the valve will never operate

the valve only works to equalise the weight of the pool with the earth around it

it’s there to stop the pool becoming a ship , the pool is filled to capacity the valve won’t operate

you could always convert solar straight to hydrogen

tunnel downwards in your garden a foot wide tube and lower a piston that fits the tube then fill with salt water

the piston is connected to an electrical lead water is allowed past the piston

hydrogen is created , oxygen is bled off and bubbles to the surface

the hydrogen is stored under pressure provided by the deep tube of water

when hydrogen is needed it’s tapped off past the piston through a valve that flows the electrical lead to the surface

the hydrogen is used to run an ICE which turns a generator

wookiemeister said:

the hydrogen is used to run an ICE which turns a generator

Go the whole hog and get a fuel cell. you just aren’t imaginative enough Wookie!

costs

salt

graphite conductors

valve

water

solar array and electronics that power electrolysis

piston

if there’s an explosion the earth takes the blow and a lightweight piston is shot into
the air

party_pants said:

wookiemeister said:

the hydrogen is used to run an ICE which turns a generator

Go the whole hog and get a fuel cell. you just aren’t imaginative enough Wookie!

they are too expensive

bill has access to engines already

you trigger the spark TDC

you’d need a regulator on the hydrogen line to the engine