Not related, but I hate this unit. Can't we just talk about Joules?
Same here. 1 kWh = 1 joule hour per second How does it make sense to have 2 different units of time in there?
"How does it make sense to have 2 different units of time in there?"
This way it's easier to calculate how much energy your appliances uses. For example, if your vacuum cleaner is 1000W (1kW), running it for an hour will use 1kWh of energy which cost you can clearly see on your electricity bill. Unless you also want to re-lable all appliances, electric engines etc. in joules.. Sure, joule makes much more sense in physical calculations.
Lithium-ion batteries require an expensive materials and overly complex manufacturing (Gigafactory). They are also dangerous as evidenced by the Samsung Note 7 debacle. Hopefully, there will be advances in making lead-acid and hydrogen fuel cells cheaper and safer. That would allow viable energy storage for solar PVs.
1kWh as aluminium is about 66g (assuming 15kWh per kilo manufacturing input) or about 4 drink cans.
25 million kWh as mass is about 1g (E=mc^2) so 1kWh is 40 nanograms or about 1/150th of a grain of sugar. (handwaving away a method for 100% efficient conversion of mass to energy... But solving that would be a _really_ good thing...)
Just drop it in a black hole and collect the Hawking radiation.
Even a single AAA battery has a lot of energy 5,071 J according to http://www.allaboutbatteries.com/Energy-tables.html . My point of reference I use to imagine energy is a major league baseball player hits a baseball with 1,234 J. 1KW/h is 3,600,000 J.
In other words: 1 kWh is the equivalent of the average MLB player hitting a home run roughly every 1.2 seconds.
.... For one hour. Your units do not check out.
He just needs to hit the ball ~ 3000 times. Imagine that exploding in your face.
Then you compare with the amount of energy in a liter of petrol (~10kW/h). And you realise how we're living literally awash in crazy amounts of energy, equivalent to having all hundreds of slaves working for us 24h a day.
1 Wh is about 0.9 kilocalories. So 1kWh is about 100g of butter. The energy expenditure of a human in one day is about 2kWh. 1kWh is about the energy needed to heat 10L of water from 0 deg celsius to 100 deg celsius.
It actually takes some extra energy to move from ice to water, and also some extra energy from water to steam, so your numbers only work out if you are strictly inside the 0-100C range. It's interesting to realize thought that we programmers are code producing machines that run on roughly 2kWh per day. If we produce 100 lines of code in a day, that's 20Wh per LOC. Not bad, actually.
Water can be 0-100 C, both temperatures included. No need for melting/turning to steam. You could start with 10 L of 0 C ice, but he said water.
It's pretty safe so long as you use a battery controller with appropriate monitoring to prevent overcharging. Recycled 18650 cells that have worked fine in laptops for years are very unlikely to suddenly explode on you for no reason. I'd be more worried about the mystery Chinese ones you can get new on the web! Here's some Materials Science students at Oxford who built packs using recycled laptop cells. They used con…
It's still not the best idea unless you can control the draw from each cell individually. Hooking these up in parallel is a horrible idea.
I came here to say just that. This is a horrible idea and definitely not something you should do. Just use sealed AGM batteries, don't burn your house down or deal with spilling chemicals everywhere. Even just drawing in parallel from batteries like this is a fire hazard. Charging is an out of your mind goal.
Even just drawing in parallel from batteries like this is a fire hazard. I think you've confused parallel with series; in parallel, the batteries will naturally balance themselves to the same voltage and discharge proportionally to their capacity. It's the series configurations that are riskier and need extra balancing circuitry. Also, I'm pretty sure the bulk of fires are from the much more fragile pouch "lipo" cell…
I think @gravypod actually meant parallel connection, it might be quite dangerous in fact - you don't even need to draw anything from the battery to mess things up. If you connect a 100 cells in parallel and one cell dies creating a short in the circuit, the rest of cells will discharge through the shorted one. When you short a single 18650 cell, it outputs about 6-7 A of current on average. Multiplying by 100 gives you 600-700 A of current flowing through a single cell. That's why people use fuses to create parallel modules.