I like his battery haha, colorful. Also nuts to test all those cells. Make sure they're all roughly the same performance. wonder how hard it would be to find a bad cell.
What does a kilowatt hour look like?
41–50 of 147 posts
Re: What does a kilowatt hour look like?
#42Re: What does a kilowatt hour look like?
#43Earlier quoted context omitted.
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.
Wow, as someone uneducated about anything related to electricity and power, seeing the picture in the article really made me want to emulate the setup. Not anymore.
You joke buy many many people don't know how volatile battery chemistry is and how different charging of Lithium cells works.
I'd not have known how much of a bad idea this was had I not been a long time fan of EEVBlog. It's an entirely different world when touching Lithium cells. Even drawing in parallel from cells from the same batch can be a bad idea.
Re: What does a kilowatt hour look like?
#44Given how popular (and damn near impossible to discern) unsafe and unprotected lithium-ion batteries are, the idea of making a homegrown power wall terrifies me in ways I can't even begin to contemplate. An 18650 battery, if combusted, can produce hydrofluoric acid with just water vapor in the air (or the water in your lungs) if they use lithium hexafluorophosphate as the electrolyte. Hydrofluoric acid can and will c…
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.
Re: What does a kilowatt hour look like?
#45I've been very curious for a very long time about people doing indoor bike workouts while storing the pedaling energy in batteries. Any of you do such things ?
You would get very little out of it. Enough to run a dim LED for a couple hours at most.
If you did it in addition to (as opposed to instead of) your exercise then the energy in the food you ate is massively greater than what you can get from the bicycle. If you eat more as a result then you wasted your money.
Re: What does a kilowatt hour look like?
#46Given how popular (and damn near impossible to discern) unsafe and unprotected lithium-ion batteries are, the idea of making a homegrown power wall terrifies me in ways I can't even begin to contemplate. An 18650 battery, if combusted, can produce hydrofluoric acid with just water vapor in the air (or the water in your lungs) if they use lithium hexafluorophosphate as the electrolyte. Hydrofluoric acid can and will c…
Building a pack from random cells like this is pretty much a cardinal sin with Li-Ion pack design. Cell resistance and state of health are carefully matched during pack manufacture to ensure cells charge and discharge evenly. Li-ion cells are pretty sensitive, so on top of that, large packs have battery management systems (BMS) to balance cell voltages and monitor for faults and damaged cells.
Attempting to charge a pack like shown has a very real risk of causing one or more of the cells to overcharge and breach, or worse, violently catch fire.
Re: What does a kilowatt hour look like?
#47I've been very curious for a very long time about people doing indoor bike workouts while storing the pedaling energy in batteries. Any of you do such things ?
Yes. These guys do bike-powered cinema installations, as well as phone charging, smoothy-making, etc.
Turns out you can generate a fair bit of energy from pedals!
Re: What does a kilowatt hour look like?
#48> David McCay - Sustainable Energy without the Hot Air
A fantastic book. A Caltech trained physicist at Cambridge does the calculations to see if the UK could get all its energy needs sustainably.
Simple, easy to understand, and enlightening. It deserves the praise they talk about.
And it's free to download.
Re: What does a kilowatt hour look like?
#49I like his battery haha, colorful. Also nuts to test all those cells. Make sure they're all roughly the same performance. wonder how hard it would be to find a bad cell.
Probably the most obvious indication would be temperature. Assuming they are in parallel, it'd be quite wise to measure their discharge curves to only select similar cells - that would also highlight any bad ones.
Re: What does a kilowatt hour look like?
#50I've been very curious for a very long time about people doing indoor bike workouts while storing the pedaling energy in batteries. Any of you do such things ?
You would get very little out of it. Enough to run a dim LED for a couple hours at most. If you did it in addition to (as opposed to instead of) your exercise then the energy in the food you ate is massively greater than what you can get from the bicycle. If you eat more as a result then you wasted your money.
It wouldn't be quite that bad. You're probably putting out something like 100-200W. Even factoring in generating and storage losses, you're looking at running a reasonably bright LED bulb for several hours on the proceeds of a 30-minute session. Still not worth the effort of building the equipment, of course.