81–90 of 142 posts
What's interesting is that if the batteries are being sourced from JDM cars the batteries are probably relatively young due to the average age of Japanese cars being relatively low (8.7 years) and the amount of yearly mileage is also half for JDM cars when compared to the US. So if you tried the same in the US it may not be as viable.
Earlier quoted context omitted.
Nah, you can buy 18650 cells, nickel strips, a spot welder, and make a BMS. Build your own battery pack.
If you don't know what you're doing, don't do this. Even if you know, probably don't. It works, and is a regular industrial process, sure, but you're trying to perform controlled melting of the protective housing of one of the many, tightly packed chemical energy bombs you're sticking together. Doesn't take too much of a mistake to go very wrong. If you're building a battery pack in this day and age, use something li…
The proper tools to do this are not that expensive anymore in the greater scheme of things. It is just a question of whether or not it is worth to do it at the scale you are doing it or pay somebody else to do it.
Of course if you buy cells that are designed to be bolted together then bolt them together.
Of course the bolts, or whatever else provides the threads, on those cells are welded on.
Earlier quoted context omitted.
Your own cells ? Like you put together a lasagna of metal sheets and chemical goops and roll it up?
Nah, you can buy 18650 cells, nickel strips, a spot welder, and make a BMS. Build your own battery pack.
Neat idea to mix batteries of different age and chemistries. I've wondered why EVs couldn't do that too with some power electronics and SW. If an EV battery could have multiple such modules, it'd: 1) Make it easier to carry a cheaper lighter less-natural-resources-consuming battery most of the time. Go to some "gas station" to rent and add more modules when taking a road trip 2) Make it cheaper to replace the 1 modul…
EV battery packs operate at voltages that are seriously hazardous. Consumers coming anywhere near those plugs is a non-starter, so even more bulk, weight, and complexity would need to be added to make the installation process foolproof.
Waterproofing is critical, the mechanism has to work flawlessly over insertion/removal cycles to keep a watertight seal.
What's interesting is that if the batteries are being sourced from JDM cars the batteries are probably relatively young due to the average age of Japanese cars being relatively low (8.7 years) and the amount of yearly mileage is also half for JDM cars when compared to the US. So if you tried the same in the US it may not be as viable.
It's almost like EV batteries don't last long...
Neat idea to mix batteries of different age and chemistries. I've wondered why EVs couldn't do that too with some power electronics and SW. If an EV battery could have multiple such modules, it'd: 1) Make it easier to carry a cheaper lighter less-natural-resources-consuming battery most of the time. Go to some "gas station" to rent and add more modules when taking a road trip 2) Make it cheaper to replace the 1 modul…
A few tradeoffs you might not be considering: EV battery packs operate at voltages that are seriously hazardous. Consumers coming anywhere near those plugs is a non-starter, so even more bulk, weight, and complexity would need to be added to make the installation process foolproof. Waterproofing is critical, the mechanism has to work flawlessly over insertion/removal cycles to keep a watertight seal.
Earlier quoted context omitted.
I guess you can put a relais/switch in for each cell in a series but then you need to account for voltage differences when taking them out. Either by over provisioning within the series and rotating in different cells. Or by have other strings take up the slack. Either way you need some form of overbooking / compensating capacity.
Nearly all EV's today would run just fine on 3.7 volts fewer. My car's high voltage circuitry seems to work down to about half of the nominal voltage.
Earlier quoted context omitted.
If you don't know what you're doing, don't do this. Even if you know, probably don't. It works, and is a regular industrial process, sure, but you're trying to perform controlled melting of the protective housing of one of the many, tightly packed chemical energy bombs you're sticking together. Doesn't take too much of a mistake to go very wrong. If you're building a battery pack in this day and age, use something li…
Generally speaking the cells that are welded on are designed to be welded on in the areas were you do the welding. Doing something other then welding on them properly is going to be more unsafe then welding. The proper tools to do this are not that expensive anymore in the greater scheme of things. It is just a question of whether or not it is worth to do it at the scale you are doing it or pay somebody else to do it…
... by automated spot welder programmed to the specified timing and temperature control from the cell spec sheet, in a controlled environment with suitable protection and fire suppression for a battery manufacturing line. Not by a hobbyist's first try with a homemade spot welder and a safety squint.
I have made such spot welder and done such spot welding. Sure it's fun to do stupid things, but it remains stupid and unnecessary. For a homebrew battery bank, this is the wrong tool, wrong cell and wrong chemistry.
Buy premade, or if you must, buy boltable prismatic lifepo cells. They can dump a lot of power if your short them, but you can drill straight through them and they'll remain stable. The random 18650 li-ion cells... Not so much.