The way I understand batteries is you plug 'em in, electrons flow in and after awhile you have a charged battery. Feel free to elaborate on the physics of this if you want. What I don’t understand is why it takes so long. I know there are rapid chargers which further confuses the issue for me. I can’t imagine rapid chargers are so cost-prohibitive that they wouldn’t be industry standard. Unless they’re trying to still charge a bit more for the rapid technology before phasing out the old, like new processor chips.
So what is the diffence in rapid vs standard? Also is it the battery and/or charger at work?
Batteries are chemically-fueled charge pumps. Batteries are exactly the same as “Fuel Cells,” except they carry their fuel inside. They don’t store any electrons, instead the path of electric current is through the battery and back out again. They go dead when their chemical fuel has all been turned into waste products. To “recharge” them, you pump the charges backwards through them, which runs the chemical reactions backwards. Waste products get turned back into fuel.
The main trouble is that the battery electrolyte (the acid or salt water or whatever) is a poor conductor, and it won’t stay cold if the value of current is too high. Charge the battery too fast, and it can boil inside and explode like a small bomb.
The second trouble is that, for some battery types, if you keep charging it after it’s “full,” it starts making hydrogen and oxygen gas. Let this go on too long, and you can ruin your battery. Also, batteries are supposed to have a pressure release valve, but if it ever malfunctioned, …the battery could go off like a small bomb.
Some battery chargers use a microprocessor and a temperature sensor that’s glued to the side of the battery. That way they can crank up the charging current to dangerous levels, figure out whether the battery is “full” or not, yet stay below the explosion threshold. With lithium metal electrodes this is a bigger deal, since a tiny hotspot on impure lithium can catch it on fire …and the battery goes off like a small bomb.
Idea: make injury lawsuits illegal, go back to 1800s in terms of safety fears, then make some Real Man’s battery chargers. Pshaw, if you’re havin’ boiler explosions all the time at work, a little battery steam-firecracker is nothin! Just dig the tiny fragment out, and buy yourself an eyepatch. Shoulda been wearin’ goggles to go with your beaver Topper.
The rate is caused by the charge circuit…not to be confused with the “charger”, which is the cable that plugs into the wall.
In cell phones…at least the ones I’m familiar with…there is a circuit that controls the rate of charge. There are typically rapid and slow chargers…they provide a different max current.
The phone controls how much actually flows into the battery. Typically, slower charge leads longer battery life.
Mad scientists wear the goggles. Igor gets the eyepatch. Now I finally get it: crude Victorian cellphone chargers.
Oh, another possibility: in electroplating, if you run the current at a low value, you get bulk metal plating. A polished surface stays polished. But if you crank the current too high, it makes the surface accumulations unstable, which grows a nano-forest of metal dendrites. It looks like black sludge which falls off the metal when disturbed. So, a single type of chemistry, yet two growth styles. Perhaps some battery types suffer from whisker growth during high recharge current. Or maybe their plates turn into unrecoverable sludge.
Great info wbeaty, never thought of the temp increase. I wish I could remember the device (mp3 player?) that had a warning not to overcharge. It didn’t give a reason why not so I ignored it. Hey, it was commercially available to everyone so there couldn’t be any actual danger, right? eyeroll hehe.
BTW, let’s stick to non-auto/marine batteries as few people recharge those. One more thing. Is the lithium in a lithium-ion the same as the lithium I take? Still don’t know if it’s classified a metal or salt.
I’m not a car person, but I’m pretty sure I was recharging my car battery today…I depleted the battery a bit by starting the car, then charged it by driving around.
What others have said. It does depend a lot on the specific chemistry. Some chemical reactions generate more heat and gas than others. To some extent the physical design of the cell also matters. Gelled electrolyte lead acid cells need to have time for the acid to move within the gel to the plates where the reaction can happen. (note that most modern non-spill L-A batteries do not suffer this problem because they are not gel-cells. The acid is contained in a fiberglass sponge instead of gel)
NiCad and NiMH cells can usually be charged really fast…10-15 minutes. LiPO are not quite as fast but have much higher energy density.
For electric cars, the batteries are often so big that the rate is limited not by the battery or the charger, but how much power you can pull from the wall outlet. Reasonably quick recharge times would require a 30A 230V outlet like a clothes drier would use.
Batteries work by chemical reaction. It’s like if you mix baking soda and vinegar, you get gas. In the case of the chemicals inside of a battery, rather than getting gas, you get electrons. A rechargeable battery uses another chemical reaction where it’s like you compress gas down onto a pile of the leftover baking soda + vinegar gunk and restore them to their previous states. But it’s like anything, there’s a certain speed at which stuff happens. A particular chemical reaction has its rate at which it takes place. You can create the ideal conditions for rust to occur or the perfect mixture of gunpowder, and you’ll get the reaction to happen as fast as it can, but not any faster. And as wbeaty pointed out, the ideal conditions aren’t necessarily going to be something that you can achieve in a portable little thing that needs to be cheap to produce.
Let me note the up-coming technology (though I’m not an expert) of “air” powered batteries:
It’s like if you know you’re going to be driving through vinegar, and you want CO2 gas, then you don’t need to store the vinegar on your car. You just put the baking soda on the front of the car and figure out a way to capture the gas.
it depends on the battery chemistry. R/C people used to beat the shit out of NiCad cells; discharging them almost flat, then rapid charging them until they’re screaming hot, then running them down again. NiMH aren’t that tolerant, but will survive a bit of abuse. lead-acid batteries are hazardous 'cos they’ll “boil off” hydrogen when punished, and pretty much any lithium cell will burn the fuck up if you look at it wrong.
but yeah, in most cases, heat is the enemy and limits how fast you can cram charge into the cell. go too fast, and they’ll overheat and vent or catch fire.
false, as has been already explained. plus, lead-acid batteries (which car/marine batteries are) are everywhere; they’re in the battery-backed UPSes that you might have your PC plugged into, they’re used for the emergency lights in your office or apartment building. Those are generally AGM or VRLA lead-acid batteries, but the chemistry is the same as the flooded-cell battery in your car.
you probably take a lithium carbonate compound. rechargeable lithium batteries use a lithium alloy as one electrode and use a lithium salt as the electrolyte.
Lotta good information here. To expand on a little of it:
“Lithium” as a medication is not lithium per se but rather a lithium salt, meaning an ionic compound of lithium and something else. In the same sense, table salt is not sodium, it’s an ionic compound of sodium and something else (chlorine). Lithium itself is a metal. It’s shiny and silvery, and it conducts electricity. It is, however, an extremely reactive metal that you never see sitting around or getting made into parts (though there are lithium aluminum alloys sometimes used in aerospace for their lightness, as lithium itself is so light it floats in water).
I think there are a few different things that go wrong with batteries when they are charged or discharged too quickly. Automobile starter batteries are interesting in this sense. They are designed to handle large currents, though not to have much of the available charge withdrawn (it severely limits their life if you do so). Their chemistry acts at a surface between metal and acid, and these batteries are made with the metal in a foamlike form to provide more surface area.
Capacitors are in some ways like batteries, though they don’t use energetic chemical reactions to store the energy (though some use chemical reactions to create a double layer to hold the charge). Capacitors are different, though, in several functional ways. For one thing, they can store power at any voltage that is larger than zero and smaller than some limiting voltage that will make them fail. The power they store is equal to their capacitance multiplied by the square of the voltage. And you can charge them very rapidly. Capacitors are used in some rechargeable vehicles and some think they may displace batteries as the storage medium in most electric vehicles some day.
the case is molded around the terminals, and as the battery gets old electrolyte can seep out. once it hits the copper cable it starts corroding it into a copper sulfate salt, thus why it’s blue-green.
missed the edit window- the reason they start seeping is that vibration and thermal cycling loosen the “grip” that the molded plastic case has on the lead terminals, so electrolyte has a chance to find its way through and onto the cable/clamp.