If I have a 12V 4Ah lead acid battery and use a battery charger that, let's say for example, can charge 10A, 50A, or 100A. If I theoretically turned it to 100A will the battery explode?

I understand that when you use a higher current the battery will charge quickly but due to resistance and flow of ions a lot more heat will be generated, so will this heat cause an explosion..or perhaps just a bursting of that battery spewing boiling acid?

And no I am not trying this in real life..I just recall seeing the scene in the Amazing Spider-Man 2 when Parker is trying to build his web shooters to be able to resist large amounts of electricity yet they keep exploding.

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    $\begingroup$ I exploded a button cell battery when I was little by attempting to charge it using a wall-wart electrical transformer. I had it on the couch and held it in place as the current went through it, and eventually it just burst and sprayed green sludge everywhere. I would guess that doing the same to a much larger 12V 4Ah sealed lead-acid battery using a 100A power supply, would be liable to cause a rather unpleasant rupture of the cell body, a shower of sulfuric acid, and a fairly toxic mess (unless there is a pressure-release vent on the battery). $\endgroup$ – DumpsterDoofus May 16 '14 at 0:32
  • $\begingroup$ Keep in mind that explosions happen only if the rate of energy dispersion (e.g. pressure relief valve, external cooling jacket) is much less than the rate of energy generated. In fact, atomic bombs only explode because an external "jacket" of one sort or another confines the nuclear reaction until a humungous amount of energy is generated. $\endgroup$ – Carl Witthoft May 16 '14 at 12:48
  • $\begingroup$ @DumpsterDoofus: the design of silver–zinc cells is different from from the design of lead acid cells. The main difference is that a lead acid cell has a ventilation hole to prevent accumulation of hydrogen gas, so it can harder be exploded by accumulation of a gas inside. $\endgroup$ – Incnis Mrsi Aug 16 '14 at 6:17
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    $\begingroup$ Be very careful about acting on any advice here. You could possibly end up being harmed. $\endgroup$ – Inquisitive Jan 31 '15 at 19:03
  • $\begingroup$ Calling electrical current "amperage" is like calling distance "meterage". You wouldn't ask "How much meterage is it from here to the grocery store". I edited the title :-) $\endgroup$ – DanielSank Apr 8 '15 at 23:58

Maybe it is worth bringing a comment into an answer:

Batteries have protective circuits.

The most basic safety device in a battery is a fuse that opens on high current. Some fuses open permanently and render the battery useless; others are more forgiving and reset. The positive thermal coefficient (PTC) is such a re-settable device that creates high resistance on excess current and reverts back to the low ON position when the condition normalizes.

So modern batteries are self protected from strong currents.

Here is a video though, which someone made by removing the protective circuits and using high charging currents on lithium batteries.

Uploaded on Aug 15, 2010

Two lithium ion batteries exploding due to overcharging. This isn't to show that lithium batteries are unsafe. I just got bored and decided to blow up a couple cells from an unused battery I had lying around by removing their circuit protection. Explosions are a lot of fun.

And here is an advertising video for safe sheds for charging lead acid batteries, and yes, they do explode when overcharged.


Supposing that the charger gives the voltage greater than 12 V (say, 15 V), we can estimate 15 V × 100 A = 1500 W, a power of a small electric kettle. It is insufficient to effect an actual explosion quickly, but the battery will possibly immediately start to spew the acid mixed with hydrogen bubbles (note that hydrogen is flammable).

Another question in: would the charger really generate 100 A in this situation? The small lead acid battery certainly has a higher internal resistance than a bigger one, for which charging at 100 A may be desirable. The charger might have some current stabilizer, but if it is a specialized 12 V battery charger, then its designers were aware that it isn’t helpful to apply, say, 28 V to such a battery. Probably, there is a transformer and a rectifier inside, and when you connect the transformer to the mains (that have a fixed AC voltage), the output has some definite maximal voltage. Even if there is a switched-mode power supply that is technically capable to raise the voltage beyond reasonable values, it won’t necessarily do it. So, in a plausible scenario the current through the battery will be constrained by its resistance and the power input will be much less than 1500 W.

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    $\begingroup$ And of that 1500W input, of course quite a few W will still be used to charge the battery. It's the excess power which generates the hydrogen gas and heat. $\endgroup$ – MSalters Aug 14 '14 at 15:22
  • $\begingroup$ have a look at youtube.com/watch?v=SMy2_qNO2Y0 where the protective circuits were removed. $\endgroup$ – anna v Jan 15 '16 at 6:44
  • $\begingroup$ Would the charger really push 100A? Depends on the charger. There is some voltage which, if forced on the terminals of the battery, would result in a 100A current. What that voltage is, I don't know, but if you asked me to design a 12V, 100A, wet-cell battery charger; l would absolutely limit the output voltage to 14.7V. You would only be able to draw 100A from my 100A charger by hooking it up to a much larger battery than the one in the question. $\endgroup$ – Solomon Slow Feb 16 '16 at 18:18

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