The reason why battery voltage drop under load?
Good afternoon!Today I found a essay talked about the reason why battery voltage drop under load and I can't wait to share with you.I hope it also will bring you some help.
Many people find that battery voltage often drop under load.There are some my opinions.First,there's no such thing as a perfect voltage source, everything (that doesn't super-conduct) has resistance and resistance means you lose a bit of your no-load voltage when current starts to flow.
Second, the lower cut-off voltage is not an exact figure, there's a bit of a trade off between the lower cut-off voltage and the battery lifespan, but below 2.5V there are some irreversible chemical reactions that occur that wreck the battery permanently. Lead-acid car batteries have similar issues (but for different reasons). I don't fully understand what reactions take place when you fully flatten a Li-Ion battery although I think there are a few kinds of lithium intermatallic compounds formed that once formed, don't then easily uniform. Much like how with Lead-Acid batteries you get sulphation on the plates (not all chemical reactions are easily reversible, it's very hard to unrust a lump of iron).
What's more,as for the maximum charging voltage, you run the risk of forming metallic Lithium "whiskers" among other unpleasant things) which can puncture the electrode separator and lead to a short circuit. Seeing as Li-Ion short circuits tend to involve copious amounts of current, lots of heat is usually generated too, and heat + Li-Ion electrolyte = boiling and fire, and once air gets in, the Lithium catches fire too. 4.2V just happens to be the voltage required to fully charge a Li-Ion battery and any more voltage will start to cause unwanted side reactions. There are a variety of electro-chemical reactions that don't really get started unless there's a certain voltage gradient present. There's a similar limit in Lead acid batteries, apply too much voltage and you start to electrolyse the water into Hydrogen and Oxygen gas which (seeing as it'll be in the perfect 2:1 ratio) is highly explosive and will eventually result in all the battery's electrolyte drying out and more of those unwanted one-way chemical reactions.
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