I have a habit of unplugging my husbands electric shaver from the wall socket but leaving the charging cord plugged into the shaver. He insists that this is very hard on the battery and will ruin the shaver. I call BS.
He says this applies to any device that uses a charging cord. Is there any merit to this?
I call BS too. If the cord is not plugged into the wall, the shaver is getting nothing from the cord. It’s invisible to the shaver.
Does he think that electrons are leaking out of the end of the cord?
It might cause undue stress on the connector on the device having it hang off like that, but as far as the charge on the battery, no, that would have no effect.
Some very cheap and simple battery chargers can be back-powered by the battery and thus drain the battery if left connected, but I have only seen evidence of this in cheap rechargeable flashlights and not in any typical retail device.
What’s on the end of the cord that plugs into the wall? Just prongs that fit the socket? Or is there a “wall wart” that resembles an over sized plug or black plastic box?
GaryM
I would think that one of the first things that the power passes through when it gets to the shaver is a diode, possible even a few of them. That should prevent any current from going backwards.
If the plug from the wall, to the device, there’s one for sure, it’s part of a rectifier to supply DC voltage to the battery. If there’s a wall wart, then that current going backwards would have the potential to supply 120v to the prongs sticking out of it.
I understand what he’s talking about, but I don’t believe it. The only thing I could see as being an issue is if it had something to recognize that the shaver had the charger plugged into it and woke up some smart charging circuity. But I doubt even that’s the case.
What’s probably happening is that you leave it unplugged and the battery goes dead before he has a chance to use it (or sooner than he expected). My ex used to do that, drove me nuts, I ended up just installing some extra outlets in the bathroom, I got sick of saying ‘could you please plug my toothbrush/shaver/whatever back in when you’re done’.
Your husband’s complaint triggers vague memories of best practices for using NiCd batteries. That might have been due to concerns of fluctuating voltage (which is allowed by NiCd chargers, but should be eliminated in lithium chargers), or it might be due to battery memory (again, a thing with NiCd but not relevant with lithium), but it was certainly decades ago and not relevant to today’s consumer appliances. So I’d say yes, but only pedantically in response to the “any” part of the question.
I can also recall being taught (which I’m aware is not the most reliable cite) that devices should be unplugged from the power adapter first, wall second, and plugged in wall first, adapter second. This ensures that the device doesn’t see the voltage spikes and drops that occur when the adapter is stabilizing. A good adapter won’t have significant problems and a good device will be able to filter them out if they occur, but it is cheap insurance against some forms of failure. That has nothing to do with batteries, though.
That said, I remember getting a half shave one morning because the shaver’s battery died. Surprises like that are never good. I mean, with a dead electric toothbrush, you can still brush your teeth; with a dead shaver, the best you can hope for is a bit of sporadic plucking. Now I happily use manual blades, but I can still relate to being irrationally protective of such devices.
Just prongs.
Then it really doesn’t make any difference. All you’re doing by having the cord plugged in is extending the prongs that are recessed into it. That’s it, nothing else. You’re not adding any electrons and, more importantly, you’re not completing any circuits.
If there was a transformer/wall wart/‘power adapter’ on the other end, it would make a circuit on the secondary coil which is why the question was asked. But it’s moot now.
As an example, it would be like saying that you’re hurting the vacuum when you leave the extension cord plugged into it when it’s not plugged into the wall, when in fact, all that does is make the cord longer. If it’s not plugged in, the vacuum, or shaver, doesn’t even know the cord exists.