A fuse at the output of a PSU is a bad idea because it increases the PSU's output impedance which may be bad for other purposes.
Err, just put it in series with the battery. No need to permanently modify your supply.
That is not what Chipguy and Kleinstein suggested in their earlier posts!
The picture from the bench filled with -appearantly- Li-ion cells and heaps of lose wires just makes me cringe. But maybe I'm too old and no longer thrilled by the idea that something I do could set the house on fire and kill the inhabitants. Think about someone who enters the room and somehow causes a short circuit (bumping the table while cleaning, knocking something over, pulling a wire, etc).
Lets face it, different people have different attitudes about their personal risk aversions with the actions they take with the hobbies and work they do. I know that probably driving is the biggest personal risk I face but I accept the randomness of the universe I find myself in. 
Yep, and in the EU, most houses are built much more rigid than those U.S. energy-wasting, thin-walled houses, made from wood, which also burn down by igniting LiPos much easier than especially here in GER.
And the traffic in GER is also much more dangerous than in U.S. because everybody is speeding like crazy.
Sorry, couldn't resist to add a few more prejudices.
Frank
So, should i send one or two of my selfmade (#13) 18650 chargers to Dave?
I'd prefer a choice of charging options in the phone config menu:
1) Charge to 4.2V - get maximum time between charges
2) Charge to 4.1V - get maximum battery longevity
Newest Sony Xperias reportedly have a mode where they "learn" your charging habits and, when connected for the overnight charge in the evening, will charge their battery quickly up to 90% , then sit and wait until morning, and only then top it up to 100%, just before you're awake. Smart.
Especially that impedance thing would become a never ending story haunting both, forum and YT comments for eternity
I've noticed this on my previous battery videos (and I have a lot of them). I still get email from 5 year old videos.
i don't know what it is about batteries...
Battery related topics seem to attract the free energy/overunity crowd like honey attracts bees.
I think this is the reason there's so much bad info on batteries that has persisted for so long, such as desulfation or the "memory effect".
I think this is the reason there's so much bad info on batteries that has persisted for so long, such as desulfation or the "memory effect".
NiCd memory effect is not bad info, it was like that at the time (15 yrs ago (?)).
I think this is the reason there's so much bad info on batteries that has persisted for so long, such as desulfation or the "memory effect".
NiCd memory effect is not bad info, it was like that at the time (15 yrs ago (?)).
The memory effect would emerge only after a set of several, very specific conditions were met.
It was very hard to reproduce in a lab and practically impossible to arise on a consumer device.
What people would atribute to the memory effect was in fact the normal battery degradation due to exceeding maximum charge cycles or otherwise mishandling the battery.
I think this is the reason there's so much bad info on batteries that has persisted for so long, such as desulfation or the "memory effect".
NiCd memory effect is not bad info, it was like that at the time (15 yrs ago (?)).
The memory effect would emerge only after a set of several, very specific conditions were met.
It was very hard to reproduce in a lab and practically impossible to arise on a consumer device.
What people would atribute to the memory effect was in fact the normal battery degradation due to exceeding maximum charge cycles or otherwise mishandling the battery.
I believe NASA discovered this problem in early Nicads in some early satellite battery failures. Some kind of whisker growth that would limit battery capacity. Solved by a manufacture process correction many decades ago but the myth of continued 'memory effect' seems to always live on.
Well, i guess certain people forget Ohms law with power losses. But you can better have a fuse in front of the mains than in front of your battery. Assuming the fuse has the same resistance P=I^2*R.
The current on the mains side is much lower, therefore the losses are much lower.
This is the same reason why working on a 115Vac mains voltage is resulting in much more losses (or thicker copper wires).
Overall, relatively speaking for just the battery power supply, it's a little far fetched. Maybe you safe 1-2% at most. Really something that keeps you awake all night.
The current on the mains side is much lower, therefore the losses are much lower.
A fuse on the output won't make much difference to a battery charger.
For most of the charge cycle you're in constant current mode so the fuse is mostly irrelevant. When you switch to constant voltage mode the current drops very rapidly towards zero. Small current means very little voltage loss.
Well, i guess certain people forget Ohms law with power losses. But you can better have a fuse in front of the mains than in front of your battery. Assuming the fuse has the same resistance P=I^2*R.
The mains fuse doesn't prevent a battery to set the secundary side of a PSU on fire. What fuses do is prevent fire by offering a defined, safe and controlled weak spot. They don't prevent electronic parts (especially semiconductors) from breaking because fuses are slow. So yes you'd need either a diode (preferred; see Rigol's document) or at least a fuse when charging a battery from a PSU. BTW chances are a PSU will activate it's crow bar or active load circuit when it sees more voltage across the terminals than expected so just use a diode.
Obviously. But why are we talking about fuses anyway?
I never said it would be a good solution to 'protect' your circuit?
If you want fast response, there are better ways.
It's also not hard to compensate for any voltage drops in these low voltage circuits.
Obviously. But why are we talking about fuses anyway?
I never said it would be a good solution to 'protect' your circuit?
What?!!
They were talking about putting a fuse between the battery and the power supply (which is a darn good idea!)
You're the one who went off on a silly tangent about putting a fuse in the primary side of the PSU...
That's not going to protect the battery from exploding if the PSU does something dumb for any reason, like essentially short out the battery due to an overvolt crobar circuit, etc... A diode and fuse is always a good idea.
The right place for the fuse would be directly at the battery holder or contact, as this would also safe you from a short in the more or less free flying cables. Just don't add unsafe cabling to tweak in a fuse.
Depending on the design of the supply, it could be possible to have one inside. The important part would be to have it in the current path only, with voltage sensing after the fuse and the fuse between the terminal and reverse protection diode and if present the crow bar. Some better supplies already have a fuse at that position.
its not about batteries, its about Lipo/LiIon. From my RC hobby, I already had two Lipos on fire personally, one of them almost burning up my house (ehmmm, should I mention not to charge them unattended...). Teslas on fire, burning iPhones and other gear hurting people, Segways in flames, airplane's possibly going down. A known of mine is selling Lipos, and he told me that he had a brand new Kokam in his stock, never touched or charged it, and it just caught fire in the shelf. Probably manufacturing defect.
I remember reading in Practical Electronics magazine about LiIon battery technology (long before they were in domestic devices) and the article said they would never be in domestic use due to the fire risk of them. There seems to have been quite a few incidents recently with devices catching fire. Recently in the east of England a womans mobile phone caught fire in her hand and it wasn't being charged at the time either.