Electronics > Beginners
Curious warning printed on a power bank
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tkamiya:
Poor performance or out of spec products are one thing but total disregard for safety is very maddening.  This behavior does not seem to be limited to electronics.  Today's battery has so much energy density, when they burst, they burst like explosives. 

All of my UPS uses sealed lead acid batteries.  They are at least predictable in failure modes.  (like come home and all unix servers are down....)
edpalmer42:

--- Quote from: magic on March 25, 2019, 08:17:30 am ---
--- Quote from: edpalmer42 on March 24, 2019, 05:43:09 pm ---I've seen one cheap speaker/media player that charges from USB and has a small Lithium internal battery.  A label says (translated from Chinglish) to limit the charging time to 3 - 5 hours.  When I looked inside, all they did was put a single diode from +5V to the battery.  This gives about 4V3 which is close enough for them.   :--

--- End quote ---
Not even a zener?

I suppose the 4.3V is regulated by some internal battery protection circuit then but still... that's just pathetic. And it overcharges the cell so lifetime may be reduced.

--- End quote ---

No, there's no battery protection circuit.  The 4V3 is close enough to the maximum Lithium charging voltage of 4V2 that, as long as you remember to limit the charge time to the specified 3 - 5 hours, the battery probably won't explode - at least for a year or two!  But don't worry, the battery is small so it probably won't shatter the case!  :palm:

Ed
macboy:

--- Quote from: magic on March 25, 2019, 08:17:30 am ---
--- Quote from: edpalmer42 on March 24, 2019, 05:43:09 pm ---I've seen one cheap speaker/media player that charges from USB and has a small Lithium internal battery.  A label says (translated from Chinglish) to limit the charging time to 3 - 5 hours.  When I looked inside, all they did was put a single diode from +5V to the battery.  This gives about 4V3 which is close enough for them.   :--

--- End quote ---
Not even a zener?

I suppose the 4.3V is regulated by some internal battery protection circuit then but still... that's just pathetic. And it overcharges the cell so lifetime may be reduced.

--- End quote ---
...Both its lifetime and yours, should the battery overcharge and catch fire.
amyk:
Before you scream your head off about the lack of safety, consider how many of these products are in use, and how many lion cell fires you've heard of...

4.2V was the safe maximum charge voltage for a long time, but in the past few years there have become more common cells with 4.35, 4.4, and now even some 4.5V maximum voltages.

Also look at the typical safety tests which cells are subjected to, in particular overcharging tests: https://www.jameco.com/Jameco/Products/ProdDS/2144243.pdf "Then charge the cell until voltage is 10 V(!) ... No fire, no explosion."

High-power RC lipos are another thing altogether. Those can be deadly even with all the protection.
magic:

--- Quote from: macboy on March 25, 2019, 10:14:02 pm ---
--- Quote from: magic on March 25, 2019, 08:17:30 am ---I suppose the 4.3V is regulated by some internal battery protection circuit then but still... that's just pathetic. And it overcharges the cell so lifetime may be reduced.

--- End quote ---
...Both its lifetime and yours, should the battery overcharge and catch fire.

--- End quote ---
It depends. I've heard li-ion charging voltage is specified a fair bit below their "catch fire" point because getting them close to the "catch fire" point would significantly reduce lifetime.
People on RC forums (of course) experimented with it and found that some cells can take 50~100mV above their spec and still work reliably and deliver some % of extra juice.

Of course  :blah: it's not recommended  :blah: do on your own risk :blah:
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