Trickle charging "not to be used" yet it is the reccomended circuit on datasheet

[ricko_uk]

Hi,
with respect to the attached datasheet, at the bottom it says "Under no circumstances trickle charging should be used".

But just below it they show the schematic of trickle charging saying it is the right charging circuit.

Can someone please explain?

Thank you

[Manul]

Trickle charging is feeding current with a compliance voltage above battery max charge voltage. Notice that the crossed out "wrong" circuit has a source voltage of 5V, thus there will be some charge current going even when battery voltage reaches it's maximum 3.55V. In the second circuit, with 3.6V source and a diode it is impossible. So second circuit is by definition not a trickle charger, it will never try to push the battery above 3.55V.

[CatalinaWOW]

Reread the datasheet.  Take every line literally.  The problem is allowing the voltage to rise above 3.4 +/- 0.15 volts.  See note 1 above the schematics you reference.

The two schematics are different in an important aspect.  The left, a classic trickle charge concept has a 5.0 V supply and a resistor to limit maximum current.  The right circuit has a 3.6 volt supply with a diode in series.  For all practical purposes it keeps the voltage from rising about the specified limits.  There will be sufficient leakage in all but very rare cases to keep the diode drop higher than 0.05 V.

The left circuit would be totally acceptable if the supply was 3.4 V.  It might not meet all folks definitions of a trickle charge circuit under that condition.

[SiliconWizard]

Yes the caution title is to make sure readers notice it, but you need to read the whole paragraph to understand what needs to be taken care of.
It's trickle charging with any circuit allowing the cell voltage to rise past the maximum recommended, which is 3.4V (I would personally recommend not exceeding 3.2V for ensuring longer lifespan), that is to be avoided.

So, in current terms, we would call that paragraph's title a clickbait.

[ricko_uk]

Thank you all!

That now makes sense.

[amyk]

These are cells meant to be float-charged, i.e. kept at the full voltage most of the time.

Note that "1000 cycles at 10% discharge" spec - these aren't meant to be fully charged and discharged like most other cells are, and are intended for backup power.

[ricko_uk]

Thank you Amyk,
yes I am using it as a RTC backup battery.