Hair trimmer needs 110VAC to charge battery...need to modify

[ocset]

Hi,
I have purchased a Hair trimmer which turns out to need a 110VAC input to charge its battery. I am in UK.
(It cost me £3.78 plus £10.99 P&P)

“Nova NS2218” Hair trimmer
Amazon (Nova NS2218 hair trimmer)
https://www.amazon.co.uk/gp/product/B087M7CQBD/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

The battery is a 1.2V, NiCd, 450mA , 2/3AA size

Anyway,  I’m  going to  surgically alter it and charge the battery via a  5V ACDC adapter plug, and put  in a 120R series resistor to limit the charge current. (plus a reverse  polarity diode).
That would give an approx.  25mA charge current. Do you think if I accidentally leave it charging for days, then this current won’t result in overcharge destruction of the NiCd?

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(Strangely, the  charger electronics in the product has a 22k series resistor , in series with a series rectifier diode,  which would limit the charge current to  some  2.5mA  average…wouldn’t  that low charge current just be used up by the battery’s leakage current?)

Without a scope or inductance meter i cant give the entire schematic of the "as sold" product,  but its something along the lines of the attached

[amyk]

NiCd can be trickle-charged indefinitely. The original charger is just a rectifier and dropper resistor in series with the mains --- for 240V operation you can add a second 22k in series.