[MadMax]

Ouch. That's a silly mistake for TM to make. Japanese mains are 100V. I would have thought that they would have manufactured product for the export market which could handle 240/120VAC.

The little "brick" charger that comes with the G18c appears to be a transformer type adaptor. Not one of the nice new switch mode power supplies which often include universal input circuitry. I would not recommend using it at North American mains voltage.

Transformer type adaptors rarely come with peak detection circuitry for cost effectiveness. I would guess that they use a timer instead. IRC, the output from transformers tends to be more noisy than high frequency switch mode regulated supplies which makes them less amenable to peak detection in the same package.

I don't know where you get 2-3% increase in charge rate. If the input voltage is increased by 20%, the subsequent open cct output voltage is also increased by 20%. IRC the ratio of the battery's internal resistance and the impedance of the transformer will not vary by charge rate at the beginning of charge. This means that you can expect 20% more current flow during the first half or so of battery charge.

20% increased voltage and 20% increased current corresponds to 44% increased power (voltage*current). I would guess that TM wouldn't release a power supply with less than 100% safety margin, but 44% certainly does eat into that margin significantly. Extenuating circumstances like poor airflow or plugging into a power bar crowded with overheating bricks will reduce this margin further. I also note that the G18C brick is manufactured in China. I wonder if it is properly specified.

As a side note, we may be confusing Vp-p and Vrms in this discussion. In general Vp-p is used in discussions for appliance and accessory specifications. Actually I'm not sure if my calculations are correct. IRC I have to convert to Vrms if I want to work with power.