Can I use the chargers interchangeably on the computers? Are there any concerns, side effects? My assumption is that using the 65w on the T400 will take longer to charge the battery. More importantly, I would like to know if there will be any damage if I use the 90w charger on the T430S.
You can interchange them without harming either ThinkPad. Note that there will be limitations with a 65W adapter:
1. It will take longer to recharge the battery.
2. It may not be powerful enough to power/recharge certain configurations, e.g. with i7 processors and/or discrete graphics processors.
3. It may not be powerful enough to power/recharge certain types of usage, e.g. when watching a DVD while at the same time running HDD intensive applications.
4. Certain features, e.g. RapidCharge on the T430s, won't work.