Why can't I find an external laptop battery charger?

[eflat]

I can't find one for a Dell battery. I would think these would be really popular since you could always have a fully charged spare to take with you.

 

[corkyg]

I always have a fully charged spare to take with me as it is. Just rotate batteries the day before you depart. No need for another charger.

Perhaps if notebook batteries were more standardized, such a niche market would be profitable. As it is now, only a fraction of each type (dozens of them) would constitute the market. It would not be profitable.