External battery charger for 17" (a1189)

[iceHorse]

Hi Guys,

Sometimes I have to keep working through power blackouts. I'm wondering if this approach would be safe:

Plug an external battery charger something like this Dekcell:

http://www.amazon.com/gp/product/B001O3VN62/ref=ox_sc_act_title_1?ie=UTF8&smid=A151D61AL6T7YU

Into one of those external-battery-car-jumper things like this DieHard:

http://www.amazon.com/DieHard-71988-Starter-Portable-AC-DC/dp/B001UOND90/ref=cm_cr_pr_product_top

Then plug my laptop battery into the Dekcell?

Any EEs in the audience?

Thanks!