External laptop battery chargers

Hello,
I own an Inspiron 1720 laptop, I have used it for a few years now and not long ago the motherboard had died. So the laptop cannot take charge from the AC adaptor anymore however, it can run if the battery had power, which it doesn't now. Are there any external battery chargers on the market? I mean adapters that plug directly into the laptop's original battery?

If anyone can find one that's been sold online it's got to be also compatible with a dell latitude e4310 (my school laptop) and a Dell Inspiron 1545 (My younger brothers laptop)

Help would be greatly appreciated!