Battery packs

I'm looking at buying a jump start battery pack from super cheap purely as a back up incase my vehicle has a flat battery. We are towing a van and don't have a second battery although do have a relay so the van won't run the car battery flat.
My question is are the large heavy duty by jump start portable batteries the way to go or are the new lithium battery packs better ?
If you have a lithium battery pack could you let me know which one you bought and the approximate cost and if they have fail or are definitely worth while
Thanks in advance
Back Expand Un-Read 0 Moderator

Sponsored Links