I don't use or own a battery tender. The jump starter pack I use is an Autowit SuperCap. It cost me a little over a $100 and has worked so far in the 3 times I've used it on 3 different vehicles. It does not have it's own battery, but can charge off a weak, but not dead battery, a wall outlet, or a USB port. It's lightweight and handy.
You only get one shot per charge, but so far it has had enough power to start with that one shot even on one car that had a totally dead battery. I wouldn't rely on it when alone out in the boonies where you might not be able to charge it, but around town it gets the job done with the downside being you need to wait for the capacitors to charge full, which can take 5 minutes or so from a battery and longer if you need to plug it into something else.
