Never heard of CTEK tenders but wil keep an eye out for them. It appears to be a proven technology so I'm not surprised to see other companies jump on this bandwagon.
I've never had any luck saving a battery that will not take a full charge. Battery tenders have done great for me making the battery maintain it's charge but they don't seem to charge a battery that is down, not charged. You might put as full of a charge as you can on it with your regular charger then put the battery tender on it. that should maintain whatever charge it took. I'll be shocked if it brings it back to full charge. Please let us know how it goes. Things might have improved since I tried doing the same a few years ago.
I've never had any luck saving a battery that will not take a full charge. Battery tenders have done great for me making the battery maintain it's charge but they don't seem to charge a battery that is down, not charged. You might put as full of a charge as you can on it with your regular charger then put the battery tender on it. that should maintain whatever charge it took. I'll be shocked if it brings it back to full charge. Please let us know how it goes. Things might have improved since I tried doing the same a few years ago.