Let me start by saying these EBL rechargeables saved my kid's baseball pitching machine from becoming a very expensive paperweight. The 10,000mAh D cells last through multiple practice sessions, though I did notice our LED lantern dims slightly faster compared to alkalines.

The charger itself feels like a sci-fi gadget with its LCD display showing real-time progress bars. I particularly love how it automatically switches to trickle charging - though be warned, this sometimes makes batteries appear 'not fully charged' if you immediately recheck them (customer service explained this is normal for their tech).

Where things get interesting is compatibility. Learned the hard way that these are strictly for 1.2V devices after they failed to power my vintage radio. The plastic battery cases? Nearly needed a crowbar to open them initially - now I just store batteries loose in a drawer.

For AA/AAA performance, they outlasted my old Energizers in TV remotes by weeks. But in high-drain devices like fans, expect about 30-40% shorter runtime than premium alkalines. The charger's discharge mode is brilliant for battery maintenance, though the single button interface means I've accidentally triggered it mid-charge more than once.

After six months of cycling through four sets: two batteries developed significantly reduced capacity while others still charge to about 90% original. Not perfect, but considering I've recharged some units over 50 times already, the economics still work in favor versus disposables.