Useful and high quality 4-series Li-Ion battery charger power supply (16.8V). It works fine. Normal delivery time. I strongly recommend the seller and product.
Relatively decent delivery: 20 Work days. Ordered Sep.11, 2018 Received Oct.10, 2018, but wasn't fully tested until Nov.5, 2018 Barrel plug checks 5.5x2.1mm as listed. LED lights up green and voltage checks 16.75v Works OK: tested to charge 4S 18650 battery pack with 4S BMS, Enhanced Version found here https://www.aliexpress.com/item/4S-40A-Li-ion-Lithium-Battery-Protection-Board-18650-Charger-PCB-BMS-For-Drill-Motor-14/1000005344408.html?spm=a2g0s.9042311.0.0.27424c4d2JPTGc When battery pack falls below 16v, charger LED turns RED, indicating that it's in CHARGE mode. Once battery pack is charged above 16v, charger LED turns GREEN. Overall, this charger seems to do the job that it was intended to, when mated to a working 4S BMS.