EVPeak CQ3 AC 100W Quad balance charger/discharger. RRP new $299 each. 7 units available. $75 each.
These units charge 4 battery packs with various chemistries (LiPo/ LiHV/ LiFe/NiMH/ NiCd/ Pb) simultaneously. 'It supports 1-6 cells LiPo/LiHV/LiFe batteries and 1-15 cells NiMH/NiCd batteries.' Often used for Drone battery charging.
Seven units available here are all second-hand. Four units appear to function as intended, but have not been extensively tested. Three units have some defects, as outlined below. Hence the cheap price. All units power-up. All charge on some ports if not all. All sold as is.
unit 5: port 4 has battery cell error. 1 -3 seem okay. unit 6: port 1 faulty menu/error. fan always on. unit 7: port 1 and 3 misread voltages.
Product Specs here https://www.ev-peak.com/prodcuts-item/ev-peak-cq3/