Tattu (Marke von Grepow) UHV 41000mAh 6S 5C 23.7V UAV Classic

The Tattu UHV 41000mAh 6S 5C 23.7V UAV Classic is an ultra-high-voltage LiPo battery from Tattu, a Grepow brand, for mid-size multicopters. Six cells in series give a nominal 23.7 V at 41 Ah; UHV means the cells reach 4.45 V instead of 4.2 V when fully charged, so the full-charge voltage of the pack is 26.7 V. The connector is a QS8.

23.7 V and 41 Ah give 971.7 Wh; at 3,790 g that is about 256 Wh/kg at pack level. The maker's figure of 280 Wh/kg is higher, and the calculated value is the one to compare. The name quotes 5C, which on 41 Ah would be roughly 205 A; 60 A is given as the maximum continuous current, and those 60 A, about 1.4 kW, are the cautious planning value. With a low current demand and a great deal of energy, the pack is designed for flight time.

971.7 Wh is far above 160 Wh. Under the IATA passenger leaflet (February 2019 edition) the pack travels only as dangerous-goods cargo, not as a spare in hand baggage; UN 38.3 testing is the precondition, and airline rules may be stricter. At 3.79 kg the pack lies just below the 4 kg that an entire aircraft of EU class C2 may weigh and in practice belongs in aircraft of classes C3 and C4.

The charger must support the 4.45 V cells; a standard profile to 4.2 V leaves capacity unused, and a profile set too high on ordinary cells overcharges. In selection the continuous current of 60 A must cover the hover current with reserve. Wear shows as growing voltage sag, swelling and cell drift at the seven-pin balance lead. After knocks and dents the pack is not charged again. Storage is in the middle of the charge range as the maker specifies, in a cool place and protected against pressure.