Review on 🔋 NOCO GENIUS2X4 Smart Charger: 4-Bank, 8-Amp (2-Amp Per Bank), Fully-Automatic Battery Charger & Maintainer for 6V and 12V Batteries. Includes Trickle Charging, Desulfator, and Temperature Compensation by David Flores

Despite claiming that this device can charge up to 40Ah and will service ANY size battery, by design this product will NOT support more than the rated charge. I bought the device specifically for servicing 4 batteries throughout the winter. A lawnmower battery and a small car battery worked fine, but two fully charged 50Ah and 70Ah deep cycle batteries could not be supported by this unit. The device enters charging mode every time it is switched on. With large batteries, even at 100% state of charge and 97% state of health, the device is never satisfied with the state of charge. It stays in charge mode for 5 consecutive days while the batteries are heavily drained, never reaching the optimization or maintenance stages. After 5 days, the safety timeout will be triggered and the device will turn off with a low battery icon. NOCO support offered me shipping under warranty when they "tested" the unit and then sent me a new unit. The new block has the same problem as the old one, because it's a design flaw, not a defect. All of these troubleshooting steps got me past the return window. I think the product has decent build quality but it doesn't work as advertised.