This phone from Xiaomi has a large 5,000 mAh battery. Kid-friendly features and durable design make it perfect for young users, but it's also a great secondary phone.
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Xiaomi Redmi 10A 4G 128GB + 4GB Factory Unlocked 6.53" 13MP Camera (Not Verizon Sprint Boost Cricket Metro At&T) + (w/Fast Car Charger Bundle) (Graphite Gray)