The cost of custom sodium-ion batteries can vary widely based on specifications, quantity, and complexity. It's important to work with a battery manufacturer to get an accurate cost estimate based on your project requirements.

Safety features can include thermal management systems, overcharge and over-discharge protection, short-circuit prevention, and cell-level monitoring to ensure safe and reliable operation.

The specifications for a custom sodium-ion battery depend on factors like voltage, capacity, size, weight, operating temperature, cycle life, and discharge rate. Working closely with a battery manufacturer or engineer is essential to define the exact requirements.