• the energy density is higher than that of lead-acid batteries, and the weight is relatively light.
• Long cycle life and good durability.
• It has certain discharge depth capability and high safety performance.
• Environmental protection, no heavy metal pollution.

Disadvantages

• the self-discharge rate is relatively high, and regular charging is required for long-term storage.
• High requirements on charging management.
• The price is higher than that of lead-acid batteries.

Applicable scenarios

it is suitable for small and medium-sized ROVs with certain requirements on performance and environmental protection, especially for applications with certain requirements on battery life.

3. Lithium ion battery (Li-ion)

features

lithium ion battery has become the mainstream choice of ROV battery system due to its high energy density, light weight and excellent charge and discharge performance. Its voltage platform is stable and can meet the demand of high power output.

Advantages

• high energy density, small size and light weight greatly improve the endurance and mobility of ROV.
• Long cycle life and high charge and discharge efficiency.
• Low self-discharge rate, suitable for long-term storage and use.
• No memory effect, flexible charging.

Disadvantages

• the cost is relatively high, and the manufacturing and maintenance costs are relatively large.
• The charging and use management requirements are strict, and a battery management system (BMS) is required to prevent overcharging, overdischarging and temperature abnormalities.
• Sensitive to ambient temperature, thermal management is required.

Applicable scenarios

4. Lithium polymer battery (Li-Po)

features

lithium polymer battery is a deformation of lithium ion battery. It adopts solid or colloidal electrolyte to make the battery lighter and more flexible in shape.

Advantages

• the shape design is flexible, and the size and shape can be customized according to the internal space of the ROV.
• High energy density and light weight.
• Fast charging speed and stable performance.

Disadvantages

• the cost is relatively high and the manufacturing process is complicated.
• The safety is less than that of lithium ion batteries, and strict protection measures are required.

Applicable scenarios

suitable for light ROVs with strict space and weight restrictions or specially designed underwater unit load device.

5. Lithium Titanate battery (Li-Ti)

features

lithium Titanate battery uses lithium titanate as negative electrode material, with extremely fast charging capability and extremely long cycle life.

Advantages

• ultra-high safety, high temperature resistance and strong overcharging ability.
• The cycle life is extremely long, which is suitable for frequent charging and discharging environment.
• The charging speed is fast and can be filled in a few minutes.
• Wide operating temperature range.

• the energy density is lower than that of lithium ion batteries, and the volume and weight are larger.
• The cost is relatively high and the manufacturing process is complicated.

Applicable scenarios

it is suitable for ROV systems with extremely high requirements for safety and high-frequency charging and discharging, especially for high-end applications in industrial and scientific research fields.

III, battery comprehensive Considerations for selection

in addition to understanding the basic characteristics of battery types, we also need to make comprehensive trade-offs based on specific application requirements when selecting ROV batteries:

• battery life requirements
  high-capacity batteries are required for long-term operation, and lithium ion and lithium polymer batteries are more suitable.

• Environment complexity
  the sealing and safety of batteries in deep sea and high pressure environment are particularly important, and the battery type with higher safety performance needs to be selected.

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Cost budget
if the budget is limited, lead-acid batteries or Ni-MH batteries can be considered, but performance losses need to be weighed.

• Size and weight limits
  it has a significant impact on the mobility of ROV and must give priority to lightweight and high energy density batteries.

• Charging and maintenance convenience
  industrial-grade ROVs are often equipped with perfect battery management systems to ensure safe and stable operation of lithium batteries.

The choice of ROV robot battery directly affects its performance and operation efficiency. Lead-acid battery and Ni-MH battery have low cost, but their energy density and life span are limited; Lithium ion and lithium polymer battery have become the mainstream choice with their advantages of high energy density and light weight; lithium Titanate batteries are outstanding in terms of safety and service life, and are suitable for high-end applications.