Portable Ultrasound Device Battery Selection: NiMH Vs 18650 Lithium Battery

Portable Ultrasound Device Battery Selection: NiMH vs 18650 Lithium Battery

1. Energy density and battery life

18650 Lithium Battery:

High energy density (200~300Wh/kg), longer battery life at the same volume, suitable for scenarios that require long working hours.

High voltage (3.6V), fewer batteries in series, simplified circuit design.

NiMH Battery:

Low energy density (60~120Wh/kg), larger volume and weight, may affect portability.

Low voltage (1.2V), more batteries in series, may increase design complexity.

Conclusion: If battery life and lightweight are required, 18650 Lithium Battery is preferred.

2. Life and number of cycles

18650 Lithium Battery:

Cycle life is about 500~1000 times (deep charge and discharge), but protection circuit is required to prevent overcharge/overdischarge.

NiMH battery:

Cycle life is about 500 times (high-quality models can reach 1,000 times), strong resistance to overcharge/overdischarge, and simple maintenance.

Conclusion: If the device needs to be charged and discharged frequently and the maintenance conditions are limited (such as remote areas), NiMH batteries may be more reliable.

3. Safety

18650 lithium battery:

There is a risk of thermal runaway (high temperature and short circuit may cause fire), and strict protection circuit and temperature management are required.

NiMH battery:

Better resistance to high temperature and overcharge, higher safety, suitable for sensitive scenarios such as medical equipment.

Conclusion: If the device is used in a high temperature environment or has extremely high safety requirements (such as medical emergency), NiMH batteries are more reliable.

4. Temperature adaptability

NiMH battery:

Good low temperature performance (-20℃~60℃), suitable for outdoor or extreme environments.

18650 lithium battery:

Low temperature capacity attenuation is obvious (efficiency decreases below 0℃), and high temperature is prone to aging.

Conclusion: If the equipment is used in cold areas, NiMH batteries have more advantages.

5. Cost and maintenance

18650 lithium battery:

The single cell cost is higher, but the energy density advantage can reduce the number of batteries, and the long-term cost may be lower.

NiMH battery:

The single cell cost is low, but more battery packs are required, and maintenance is simpler (no complex BMS requirements).

Conclusion: NiMH batteries are more economical when the budget is limited or the design needs to be simplified.

6. Environmental protection and recycling

NiMH batteries do not contain heavy metals (such as cobalt in lithium batteries), are easier to recycle, and meet the environmental protection requirements of medical equipment.

Comprehensive recommendations

Scenarios where 18650 lithium batteries are preferred:

Long battery life and light weight are required (such as frequently moving medical inspections).

The equipment has a complete battery management system (BMS) and heat dissipation design.

Use at normal temperature.

Scenarios where NiMH batteries are preferred:

Safety is the first priority (such as emergency equipment).

Extreme temperature environment (polar regions, outdoor).

Maintenance conditions are limited or batteries need to be replaced quickly.

Additional considerations

Hybrid solution: Some equipment can adopt the design of "lithium battery main power supply + nickel-metal hydride backup" to take into account both battery life and emergency safety.

New battery: Lithium iron phosphate battery (LiFePO4) can also be evaluated, which has a safety level between the two and a longer life.