Almost every underwater drone has a lithium battery inside. It is powerful but delicate: charge it the wrong way, or leave it empty in the cellar for months, and you lose running time, in the worst case for good. The good news is that the manufacturers give clear rules, and they are easy to follow.
- Storage: Never full and never empty. QYSEA says 50 to 60 per cent, Chasing 50 to 70 per cent.
- Diving: For the M2 series, Chasing recommends not diving below 25 per cent battery.
- After use: Rinse with fresh water, and extra thoroughly after the sea.
- Over winter: Top it up after three months at the latest.
Why battery care matters
A battery lasts for a limited number of charge cycles. QYSEA quotes 300 to 500 cycles for its drones, Chasing at least 300 for the Dory. At the same time, QYSEA's warranty covers the battery for only 6 months or 200 cycles. Every avoidable strain therefore costs you real money.
Charging properly
- Use the original charger. That way the charging voltage is guaranteed to be right.
- Don't run it flat. For the M2 series, Chasing recommends not diving below 25 per cent battery. That is kinder to the battery and leaves you enough reserve for the way back.
- Allow for charging time. According to Chasing, the Gladius Mini S takes about 3.5 hours and the M2 S about 4.5 hours.
- Don't charge in the cold or the heat. Chasing gives an operating temperature of −10 to 45 °C. It is best to charge at room temperature.
Storing and overwintering
This is where most mistakes happen. The manufacturers agree: never store a battery full or empty.
| Manufacturer | Charge level for storage | Topping up |
|---|---|---|
| QYSEA (FIFISH) | 50–60% | once every 90 days, charge fully and then discharge again |
| Chasing (M2 series) | 50–70% | top up regularly |
For winter, that means: clean and dry the drone after the last dive, bring the battery to about half, store it somewhere cool, dry and frost-free, and put a date in your calendar to top it up after three months at the latest.
After the dive
Battery care also includes looking after the drone itself, because water and sand are hard on motors and seals:
- Rinse with fresh water: Chasing recommends cleaning the motors and propellers with clean water after every outing. After the sea, Chasing says to leave the drone in fresh water for an hour and then run the motors for about ten minutes.
- Check the motors: QYSEA advises removing dirt from the motors and replacing damaged propellers.
- Dry the connectors: Wipe water droplets off the tether connector and check the sealing ring (O-ring) for cracks.
- Keep the firmware up to date: Updates often improve battery management too.
Checklist to print
- Don't dive below 25%
- Charge at room temperature
- After salt water: soak in fresh water and run the motors briefly
- Charge to 50–60% for storage
- Top up at least every 3 months
- Store somewhere cool, dry and frost-free
Frequently asked questions
How many charge cycles does an underwater drone battery last?
QYSEA quotes 300 to 500 cycles for its drones, Chasing at least 300 for the Dory. However, QYSEA limits the battery warranty to 6 months or 200 cycles.
What charge level should I store the battery at?
The manufacturers agree: never full and never empty. QYSEA recommends 50 to 60 per cent, plus a full charge and discharge once every 90 days. For the M2 series, Chasing gives 50 to 70 per cent and regular top-ups.
How far can I run the battery down?
For the M2 series, Chasing recommends not diving below 25 per cent battery. That is kinder to the battery and leaves you enough reserve for the way back.
How long does charging take?
According to Chasing, the Gladius Mini S needs about 3.5 hours and the M2 S about 4.5 hours. It is best to charge at room temperature and with the original charger.
What do I have to do after a dive in salt water?
Chasing recommends cleaning the motors and propellers with clean water after every outing. After the sea, Chasing says to leave the drone in fresh water for an hour and then run the motors for about ten minutes.
Jot down the running time after every dive. If the figures drop noticeably over the months, you will spot early that the battery is fading and can get a replacement in good time, before it lets you down in the middle of a lake.
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