The OpenROV team and community have been experimenting continuously with different battery configurations and chemistry. We are ready to publish our conclusions about what we think will be a better source of power for OpenROVs.
What you need to know in brief:
- We're changing our recommendation to safer, more reliable batteries
- The new batteries will work with all 2.5, and 2.6 ROVs but require an adapter (see below), new ROVs acquired through our webstore will include adapters
- The new batteries use the same charger as the old batteries but with caution (see below)
- The new batteries, chargers, and adapters can now be found on the webstore
We're changing our recommended batteries!
For the last few months we've been recommending the Trustfire 26650 Li-Ion batteries to our users. These batteries are commonly available, offer good charging and discharging profile and contain a protection circuit. While these batteries perform well under laboratory conditions there were two main problems with them in practice. First, the protection circuitry was too sensitive for us and this would frequently trip and require a reset. Many ROV users have experienced this symptom without realizing that this was the cause. Second, the physical package of this battery is very easily compromised by water, sand, sunscreen, margaritas, and falls from moderate heights. Based on feedback from the community and tireless in-house testing we're now recommending a different battery chemistry.
Enter the Batteryspace Li-FePO4. Switching from a Li-Ion to a Li-FePO4 chemistry is good for a number of reasons. They are more reliable, safer, and have a better charging cycle lifespan.
These batteries will work inside existing 2.4, 2.5, and 2.6 OpenROVs.
The Li-PO4 batteries have two main drawbacks. One, they are slightly shorter than the Li-Ions. Two, they don't have a built in protection circuit. In order to solve both these problems, we've developed a battery adapter with a polyfuse built in. The polyfuse will protect against over-current situations and the adapter's arrangement will mean that users wanting to use the new battery configuration can do so without rebuilding their battery tubes. The battery adapter build instructions can be found on our dozuki's upgrades page, here.
The new batteries use the same charger as the old batteries, but LOOK OUT FOR THIS:
Charging the Li-FePO4 batteries is the same as the Li-Ion batteries from Trustfire. BUT: the battery chargers must be set to the lower of the two voltages (3.0V instead of 4.2V) on the toggle switch. CHARGING THE Li-FePO4 BATTERIES ON 4.2V MAY DAMAGE THE BATTERIES! Please refer to the picture below for clarification.
Safety regarding Lithium batteries should be considered.
Even though we've moved to a safer chemistry of lithium battery, these aren't things to mess around with. Regardless of whichever power source you choose to power your ROV, take time and precaution to consider the safety. Batteryspace has a great section about these batteries here.
These things are available on the webstore.
6x Li-FePO4 Batteries
Battery Tube Adapters -- You only need to buy this IF you are planning to use the Li-FePO4 batteries AND you have a version 2.5 or 2.6 with a serial number below 1200. ROVs purchased through the webstore as of the date of this post (these will have serial numbers 1200 and higher) will have these adapters included.