I first learned about the P-Squared Group and their great little LiPo Smart battery chargers for the DJI Phantom 2 and Phantom 3 quadcopters at the InterDrone conference in Las Vegas this year. They loaned us one of their chargers for the Multicopter Warehouse booth I was working out of and we were totally blown away by how fast we could charge 4 Phantom 3 (P3) batteries for the demo quad we were flying in the cage!
About the P-Squared Quadchargers
The chargers are unique in that they have built-in custom-designed circuitry that intelligently charges up to 4 (four) DJI Phantom 2 or Phantom 3 smart batteries at the same time, delivering just the amount of voltage for each battery, no matter what percentage it starts off at.
- Compact and light weight: weighs just 2.5 pounds
- Fast: charges one, two, three or four DJI smart batteries in average of one hour
- Automatic battery monitoring and management ability: input current, input voltage, battery temperature
- Convenience: small, portable carrying/storage case
- Vehicle charging: available with vehicle charging cable (P2 Quadcharger only)
- Safety: auto safety cutoff
- Warranty: one-year limited
They offer two different models for each the Phantom 2 and Phantom 3 batteries – a P2 Quadcharger PRO which uses an external power supply for rapid charging, or their P2 Quadcharger GO, which you simply plug in the OEM DJI charger and walk away, allowing it to charge up all four batteries safely in the same amount of time you might charge them all manually if you’re sitting there watching and waiting for them once at a time (great for overnight charges of your packs or in your hotel room).
The P3 Quadcharger PRO comes in two options: the charger by itself (you provide your own 20-28VDC 20A+ power supply) or as a package with an included 20A AC/DC power supply matched to the charger’s specs. The unit I tested was the Standalone P3 Quadcharger PRO as I already had dual 12v power supplies for running my Hyperion charger for all my other “non-smart” LiPo batteries and I wanted to see how well it would work in series. (More on that in my testing section below).
The P2 Quadcharger PRO is also available by itself (you provide your own 13.6-18VDC 17A+ power supply) or as a package with an included 17A AC/DC power supply matched to the charger’s specs. The P2 Quadcharger GO uses the OEM charger from DJI as well and takes longer to charge four batteries than the PRO version, but may be faster than using the OEM charger alone.
How do the P-Squared Quadchargers work?
I’ve been asking a lot of technical questions from the P-Squared engineers, because as I’ve been testing them and sharing my results with my colleagues, they all ask me a million questions I really can’t answer directly – until now. Here’s some technical information for those with all the questions:
Technical Description and Info from P-Squared about the P2 Quadcharger*:
*also applies to the P3 Quadchargers
“The features of the P2 Quadcharger make it the only charger the UAV owner or user will ever need,” says John Podrovitz, director of business development with P-Squared Group. Thanks to built-in intelligent design, he explains, the P2 Quadcharger offers users several advanced features.
The DJI batteries, as promised by the ‘Intelligent’ part of their name, will protect themselves from being overdischarged or overcharged but they don’t protect themselves from being charged at an excessive rate. These batteries are rated at 5200mAH (5.2AH) and a maximum 35C discharge rate. This equates to a maximum discharge rate of 182A, but the charge rate is a different story. The DJI charger charges at less than 1C (4.2A) and many LiPo manufacturers recommend no more than 1C.
The P2 Quad Charger (P2QC) will charge 4 batteries at least as quickly as the DJI charger will charge 1 battery. Our data suggests that it will charge faster than the DJI charger because of the sophistication of our design. We follow the industry recommended charging profile for LiPo batteries which includes three phases:
- Constant Current
- Constant Voltage
The Preconditioning phase is mostly to detect and properly handle a LiPo battery that has been overdischarged. If the voltage is below 3V it starts the charge at 1/10 C until the voltage reaches a preset value at which point the charge ramps up to the maximum charge rate. This is probably not going to occur with a DJI Phantom 2 battery but adds another level of safety.
The constant current phase assures that the battery is charged at the maximum safe rate. Some users charge LiPo batteries at a higher (2C to 4C) rate but this should only be done very cautiously with constant observation. LiPo batteries have been known to bulge or explode and catch on fire if charged at an excessive rate. The P2QC charges at a rapid but safe rate, but lithium batteries should always be monitored during the charge cycle. The intrinsic temperature monitoring of the P2QC adds even more safety to the charging process. No lithium battery charger can claim to be completely safe under all conditions and damaged batteries should be safely discarded..
Once the terminal voltage reaches a specific value the P2QC switches to the constant voltage phase and the charge current tappers off to safely top off the battery for maximum charge.
The DJI battery will normally shut off when the charge reaches 98% or 99%. The P2QC will terminate the charge if the battery fails to selfterminate. The P2QC also provides an internal safety timer that will stop the charge when a maximum time has elapsed (about 4 times the normal charge time) which would indicate that there is a problem with the battery.
This custom-designed circuit has many unique features to ensure the best and fastest charge possible for DJI P3 batteries. It has 4 independent intelligent charge circuits that use the LiPobattery industry recommended charge profile. This profile manages every aspect of charging the batteries like sensing the initial battery terminal voltage and deciding if the battery can handle the full charge current or if it needs to be charged at a low current for an initial period.
It also ensures that the battery charging conditions meet all of DJI’s published specifications such as the safe charging temperature of 0°C to 40C. We take this a step further by constantly monitoring the temperature of each battery independently and modifying or halting the charge if any battery exceeds these limits.
Once the battery passes all of our qualifications we initiate an advanced charge process that adds the maximum safe energy to the battery to allow charging as quickly as possible without damaging the batteries.
This graphic illustrates the advanced charge profile we use in all of our PRO chargers. We start out with a constant current until the battery terminal voltage reaches a very specific level at which point we change to a constant voltage. We maintain this voltage until the battery has reached its full charge.
We have not been able to find any technical information from DJI about their batteries, but our lab tests indicate that the charge profile that they use is no safer than ours and yet does not put as much energy into the battery as quickly as our advanced profile does. That’s why we can charge one battery faster than they do and then we multiply it by 4 batteries.
This design is the product of more than a year’s research and testing. We are constantly looking for ways to make it better.
On the topic of deep cycling, read DJI’s manual for the P2 and P3 batteries:
“Charge and discharge the battery completely once every 20 charge/discharge cycles. Discharge the battery until there is less than 8% power or until it can no longer be turned on, then recharge it to the maximum capacity. This power cycling procedure will optimize the battery life.”
They didn’t want to add any size or cost to their QuadChargers to accommodate a discharge cycle, but are looking at doing it in future products if they get enough demand for it. They have also considered a separate intelligent “discharger” that could be programmed for any LiPo including the DJI batteries.
My Test Results
So – do the P3 and P2 Quadchargers hold up to their claims?
At least in my (unofficial) bench test results they have.
My batteries are generally run down to about 25% by the time I land and shut off the copter; sometimes a bit lower but that’s the average. I’ve learned to keep an eye on them and try to do a lower power drain to around 5% occasionally when I’ve got time to do so and that will help make them last longer. The general rule is around 20 cycles of the battery to deep discharge.
The 3 units I tested were:
- P3 Quadcharger PRO Standalone ($280)
- P3 Quadcharger GO ($79)
- P2 Quadcharger PRO + 17A AC/DC PS Package ($249)
I’ve done several trial runs with the P3 Quadcharger PRO and my own power supply setup (2x 575W 12VDC/47A wired in series for 24VDC) and each time I get 4 P3 batteries completely charged in about 50 minutes. Since the P3 Quadcharger has 4 independent charing circuits, as one battery completes a charge cycle, it just stops charging while the remaining batteries can continue on.
This also makes it easy to charge only a couple batteries if you need to quickly top off your used batteries in your kit before heading out to fly.
Testing the P2 Quadcharger PRO with the package 17A power supply, my tests have averaged at just an hour for 4 Phantom 2 batteries. This is much better than using 4 chargers simultaneously and a lot less hassle for setup (and only one power cord).
My tests for the P3 Quadcharger GO were not timed – only that I knew I could easily “set it and forget it” and come back with fully charged batteries without having to babysit them or keep swapping batteries on charging cables. This also works really well with my car’s power inverter. They also have a 12V DC power cable accessory but that will only work with the P2 Quadcharger.
Since the lid on the P3 and P2 Quadchargers is vented, and the built-in fan of the P3 Quadcharger PRO kicks in under power, there’s no risk of overheating while charging. Once charging is complete, simply unplug and carry it off or pack in your car. The charger acts as a case that keeps your batteries protected while in transit. The P3 Quadcharger GO is great for air travel too as it will fit in a carry-on with 4 batteries should you chose to check your Phantom 3 in a flight case with your baggage.
I’m really hoping the folks at P-Squared develop an Inspire 1 Quadcharger as well. I’m really fond of this design and how compact it is, compared to others I’ve seen on the market. Send them an email through their website and show your interest as well!