Charging LiPo Batteries in the Field for FPV Drones

LiPo Batteries

LiPo Batteries

Charging FPV drone LiPo batteries in the field allows you to fly longer without bringing too many packs. I will share my field charging solution which I think is more economical and practical than buying more LiPo batteries.

FPV drones have shockingly short flight time (5 to 6 minutes on average). To make matter worse, most people fly in a field where there’s no access to electricity to recharge their batteries.

When I go flying, I can easily go though 10 to 20 batteries in an afternoon. You can certainly just buy a couple of dozens of batteries enough for a whole session, but I find making a portable charging station way more cost effective and allows me to stay out longer in the field.

My Field Charging Solution

Here’s my setup:

  • Main power source: Hailong 48V 15Ah Battery for e-bike
  • Charger: you can use anything that can be powered by DC
  • 24V 10A Stepdown Voltage Regulator
  • Hailong battery connector (5-pin male)
  • Voltage display for main battery (5V-120V 2-wire)

This is the battery for my e-bike, which I also use for field charging. For just under $300, you get a 720Wh battery (equivalent to over three 6S 10000mAh packs), which is enough to charge 30 6S 1100mAh packs (24.42Wh)! It has more than enough juice for going to the field and back while charging my drone batteries. You can certainly get one of these batteries just for field charging too even if you don’t have an e-bike.

I don’t use parallel charging board, simply using two separate chargers for charging two batteries at once.I also soldered a voltage display to the input of the voltage regulator so I can keep track of the voltage of the battery just in case I over-discharging it.

 

 

Here’s another setup of mine:

  • Main power source: 6S 10000mAh LiPo battery
  • If the battery comes with XT90 connector, you will need an XT90 to XT60 Adapter
  • Charger: you can use anything that can be powered by DC
  • Parallel Charging Board
  • Voltage Checker

How to Charge LiPo Batteries in the Field

I normally bring 8 batteries with me, this pretty much can keep me flying while charging non-stop. You might be able to make it work with fewer batteries, but you might have to wait a bit between flights.

I prefer to charge 2 batteries at a time at 2C, which should only take roughly 20 mins to complete (there’s some charge left in the pack when I land so they are not completely empty). For example to charge a 6S 1100mAh, I set the charge current to 2.2A, for 4S 1500mAh it would be 3A.

It’s a good idea to rest your batteries for at least a few minutes between discharging and charging, just let them cool down and reduce the change of overheat.

 

Reverse Charging

As we all know, it’s a bad idea to leave LiPo batteries fully charged for too long for battery lifespan reasons. When you have fully charged batteries left at the end of the day, you want to find a way to quickly discharge them (rather than flying them). “Reverse charge” is a good option – it means using your fully charged LiPo as the charger power source, to charge the big battery, or other empty batteries.

 

Portable Power Supply Options

If you have a lot of batteries to be recharged in the field, or need to power multiple chargers, a portable generator is a good option. They are powerful and often have DC as well as AC outputs. Generators are noisier, bulkier and more expensive than other options in our list but they are great for day-long events.

Solar generators are another great option especially for sunny day camping/flying.

I personally prefer the simplicity of a high capacity battery (either LiPo or Li-ion) which I can easily carry in my backpack.

Car Batteries

Most LiPo chargers these days support a wide range of input voltage (e.g. from 7V to 24V), this means you can use a lead acid car battery to power you LiPo charger. And because a lot of us drive our cars to get to where we want to fly, this seems to be an easy solution for charging in the field. However, I don’t recommend it in case you discharge it too much and your car might not start. You don’t want to get stuck in the middle of nowhere at 7pm do you? 🙂

You may get a separate car battery just dedicated for charging your batteries. But they can cost a lot and also heavy to move around. And if you are going to be regularly discharging it you are going to need a battery charger to charge it back up. Also car batteries aren’t designed to be discharged all the way and then charged back up. For these reasons I would avoid using car batteries for field charging.

Deep Cycle Batteries

Compared to car batteries, deep cycle batteries are the better option. They are designed with thicker lead plates that allow it to be fully discharged and fully charged for many cycles. This is ideal for field charging LiPo batteries.

High Capacity Lipo/Li-Ion Batteries

A large LiPo or Li-ion battery pack is perfect for charging in the field, and they are relatively easy to select. There are only two things you need to keep in mind: input voltage and capacity.

  1. For input voltage, go with 6S, with 4S being the second choice. Most chargers support these voltages directly, and some chargers can output more power and work more efficiently with the higher input voltage, especially if you are charging 6S LiPo batteries.
  2. For capacity, I would recommend the biggest you can afford / willing to carry. The higher the capacity, the more times you are going to be able to use it to charge in the field.

The great thing about using a high capacity LiPo or Liion battery is that you don’t have to buy an extra charger like you do with a lead acid battery. You can just use the same charger that you would use for your quad batteries.

Some large LiPo packs come with XT90 connector, which requires a XT90 to XT60 adapter to plug it into your charger, but they only cost a couple of dollars.

Portable Generator

Why use a battery when you can make the electricity yourself?

There are a number of advantages to using a portable generator:

  1. You don’t need to worry about capacity. Most generators will be able to provide more than enough energy to power multiple chargers, even with parallel charging multiple LiPo’s per charger.
  2. Most generators have both an standard AC output as well as a 12V DC output. This means you can basically use any LiPo chargers out there.
  3. You don’t have to worry about charging up yet another battery, all you have to do is fill it up with gas.

However generators are noisier than using batteries and they will be more costly. But they are a great option if you are running an event or camping in the middle of nowhere for several days.

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