How to charge LiPo batteries in the field

In this article we will talk about the ways of how to charge LiPo batteries in the field where there is no electricity.

For us mini quad pilots, it’s easy to go through 10, 20 or even more LiPo batteries in a flight session. You can certainly buy as many batteries as you need for a single session, but there is a more cost effective way to do it.

By bringing a portable charging station with you, you can recharge used and empty batteries in the field. You can recharge whatever you need and therefore if you were leaving early you wouldn’t go home with as many fully charged batteries.

To sum up, the benefits of charging in the fields are:

  • it requires fewer LiPo packs – more cost effective
  • smaller chance of going home with fully charged LiPo
  • the charger can be shared between buddies for a good long session

Portable Charger

As a good portable charger, it’s best to pick one that doesn’t have integrated PSU, so you can power it with low voltage DC power which is widely available on many portable power sources. Many chargers work with 12V DC, though one with wide input voltage would be preferable such as 11V to 18V.

Charger specification depends on what kind of portable power sources you use.

Light weight and compact are also a bonus when it comes to portability.

Some particularly popular chargers for field charging are the iSDT series (SC608, Q6, SC620), because they support a very wide input voltage (9V-32V) and come with a XT60 connector that allows you to use LiPo batteries as power source. They are also good for indoor everyday charging.

Here is my review of the iSDT SC-620. Product Page for Q6: http://bit.ly/isdt-q6.

To sum it up, you want the charger to:

  • allow wide range DC input voltage that is compatible with your portable power sources
  • light weight and compact for easier transportation

Portable Power Supply

To power the charger without access to a wall socket and electricity, you’ll need a portable power source. Here are some common solutions:

Name High Capacity LiPo Batteries Portable Generator Deep-cycle Batteries Solar Generator
Fuel Rechargeable Varies – Petrol/Diesel Rechargeable Rechargeable – Sun
Voltage 11.1V – 25.2V (3S-6S) Varies – AC and DC 12V Varies – AC and DC
Capacity Low (Up to 16Ah or more) High High (20Ah – 120Ah) Medium
Weight Light (1Kg – 2Kg) Heavy Heavy (5Kg – 35Kg) Medium
Price Cheap Expensive $50 – $300 Expensive
Example
Products
4S 16000mAh
6S 16000mAh
Wen DeepCycle Suaoki

High Capacity LiPo

The most popular and portable solution is probably using a large LiPo battery as the power source. For example, a 4S 16000mAh (16Ah) can charge at least 10x smaller 4S 1300mAh. Some prefer higher cell count batteries as they can store more energy under the same capacity, and thus can charge more packs. For example a 6S 16000mAh has 50% more energy than the 4S 16000mAh.

Energy stored (Watt-hour, wh) = voltage x capacity

However, make sure your charger supports the voltage of the portable power source as input.

C rating is not that important with LiPo batteries at such high capacity, and because we don’t tend to draw too much current at any instance. 5C or 10C are more than enough.

Other Portable Power Source

Although you can use your car battery to charge your batteries, we recommend using a separately deep cycle battery just for your LiPo charging so you don’t accidentally kill the battery in your car. (unless you are as smart as Walter White)

If you have a lot of batteries to be recharged in the field, or need to power multiple chargers, you may get a portable generator. They are powerful and often have DC as well as AC output which is compatible with a wider range of chargers. But generators are also noisier and more expensive than other options in our list.

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

Horváth Csaba showed us how he use a parallel board to “reverse parallel charge” in the field, by connecting several spare 3S batteries he has as power supply for the charger.

5 thoughts on “How to charge LiPo batteries in the field

  1. Alex

    How can you estimated the amount of charging a field lipo can do? For example, how many 1500mah 4s packs discharged to 3.6 a cell can a 20000mah lipo bring up to 4.2 a cell?

    Reply
    1. Oscar Post author

      you probably have to try and see, because it largely depends on your charger’s efficiency.
      But as a good estimation, you can use this formula:

      Number of packs = (source voltage) * (source capacity) * 80% / (target voltage) * (target capacity)
      *assuming your charger has roughly 80% efficiency

      In your case, 20Ah*16V*0.8 / 1.5A*16V = 10.7
      so about 10 packs.

      Reply
  2. Slawek

    Oscar, you have mistake in article. 6S battery has more than 50% more energy than 4S battery (with the same capacity). You propablly mean 3S.

    Reply

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