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: AliExpress | Amazon
- Charger: you can use anything that can be powered by DC, here are the chargers I recommend
- 24V 10A Stepdown Voltage Regulator: AliExpress | Amazon
- Hailong battery connector (5-pin male): AliExpress | Amazon
- Voltage display for main battery (5V-120V 2-wire): AliExpress
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 (Buy: Amazon, Banggood)
- If the battery comes with XT90 connector, you will need an XT90 to XT60 Adapter (Buy: Amazon, Banggood)
- Charger: you can use anything that can be powered by DC, here are what I recommend
- Parallel Charging Board (Tutorial | Buy: AliExpress, Banggood, Amazon)
- Voltage Checker (Buy: GetFPV, Banggood)
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.
How many batteries can you charge?
To work out how many drone batteries you can charge using your big battery, you need to convert both of them to “watt hours” first, which is the amount of energy in these batteries.
Using this equation we can calculate the total energy in a battery.
Energy (Watt-hour) = nominal voltage x capacity
For a 6S 1100mAh (1.1Ah):
3.7 x 6 x 1.1 = 24.42Wh
For a 6S 10000mah (10A):
3.7 x 6 x 10 = 222Wh
That means a big 6S 10000mAh battery can charge roughly 9 to 10 smaller 6S 1100mAh packs. Buying one of these 6S 10000mAh battery is way cheaper than buying 9 or 10 of the smaller packs, you can potentially save 40-50%. You can also share your charger with your friends in the field which is nice.
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
Apart from a high capacity LiPo battery, you can also find some other power sources for your field charging solution, such as solar generator or portable generator.
|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 (10Ah – 16Ah+)||High||High (20Ah – 120Ah)||Medium|
|Weight||Light (1Kg – 2Kg)||Heavy||Heavy (5Kg – 35Kg)||Medium|
|Price||Cheap||Expensive||$50 – $300||Expensive|
|Wen (Amazon)||DeepCycle (Amazon)||Suaoki (Amazon)|
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.
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. If you need a refresher on what those terms mean, check out my LiPo battery guide here.
- 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.
- 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.
Why use a battery when you can make the electricity yourself?
There are a number of advantages to using a portable generator:
- 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.
- 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.
- 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.
- Jul 2017 – Article created
- Apr 2018 – Updated info about my own field charging solution and how it compares to buying extra lipo batteries
- Feb 2023 – Updated product links and info, shortened URL
Thanks for the timely info since so much of what’s online is over a decade old!
I’m charging all my (fixed wing plane) flight batteries (3s, 4s,6s) at 1C rate at home for best safety and battery life. This is using an inexpensive 110v to 24v 350w switching power supply and 200w pocket charger. In the field I’m planning to charge at 2C from 12v car battery or parallel lipo pack for 24v supply. I’ll allow some cool down time between cycles with 2-3 max cycles at the field. I much prefer the 24v input if possible BTW. Only question is whether this regiment has significant impact on battery lifespan… any thoughts?
Speaking from personal experience, you are treating your batteries with much more care than I am, and I don’t really find my batteries lifespan impacted in any noticable way really. And I usually damage them physically before they are “too old to use”.
yet again i ask a stupid question, and oscar is here with a clever answer, hopefully hehehe. i’m trying to hike and camp to cool locations, i’m wondering if a 12v solar panel will be able to charge a lipo via a cheap 12v lipo charger? the panels i’ve looked at only mention voltage out and watts, eg 12v and 20w trickle chargers for boats etc to avoid flat battery. do you think one of these panels could charge a couple of lipos in a reasonable time, 4 or 5 hours…. right now i’m carrying 8 good 4s lipos and 4 duff lipos to recharge the good ones, but weight is a big issue obviously.
It’s going to be a more complicated setup than what you expect. I’ve never actually done it but i looked into it a bit. First you need something called a voltage regulator / charging controller that connects to the solar panel for charging a main battery (not your LiPo), the charging controller should recommend which type of battery you should use, most people use a car battery. These charging controller aren’t designed for charging lipo (i think the output voltage is fixed, it doesn’t increase with the battery voltage like LiPo chargers). Because the voltage from the solar panel can fluctuate a lot and your Lipo charger is not going to like it if you connect them directly. Then you power your charger from that main battery. I have seen other people do that, a 1m x 1m panel maybe can charge a 4S 1300mah in under an hour? of course that depends a lot on the weather and your hardware.
You said you are charging at 2c, how is it possible it complete the change in 20 minutes ? 2c is double the mAh of the battery meaning exactly 30 minutes, without the balancing tickle change which sometimes takes another 10-20 minutes.
I am not charging from empty. You don’t completely empty the pack when you land do you? So really i charge batteries from around 3.7-3.75V, probably still 20-30% mah left in the pack.
And you don’t need to wait until it’s completely 100%, the last 5% takes forever and I normally just unplug them and fly when it gets to about 95% complete.
How about using a good grade inverter 1200 to 4000 w and using the home charger
Great setup! Would you consider using an e-bike battery pack as a power source for field charging?
Yea, why not?
Hi Can you charge a lipo, and have a voltage checker connected in parallel with the battery? Regards, Rich
Can I use a 12v car battery to field charge? Or even a 24 volt.
Also if my power source is 12 volt car battery. Would I been able to charge 4S lipo batteries? How does that work if 4S is much more than 12 volt.
Correct me if this statement is wrong. My lipo Charger is capable of 8-36 dc volt input capable. I obtain a 24volt RV or Marine battery. This setup should work.
Depends on the charger you plan to use. For the iSDT chargers I recommend they should be able to take both 12V as well as 24V.
Yes you can charge 4S with 12V input, chargers can “step up” the voltage.
Hi guys if you field charge you need to go check this new product from rcharlance…
I’ve just bought 2!
It has 1 xt60 input for power source (with voltage monitor and alarm) and 2 xt60 outputs
Thanks for the great info as always Oscar!
here you wrote that you charge at 1c https://oscarliang.com/parallel-charging-multiple-lipo/
Well, I am not in the house anymore so I charge at higher current :D
How long would you recommend a 10C battery like the multi star be kept at “near full” or even full charge.
Ie If it was charged , ready for the weekend, but not used at all; and discharged on a Sunday evening wold that be “OK”.
I say this as I have a basic understanding (right or wrong) that high C lipos suffer the most when kept at full charge versus low C lipos.
It’s hard to say, personally, i wouldn’t worry about it for a week or two. Any longer you might want to put it in storage charge.
Why use a 6s battery to charge with instead of 4 or even 3s? Since it’s the mah you’re after here, not the voltage, aren’t the extra cells just taking up space, why would you want more voltage when charging, as opposed to amperage?
The energy stored in a battery is a result of voltage and capacity :) so the higher the voltage the more energy you get.
With upcoming 6S battery flying style, not sure a 6S-10Ah battery might be enough for charging.
why not? you can even use 4S to charge 6S on iSDT charger they can step up the voltage.
Oscar, I’ve been field charging for about a year. I mainly use the battery on my SUV (the charger will shut down when input voltage gets too low. I also have a built-in inverter that I can use also, but either the vehicle must be running or the ignition turned on…
I have looked at buying a large capacity 6s battery in the past and then just now after reading your article. Where on God’s green earth are you guys buying 6s 160000mah batteries for “cheap”? the lowest price I’ve seen is around $200 from sketchy retailers….
My mistake I meant, 6s 16,000mah, but I’d be happy with a 10,000mah suggestion (4s or 6s for under $100)! Thanks
Ebay 6s 10k 78$ shipped:
Try Hobbyking, they are generally cheaper there, but beware of the shipping cost :)
Thats sounds good! I have a skyrc imax b6ac v2 and it has both ac and dc input. Can I use this as a field charger if I buy an xt60 to jack adapter?
I bought the 6s 5200mah Multistar for USD22 during a Hobbyking sale for this very purpose. Cheap and small enough capacity in terms of WH to be able to hand carry into a plane (limited to 160Wh and below) if I want to go overseas on a flight.
6S 10A is just too big.
These 6S 5200mah are currently on sale at HobbyKing for a ridiculously low price.
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?
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.
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.
The way I calculated it was (6-4)/4 = 0.5 :)
It isn’t correct
It’s above 66%
You got it backwards. The 0.66 is how much energy 4S has compared 6S. 4S has only 2/3 the energy of the 6S. This is so because the 6S has 50% more, it is 1.5 times the energy of a 4S. Both calculations are correct, just saying it in the opposite order.