DIY 4S battery pack from 18650 Li-Ion for RC FPV drone

've made me an endurance Li-Ion battery pack for my 7 inch endurance quadcopter. With good quality Sony 18650 VTC6 it is possible to get 20A constant current which is enough for an airplane or endurance quadcopter. Works just fine and with reasoable speed of 40-50 km/h I'm getting more than 15 minutes of real flight. Not hover. Flight. And at the end, it still has some juice inside. Not bad, not bad at all.

How to solder 18650 Li-Ion batteries

All 18650 Li-Ion batteries are hard to solder. Well, not only 18650 but all nickel plated metal elements can be very hard to solder. But only if you do not have the proper tools. In this case, proper flux: soldering acid. Forget about sanding, scratching and other voodoo. Just watch the video, it will clearly show what I have in mind!

No more sanding or scratching of 18650 Li-Ion connectors. A drop of soldering acid sill all that you need!

Getting started with 18650 Li-Ion batteries

18650 Lithium-Ion batteries are the workhorse of modern consumer (and not only consumer) technology. If you have anything that is battery operated and there is a "Li-Ion" mark anywhere on it, probably it is powered by 18650 Li-Ion battery. Laptop batteries, cordless drills, cordless tools, e-cigarettes. All of them (probably) have 18650 cells inside.

In this video, I will just go with the basics of 18650 cells. Dimensions, protected / not protected difference, weight and so on. Expect more in the future!

Tutorial: replace battery in RunCam HD

My RunCam HD died after 5 months in a drawer. Reason: battery destroyed. It had enough energy for approx. 2 seconds of operation. So I had a choice: buy original battery from RunCam for $9.99 plus shipment, or fix it DIY style. I’ve choces the second option.

Luckily for us, RunCam used generic 803035 LiPo 1S, 3,7V battery that can be purchased in specialized stores. I’ve paid around $6 for mine, but if you look hard enough, you should find something even cheaper. Also, luckily (or not) there is a battery plug: 2 pin JST 1.25mm.

Runcam HD inside

Continue reading Tutorial: replace battery in RunCam HD

How to connect APM Power Meter to Cleanflight and INAV

This topic was eluding me for some time now. It’s time fix the problem and finally present a short tutorial how to connect 90A APM Power Meter for flight controller boards like Naza32, SP Racing F3 or any other running Cleanflight / Betaflight / INAV software and equipped with Current Meter ADC input.

I will not show where to connect APM Power Meter to flight controller, since this differs from board to board. Some boards have dedicated pins, on some boards PWM input pins are used for Current Meter ADC. You have to refer FC documentation and / or flight controller software documentation.

Continue reading How to connect APM Power Meter to Cleanflight and INAV

How to dispose / utilize LiPo batteries

LiPo batteries that run RC hobby are potentially dangerous devices. When not handled properly they can ignite or even explode. And they do not live forever. Even the best battery, no matter how taken care off, loses capacity, swells and has to be disposed. When we combine both facts we face a problem: how to dispose old LiPo batteries if they can catch fire? It’s extremely hard to find a place that accepts them for utilization. Throwing out with garbage is not a good idea. Disposing with popular alkaline batteries might sound as a good idea, but it is not either. So, how to utilize old LiPos? This is quite easy…

  1. Build a LiPo discharge device using 24V halogen light bulb. No high-tech here, just a way to connect light bulb to a battery. 12W halogen is generally a good option for both 3S and 4S LiPos
  2. Put a battery inside ceramic pot with some sand (not flammable if thing go very very wrong for any reason), connect “discharge device” and let it do its job. Light bulb limits discharge current, so LiPo should discharge nicely without extra swelling or overheating Magical LiPo tree Continue reading How to dispose / utilize LiPo batteries

The best way to mount LiPo on a drone: 3M Dual Lock

LiPo battery, as the heaviest single element of any racer quadcopter, is mostly the first one to fell off during crash. Or displace in high-g maneuvers. Or simple fell off in flight. Like on this picture below I’ve found on Reddit. Grrrr… for sure this is something I would like not to see personally again. And I’ve seen it on my first build based on X525 frame.

battery fell off

So, solid and strong battery mount is a must. Battery strap for sure. Even few in case of heavier ones. But battery strap is not enough. LiPo can always slip out. To prohibit that, I’ve been using velcro strips and it worked fine. But velcro has a few drawbacks: it is not very strong connection, allows some movement, and looses strength after some time. Few weeks ago I’ve discovered something that is way way better than regular velcro: 3M SJ3550 Dual Lock Reclosable Fastener. Continue reading The best way to mount LiPo on a drone: 3M Dual Lock

Three flying weekends with Turnigy Graphene batteries

It is still too early to decide if new Turnigy Graphene are worth the money, but after 3 flying weekends with them I do have some thoughts about them already.

Turnigy Graphene LiPo Battery

  1. They discharge differently than Turnigy Nano-Tech I'm using in parallel. Discharge curve seems to be flatter
  2. Voltage drop on high load is much smaller comparing to Nano-Tech. Also, they do not regain voltage when disconnected. I usually try to fly until voltage goes below 3.5V per cell. More less 4:30 up to 5 minutes of flight with my regular style. Before charge Nano-tech's voltage usually goes up to 3.7V. With Graphene, it's different story. Before charge voltage per cell is around 3.65V. Maybe it's only half volt, but does tell something about discharge curve and general battery performance
  3. Althought they behave different than Nano-techs, they both accept more less the same charge during load
  4. My Graphenes are new, while Nano-techs not, but Graphenes seems to balance faster. Looks like cells are a better match. I still would have to confirm this
  5. They are indeed quite heavy, but I did not noticed lower flight times or worse performance

Battery C rate: do I need a lot of it?

One of the values that describe LiPo batteries used in RC crafts is so called C rating. For example: 3S 1300mAh 45-90C. Or 3S 5000mAh 25-30C. Or 4S 1300mAh 65-95C. S is simple, it tells the voltage. mAh or Ah tell capacity.

But what about C rate? According to Wikipedia is can be described as:

The C-rate is a measure of the rate at which a battery is being discharged. It is defined as the discharge current divided by the theoretical current draw under which the battery would deliver its nominal rated capacity in one hour. A 1C discharge rate would deliver the battery’s rated capacity in 1 hour. A 2C discharge rate means it will discharge twice as fast (30 minutes). A 1C discharge rate on a 1.6 Ah battery means a discharge current of 1.6 A. A 2C rate would mean a discharge current of 3.2 A.

So, if we take a look at Turnigy Nano-tech 3S 1300mAh 45-90C we will know that:

  • Constant discharge current on 45C is 58.5A
  • Burst discharge current (10 seconds) on 90C is 117A

Neat, yeah? Almost 60A constant current! That gives 15A per motor. And that a lot on 250 or smaller quad. So, I should be fine! Continue reading Battery C rate: do I need a lot of it?