Drone near misses with manned aircraft show a need for education and training

As many of you may have heard, on the 22nd of July 2014 the pilot of an Airbus A320 reported sighting a “small black object” to the left as he prepared for landing at Heathrow airport. The airbus was 700ft up when the object was reported passing approximately 20ft over the wing. The pilot was able to land the plane safely, but stated “it was a distraction during a critical phase of flight.” The UK Airprox Board(UKAB) gave this incident an A rating, meaning that there had been “a serious risk of collision”. Investigations were unable to trace the operator responsible.

This incident demonstrates a need for a greater public understanding of drone operations. As statistics come through about the volume of drones being sold monthly and marketing campaigns push for making a drone the gift to get this Christmas, the importance of understanding the rules and regulations surrounding this emerging industry has never been greater.

The operator of the drone involved in the Heathrow near-miss was breaking numerous regulations from take off. The Air Navigation Order 2009 defines a congested area as being “any area of a city, town or settlement which is substantially used for residential, industrial, commercial or recreational purposes.” You must have permission from the CAA to land or operate within a congested area. Article 138 of the ANO states “A person must not recklessly or negligently cause or permit an aircraft to endanger any person or property”. I believe not only the pilot of the airbus, but the UKAB agrees flying a drone within 20ft of an aircraft is reckless when they gave this incident an A rating. Additionally articles 166 and 167 state the operator must maintain direct, unaided visual contact to monitor its flight path, the operator must not fly in Class A, C, D or E airspace without permission from the air traffic control unit, operators shouldn’t fly at a height of more than 400ft or within 50m of any vessel, vehicle, or structure not under the operators control. New FPV regulations do allow for flights to be higher than 400 feet, but not in the class D airspace around Heathrow and a competent spotter needs to be with the remote pilot at all times.

With at least one other drone near miss currently being put through the UKAB, it is possible that there are recreational drone pilots who may be keen to fly in these areas simply to obtain footage of manned aircraft in flight. I cannot stress how dangerous this could be for the crew and passengers of a manned aircraft.

With the recreational drone market expanding, there’s no reason for anyone to be left stranded on the ground. If you or someone you know received a drone this Christmas it is important to understand the regulations. By following the regulations set out people can experience the wonder that flying a drone can bring without sacrificing any person or property’s safety.

The UKAB report for the Heathrow near-miss can be found here: http://www.airproxboard.org.uk/docs/423/2014117.pdf

You can find more information on the legislation on the CAA Unmanned Aircraft page.

The CAA recently released an information leaflet for owners of recreational drones.

If you are planning on getting or giving someone a drone for hobby flying you can find out more from the British Model Flying Association.

For initial UK drone flight training please contact us via the HexCam website. In early 2015, we hope to offer a full route to a CAA Permission for Aerial Work, which is required to operate drones commercially in UK airspace. New information and websites coming soon.

We would like to wish you a happy and prosperous 2015.


New technologies mean new CCTV code

Anybody involved in UK RPAS operations should read this, input, and be prepared to deal with the implications.

By Jonathan Bamford, Head of Strategic Liason.

It’s fair to say that 2000, when we first published our guidance on CCTV, feels like a very long time ago. Back then, what we meant by CCTV needed little explanation, immediately conjuring up thoughts of video cameras on poles.

ico-blog-droneHow times change. Today we’ve begun consulting on an updated version of our CCTV code of practice that includes everything from automatic recognition of car number plates to flying drones.

Those two examples are both from the emerging technologies section, which perhaps makes for some of the most interesting reading. There’s a section in there on body worn cameras, for instance, which have attracted headlines recently as the Metropolitan Police Service announced their roll out.

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Preparing your UAS operations manual for the CAA

Please note: This post is fairly out of date. Some of the information is still useful but please see this post as well.

Even now, a couple of years after I got into this industry, there appears to be a lot of confusion about the format and purpose of the UAS, RPAS or UAV Operations Manual that is required by the Civil Aviation Authority (CAA) when registering for Permission for Aerial Work (PFAW) in the UK. As a result I thought I’d just write down a few thoughts now and maybe add to it later.

As always, a little disclaimer: I get a lot of questions about multirotor equipment so I thought I’d start creating some posts about that. Please bear in mind that I learn a lot from reading around the blogs and forums and talking to people in RC shops so any inaccuracies are completely due to my own misunderstanding. By reading this you accept that, although I hope it will aid with your own understanding, it is written in good faith and I can’t take responsibility for any damage to yourself or your equipment that occurs through the use of this information. If you see anything that I have got wrong or you feel is dangerous, please contact me through the HexCam website or Facebook page and I will rectify it as soon as possible.

What is the Operations Manual not?

1) It is not an instruction manual: Occasionally I get people sending me an Operations Manual for review and it is a print out of a Phantom or Wookong manual. So the first thing to say is an Ops Manual is NOT an instruction manual for your RPAS. There will be aspects of the Ops Manual that describe some of the functions but your system and transmitter instruction manuals should only feature as documents for reference in the manual.

2) It is not a “paperwork exercise” to be shoved in a drawer once you get your PFAW: Your Ops Manual is an absolutely key document that should be very carefully thought through and should be regularly used and updated in line with experience and the evolution of your business. If you feel it is just a hoop to jump through and are not prepared to read through the relevant CAA documentation (which isn’t a huge amount) then I suggest you walk away from this profession now.

So what is your Operations Manual?

Put very simply, your Ops Manual covers four things: Who you are, what you are flying, what you want to do with your RPAS and how you will do it safely.

The core remit of the CAA is to ensure that all airspace users are operating in a way that ensures the safety of the public, property and other airspace users. As a result, the Ops Manual for the CAA only needs information about your RPAS to the extent that it impacts safety. So things like failsafe procedures will feature. Privacy will not feature, although I would suggest that you also begin to think about putting together some kind of privacy and data protection policy to hold separately within your business.

Resource Group who run the RPQ-s and EuroUSC who run the BNUC-S both provide information and guidance on production of the Ops Manual when you carry out your theory ground school. Both companies also offer different levels of Ops Manual review, including paid options.

You can also find a basic template on the CAA website as an appendix to CAP 722 (Section 3, Chapter 1, Annex 1) which on the PDF starts on page 73! There is also a direct link from the CAA UAS pages.

If completing the BNUC-S, you will be required to submit a completed Operations Manual for approval in advance of your flight examination and you will not be able to complete the flight examination until the Ops Manual has been approved by EuroUSC.

If completing the RPQ-s the Ops Manual does not have to be completed before the flight examination, but, as you have to demonstrate your operating procedures and use flight reference cards during your examination, it makes a lot of sense to complete the manual before the examination if possible.

If you are writing a manual for a “standard” Permission for Aerial Work, then your sections safety and incident management really need to address how you will work safely within articles 138, 166 and 167 of the Air Navigation Order:

Article 138: A person must not recklessly or negligently cause or permit an aircraft to endanger
any person or property.

Article 166: (1) A person must not cause or permit any article or animal (whether or not attached to
a parachute) to be dropped from a small unmanned aircraft so as to endanger persons
or property.
(2) The person in charge of a small unmanned aircraft may only fly the aircraft if
reasonably satisfied that the flight can safely be made.
(3) The person in charge of a small unmanned aircraft must maintain direct, unaided
visual contact with the aircraft sufficient to monitor its flight path in relation to other
aircraft, persons, vehicles, vessels and structures for the purpose of avoiding
(4) The person in charge of a small unmanned aircraft which has a mass of more than 7kg
excluding its fuel but including any articles or equipment installed in or attached to the
aircraft at the commencement of its flight, must not fly the aircraft:
(a) in Class A, C, D or E airspace unless the permission of the appropriate air traffic
control unit has been obtained;
(b) within an aerodrome traffic zone during the notified hours of watch of the air
traffic control unit (if any) at that aerodrome unless the permission of any such
air traffic control unit has been obtained; or
(c) at a height of more than 400 feet above the surface unless it is flying in airspace
described in sub-paragraph (a) or (b) and in accordance with the requirements for
that airspace.
(5) The person in charge of a small unmanned aircraft must not fly the aircraft for the
purposes of aerial work except in accordance with a permission granted by the CAA.

Article 167: (1) The person in charge of a small unmanned surveillance aircraft must not fly the
aircraft in any of the circumstances described in paragraph (2) except in accordance
with a permission issued by the CAA.
(2) The circumstances referred to in paragraph (1) are:
(a) over or within 150 metres of any congested area;
(b) over or within 150 metres of an organised open-air assembly of more than 1,000
(c) within 50 metres of any vessel, vehicle or structure which is not under the
control of the person in charge of the aircraft; or
(d) subject to paragraphs (3) and (4), within 50 metres of any person.
(3) Subject to paragraph (4), during take-off or landing, a small unmanned surveillance
aircraft must not be flown within 30 metres of any person.
(4) Paragraphs (2)(d) and (3) do not apply to the person in charge of the small unmanned
surveillance aircraft or a person under the control of the person in charge of the
(5) In this article ‘a small unmanned surveillance aircraft’ means a small unmanned
aircraft which is equipped to undertake any form of surveillance or data acquisition.

If you want to operate beyond these limitations on a regular basis, you need to apply for an exemption at the time you apply to the CAA for your PFAW. So, for example, you might wish to apply for increased altitude, closer separation distances or night flying. The CAA have stated that they are happy to receive applications for exemptions to standard permissions as long as you can provide an adequate safety case for the exemption applied for, these are considered on a case by case basis. The CAA also consider one-off exemptions.

The Permission for Aerial Work will look slightly different if your RPAS is heavier than 7Kg as it will include conditions for congested areas.

Where do I start?

Here is a starter list of things I would suggest you get together before you start:

  1. Coffee and biscuits
  2. Details and specs of your RPAS and cameras
  3. Links to instruction manuals for the RPAS, Transmitter, AV equipment, relevant CAA documents.
  4. Your company details if applicable.
  5. A list of potential applications for your RPAS.
  6. Your operating procedure (to include, how you setup before you fly, pre-flight checks, in-flight procedures (take-off, flight, landing), post-flight checks and emergency procedures).
  7. Think about what you would do in the event of an incident and how the RPAS would behave in response to events such as transmitter loss, motor failure, malicious interference, GPS signal loss.
  8. Insurance details.
  9. How you will survey and risk assess each flight site.

I suggest you stick to the CAA layout so it makes it easier for them to check your document, the skeleton documents provided by Resource UAS and EuroUSC broadly follow the CAA template.

The key thing is to make it a manual that YOU (and your employees) can use practically in the office and the field. Don’t see it as an Operations manual “for the CAA”; it is a manual for you, that details exactly how you and representatives of your business will operate safely and legally in UK airspace. You just have to get it approved by the CAA to get your Permission for Aerial Work.

Can we help?

Yes we can. We do provide assistance with Operations Manuals every now and again, using a model we have developed over the last two years, that has been approved by the CAA three times and was highly commended by EuroUSC. The cost will depend on the scope of your manual and will vary depending if it is a simple check of an already drafted manual or if it is a new manual to be written from scratch. Either way, we work closely with you to ensure that you take ownership of your manual, so that it is not just a copy of ours, but is a working document within your business.

No we can’t. I’m sorry but due to the increasingly rapid changes in legislation and the differing requirements of the NQEs we can no longer help with the operations manual process.

Any questions, you know where I am. Elliott – HexCam

CAA publish list of commercial UK UAS/UAV operators

Last week the Civil Aviation Authority (CAA) published a list of UAS operators who have a permission for aerial work in the UK. In case you are wondering we are number 117! Although the list is now alphabetical.

What’s so important about a list?

A number of us in the industry have been asking for this for a while and I see it as a great step forward in legitimising the industry and allowing customers to know that they are contracting a UAS operator who has demonstrated that they meet the level of competence expected by the CAA. The UK is leading the way on the legislative side of incorporation of UAVs into commercial airspace, we see this as a similar kind of list to those produced by other industries, such as Gas Safe for UK gas engineers. Inclusion on a list may not seem very important, but it is important for end users to ensure that the company they choose to use is on the list for the following reasons: Any individual/company who is on the list has carried out the following and been issued a permission for aerial work from the CAA:

  1. Demonstrated competent flight skills either through the RPQ-s, BNUC-S, or pre-existing arrangements for early registrants.
  2. Carried out a flight examination to demonstrate both their own skills and the failsafe features of their aircraft.
  3. Carried out a theory examination demonstrating a working knowledge including meteorology, UK airspace legislation and operational safety.
  4. Submitted, and had approved, an Operations Manual showing their own operational, safety and risk assessment procedures.
  5. Submitted proof of public liability insurance.
  6. Agreed to maintain operational and equipment logs allowing pilot experience to be shown and encouraging good maintenance of equipment, motors and batteries.

Where can I find the list?

The permanent link to the up-to-date list of UAS operators with a permission to conduct aerial work is the last link at the bottom of the CAA UAS page: http://www.caa.co.uk/default.aspx?catid=1995

What should I do if the company I’m considering is not on the list?

Firstly, please bear in mind that the list will only be updated every three months. But the company should be able to show you their permission for aerial work certificate and their RPQ-s or BNUC-S certificate and photo ID card. Some companies and individuals aren’t aware that any legislation exists, but they do need to comply with it. If you suspect they are not a registered company then please contact the CAA at the link above. The CAA will then contact the company to inform them of the legislation surrounding aerial work. Hopefully, any legitimate company will then be happy to get themselves on the list. If you have any questions about UAS equipment, training or operations, please do not hesitate to contact me through the HexCam website. Elliott – HexCam

Unmanned Aerial Filming Guide

I wrote this content to be published on The Knowledge Online back in February 2013. It wasn’t really my intention to post it on here but as several other companies have decided that it is fine to use it uncredited or to pass it off as their own text, I thought I would put it on here. Not only that but I have added a couple of extras as well which I have put in italics. So you can consider this a director’s cut if you like! 🙂

You can view the original article here as posted (and credited) by The Knowledge, which is a fab website by the way and well worth a look around: http://www.theknowledgeonline.com/guides/post/2013/02/11/A-guide-to-using-radio-controlled-aircraft-for-aerial-filming

If you would like unmanned aerial filming have a look at the HexCam website and give us a call!

A Guide to Unmanned Aerial Filming – the director’s cut!


I will use the term UAV throughout this article but you may find them online under different names and acronyms. This is because there is no standard term for this kind of equipment. The common names are:

UAV (unmanned aerial vehicle)
UAS (unmanned aerial system)
SUSA (small unmanned surveillance aircraft)
ROV (remotely operated vehicle)
RPA (remotely piloted aircraft)
Multirotor (tricopter, quadcopter, hexacopter, octocopter)
RPAS (remotely piloted aircaft system) – this is likely to be adopted as the industry standard

This list is not exhaustive. While there are fixed wing operators out there, the majority of these are not used for filming, therefore this guide will focus on multirotor and helicopter use as these are becoming most commonly used.

Why use a UAV?

Recent advances in camera, flight and battery technology mean that UAVs are now capable of obtaining footage at a quality comparable to that achieved by manned aircraft. Combined with the fact that UAVs can be used closer to the ground and nearer to people than manned aircraft, this means that they are becoming an incredibly versatile tool for filmmakers across a wide variety of genres. UAVs have been used to replace dolly and jib shots in awkward locations and can be used for dramatic lift and zoom shots.

The majority of UAV operators will be significantly cheaper than hiring a helicopter. The ability to monitor the footage from the ground allows for directorial input to the flight team and immediate review of the footage. Control methods vary and include traditional transmitters, tablet and laptop control. The control method employed will be dictated by the type of filming required.

What about the legislation concerning UAVs?

If a company or individual is operating their UAV commercially (which the Civil Aviation Authority defines as getting any kind of valuable consideration for your work) then their aircraft must be registered with the CAA and have a permit for aerial work. Any reputable company will be able to show you their permissions document for the aircraft they are going to use. This clearly shows the conditions they can fly under. The conditions vary slightly for different aircraft. If a company is operating without a permit for aerial work then it is possible that the pilot’s experience is questionable and it is unlikely that they are insured.

What qualifications do I look for?

Aside from checking the permit that allows aerial work, the CAA requires that pilots demonstrate a level of skill when they register their aircraft. Until recently it was possible to obtain a permission for aerial work with a British Model Flying Association Helicopter A certificate. New registrations are now generally required to complete a BNUC-S qualification, which is administered by a company called EuroUSC. There is now an alternative qualification called the RPQ-s which is administered by Resource UAS.

Both qualifications consist of a theory exam and flight exam. The aim is to show that the pilot is knowledgeable about their own aircraft and how they can use it in UK airspace. The qualification is type specific so if, for example, a pilot is qualified only to use an octocopter, they should not be flying a helicopter for aerial work. All operators who have completed the BNUC-S or RPQ-s should be able to show you their certificate, which should tie in with the details on their permission for aerial work.

What are the limitations?

In order to make sure UAVs and manned aircraft are working in separate airspace, there are a number of limitations placed on UAV use.

These are the main ones to keep in mind:
•    The maximum altitude is 400 feet (120 metres)
•    The maximum distance from the operator is 500 metres
•    The minimum visibility needs to be 5 km
•    UAV must be flown in line of sight of the operator
•    UAVs cannot be flown at night without special permission
•    Permission must be obtained from the owner of the take-off point
•    UAVs cannot be flown within 50 metres of structures, vehicles or people that are not under the control of the person in  charge of the aircraft.

This final point may sound very limiting but the key phrase here is “…under the control of…” It is perfectly acceptable to fly close to buildings and actors, for example, as long as permission has been obtained and the actors have been briefed about the use of the UAV. It would be highly irresponsible to fly over or near members of the public who are not aware of the purpose of the flight.

It is possible to get exemptions to fly higher and in congested areas. This is at the discretion of the CAA, may take up to 21 days to arrange and could attracta permission fee

How to get insurance

There are specialist UAV insurance companies that are able to provide cover for UAV operations. As a bare minimum, the CAA recommends that the company or individual should have public liability insurance. Some insurance companies will not cover UAV use in high-risk areas though so do check this beforehand.

Most operators will have cover for their own equipment or cameras, but if you ask the company to use your cameras, their insurance will not normally cover your equipment. Flying hired cameras may be possible, but it is advised that the hire company is informed of this as their insurance may not cover UAV use.

Which size camera do I need?

The type of UAV and the size of a camera are closely linked. The size of the UAV will generally dictate the camera payload. The type of camera mount or gimbal the UAV uses is also very important.

Most individuals start off with a small quadcopter that is probably capable of carrying a small compact camera or something like a GoPro. There are octocopters and helicopters that are capable of carrying cameras such as the Canon C300, RED Epic or Sony FS700. The DJI Phantom is a great little quadcopter, capable of carrying a GoPro Hero 3 on a fully stabilised gimbal, meaning that full HD stabilised aerial footage can be obtained for around £1000 including the upgraded Phantom, mini ZenMuse, GoPro Hero 3 modded to remove fisheye. Please contact us if you’d like more details!

Most operators will have a camera that they have set up for their equipment. This will normally mean they have gone for a compromise between weight and quality. There is some very good quality Panasonic GH2 footage coming through as an incredible new gimbal has been produced specifically for it.

Generally, the bigger the camera, the shorter the flight time. With the larger cameras, flight times may be limited to 4-5 minutes per battery pack. However, in filmmaking, shot sequences are usually very short so this isn’t a major problem. Don’t be afraid to ask companies for samples of previous work and references.

Camera gimbals are generally servo stabilised but some are better than others. Again, it is worth asking for a demonstration or sample footage. Some operators use a single pilot and camera operator setup, while others have a separate pilot and camera operator. This may affect costs as well as the quality of the final product. Costs of UAV hire, at present, tend to vary considerably but are generally proportionate to the video quality that the operator can achieve.

Legislation links:

CAA guidance
RPQ-s details
BNUC-S details

This guide was compiled with the help of Elliott Corke of HexCam; UAV imagery, equipment and training.

Lithium polymer battery chargers for multirotors

This follows on from my post on lithium polymer batteries but I just need to put in the same disclaimer!

I get a lot of questions about multirotor equipment so I thought I’d start creating some posts about that. Please bear in mind that I learn a lot from reading around the blogs and forums and talking to people in RC shops so any inaccuracies are completely due to my own misunderstanding. By reading this you accept that, although I hope it will aid with your own understanding, it is written in good faith and I can’t take responsibility for any damage to yourself or your equipment that occurs through the use of this information. If you see anything that I have got wrong or you feel is dangerous, please contact me through the HexCam website or Facebook page and I will rectify it as soon as possible. Please treat lithium polymer batteries and multirotors with same respect you would give to other electrical and mechanical equipment. Look after them and they will look after you.

You also need to know the following: I am not paid to review or endorse any products but I do have a partnership arrangement with Versadrones to act as their demonstrator and trainer in the UK.


Getting the right lithium polymer (lipo) battery charger can be a real minefield. The main reason for this is that often the charger companies only tell half the story. So I will try to clarify it, but am not going to promise anything as I sometimes still get a little confused myself. It is, however, vitally important that you get the right charger for the kind of aerial imagery business you are running. If not, you will find yourself very frustrated. A decent battery charger and power supply can be pretty expensive. But as someone who has a number of “retired” chargers around the office, I would say that you need to see it as an investment. A good charger will maintain battery health, allowing batteries to remain in use for more charge cycles, it can also save you time if you don’t have to be monitoring the charger continuously just to get all your batteries charged in time! If you look across the net you’ll find all kinds of homebuild arangements for providing power. There are ways of doing this, and I have done so myself on occasion. However, I am also aware that for most people the idea of stripping down a server power supply is pretty daunting, so I’m going to focus on professional solutions that might just survive a portable appliance test! If you are up for a bit of homebuilding just have a look around the RC forums. People have built some amazing setups.

What do I need to start charging lipo batteries?

The first thing to say here is that lithium polymer batteries need a specific lipo charger. If you try to charge them with anything else you are risking a fire. The technology (and people’s understanding) has improved over the last few years. If charging indoors, keep the batteries in lipo bags or some kind of metal case.

You are probably going to want two things… a mains operated charging system that can be used for charging back at base and a mobile system while you are out operating. Generally, the charger will be the same but your power supply will change. If you have bought something like a DJI Phantom you will get a neat little all in one plug and charger with it. No problem for small batteries like that so just get on with it and fly! I would still suggest following the 20% rule from my lipo battery post though.

It is recommended that batteries are charged at a 1C charge rate. This means a 3000mAh battery should be charged at a maximum of 3 amps, a 5000mAh battery at 5 amps, etc. Many batteries are now rated for higher charge rates but there is a possibility of battery chemistry damage if high rates are used too regularly. If in doubt, charge at 1C or below. There are ways of doing this efficiently!

The parts of a charge station and lipo battery storage

  1. The balance charger
  2. The power supply (home)
  3. The power supply (field)
  4. (optional) Parallel charge board or harness
  5. Lipo bag/box

1) The balance charger

I have just sat for about 5 minutes trying to work out how to start this so it may be a little incoherent on first release, I will try to hone it later. Most people find that their first charger is underpowered and wonder why it won’t charge their shiny new 6S lipos in under three hours! When buying a charger, you need to look for several things: input voltage, output voltage, maximum current (amps -A) and very importantly maximum power output in watts (W). I’m going to start by considering charging a single battery on a single channel charger as it is where most people start. Something like the imax B6. When you look at the box below, you think great; it’ll charge up to 5A, so my 6S 5000mAh battery will charge fully in an hour no problem… it even says so on the box… Right?

iMax B6 lipo charger

iMax B6… my first charger.

Wrong. It is true that a 5A charge would give a 1C charge rate for a 5000mAh battery (5A = 5000mA). However, what this doesn’t take into account is the battery voltage or total wattage of the charger. The charger has an input voltage of 11-18V and a total power of 50 watts (not found anywhere on the box).

In this example, I am using an 18V power supply capable of delivering 540W. As a result it can potentially power more than 10 of these B6 chargers at a time.

As you can see from the next photo, the charger will only charge at 2.2A (less than 0.5C). The reason for this is that we are trying to charge a 22.9V battery at a maximum of 50W.

iMax B6 charger

The iMax B6 trying to charge a 6S 5000mAh lipo.

Here is a simple equation: W = A x V. By rearranging that we get: A = W/V.  So 50 divided by 22.9 is…. 2.18A. So basically, this charger is maxed out as it has hit the maximum 50 watt limit. At this rate the battery will take about 2 hours to charge. The B6 also has a 240 minute timeout set as standard (a good safety feature) so it may time out before it charges.

We can quickly work out the maximum battery size that will actually charge at 5A on this charger using the same equation as before.

Rearranging it again we get: V = W/A

So the maximum voltage that will charge at 5A is 50 divided by 10: 10 volts.

Remember a 2S lipo has nominal voltage of 7.4V and a 3S is 11.1V. As a result, this charger would charge a 2S lipo at 5A but as soon as you get to 3S or more, the wattage will max out. This charger does have its uses; I now use it to charge my 2S and 3S AV receiver and LCD batteries as it is a good lightweight charger and frees up my main charger for the big lipos.

This next charger, the Hobbyking Eco 6-10 is very similar to the B6 in most ways. In fact, the user interface on a lot of these chargers is identical. You do have to manually choose a normal charge or balance charge.

Hobbyking Eco 6-10 charger

A step up from the B6

As you can see, with this charger I put in exactly the same settings and am getting a constant 5A charge. So what is the difference? Well, the big 200W on the front gives a major clue. The battery is currently at 23.75V as you can see if you enlarge the photo. Going back to our equation: A = W/V… 200W divided by 23.75 is 8.4, so theoretically this charger could charge my 6S lipo at up to 8.4A at this stage of the charge cycle.

This charger will give a maximum 10A charge so I set it to that to see what would happen. As you can see from the next photo, The wattage has become the limiting factor as suspected and we are limited to 8.4 amps, which on this battery is a 1.7C charge rate (this battery is rated up to 5C charge).

Hobbyking Eco 6-10

I set this up for a 10A charge but it is limited by maximum wattage to 8.4A

In the words of the great Professor Brian Cox “…and that’s why I love physics!”

It is completely predictable, if you know your batteries and can use one simple equation you can work out the minimum requirements of your charge system for the batteries you are going to use.

There are variations on these types of charger so that there are multiple chargers in unit. There are a few out there, that are basically four iMax B6 chargers in one box. The key thing to look for there is the wattage again, particularly with respect to the maximum wattage each channel can support.

My current charger that I use both in the workshop and out on projects is the Fusion Emperor L712B Pro. This is a two channel charger capable of 500W per channel.

Fusion Emperor L712B Pro

This charger gets taken everywhere!

As you can see, both channels are plodding away at 5A no problem. There is also no balance charge option on this charger, the balancing is part of every charge (evening the individual cell voltages out so that they all end up as close as possible to 4.2V).  It also gives you % charge and loads of other useful information on other screens.

At 500W (max 20A) per channel, using the equation A = W/A and the information from the bottom channel on the photo:

500/23.94=20.88A, so I could charge this battery at the maximum 20A (a 4C charge rate). Alternatively I could charge 4 of these batteries in parallel at 5A on each channel, meaning I could charge 8 6S 5000mAh batteries in one hour.



2) The power supply (home)

At this point a new limiting factor has come into play. In order to use the maximum 500W on each channel, I need to be able to use 1000W of power. You may remember, this power supply only provides 540W, so I’m going to be able to use about 270W per channel which means with this power supply I will only be able to charge 4 lipos at the 1C rate. In order to get the full potential from your charger, the power supply you are using must be able to supply at least the same wattage as the charger, so all I need to do to be able to charge my 8 batteries at a time is to buy a minimum 1000W power supply and it is sorted. Right? Pretty much! Just check that the power supply is also able to supply the minimum amps required too. Also, the charger will work most effectively if you are able to supply power at a higher voltage than the batteries you are charging. So to get the most out of my Fusion Pro I need a power supply that will provide a minimum of 40 amps at 24V and a minimum of 1000W total power. There are some people who will realise it isn’t quite that simple, but I’m trying to keep it as simple as possible. Make sure your power supply voltage does not exceed the voltage of your charger or you will blow it up! For example, I wouldn’t use the iMax B6 ona 24V supply as it is only rated up to 18V.

Something like this SkyRC power supply is great as it has fully adjustable voltage and can provide up to 1200W at up to 50A which will easily let me use the full potential of my Emperor Pro. With chargers improving all the time even this power supply may not be enough!

All very well, but what about when you’re out filming and haven’t got an extension lead into a convenient building…

3) The power supply (field)

Up until now I have generally used a direct connection to my car battery to provide power to my charger when out on location with no mains power. I did experiment with an inverter to convert the output to AC and then plug in the 18V supply, but it was inefficient and also a mess of wires to set up. Using your car battery without the car running also runs the risk of draining the battery. Car batteries also aren’t designed to be deep cycled so you may be reducing the life of your battery. So now I am moving towards a system using either a 24V deep cycle leisure battery or two 12V leisure batteries in series to give 24V.

field lipo charger

Using deep cycle leisure batteries in Rotarama’s field charging system

Here, in a setup used by my friends at Rotarama, as you can see, we are using two 12V deep cycle leisure batteries in series to give a 24V output.

These batteries have a combined capacity of 220,000mAh. Enough to charge Our 5000mAh batteries 44 times. More actually as you’ll remember, with the 20% rule, we shouldn’t be putting more than 4000mAh in each time anyway.. More than enough for a day’s work!

If you look carefully at this picture, you will see that we currently have two batteries in parallel on the left hand channel and nothing on the right. As we use our batteries in pairs, it is logical that we charge them in parallel pairs too. Parallel charging can be carried out with any batteries of the same voltage. I feel it is best to only charge batteries in parallel if they are the same capacity and state of charge as well. You can see we are using a parallel charge board that will take up to 6 batteries in parallel.

Which neatly leads us on to our penultimate section….

4) (optional) Parallel charge board or harness

Bearing in mind the equation we talked about earlier, it may be possible to get more out of your charger by using parallel charging.

If you look back at my battery post, you’ll remember that putting lithium polymer batteries in parallel is not only possible, but can be very advantageous at times. It works with charge as well as discharge. So if I put my two 5000mAh 6S in parallel and the balance leads also in parallel using the special board (parallel boards for most types of connectors are readily available at most RC shops and online) then I effectively have one 10000mAh 6S2P battery. As a result I can charge the pair at 10A and each battery is getting the equivalent of 5A (back to the 1C charge rate). If I added a third battery I would create a 15000mAh 6S3P battery which could be charged at 15A to give the 1C charge rate.

5) Lipo bags and boxes

I don’t like to get hyped up over danger. For every scary lipo fire you may see on the forums there are literally thousands of successful charges. Also, incidences seem to have reduced considerably over the last few years as technology and understanding has improved. However, there area number of things you can do to make sure you charge safely.

  • Use lipo bags for containment in the event of a fire.
  • Store your lithium polymer batteries in a metal case. A lot of people use ammo cases!
  • Always charge on a non-flammable surface.
  • Keep a small portable powder fire extinguisher near your charge station and out on location.
  • Keep a log of battery charges. Changes in capacity and cell balance can indicate a battery that is degrading.

I hope all this helps to some degree. If you want to discuss anything, do get in touch!

Fly safe!

Elliott – HexCam

I am publishing this as I type… so more will keep appearing throughout the day.

Lithium polymer batteries and balance chargers for multirotors

I get a lot of questions about multirotor equipment so I thought I’d start creating some posts about that. Please bear in mind that I learn a lot from reading around the blogs and forums so any inaccuracies are completely due to my own misunderstanding. By reading this you accept that, although I hope it will aid with your own understanding, it is written in good faith and I can’t take responsibility for any damage to yourself or your equipment that occurs through the use of this information. If you see anything that I have got wrong or you feel is dangerous, please contact me through the HexCam website or Facebook page and I will rectify it as soon as possible. Please treat lithium polymer batteries and multirotors with same respect you would give to other electrical and mechanical equipment. Look after them and they will look after you.

You also need to know the following: I am not paid to review or endorse any products but I do have a partnership arrangement with Versadrones to act as their demonstrator and trainer in the UK.


It worries me that people are prepared to skimp a little bit on their lipo batteries. It is worth bearing in mind that anything that can fly can fall, so I tend to look around for the best batteries I can within my budget. However, there are now a vast number of different lipo batteries, chargers and power supplies out there which leads to some confusion. I tend to buy my batteries from Hobbyking who now have a UK warehouse and have come to prefer the Turnigy and Turnigy NanoTech batteries. My reasons being that they hold good cell balance and seem to maintain battery health for a good period of time whilst being reasonably priced. I’m going to try to keep this as non-technical as possible, but when talking about batteries you have to get a bit technical. As a result I suggest you get a coffee (or maybe a beer if it is late enough in the day), maybe a notebook and possibly some biscuits as well. Sitting comfortably? Then I’ll begin…

Lithium polymer battery basics

What on earth is 3S, 4S, 6S etc?

I’m not going to go into the chemistry of lithium polymer batteries in this blog, but the basic unit of the battery is the cell. A battery is generally made up of between 2 and 10 cells in series. Each cell has a nominal voltage of 3.7 volts and a fully charged voltage of 4.2 volts. So 3S means 3 cells in series. Putting cells in series multiplies the voltage of each cell by the number of cells. A 3S battery has a nominal voltage of 11.1 volts (3 times 3.7V) and a fully charged voltage of 12.6 volts (3 times 4.2V). A 6S battery (now standard on a lot of larger multirotors) has 6 cells in series so has a nominal voltage of 22.2V and a fully charged voltage of 25.2V.
With me still?

But I saw 6S2P!!! What is that?

OK. Unlike most other types of battery, lithium polymer batteries can be connected in parallel (P) too. This is incredibly useful as it means by having two batteries the same connected in parallel you can maintain the original voltage but double the capacity. 6S2P means we have two 6S batteries connected in parallel. So, if each battery is 5000mAh, by connecting them as 6S2P we now have 10000mAh at 22.2V. In some uses this would effectively double the life of the battery. When flying, you have to take into account the extra weight you are adding with the extra capacity. As a result, if a single battery gives you 10 minutes of flight time running two in parallel will give you around 16-17 minutes. So, you lose some flight time but gain a degree of redundancy in the system in case of one battery failing. Your call! I prefer to fly with two batteries where possible.

5000 what?

This one is a bit simpler, The mAh or Ah refers to the capacity of the battery. As a compromise between weight and power we tend to use 5000-6000mAh batteries and connect them in parallel. So a typical hexacopter will run on 6S2P with each lipo having a 5000mAh capacity, giving 10000mAh to play with, of which we recommend about 8000mAh is actually used. Leaving 20% in your batteries not only gives you a safety barrier, it also means that if you do suddenly need that last bit of power on landing, it is there. Discharging a battery repeatedly below 20% will cause damage to the battery chemistry which could then fail during flight or charging.
Here is a video of one of our hexacopters. You can see the two 6S 5000mAh Turnigy Nanotechs on top. They are connected in parallel to give 6S2P at 10000mAh:

I found some more numbers! 25-35C. What’s that!?

Lithium polymer batteries almost always have a “C” (capacity) value associated with the other battery information. In fact, they may have two, one for charge rate and one for dicharge rate. The C value is the recommended or maximum rate at which current can flow through the battery without causing damage to the battery chemistry. These days batteries tend to start at around 20C for discharge (use) and can go up to around 100C. So what would a 1C rate look like? The easiest way to think of it is a 1C rate would use the capacity of the battery in 1 hour. So a 5000mAh battery used at 1C would be down to 0% after an hour. If you double the C rate it halves the time. So at 2C it would last 30 minutes and at 4C it would last 15 minutes. Most of my copters tend to use power at around the 5-6C rate when hovering, so a single 6C battery will last around 10-12 minutes. However, if I suddenly put my copter into full vertical lift it will draw more power and so the C rate will shoot up. If a battery says 25-35C, it means that the continuous discharge it can cope with is 25C with a peak discharge of 35C that should only be reached for seconds at a time. It is recommended that you choose a battery where all your usage will be at or below the continuous discharge rate. For most hexacopters 25C continuous discharge should be perfectly adequate. The discharge rates going up towards 100C are really aimed at pilots carrying out extreme flying with very rapid changes in power output, for example 3D helicopter flight. With aerial filming, the majority of flight is gentle movement and hovering.

The charge C rate

Conventionally, it is recommended that batteries are charged at the 1C rate. This means that a battery will take around an hour to charge and a little longer with balancing. However, you will find that batteries now have charge rates of up to 5C. I tend not to charge my batteries above 1.5C. Rapid charging will eventually degrade battery life. Of course if you are using batteries in 10 minutes and then they take an hour to charge, there is a mismatch in supply and demand if you are out on a long shoot. At this point you have a few options:

  1. You carry enough charged batteries to do the whole shoot
  2. You carry fewer batteries but have a charger solution that allows you to match supply and demand
  3. You have an intermediate amount of batteries and accept that as the day proceeds demand may exceed supply!

This conundrum leads me into chargers and home and portable power supplies, which I will blog about in the next installment.

I will also talk about lithium polymer battery safety soon as, although the safety has come on a long way in the last couple of years, lithium polymer technology should still be treated as potentially volatile, particularly when it comes to storage, transport and treatment after a crash.

Fly safe!

Elliott – HexCam