XT30 Battery Discharger

The other day I was charging up some batteries to fly and was surprised when a ground lead snapped off of its XT300 connector when I was pulled it off of the charger. That’s bad because one it couldn’t fly it and two I’d just finished charging it up so the battery was at it’s most dangerous.

I checked the rest of the batteries and noticed that there was one other one where the ground lead wasn’t stiff at the XT30 connector like it should have been. It hadn’t come loose yet, but I figured it would soon. I left it alone at this stage though so I could fly it and run the battery down.

I joked online about resoldering the connections, but I never seriously contemplated doing that. I’ve soldered a lot of XT30 connectors but never where the wires were attached to a battery. It’s possible to do, but you have to be careful about getting the wire too hot and damaging the battery’s wiring connecting the cells together or worse damaging the actual cells and potentially causing one or more to fail. Batteries are cheap enough that I’d rather just replace one than risk causing a fire trying to repair one, especially one that I’d been flying for months and pretty much had gotten my money’s worth on anyway.

It did make me realize a bad habit I’d picked up though. I’ve gotten pretty used to using the leads to disconnect XT30’s either from the quadcopter or from charging boards. I don’t know for sure that my habit was the sole cause for those two battery leads breaking, but it’s likely that it contributed. I have four more from that set that are all fine, but I’ve still tried to be better about using the plastic housing on the XT30 and the balance plugs to disconnect rather than grabbing the wires.

Disposing of batteries requires discharging them down to zero, and that’s a bit of a trick as most battery chargers that have a discharge setting won’t go below 3.2 volts as that’s usually the absolute minimum before damage will occur to the battery. So while I could discharge both batteries down to 3.2 volts, I couldn’t get them to zero and so safe to take to recycling without making something.

There are a few different ways to completely discharge a battery that carry varying amounts of danger with them from the completely safe and very slow saltwater bath to the very dangerous and not smart puncturing the cells with a nail. I opted to a fairly safe and fast method of using light bulbs. The only danger here is the heat that the bulbs generate while discharging, but that’s easily managed by hanging it off of the edge of my desk.

One thing I didn’t want to do though was just solder a bulb to an XT30 connector and leave it at that since eventually the bulb would need to be replaced, even if it would probably take a long time for that to happen. I found a set of bulb sockets on Amazon that looked like they would work pretty well along with some Halogen bulbs.

After that it was just a matter of soldering an XT30 connector that I could plug batteries into and soldering that to one of the bulb sockets, which I decided to shorten as much as possible to limit the amount of current traveling through those thinner wires.

Once I had it soldered and heat shrink over the connections I was able to test it out on the battery where the ground lead hadn’t quite come loose yet. I tried to keep a battery tester on it but since I’d flown that battery after charging it, it was already down to about 3.5 volts and once it went below 3.2 volts there wasn’t enough juice for the tester to run.

The other battery required a little extra effort to discharge. My multimeter came with a set of cables, one red and one black, that had alligator clips on the ends, and I was able to use one of those to connect the ground lead to the XT30 connector. That seemed much safer to me than trying to hold the wire against the connector with a pair of pliers. Thankfully it didn’t take long for the halogen bulb to kill the battery, but it did produce a pretty impressive amount of heat. I could feel it just by holding my hand over the bulb, and I’m sure it was hot enough that I would have gotten a nice blister if I’d have touched it. It did cool off afterwards quite quickly though.

After killing both batteries I cut the leads and balance plugs. The trick with this is not to cut both wires at once which would short them out. It shouldn’t matter since I’d discharged both batteries down to where the bulb wouldn’t light but that didn’t necessarily mean they were at zero volts, it was just too little voltage to light the bulb. It’s just a good habit to havy anyway.

I gut the red wire short since the black ones were both snapped off at the lead. That way the wires can’t come into accidental contact like they might if their lengths were similar. Then I taped all of the wires to the battery just to make sure that nothing could come in contact with the wire ends. It’s probably overkill, especially for a relatively small 2S battery, but I’d prefer to err on the side of caution.

Discharged and taped up, I put them aside for the next time I’m near the battery recycling center for disposal.

XT30 Switch

When troubleshooting a quad problem or when getting a new build configured, I’m regularly plugging in a battery to a quad to power the motors, VTX, and receiver, and then unplugging it again. I don’t like to leave the battery plugged in any longer than necessary since the VTX can quickly overheat and damage itself. They’re designed with the expectation that the quad will be moving and getting a lot of airflow to cool off. Even with the VTX set to it’s lowest power of 25 mW, I’d still just prefer not to leave it powered any longer than necessary.

So that means dozens of cycles of plugging in an XT30 connector and then unplugging it again, which quickly becomes tedious and hard on the finger tips.

With my HD toothpick build coming up I was thinking about this, and realized I could get an in-line switch and add XT30 connectors to either end as a way to easily switch the battery on and off. Even better since that could also plug into my smoke stopper as well.

I did a little research on Amazon and settled on these inline 250V 10A appliance switches. I would never be drawing anywhere near 10 amps while powering a quad on my bench, so it seemed more heavy duty than I’d need but I always like to be extra safe when dealing with electricity. When they showed up I was pretty happy with the quality of the housing and the hardware inside.

Making the switch was pretty easy, there was no soldering to do for the switch itself, I just had to make the XT30 male and female ends, which is a very easy soldering project. I cut some 14AWG silicone wire to what I thought was a decent length and laid out those with some heat shrink, the switch, and the XT30’s just to try to get everything straight in my head and make sure I’d thought it all through.

Soldering the XT30 connectors only took a few minutes to do, and I also went ahead and tinned the wire ends that were going into the switch just to make sure that the wires were as durable as possible.

Then it was just a matter of connecting the wires inside the switch keeping the positive and negatives lined up correctly. Except I found on my first test that plugging in the battery, the switch was live in the off position and the led light wasn’t working. I had to take it apart and swap the sides for the male and female connectors.

For the second test the switch worked as expected except that the LED wouldn’t come on. I tried a different switch with the same issue. So I’m not sure if the LED’s are just set for a higher voltage like you’d get from a house line or maybe it’s an AC versus DC thing, but the switch part worked like a charm which was the important part for me.

For such a simple and easy project, I think it’s going to make a world of difference the next time I’m trying to bind a receiver and I have to press a tiny receiver button with a pair of tweezers while simultaneously plugging in a battery. Something which really requires an extra person to do without swearing, and now should be pretty easy to do with just two hands.

1S Charging Adapter

When I first got into flying I was using a whoop style quad that flew on a 1S LiPo battery, which means a single celled lithium-ion polymer battery. The kit I bought came with a small USB charger that would handle up to four batteries and took quite a while to charge them completely.

I soon upgraded to a parallel board that would do six batteries and had a DC wall converter that would handle 3 amps, USB 2.0 caps out at 0.5 amps for comparison. It was much faster and better but it couldn’t do one important thing. After flying, I basically had to charge the batteries back to full, and Lipo batteries have a much better longevity if they’re left charged to what’s called storage voltage, basically about half way charged at 3.8 volts and about 30-50% capacity. Technically I could keep an eye on the charger while it was working and stop it once the batteries hit storage voltage, but sitting and watching batteries charge is not any more fun than watching paint dry.

Unfortunately there weren’t any chargers on the market at the time that would do storage charging for 1S batteries. I was looking at a charger geared for higher cell-count batteries anyway as I already knew I was going to be getting into bigger quads, and I happened across a forum page that talked about making an adapter cable to charge 1S batteries on multi-cell chargers. The adapter works by combining all of the 1S connectors in series to make the individual batteries look like cells in a single battery to the charger. It didn’t look too hard and would be a good way for me to practice soldering.

To make one I needed 1S female connectors, silicone wire, a balance lead, and an XT60 power connector. The number of 1S connectors depended on the size of the balance lead. I went for a 6S to be able to charge as many 1S batteries at a time as possible. This did mean that I couldn’t just charge one or two batteries on an adapter like this, I’d always have to do six at a time and all six needed to be the same capacity.

Soldering these up in series involved soldering the red wire on the yellow XT60 connector and the red wire on the balance lead to the red wire of the top-most 1S connector.

From there it was just a matter of connecting the next black wire on the balance lead to the black wire of the 1S connector along with the red wire of the neighboring adapter, and repeating across all 6 balance lead wires until getting the the last one where the black wire of the XT60 is included in the solder joint as well. It was an ideal project for someone getting into the hobby and needing practice soldering. Especially when I forgot to slid the heat shrink over some wires before soldering them, so I’d have to desolder the joint and redo it with the heat shrink in place.

The last stage was to add some heat shrink over the whole adapter. This last bit isn’t to electrically isolate any solder joints, but just to bind all of the wires together and make the adapter easier to use.

Balance chargers like my HOTA D6 Pro Dual use the combination of the power and balance leads to make sure that all of the individual cells in a battery are charging evenly. This let me treat six 1S 300mAh capacity batteries as a single 6S 300mAh capacity battery and more easily charge, storage charge, or even discharge batteries than any of the options I had at the time.

Just recently there’ve been parallel charging boards that have come out that will do 1S batteries by adding a jumper from a balance port to a power port. This loses one spot on the parallel board but it means that the charger treats the batteries as a single 1S battery with five times the capacity, so the charger can push more amps and charge the batteries faster. It also isn’t limited by needing exactly six batteries like my original cable so I can charge anywhere between one and five batteries, since the sixth slot is take up by the jumper.

Building a Quad – Assembly

After picking the parts the first thing I did was take the flight controller and plug it into USB and connect it to Betaflight to check two things. First just to make sure that it powered up before I started doing any soldering on it. So in case I got a defective part I would be sure that it wasn’t something I did on the workbench that broke it, and I’d more easily be able to get a replacement. The second thing was to see if it was to record the firmware target that the flight controller was using and make sure it was the most recent firmware version.

Then next thing to do to prepare for the build was to flash the receiver with the most recent firmware version from FrSky. This was a new process to me and involved downloading the firmware from the vendor, storing it on an SD card that I inserted into my radio, and then plugging the receiver into the radio using a wiring harness that the receiver came, then flashing the firmware.

Finally it was time to start building the quad, starting with the frame. I’d already watched a video of a more experience builder putting one together, but seeing it done once and doing it yourself tend to be very different experiences. For fun and to try to stay organized, I started out by organizing all of the pieces.

There’s four arms, blue standoffs, a top plate, a pair of bottom plates that sandwich the arms, and miscellaneous screws. Putting it together wasn’t too much different from assembling a Lego kit or any of the various children’s toys that I’ve had to put together after a birthday party or on Christmas morning. I think it took me about 20 minutes to get the bottom plate and arms assembled and be ready to starting on installing the motors and the electronics.

Before I started installing any of the electronics, I needed to tin all of the pads, and I figured that would be easier to do before I put them on the frame. In all of the build videos I’d watched to get ready for this, the builder would just put the board on the frame and then add the solder from there, but I was coming into this with just a little bit of soldering experience and I wanted to give myself the best chance at success. So I laid out all of the boards in the flight stack and made sure I knew which wires ran to which pad.

Then I tinned all of the boards at once: flight controller, four-in-one ESC, and VTX. The Caddx HD capture board on the camera had plugs and didn’t need any soldering.

Putting the ESC onto the frame as the base of the flight stack and installing the motors marked the first real part of the build for me as the quadcopter started to take shape. The process itself was pretty simple: screw a motor onto an arm, run the motor wires to the ESC, measure and cut the wires, solder them to the ESC. But cutting wires like that was a bit nerve wracking for me, as I was paranoid about cutting the wires too short and too long. On the one side I’d end up without enough slack and have to solder additional wire back on along with heat shrinking the joint, and on the other side I was trying to have a clean build plus extra wire would also contribute to extra weight. Which a few grams doesn’t sound like a lot but for a small 3″ build like this every gram counts.

After that the next step was the battery lead. As often seems to happen to me with this hobby, the part I was thinking was going to be easy turned out to be pretty difficult. It took a lot of work for me to get these two leads soldered onto the main battery pads of the ESC board. The heavy gauge wire and the big soldering pads on the board required a lot more heat than I’d been using up until now in order to get the joints flowed together properly.

Soldering the rest of the electronics was pretty easy. The hard part had been getting the documentation online for the various parts and making sure I knew which pads to use on the flight controller for the camera and the VTX. It had a pin header that plugged straight into the ESC board which made assembling the rest of the flight stack pretty easy.

Then came the big moment, plugging in the battery for the first time to see if it all worked. After going over all of the solder joints with a multimeter to see if I had shorted anything, I took the battery and plugged into a smoke stopper before plugging that into the battery lead on my new quadcopter. A smoke stopper is basically a fuse that will trip in the case when there’s a short somewhere so that you don’t release the magic smoke from the electronics. I’d bought one with a light and a reusable fuse at the same time that I ordered my parts.

The smoke stopper lit up green and the leds on the flight controller, receiver, and VTX are lit up as well. The best part though was hearing the startup tones playing as the flight controller and motors synced up.

After the battery test I connected it to my computer and went into Betaflight to check that all of the motors were spinning the right direction, and then change the settings on the two that weren’t. Then I plugged in a battery again and I checked that my radio would connect, and that I was getting a video signal in my goggles from the VTX.

At this point I figured I was just about done, I just needed to put the top plate on and the props. Which naturally is when I ran into the one problem that gave me the most trouble in the whole build.

When I picked out all of the parts, I remember adding up all of the heights to make sure that it would fit inside the frame. But I was looking at the height of the standoffs on the frame and not the length of the screws for the flight stack which were a couple of millimeters shorter. That makes sense to me now since you don’t want those touching the top plate and transferring impacts from the top plate into the flight stack, but it meant that I was just a couple of millimeters short on getting the top plate on my brand new build.

It took more time rearranging the parts and trying difference spacers between the boards to get everything to fit than it did to do the whole rest of the build, or at least that’s what it felt like to me, but in the end I did manage to squeeze everything in. I wasn’t completely happy with the solution but it would do until I could order slightly taller standoffs and longer stack screws.

Building a Quad – Picking the Parts

With the weather warming up I started looking into building a larger sized quad to fly outside. I decided I didn’t want to go straight to a full sized quadcopter with 5″ props which is the standard for FPV freestyle. I wanted to be able to fly comfortably in my yard, so that I could get more time in during the week, rather than always having to go to a field or park. So I settled on a 3″ build plan, because I’d heard that building for smaller props than that wasn’t as good of an experience.

Build a quad from scratch was a daunting experience because of all of the different pieces that needed to be selected and work together. You have to decide on a frame, what size of motors, the camera, the video transmitter (VTX), the receiver, the antennas, the props, the electronic speed controllers (ESCs), and the flight controller. Each component has an impact on the others too. There’s the obvious factor of the weight of the different components versus the thrust that the motors and props will generate, but also just compatibility between the amount of space in the frame for components and the mounting pattern versus the size of the flight controller and other electronics.

I started with the motors and got some advice from some local pilots to look at 1407’s as a good size for flying 3″ props. Then I used a site called RotorBuilds to figure out the rest of the parts list. It’s a site where people post their quadcopter builds. Some with detailed articles and photo albums of the step-by-step and others with just a short description of how it flies. But all of them have a parts list with links to vendors on them. So I ended up searching the site by the size of motors I was looking at building with and getting ideas from that on what parts I was going to buy. One build in particular I ended up being interested in was a 3″ Xilo Phreak because the guy mentioned how durable it was, and I figured as someone just starting out that getting a quad that could handle some hard crashes would be a good idea. I also liked that the Phreak frame had replaceable arms, so I figured in a worse case scenario if I crashed and broke one I wouldn’t have to rebuild the whole baseplate.

For the flight controller, I ended up going with the one mentioned in that RotorBuilds parts list. The HGLRC stack came as a combo with a four-in-one ESC and a VTX so I didn’t have to worry about them working together and the price on the full stack was just a little cheaper than what I’d have spent on separate boards.

When looking at cameras, the major factor in picking one was that I wanted to do HD capture from this quad, and a 3″ build though is too small to carry a GoPro. Plus there was the fact that I didn’t own a GoPro and I didn’t feel like spending a couple hundred dollars to get one. So I had only two choices: a RunCam Split or a Caddx Turtle. Both of these are camera and HD capture board pairs where the camera signal passes through the board first for recording, then goes to the flight controller to get the onscreen display overlay, and lastly goes to the VTX. This allows capturing HD quality video to an SD card on the quad without any analog transmission, but adds some latency to the signal. Latency is a big point of contention among pilots. It is the amount of lag between the camera on the quad capturing an image and that image showing in the pilot’s goggles. Some people seem to be able to notice and be bothered by tiny amounts of latency in that setup, and try to stay away from these types of split capture boards. I’ve never really noticed a problem with it though. I picked the Caddx because it came in black and was a slightly newer design.

The receiver and antennas were that last parts and those were pretty much a given. Since my radio uses the FrSky protocol, and I wanted telemetry on the quad, I only had one option in the R-XSR. For the antennas I had an omni and patch Axii on my goggles already so I got another omni with the same polarization for the quad build.

I was doing all of this near Easter so many of the sites were running sales. I ended up getting most of the parts from GetFpv.com. They didn’t have the receiver in stock though, so I ordered that plus a couple of batteries and a smoke stopper from RaceDayQuads.com. Then I just had to wait for everything to show up.

Here’s the final parts list:

Repairs and Race Gates

Once I got to the stage where I was flying more than crashing, I started thinking about the next steps which in my mind was getting outside to fly and flying something bigger than a tiny whoop. That left me with two options buy a bigger quad or build one, and I really wanted to build one after going the easier route for the whoop. This meant I needed to get some practice soldering. Preferably on something cheaper than a $10 motor or a $40+ four-in-one ESC board. Which is when I ran across the idea of making a balance charging connector for 1S batteries.

Now you can buy one of these pretty cheaply, I got one from Amazon for less than $9. But that doesn’t get me practice with soldering or using heat shrink and is just not as fun. So I used this forum post I ran across the make one instead. It’s hard to compare the prices since the wire I bought was $7 on it’s own but I barely used any in making this. But the experience in using the soldering iron and the heat gun was well worth it to me.

Most of the soldering done, before the heatshrink was applied.

Basically the batteries are wired in series so that the charge just see’s a single 4S battery in this case. The charge and discharge goes through the XT60 that I soldered on after this picture was taken, while the balance lead has the tree-like wiring to connect the individual batteries together as cells. This allows me to charge 4 1S batteries at the same time, as long as they are all identical type and very close to the same voltage. Which is why I was making a 4S one. I’d already bought a 6S one from Amazon but it meant I couldn’t use it unless I’d flown 6 packs, which some nights I didn’t do.

After that my next foray into soldering wasn’t an optional project. I dropped my radio and snapped of a switch. Not just any switch either but the switch that I’d mapped for arming the quad. Now I did just remap that function to a different switch, but it messed with my muscle memory so it wasn’t going to be a long term solution. So I ordered a new 2 position switch which ran about $5.

This wasn’t actually the first time I’d opened up the radio. When I first got it the left stick which is for throttle and yaw control had a ratchet on it. Which mean that the throttle didn’t move smoothly bit had little stops built into it. I believe this is helpful for RC planes, but it’s not good for quads, so I had already been inside to radio to change it. That time wasn’t too intimidating since I was just adjusting some screws, whereas now I was planning to do some soldering, so I was a bit more worried about screwing something up.

There’s a lot in these devices, but it really wasn’t that bad once I took a little time to look at it. I had to unscrew the old switch from the housing, then remove the heat shrink, and desolder three wires from it. None of which was too bad. The hard part was figuring out the orientation of the new switch since I didn’t think to take pictures of the old one before I removed it. I eventually noticed that the housing and the switch had matching grooves, so that clued me in enough to solder the wires back onto the new switch and put everything back in place correctly. I think the whole operation took me an hour to do, but I’m sure it would’ve taken half that time had I paid more attention to the original wiring and part orientation.

Besides learning to solder and repairing my gear, I also made some race gates. I’d gotten three orange plastic ones for my birthday and they made flying in the house a lot more fun, but I wanted a few more and didn’t want to spend $30 or more on another set. Instead I got an idea from another local pilot who made some gates using poster board and copper pipe fittings.

I made a trip to the local craft supply store for a few sheets of poster board and a couple rolls of duct tape. I already had some scrap 2×4’s and a bunch of dowel rods as well as a hot glue gun. I used the original gates I had gotten as a template for the inside dimension and then I cut six two inch strips of poster board, so I could have double pieces at the top an bottom. The thickness matched up pretty well with the smallest sized dowel that I had, so I was able to make a fork with dowels and scrap wood for the gate to slot into.

Then it was a matter of cutting pieces for the stand’s base, adding some rubber feet so they wouldn’t slide, and cutting some larger diameter dowels for the height I wanted the gate to be. I added duct tape one all four sides at the center line to help find the center of the gate when flying.

I made four of them and had enough supplies for a couple more still. They work great and I got a lot of compliments on them from the guy who’s gates I’d gotten the original idea from.

Here’s a flight from late February where I’m using both the homemade and bought gates in the house. I really got these are the right time as I’d started to get pretty tired of flying inside by this stage. I was really itching for nicer weather to get here so I could start flying outside.