GM Multi - Solo Charger




Introduction: GM Multi - Solo Charger

About: I'm a Commercial Pilot who not only enjoys flying but also likes building/creating things with my hands.

The GM Multi - Solo Charger is of my design and is made for the 3DR Solo Smart Drone. My goal behind building this charger was to be able to charge a full backpack worth of the Solo's batteries (holds five) at once. Additionally, I wanted to make a charger that would have an improved charge time over that of the stock chargers. I also wanted the charger to be able to break down easily and be adaptive to multiple power sources (car batteries, plug in power source, and whatever you can think of.) The Yeeco DC to DC boost drivers that I use in this charger provide the adaptability I was looking for, and also benefit you, as they will except 10-32v input voltage. Lastly, another big design consideration of mine was to use the correct wire gauges throughout the charger. While some people might be worried about the 12 gauge wire getting hot one should note, at most, this charger will pull around 33amps collectively. 12 gauge is rated at pulling 41amps. I hope that you have as much fun building this charger as I had designing it! Remember the GM Multi - Solo Charger and it's case .stl files are fully open source, so feel free to do whatever you like with them. I only ask that you don't change the name of the charger, but instead do for example, (GM Multi - Solo Charger Steve's Version or something similar.) I only ask this so that this charger, and your particular versions of this charger, are easily searchable. #fly3dr

****Due to the high demand of this product I've created a business to sell this charger***

Buy Assembled:-

Printed Kit Available At:-

Step 1: Ordering Components (do Not Follow the Wiring Diagram/early Prototype)

(x5) Yeeco DC to DC DC DC Converter:-

(x1) DC 12V 50A Universal Regulated Switching Power Supply:-

(x1) 20 gauge 25' Red/Black Hookup Wire 12V DC:-

(x1) 12 Gauge Silicone Wire 10 Feet:-

(x1) Assorted Heat Shrink Tube 10 Sizes:-

(x1) Copper Plated Metal Battery Clips Alligator Clamps 50A:-

(x2 packs) XT60 Connectors 5 Pairs:-

(x5) but have to buy 6 to place order) MOLEX 46437-1087 Connecters:- (or if they are out of stock of the factory plugs print this:- and then buy these extension cord repair to get the prongs

(x1 pack) Phillips Flat Head Machine Screw 18-8 Stainless Steel:-

(x1) M3 x 14 screws:-

(x1) 140/141/142 Series Barrier BlocksConnectivity Solutions:-

(x1) AC Power Cord:-

(x1) 12v Fan:-


Medium and small philips screwdriver

Small flathead screwdriver


Solderer and solder

Lighter/match/heat gun or hair dryer on high

Hot glue or epoxy (recommend hot glue)

#64 rubber bands (if you don't use rubber bands you will need four M3 x 16 screws)

Some free time (:

I am assuming you have a solderer and a basic understanding of soldering.

Total estimated cost: $210.00 USA

Oh and a few beers of course.

Step 2: Download and Print the Case Out

I designed a 3d printable case for this charger so that all the components are evenly spaced, and so the charger looks nice. I keep all my .stl files open source as well, and they can be found at the following link bellow. As a word of caution for you guys with smaller printers, the case measures 300mm by 140mm. But don't fear, I provided the google SketchUp file on Thingiverse so that you could modify the case to fit your needs. I printed the case in PLA with 30% honeycomb infill and sliced it using the latest version of Slic3r 1.2.9.

Thingiverse Link to all files:-

Printed Kit Available At:-

Step 3: Connecting the A/C Cord to the Power Supply

Take the A/C cord and cut off the triangle shaped end (the end without prongs) and strip away the outer black insulation exposing the three inner wires. You can use scissors or a razor to cut off the outer black insulation, be careful to not cut through any of the three inner wires. You will want to strip off about 2 inches of the outer black insulation. Next strip off about 1/4 inch each off the three inner wires. The inner black wire is known as line or (L) and should be screwed into its connector on the power supply. The white wire is known as neutral or (N) and should be screwed into its connector as well. The green wire called ground goes into the connector on the power supply that has the symbol that looks like an upside-down T with a two of lines under it. Lastly, check to make sure the power supply is switched to 120 USA or 220 Europe, the switch to do this is found on the side of the power supply. Switch it so you see the voltage you want on the switch. Plug it in to make sure it works (fan comes on) and then unplug and set aside. Be careful not to touch any of the connections or you will get the tickle of your life.

Step 4: Installing the Yeeco Boost Modules

Screw in all five Yeeco's in the orientation depicted in the pictures (fuse facing the back) It is best to avoid screwing each screw down all the way right away, but instead screw each screw only halfway in until all four screws for that Yeeco are screwed partially in, and then tighten them all down. Remember you are not tightening a down a cylinder head; only screw in until in gets fairly snug. Also, tighten diagonally like when you screw on the wheel to your car.

Step 5: Installing the BusBar

In this step, we are going to be getting the BusBar set up and installed in the bottom case. First off why don't you get out your package of 12 gauge wire and the BusBar. Once you have those things out we are going to want to strip the the black wire enough to cover six pegs on the BusBar. Once you do this twist all the strands together and tin them as seen in the pictures, you will then want to tin all 12 pegs on the BusBar. Now solder on the black wire to its six pegs on the BusBar as shown on the pictures. Make sure to get a good solder flow between the wire and the pegs or else heat will be generated. Do the same thing for the red wire but it goes on the other six pegs. Make sure you solder it exactly as I am or else you will be hooking up reversed voltages later on. Also be mindful of the middle where there is only a small gap separating negative from positive. After those are soldered in, bend the black wire as shown and route it in a loop around the mounting pegs for the BusBar. Lay the red wire on top of it as it comes around as shown in the pictures. Pull lightly on the black wire to get the slack out of it. Screw in the BusBar with four M3 14 screws. Once done cut the excess 12 gauge wire off the BusBar as shown in the pictures. Tin one of the Female XT60 connectors as shown and put some heat shrink on the wires(make sure to push it as far back as you can so the heat from soldering doesn't shrink it prematurely.) Next push in the female XT60 Connector in as shown and strip about 1/4inch off both of the 12 gauge wire leads coming off the BusBar. Make sure again that you follow the pictures exactly to ensure you solder the correct polarity on the right terminal of the connector. The flat side is positive/red and the triangle shaped side is negative/black. Just follow the pictures and you will be golden, or so they say. Lastly push up the heat shrink and heat it with your heat gun (hopefully you have one, try a hair dryer if you don't on high heat setting.) Go throw one back, you deserve it, then proceed on.

Step 6: Using Up the Rest of the 12 Gauge Wire (making Power Input Connectors)

Take your left over 12 gauge wire and line the leads up end to end. Cut off the extra red wire and save it for later. Now cut the folded 12 gauge wire in half, you should now have four equal lengths of wire. Strip the ends of one pair and solder a male XT60 connector to both ends of the pair of wires (making a male to male power in cable) Remember the flat side is red/positive and the triangle side is black/negative. Take the other pair of wires and grab out a pair of alligator clips.Pull off the plastic covering on the side with the tiny prongs. Strip both wires to about 1/2 inch and place in alligator clips. Crimp down the tiny tabs on the insulation of the 12 gauge wire, don't do it too tight. Solder the exposed 12 gauge wire very well to the clip. Then solder on a male XT60 connector to the other side. Remember to put the plastic back on the alligator clips and put heat shrink on before you solder the male XT60 connector (yeah Bob, I'm talking to you.) Take the red wire we saved and cut it in half. Solder on a female XT60 connector and put some heat shrink on (shrink a longer piece on the negative/triangle side so it looks like a negative/black wire) Strip the other side but do not tin it like I did, makes it too thick. Hook up the negative/black wire to COM (common ground) and the red wire/positive to +V. Boom you are a pro. Take a sip and move on.

Step 7: Installing the 20 Gauge Wire From the BusBar to the Yeeco's Input Sides

Get out the 20 gauge wire and strip the ends of it. Unscrew all the Yeecos inputs as shown (unscrew until the screw is flush with the top of the connector) Screw in the striped wires as shown and screw them down. Do a light pull test to make sure they are screwed in well. Then split apart the wires and measure their lengths to the BusBar. From how the BusBar is oriented in the pictures, looking left to right, posts 1-6 are positive/red wires and posts 7-12 are negative/black wires. Posts 6 and 12 will be used in one of the very last steps. Cut the wires so that Yeeco #1's red wire is on post 1 and the black wire is on post 7. Cut the wire and strip it. Place the wire under it's said terminal post on the BusBar (unscrew and lift tab and then screw down tight). Repeat for each remaining Yeeco. Each Yeeco gets its own post/terminal.

Step 8: Wiring the Yeecos Outputs and Securing the XT60 Connectors

Feeling lucky? Well lets see how it goes with this step. Grab your 20 gauge wire and cut it as shown in the pictures (cut enough so that it spans from the the Yeecos output terminal to the wall of the case, make sure you go to the actual wall of the case as shown in the pictures. Then cut four other lengths of wires (based on the wire you just cut) that size so that you have five equal pairs of wires. Then get out five female XT60 connectors and split apart those five stands of wires. Strip both ends of all the wires (oh the horror) after that tedious work, take another sip now. You should have a small buzz going by now. Tin the posts of the XT60 connectors and solder in the wires to all five of the connectors, making sure you are soldering in the correct polarity (red/positive flat side; black/negative triangle side.) Slap some heat shrink on those and shrink em' down real good and then unscrew all the Yeeco's outputs the same way as you did for the inputs. Follow the pictures for the next steps. Put the connector in the first connector hole in the case as shown. Make sure to put it in the right direction. Then screw in the striped leads into their correct terminals (red/positive goes in the terminal next to the two blue pots/rectangles) I found it easiest to push the XT60 connector in halfway and then with one finger line the wires up with the Yeeco terminals as I push the XT60 connector in until the wires are fully in the Yeeco terminals. Screw them down and then do the same for the rest of connectors. Once you are done grab your hot glue gun(what i used) or epoxy. Pull the XT60 connectors out as far as they will go without pulling out your wires and squirt some glue on the back are of the connector and quickly push it in all the way. Hold it there until the glue dries and then do the same for the rest of the connectors (don't forget about the the power input connector in the corner.) Nicely done chief.

Step 9: Powering Up the System for the First Time...

Well depending on your wiring skills or direction following (cough cough Bob) this could be quite eventful. Grab your Male to Male XT60 connector that we made earlier and plug one end of it into the power input connector on the charger (the connector to the BusBar) and then plug the other end into the power supply connector we made earlier. Then take a deep breath and plug in the power supply to the wall. You should see five green lights inside the charger box. If not oh no, you messed up unplug the power supply (it has a self resetting fuse after a few minutes) and then track down your short or loose connection. Now hopefully for everyone it just works fine and you don't have to troubleshoot. Grab out your voltmeter and set it to dc mode (straight line with a dashed line) and slip its leads into the first Yeeco output connector, DO NOT let the leads touch each other. You should see some random voltage around 19volts. Grab your tiny flat head screwdriver and adjust the pot/blue rectangle that is marked CV. Turn the screw counter clockwise to decrease voltage and clockwise to increase. Set the voltage to 16.8 volts (watch your meter as you adjust the screw) Do the same for the remaining Yeeco's. Unplug and set aside once you are finished doing this.

Step 10: Making the Solo Charging Cables

Take you remaining 20 gauge wire and cut five 34ich lengths out of it (you should have some left over for another project) Grab five of those Molex connectors and put on the 3d printed direction cover we printed out earlier (the tab should be on the side with all the little pointy tabs. Next cut off all the tiny tabs with dike cutters, making sure that when you are done that they are not touching the other side at all (aka shorting it.) Do not split the wires apart but only do so at the very ends so that we can strip and solder them on. Make sure that you solder quickly so you don't heat the connector up too much but make sure you get a good flow of solder between the two posts on the each side. Insert the wire in (will help solder to bridge the gap and let cool. Do the same for the other side. Next cut and put put on the heat shrink as shown. Be careful not to melt the PLA direction cover. It probably got a little bendy as you were soldering. Then on the other side of the wire put on a male XT60 connector, remembering to put heat shrink on first (damn Bob you did it again) Do these steps for the rest of the 34 inch lengths of wires to make five cables. Next plug in your hot glue gun or get your epoxy out and squeeze a generous amount out on the back of the Molex connector as shown. Then put a perimeter of glue around the 3d printed direction cover making sure it is seated all the way down and oriented correctly. Nice! you now have five high quality charging cables. DO NOT PLUG IN YOUR BATTERIES YET!!!

Step 11: Setting the Proper Current

Okay, now you really need to follow these directions carefully. Make sure you have a solo battery that is under 10% charge like 7% and set aside (real tough job right?) Do not turn the charger on until I tell you to do so.Grab your volt/amp meter and plug you terminals into their correct holes to measure amps. Then set your meter on Amps as shown in the picture, make sure it is NOT on mA/uA. Then grab out an alligator clip jumper and hook it to the positive/red side of the plug on the charger. Then connect the other end of the alligator plug to the positive/red side of your solo charging cable. Next, grab the leads of your meter and stick one on the negative/black side of the same charging port. Then stick the other lead in the negative side of your solo charging cable. Take your small flathead screwdriver and one each of the five Yeecos turn the pot/blue rectangle (the one right by the part we adjusted earlier) labeled CC. Unscrew it (counterclockwise) until it gets hard to keep turning (do not force it, it may take quite a few turns until it stops). Do this for every Yeeco. Double check nothing is shorted and plug in your solo battery to the other end of our current measuring setup and then power up the charger. You should see, on your meter about .130mA. Screw in (clockwise) the CC screw on the first Yeeco slowly while monitoring the current (it is normal for the power supply fan to spin up, as you are increasing the current draw through it as well) You should start to see the current draw increase as you screw it in. Keep screwing until you the current doesn't increase anymore or until you reach 5.9amps. If you didn't get to 5.9amps give the adjustment knob another half turn and call it good. Do the same thing for the remaining Yeecos (just move the leads from the first charging port to the next one, making sure to not short out anything and keeping the polarity correct) Once finished unplug everything and get your case cover and fan. Move to the next step sailor.

Step 12: Setting Up the Fan and the Lid

Well boys we are about finished. Grab the old lid and install the fan as shown (put some glue around the fans parameter and on the screws so they don't fall out on top of the Yeecos. Remember those two blank terminals on the BusBar (6th and 12th)? Yeah we are going to be hooking the fan up to them now. Follow the pictures and then put on the lid. I made screw holes but I decided to use four #64 rubber bands to hold the lid on. Without the rubber bands the case slides around easily on the table (basically using them as feet) . The rubber bands also allow for easy in-the-field access to the inner parts. Throw back to holding on my Aircore 40's wings on with #64 rubber bands (model rc plane).

Step 13: Troubleshooting Guide

Troubleshooting Guide

Note:- Written extended troubleshooting found at the product homepage at:-

If you found this tutorial helpful feel free to send me a donation at: (will show up as Betsy but is the correct account) and I can buy myself a full backpack worth of batteries. If you don't feel like it, no worries I hope you enjoyed making your charger. #fly3dr

Helpful resources:

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29 Discussions

Continuing on my last post about the Molex 46437-1087: Do you know anyone that is printing and selling them? I followed that link and it appears to only be the plans to print your own. I searched for quite a while and absolutely everyone is sold out. I really need to find a source for this or it appears this whole project will be for not... But thank you again for everything you have done to fill the HUGE gap of a missing multi-charger for these devices.

7 replies

I'll include the printed connectors in your kit for you, since everyone seems to be out of stock. The base is currently printing out and I'll try to get it mailed by tommorow afternoon or saturday morning.

You rock... I will make sure to send you some pictures when I finish the build.

Would it be too much to ask for one additional connector, just incase I decide to play with the mounting/configuration of the prongs? I just need to make sure whatever I come up with is reliable & consistent as one of my instructors will be the one using it once I build it. i happen to have one of those connectors you sent the link to. I ripped it apart and see exactly what you meant, great idea. I don't want to be scarred of ruining a connector during my creation process... I have no issue paying you extra as I do not know how much time & expense it for you to fulfill that request. If its too much than ill be fine, ill just be really really careful while I mount the prong & wires etc. Thank you again and I look forward to assembling your design... :-)

Not a problem, I'll include a couple extra in there for you.

Once again, thank you sir, I have been searching since I first stumbled upon your site. I must have checked a dozen or so suppliers and everyone is out. Not sure if they discontinued them or only do a run every year or so.

I REALLY appreciate you doing that for me. I don't suppose you happen to know the part number for the metal inserts/prongs? If not I can do the research on that part. I bet you could sell a ton of those connectors on the forums as there are a lot of people looking for them. I was about to post a want add in the them paying for bad power supplies just so i could cut off the cord for the connector.

Not a problem, I'm happy to help. I did a lot of searching and I haven't been able to find anyone who sells just the prong. I chatted with the digikey guys for awhile trying to track one down but they couldn't find one on their site or know of anywhere else to look. I then remembered once seeing an extention cord plug repair at a Home Depot. I did a quick search and found the cheap ones below that can be unscrewed easily. That's probably your best bet at getting the prongs much cheaper than the offical plugs anyways.

can you please verify that the Yeeco Converter is the 150 watt version?

2 replies

Yep, the 150 watt one is the correct one. Also for the busbar use this one:- And then get 12 of these jumpers It is best to apply a fair amount of solder to increase the thickness of the jumpers after screwing them down. Solder the wires directly to them making sure to have solder flow underneath the arc of the jumper.

You are awesome, thank you sir!!!! I have been searching for the solo battery connector with no luck. Is the best option still one identified on the post below?

Mmolex connectors are out of stock at verical. Any other suppliers you can recomend?

1 reply

Hi Grant, would you mind sharing your STL plans for the box printed?

1 reply

Just finished making a 4 battery charger based on your design. Thanks for such a clear set of instructions.

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2 replies

Looks great!. Looks like you used a pre-made box, Which box did you use?
Also how did you conjure your charging plugs?

Thanks for the kind words! Your designed turned out very nice and I like that you were able to adjust the design to meet your own needs. I also like how you were able to make your own charging plugs, without using the special Molex connectors. The fan setup looks nice as well, looks like you are using one to blow fresh air into the charger and using the other to blow warm air out. Thanks for sharing the pictures; it's cool to see what others come up with.

so id like to do this with 4 batteries if possible. Do you think I would still need the 50a power supply? what would happen if I ran it on a 30a power supply (which I currently have).

1 reply

You should be okay to use your 30amp power supply. 5*4 = 20amps. Assume a high number of 5amps of loss due to: inefficiencies, heat, resistance, and that will bring the total to about 25amps. This would mean that you would be running your power supply at about 83.3% capacity. This is acceptable, especially since the amp draw significantly decreases after the first 20mins of charging empty batteries.