Category: Battery Building Instructions

Building an RC battery with Maker Battery modules is surprisingly easy. Just follow the steps below to build your own RC battery!

Step 1: Measure module voltage

Start by measuring the voltage of all of your cell modules to ensure that they’re all more or less identical. They can be off by a few hundredths, but any more than that might indicate that one or more cells have an issue. This is incredibly rare as these cells are checked at the factory and then double checked before shipping, but this triple check is just one last step to ensure that you’re building a top quality battery.

Step 2: Layout your modules

Now you’ll begin your module layout. This will determine the final size and shape of your battery. For most applications a simple linear pack is preferred. If you have a specific battery box that you’re trying to fit your battery into then you might want to get a little more creative with your arrangement.

Generally speaking there are two different straight layout methods: straight packing and offset packing.

Straight packing with result in a narrower yet longer battery, while offset packing is a bit wider yet smaller overall volume. This is because offset packing is a more efficient use of space, leaving less dead air space between the battery cells.

For this tutorial we are going to use straight packing to give us a narrower yet longer battery, but the same steps apply for either method so feel free to use offset packing if you’d like.

When you arrange your cells, make sure you set them up like in the picture above with alternating sides facing up. This will make it easier to perform your series connections later on.

Now go ahead and hot glue your modules together into the correct orientation. Use a decent amount so you have a good connection, but you don’t have to drown your modules in glue either. These are fairly light weight packs so there isn’t a lot of stress on them from their own weight.

Step 3: Label your modules

You can use the + and – stickers in your Maker Battery kit and/or a marker to label the positive and negative ends of your modules as well as to number the cells. These module numbers will help you keep track of the modules later on when you’re connecting the balance wires. These stickers and labels aren’t 100% necessary, but they can be a nice help when you’re performing the critical series connections. I recommend not skipping this step.

Step 4: Tinning the modules

In order to solder your cell modules together you’ll first need to tin them. For this process you’ll need two things to ensure good tinning: a good 60W or higher adjustable temperature soldering iron and some quality 60/40 lead electrical solder. Don’t skimp on either. A decent soldering iron can cost $15 and good solder another $10. They’re both worth it. You want to spend as little time heating the cell modules as possible and to do that you need a strong soldering iron that can transfer heat quickly. A weak soldering iron has to sit on the nickel for a long time, which ends up transferring all the heat to the cells. You want just a couple seconds of contact.

To tin the nickel, touch the tip of your soldering iron to the nickel in between the cells and then touch a piece of solder to the point between the soldering iron and the nickel. You’ll see the solder melt and then within another second begin to blend into the nickel strip. At that point you can remove the soldering iron and move to the next point.

Make sure that you’re soldering on the point in between cells and not directly on top of them. The nickel will heat and tin faster in between cells and that point will also keep the heat as far from the cell as possible.

 

Step 5: Cutting the nickel strips

Now find your roll of nickel strip and open it up. Be careful not to let it get away from you and short circuit your battery terminals.

Cut the first few pieces of nickel strip to approximately 3/4″ or 2 cm in length. You don’t need to measure them out exactly; just eyeball it. They should be long enough to span from one solder blob to another on two consecutive modules.

You can use any ordinary pair of scissors to cut the nickel. Depending how you hold the nickel when you cut it, you might find that you get funny corners that turn up at a sharp angle. If this happens, just push the corner against the table to flatten it back down. It’s not a major problem, but the sharply bent corner can sometimes catch on your gloves and cause you to accidentally drag the nickel away from where you intend to place it. It’s more of a problem on the backside of the battery once you’ve already done the first set of series connections. At that point it’s easier to accidentally cause a short circuit on the backside of the battery.

When you cut the nickel strips, you’ll probably notice that they make a slight arc from the shape of the roll. I like to place the nickel strips on the modules with the arc facing down like a rainbow. This keeps the two ends on the solder blobs. If you do it the other way and place the nickel strip down like a bowl it may rock oddly.

Step 6: Soldering the nickel strips

Below you can see the wiring diagram (or nickel strip diagram since we aren’t using wires yet) for the 5s RC battery pack we are making. It is very important that you do these series connections correctly. It’s quite easy to accidentally lay a piece of nickel strip on the wrong connection and cause a short circuit, so pay attention and double check before you lay down each piece of nickel.

When you solder the strips, the name of the game is just like during tinning: try to spend as little time heating the modules as possible. The whole soldering operation should take about 2-3 seconds, though you’ll get it down under 2 seconds with some practice.

This is also where that chopstick, popsicle stick, tooth pick, matchstick or other piece of wood is going to be used. The soldering procedure I use is as follows:

1. hold the chopstick in my mouth (easier to reach when switching it to my hand)
2. put the nickel strip onto the module so it overlaps the solder spots I previously tinned
3. hold the soldering iron in my right hand and solder in my left hand (switch if you’re a lefty)
4. place the tip of the soldering iron on the edge of the nickel strip to heat it while contacting the solder to the soldering iron and the nickel strip
5. merge the module’s pre-tinned solder blob into the new solder blob that I just put on the nickel strip
6. simultaneously while merging the solder blobs, drop the solder and pick up the chopstick with my left hand
7. use the chopstick to hold the nickel strip down while removing the soldering iron and hold until cool

You’ll want to solder the first two series connections between +1 and -2 and then the second series connections between +3 and -4. However, that’s only two strips of nickel for each series connection. Each strip of nickel can handle about 7.5A and so to get our full 30A current carrying capacity we need four strips. So to get four strips we will simply solder two more strips right on top of the connections we already made. Each connection will be two sets of two stacked nickel strips, as shown in the photo below.

After you’ve finished this side of the battery, you’ll need to turn it over and work on the back side. That’s where you’ll connect the “gaps” that we left on the top side of the battery, such as from +1 to -2 and +3 to -4. Be very careful though that you don’t complete any connections that are already completed on the other side of the battery. Look at the wiring diagram at the top of Step 6 again to see which connections you need to make. Notice how if a connection is made on the top side of the battery, it is left open on the bottom and vice versa. This way we are always wiring the modules in series. Your final connections should look like this:

Step 7: Adding the wires

Now we’ll add the discharge and the balance wires to the battery. Let’s start with the discharge wires on our yellow XT90 connector. You’ll need to strip back about an inch or so (2.5 cm) from the insulation on the red positive wire and tin the wire with solder. I find that a set of helping hands makes this much easier.

Next you’ll simply solder that red discharge wire onto the pre-tinned spots on your last module’s positive terminal. In this battery, that’s the 5+ terminal. Again, helping hands comes in pretty handy here. (Get it? Sorry…)

Continue the same way with the black discharge wire. Strip it, tin it, thens older it onto the -1 terminal of your battery. No matter how many modules you have in series, the black discharge wire always goes on the -1 terminal.

Once you’ve finished with the discharge wires, we can move on to the balance wires. I like to start by simply taping the entire balance wire bundle to the side of the pack, that way I can keep it nice and organized. You can use simple electrical tape, but I prefer kapton tape. It only costs about a buck more, but it’s stickier, easier to work with, non static and heat resistant. It simply works great for battery building and it’s what the professionals use.

Start with the red wire and solder it to the positive terminal of the highest numbered module you have, which is the 5+ terminal in this case. You can solder it directly onto the thick red discharge wire if that’s easier. Then simply work backwards, taking the wire next to the red wire and soldering it to the positive terminal of each successively lower module. If you’ve done it correctly then the second to last wire will go on the +1 terminal and the last wire will go on the -1 terminal.

Now is a good time to double check that you are getting the proper voltage at your discharge connector. These batteries are pretty hard to mess up, but if you aren’t getting the expected voltage, just double check your connections and make sure you soldered all the wires and nickel strip in the right places. Also, remember that you won’t get your full pack voltage yet because these cell modules are only partially charged. You should get the sum of however many modules you have in series.

Assuming everything checks out, go ahead and tape up all of your wires so they lay flush against your battery and won’t vibrate or work themselves loose over time. Again, I like to use kapton tape here but you can also use electrical tape.

Step 8: Sealing the battery

This is the last step: heat shrinking the battery. You’ll find two pieces of heat shrink in your kit, one should be a bit wider than the other. Start with the widest piece and slide it over the longest dimension of your battery. You want an overhang of about 1/2″ or 1.5cm on the sides. If you used straight packing like I did here, you’ll likely need to trim your heat shrink just a bit so you only have 1/2″ or 1.5cm of overlap on the sides. The heat shrink will come a bit wider to accommodate other layout styles.

Now use either a hair dryer on its highest setting or a heat gun on a lower setting to heat the shrink tube evenly. Hair dryers of 2,000W seem to work well, while lower powered ones may work, but can take longer.

I like to start on the two exposed ends and shrink those first to make sure they grab around the sides of the battery well, then I go back and heat the middle. Turn the battery around while heating to ensure that all parts of the heat shrink actually shrink down and squeeze the battery.

Next, take the second piece of shrink tube and slide it down over the entire battery. Again, make sure you’ve got about 1/2″ or 1.5 cm of overlap on each end. Now repeat the heat shrinking process and evenly heat the shrink tube, starting at the ends, until the entire shrink tube is wrapped around the battery.

If you wind up with any pieces on the ends that didn’t shrink down all the way and stick out like wrinkled folds, you use a pair of scissors to cut those back. Then reheat the spot to smooth the edge.

The final step is simply to add your sticker to the outside of the battery in order to show everyone that this is a Maker Battery and you built it yourself!

Congratulations, you’ve finished building your battery! Good luck with your project and have fun!

These instructions demonstrate how to use triangular Maker Battery modules to build a battery. In this case, we are going to be building a 48V 10AH battery, but you can use these instructions to build any voltage and capacity battery you’d like simply by altering the number and placement of cell modules.

Step 1: Measuring cell voltage

Before you can start laying out your battery, you want to do one last double check to ensure that all of your battery modules are at the same voltage. They are checked at the factory, but this is just one final test before you begin. Simply measure the voltage of each module with a digital multimeter. You should see that all of your cell modules are basically identical. Any difference of more than a few hundredths of a volt would indicate that one cell group might be slightly discharging itself. This is incredibly rare, but you should still check for it before you assemble your pack. In this case, all cells measured out at about 3.502V. Anything between about 3.49 and 3.51 would be fine for these cell modules – as long as they are all within a few hundredths of a volt. These modules were all within a few thousandths – perfect!

 

Step 2: Cell module layout

Cell layout is where you have the most freedom to be creative and build any size or shape of battery you’d like. These triangular cell modules lend themselves really well to interesting shapes and geometries. In this walk-through we are going to be building a simple 48V (13s) 10AH battery using 13 cell modules wired in series, but you can use more or less cell modules to create any voltage battery you’d like. This is the orientation that I’ll be using in this walk-through:

There are many possible layouts to achieve all sorts of interesting geometries. Just remember to think about how you’ll connect your cells when you lay down the nickel strips. Also, if you’re using the Maker Batteries kit with supplied heat shrink, know that if your battery is too much wider than this layout the heat shrink won’t fit. You have enough room to do a 4-cell-wide pack using the included heat shrink. The format we’ll be using in this tutorial is a slightly small, yet longer, 3-cell-wide layout.

After you’ve decided on your layout, you’ll just need to hot glue your cell modules together into whichever shape you chose. I like to glue the modules together into larger groups of four modules, and then glue those together. You can also just glue them together one at a time. Whatever is most comfortable for you.

Step 3: Label your cells

Next add your positive and negative stickers to help you keep your orientation while you’re working on the battery. Just remember that the end with the green paper insulation gaskets is the positive end of the cell module, while the bare end (red and silver) is the negative end, and apply your stickers accordingly.

I personally like to follow up the stickers with a written cell number. You can also skip the stickers and just write “+1”, “-2”, etc. Whatever feels most comfortable for you. The numbers help me ensure that I’m connecting the correct cells when I get to the next step.

 

Step 4: Tinning the nickel triangles

Now it’s time to take out your soldering iron. You’ll want to use a good quality, adjustable temperature soldering iron. Something of at least 60W should be perfect. The cheap little beginner soldering irons in the 20W-40W aren’t great because they don’t generate enough heat and also lose their heat quickly. This means that you have to spend much longer trying to transfer heat to the nickel, which ends up heating the actual cells. The whole point of this operation is to transfer as little heat to the cells as possible. It sounds counter-intuitive, but a hotter soldering iron will help us heat the actual cells less because we can spend less time touching the nickel with the soldering iron.

You’ll also want to make sure you’re using a good rosin core electrical solder. I prefer 60/40 lead solder. It’s toxic, so don’t breathe in the fumes, but it gives the best solder connection and flows nicely. If you try to use the cheap solder that comes with your soldering iron, it’s just not going to work well. Spend $10 and get some good lead electrical solder.

Let’s start at the beginning of our battery. The negative end of #1 is going to be the negative terminal of our whole battery, so we’ll skip that for now. Instead, we’ll move to the first series connection we have on the top side of the battery, which is the connection between +2 and -3, shown in the diagram below.

Before we can solder this connection, we’re going to tin the nickel triangle. Tinning means heating up the metal first with the soldering iron, then adding a bit of solder until it appears to merge with the metal, and then removing the heat. This bonds a blob of solder to the nickel triangle and makes it easier to solder something else to the triangle.

When you solder to these triangles, you want to try to avoid soldering directly on top of the cells. Instead, solder in the areas between cells. These ‘between’ areas with nothing behind them will heat faster which gives you a better solder joint, and will also keep you from passing the heat directly onto the cells.

The points that you choose to tin the nickel triangles will depend on how many pieces of nickel strip you’ll be soldering next to each other. When possible, two pieces of nickel strip side by side are better, but sometimes you’ll only have room for one piece. In this first connection, I’m going to solder two pieces of nickel next to each other so I’ll tin the nickel triangle in two places on each of the triangles.

 

Step 5: Preparing the nickel strip

Now you’ll need to unroll your nickel strip and begin cutting the first few pieces. In this orientation, I’ll need pieces that just under an inch long, approximately 2 centimeters. It’s not super critical and I never break out my ruler to make sure they’re all the same, I just eyeball it and cut the nickel strip as needed.

Start by cutting out 4 pieces of nickel strip for this connection. A pair of scissors is all you need, the nickel is fairly soft. Don’t use your good sewing scissors though – any pair from your junk draw will work.

You might notice that you get a funny, turned up corner when you cut the nickel, depending on how you hold it when cutting. If this happens, just bend the corner back down. It won’t hurt anything, but it can get caught on your gloves or other things when you’re laying it on the battery and that could cause an issue if a nickel piece slips and causes a short circuit.

Next, take a look at the strips of nickel you just cut. They probably have a slight arc in them, right? That’s because they’re fresh off the roll. You can try to flatten them but they’ll probably never be perfectly flat, which is just fine. When you put them on your battery, just put them with the arc facing down, so it’s like a rainbow and not a bowl. That way the two ends are making contact with the nickel triangles. When you hold the piece of nickel strip down during the soldering process it will become flat.

Step 6: Soldering the nickel strip

This is the most critical of all steps and will define the quality of your battery. You want to take your time here. Go slow and ensure that you’re making good quality solder connections.

This is also potentially the most dangerous part of battery building, because this is where you begin increasing the combined voltage of the battery modules and are working with many exposed contacts. Again, go slow and just pay attention to what you’re doing. As long as you think about each connection you’re making and ensure it is correct, you’ll be fine.

This is also the time to double check you don’t have any random bits of metal laying around your table or any jewelry/tools that could fall on the battery and cause a short circuit. Keep your nickel strips off to one side while you’re working so they don’t interfere with your battery.

 

 

Now go ahead and begin your first series connection by laying down a piece of nickel strip between the first two modules that you’ve already tinned and then solder one side of the nickel strip to the nickel triangle.

The goal here is to spend as little time heating it as possible. Here’s the procedure I use: Lay the end of the nickel strip over the solder blob you already tinned on the nickel triangle. Now heat the nickel strip with the soldering iron while applying just a bit of solder to the tip of the soldering iron. That bit of solder you added will quickly bond to the nickel strip, and then a second later should merge with the solder blob you already put on the nickel triangle. While the solder blobs are merging, drop the solder from your non-soldering iron hand and pick up your chopstick. Use it to press the nickel strip down and then remove the soldering iron. Gently blow on the soldered connection while still holding it down with the chopstick. After about 3-5 seconds the solder will be hardened and you should be able to lift up the chopstick.

This is now a series connection, but it’s not completely finished yet. You put down one piece of nickel strip, but that single piece is only able to carry about 7.5 amps of current. For higher safety and lower resistance, we need to add a few more nickel strips along with that one. I generally put four pieces of nickel strip per connection, giving a maximum continuous current handling of about 30A. If you skimp out and only put one or two, your battery will get much hotter and run less efficiently. Always try to use at least four strips of nickel for each series connection.

There is enough room in this configuration for two strips of nickel next to each other, so go ahead and solder a second nickel strip right next to the first strip. Then after you have two strips, solder another two directly on top of the first two. You’ll follow the same procedure as when you soldered on your first strip. Just lay down a piece of nickel strip on top of the existing piece, add some solder to the end of the new piece and merge the solder blob holding the first strip into the second strip. Sometimes using slightly shorter strips for the piggy-backed pieces can help make the process easier.

Congratulations, you’ve just soldered your first series connection! Now just a dozen or so more, depending on the size of your battery. For this 48V battery we’ll continue on to the next series connection on this side of the battery, which is from +4 to -5, as shown in the diagram below.

Perform this second series connection exactly like you did for the first one. Tin the center of the nickel triangles, then lay down two strips of nickel next to each other. Complete the first two nickel strips soldering operations, then add another two strips of nickel on top of the first two.

Now you should have your first two series connections completed on this side of the battery. Continue with all the remaining series connections on this side of the battery. In the case of our 48V battery layout here, that means we’ll make connections between +6 to -7, then +8 to -9, then +10 to -11, and finally +12 to -13.

Once you’ve got all of your connections done on this side of the battery it should look approximately like the photo below. Note that the picture was taken before the last series connection was completed, and shows only two nickel strips on the last connection instead of four.

After we’ve finished all of the connections on this side of the battery, we’ll flip the battery over and work on the series connections on the other side.

Now that we are working on the backside of the battery, we need to pay extra careful attention that we are making the proper connections. These series connections will basically “fill in” the connections that were skipped on the first side of the battery we started with. You’ll remember that we didn’t solder between modules 1 and 2, 3 and 4, 5 and 6, 7 and 8, 9 and 10, or 11 and 12 on the first side of the battery. Well, now it’s time to make those connections.

Before you make a connection on the backside of the battery, double check that the same connection is not made on the other side. Just lift the battery up and do a quick sanity check to ensure that you’re placing your nickel strip in the right spot. It’s easy to lose focus for a second and lay down a nickel strip in the wrong spot. But since the other side of the battery is already connected, misplacing a piece of nickel strip now could lead to a short circuit that will quickly heat your nickel strip up to a glowing, red hot beacon of your mistake. You want to avoid this.

You’ll notice in the picture above that the battery has been flipped over its end like a cartwheel, not around its long axis like a rotisserie. It doesn’t matter how you flip it; I’m just pointing it out so that you pay attention to the orientation. Now module 1 is on the right and module 13 is on the left.

We’ll complete all of the series connections that are left on this side of the battery, being careful to double check that we are making the right connections. However, you’ll notice on this side of the battery we don’t have room for two nickel strips to lay side by side. This is due to the skinny orientation we chose that has only 3 cells wide. This is fine, it just means that we’ll need to stack four nickel strips on top of each other instead of 2 x 2 like we did on the other side of the battery. Again, using progressively shorter nickel strips can make this easier. It will start to look like layers of a wedding cake as the nickel strips stack up.

Once you’ve completed all of the series connections on this side of the battery, you can go back and tin in the center of the -1 and +13 modules’ nickel triangle, as seen in the photo above. This is where we’ll be connecting our discharge wires in the next step.

Step 7: Adding the Battery Management System (BMS)

Before we add our BMS, we’ll do another quick sanity check to ensure we’ve made our series connections properly. Grab your digital multimeter and measure between the -1 module and the +13 module. You should get the appropriate pack voltage for whatever you are building. We have a 48V battery consisting of 13 series cells, so we’ll get 45.5V (3.5V x 13 modules).

If you don’t get your correct voltage, make sure that you didn’t forget a series connection somewhere.

Now you’ll need to decide where to mount your BMS. It can go pretty much anywhere, but I like to put it on the sides or end of the pack, and not on top of the terminals, just in case the heat shrink ever wore through and caused a short circuit on the terminals. You could cut a piece of foam from the smaller strip of foam in your kit supplies though and place it between the contacts and the BMS if you really have to put it there though.

I generally like to put my BMS on the end of the pack so that the battery has a uniform thickness throughout. I usually stick it closer to the positive end of the pack as well so that the positive charge wire can easily reach the last positive terminal of the battery.

Go ahead and hot glue your BMS to the end of the pack, or cut a piece of foam from the smaller foam strip and place it under the BMS first to add extra padding. If your battery is going to get a lot of shock loading, like on an electric bicycle, then this extra padding can help isolate the BMS a bit more.

On this pack, I’m going to be placing the BMS on the side just before the end of the pack. With only three cells wide, the pack isn’t quite wide enough to fit the BMS at the end without sticking out on the sides.

Next you’ll need to solder the thick red discharge wire coming from the yellow XT-90 connector to the positive nickel triangle on your last cell module. In this case on a 48V battery, it’s the 13th module’s positive terminal. Before you solder it though, lay out the discharge wires in the orientation you expect them to exit the pack. Then cut the discharge wire to whatever length is necessary. If you want to leave it long, you can just go ahead and solder it without cutting, and that will give you a longer discharge wire.

Strip the end of the red discharge cable and solder it to the last cell module’s positive terminal, then do the same with the thin red wire coming from the charging connector. Just remember that you need to solder these in the center of the triangle, staying away from the corners. Use high heat and a short period of contact between the soldering iron and the nickel triangle.

 

Next, you’re going to solder the red wire from the set of many thin balance wires on the other side of your BMS. Depending on your kit, your BMS might not have a single red wire and instead just have a number of white wires followed by a single black wire. Either way, the correct wire from the balance wire connector to solder to the positive terminal of the last cell module is the last wire, as shown in the photo above. To confirm, count the small balance wires and you’ll find that you have one more than the number of cell modules. In this case, I have 14 small balance wires. This is because two wires will eventually get soldered to the first cell module, one on the positive terminal and one on the negative terminal.

Now that you’ve soldered your first balance wire, continue with the rest in the same way. The next small balance wire will be +12, and you’ll likely need to flip over your battery to reach the +12 nickel triangle if you used a similar layout to mine.

 

Continue with all of the balance wires until you’ve reached the last wire, a thin black one. This will be soldered onto the negative end of module 1. You may want to wait to solder this until you solder on the thick black wire coming from the BMS. This should also get soldered to the -1 terminal, but will carry all of the current of the battery so this should be a very good solder joint. Measure how much slack you need in the thick black wire and then cut the wire to length. Strip, tin and solder it to the -1 terminal, then solder on that thin black balance wire as well.

Lastly, you’ll notice that you still have two wires coming off of your BMS. Depending on the model of kit you have, these two wires will either be a loop, or two individual wires that are soldered together at the end, like in the photo below. These are for adding an on/off switch for your BMS, if you’d like. The switch will give you a way to turn off your BMS unit. This could be handy if your system has no other switch, or if you plan on leaving the battery dormant for a long period of time (e.g. months). This specific battery is going to go onto an electric bicycle that already has a system switch, so I’m not going to add a switch here on the BMS. If you wanted to though, any toggle switch that completes this circuit will work just fine as a switch for the BMS.

Because I’m not adding a switch, I’m just going to cover this soldered connection with a piece of heat shrink or tape and then tape the wires down with the rest of the wires onto my battery.

In fact, now is the time to tape down all of your wires to the pack. Just lay all of the wires out flat and in line with each other and tape them down with either electrical tape or kapton tape. Electrical tape will work, but kapton tape costs only a dollar or two more and is much nicer, since it doesn’t leave any gummy residue and has higher adhesive strength. It’s also won’t build up a static charge.

Lastly, we’ll do another sanity test just to ensure that everything is correctly wired. Grab your digital multimeter and measure the voltage from your yellow XT-90 discharge connector. You should be seeing your proper pack voltage, which will be a sum of the voltages of the individual modules. Remember, even if your pack is 48V, you likely won’t see 48V on the meter because your cells will come in a state of charge between 30%-50%.

Check the voltage at your charge connector too, but don’t measure directly from the connector. Instead, take the loose charger connector that came in your kit (which you can use later to add to your charger) and spread apart the exposed wires at the end. Make sure they aren’t even close to touching. Now plug it into your charger connector on the BMS and measure the voltage from those exposed wire ends. You should see almost exactly the same voltage as from the discharge connector.

If either of these voltages aren’t your correct pack voltage, this means you have a connection error somewhere. Check all of your balance wire connections as well as your charge and discharge connections. You likely just connected a wire in the wrong order somewhere.

Step 8: Sealing your battery

Now you’ve got a fully functional battery, but you’ll want to wrap it up to protect it. Your kit includes both foam and heat shrink. You should at least use the heat shrink, but the foam is somewhat optional. If your battery will always be sitting in one place, like for use as a home back-up battery, you likely don’t need the foam. However, if your battery will be moving around, like for an electric bicycle battery, you’ll want the foam for added protection. It does reduce the heat dissipation a bit, which is why you can leave it off for stationary applications, but its protective advantages more than outweigh the small efficiency losses from heat dissipation.

Begin by laying your battery on the foam and wrapping the foam around your battery with the paper still on it. If the foam is too big, cut it down to size with a pair of scissors.

Then remove the paper backing and roll the foam around your battery. Lastly, cut out a couple pieces from the smaller foam strip and use them to cover the two ends of your battery.

Now that you’ve got your battery all wrapped in foam, we can use those two pieces of heat shrink you received in your kit.

You’ll want to start with the piece of heat shrink that opens wider, i.e. the one that’s easier to get your leg into than your arm. Slide your battery into this first piece of heat shrink and check that you’ve got about 3/4″ or 2 cm of overhang on both sides. If you have much more than that you’ll end up with edges that don’t shrink down all the way. I recommend cutting the heat shrink back until you’ve got just about 3/4″ or 2cm of overhang. But be careful, because if you remove too much then you can’t add the heat shrink back after you’ve cut it off. You can always cut the heat shrink back after you’ve already shrunk it, though it’s a bit more difficult. So if you are worried about cutting off too much then err on the side of leaving it too long and just trim it afterwards.

Make sure your battery is centered in the heat shrink and then use your heat gun or hair dryer to spread even heat over the entire battery. If you’re using a heat gun, start out on a fairly low setting. Some heat guns can get way too hot for heat shrink and end up melting it. For a hair dryer, you’ll need a fairly powerful model. My wife’s 2,000W hair dryer works great! I’ve used a 1,875W model and it worked, but not nearly as well.

On this first piece of heat shrink, I like to start by shrinking the open edges first so they wrap well around the edges of the battery, and then shrink the middle. Notice in the photo above that I have some wavy edges on the ends of the battery. That is an indication that the heat shrink was just a bit too long on either side. You can either heat that and press the wavy parts flat, or trim them back.

Next you’ll use the longer, narrower heat shrink to fully seal the battery. For this piece, I like to have about a 1/2″ or 1.5 cm overlap on each end. The overhang is smaller here because the heat shrink will shrink less than the previous piece, and so the same amount of overhang would often result in too much loose heat shrink after shrinking.

One other note: You’ll notice in the photo above that I have cut a slight arc out of the top half of the heat shrink. This is due to the angle at the end of the battery. A straight cut would result in too much heat shrink on the top, so I cut a small arc to remove some of that extra heat shrink. If this is your first time heat shrinking a large battery like this, I recommend not cutting out this arc until after you’ve shrunk the heat shrink and can better gauge where the cut needs to be made.

Again, I like to start the heat at the ends of the heat shrink to make sure they wrap around the edges of the battery and grab on tight, and only then move the heat to the center of the heat shrink to finish shrinking all the way around the battery.

If you are worried that you might have cut too much off and made your heat shrink too short, definitely start shrinking at the ends. Heat shrink mostly shrinks radially, where it has about a 50% shrink ratio. But it will still shrink a little longitudinally with about a 5% shrink ratio. So if it’s short, it will get even shorter. All the more reason to shrink the ends first to ‘lock’ them in and then shrink the middle.

The above photo shows what it looks like when the heat shrink was a little too long. You get those wavy parts at the end where the heat shrink kept shrinking but got smaller than opening in the end of the heat shrink, causing it to fold. It’s not a big deal and you can leave it like this, though the hard edges that poke out might chafe at a bag or other battery container. You can also heat the end again and press the folds flat, or cut the folds back and reheat the end to create a smooth edge again.

Lastly, peel off your label and apply it to your battery so that everyone knows that you made this battery yourself!

And that’s it, you’ve built your own battery using Maker Battery triangle modules! Now what are you going to do with it? If you’ve got a neat project that you documented well, let us know and maybe it will get featured in the community projects section of the site!