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!