Where This Build Guide Comes From

Every step in this article comes from one source video — EbikeSchool.com’s How to build a DIY ebike battery from 18650 cells, which has been watched more than 1.5 million times. In the video, Micah builds a complete 24V ebike battery from Panasonic 18650 PF cells: he plans the layout on paper, voltage-matches every cell, welds pure nickel strip with a spot welder, wires a 20A BMS, and finishes the pack with EVA foam and heat shrink. The video runs about 27 minutes and every step is shown on camera. If you would rather watch the build before reading the breakdown, the video is right here:

EbikeSchool.com — “How to build a DIY ebike battery from 18650 cells”
Watch on YouTube →
1.5M+ views. Micah from EbikeSchool.com builds a 7S2P 24V ebike battery from Panasonic 18650 PF cells — layout on paper, voltage matching, pure nickel spot welding, BMS hookup and shrink-wrap finishing.

Why Build Your Own Ebike Battery?

A DIY 18650 pack exists for one reason: you can build any size battery you want, of any capacity, using exactly the same methods — just by adding more cells in series or in parallel. The video builds a deliberately small 24V 5.8Ah pack for a low-powered bike, but Micah is explicit that the process scales: more cells in series raises the voltage, more cells in parallel raises the capacity, and that is the whole trick.

For a buyer this matters in two ways. If you enjoy the build, a homemade pack can be cheaper than a commercial unit at the same capacity, and you control the cell quality and layout. If you would rather buy, knowing how packs are built helps you read specifications honestly — because the same 18650 cells and the same welding methods go into the commercial packs you are comparing.

Cell Selection: Why Panasonic 18650 PF Cells

The build uses Panasonic 18650 PF cells, and the video explains the selection logic: these cells can discharge at up to 10 amps per cell, which suits the build’s needs comfortably. With only two cells in parallel (2P) and a bike controller rated at 10A, the pack gets roughly a 2x safety factor — the battery is never asked to work at its limit, which is exactly how a pack stays healthy for thousands of cycles.

Micah notes there are many cell types on the market and links several he commonly uses, because the right cell depends on the application: high-drain cells for powerful bikes, high-capacity cells for range-focused cruisers. The lesson that transfers to any build: match the cell’s discharge rating to your controller current, and keep a safety margin instead of squeezing every amp out of the datasheet.

Designing the Layout on Paper First

The video’s first step is planning on paper, and it is the step beginners skip and later regret. Micah traces the outline of a cell to get the approximate size, then draws however many cells he plans to use in the intended layout. For this build that is a straight battery: seven cells in series (7S) and two in parallel (2P), giving the nominal 24V.

He shades the positive ends and leaves the negatives empty, so positives are dark and negatives light, then labels every cell. The critical habit from the video: draw both sides of the paper so you can flip it over in real life the same way you flip the battery, and double-check which connections are done on the opposite side. When series connections alternate sides (plus-1 to minus-2 on one side, minus-2 to plus-3 on the other), a one-side drawing guarantees you will weld a short somewhere.

Voltage Matching Every Cell Before Assembly

Before a single weld, Micah measures the voltage of every cell with a multimeter to make sure they are all the same. His rule: cells should be within about one or two hundredths of a volt of each other before they are connected in parallel. In the video all the cells read 3.63V — effectively identical.

This is the cheapest form of cell matching, and it matters because cells at different voltages force current to flow between them the moment they touch in parallel. With matched cells the pack starts balanced, the BMS does not have to fight to equalize anything, and capacity and cycle life stay where they should be. If cells are far apart, the correct move is to charge the low ones slowly or reject the batch — never to weld them together and hope.

Holding the Cells: Hot Glue, Spacers and Nickel Strip

The video uses hot glue to hold the cells together into a block, and explains why: hot glue makes the smallest possible battery because there is no extra material between cells. The alternative is the black snap-together plastic spacers many builders use, which align the cells neatly — but they take up more room and make a bigger pack. Micah has built dozens of batteries this way and it works well; he links the spacers too, so both methods are legitimate choices.

What matters is that the cells are held rigidly and aligned before welding, because the nickel strip has to land squarely on every terminal. Once the block is glued, Micah puts on gloves and removes jewelry — a non-negotiable safety step, since a metal ring or a stray conductor bridging two terminals creates a dead short across the whole string.

On the connector side, the video is specific about the material: use pure 100% nickel strip, not nickel-plated steel. The plated steel strips are cheaper but give a lot more resistance, and the battery heats up more under load — heat that shortens cell life and, in a worst case, is a safety concern. Micah uses 0.15mm thick, 8mm wide pure nickel strip, cutting lengths to cover however many cells are in parallel — here about four centimeters for two cells.

For a builder, the material grade is where the savings temptation bites. Nickel-plated steel looks similar on a shelf and is cheaper by weight, but the resistance penalty shows up exactly when the battery is working hardest — full throttle on a hill — which is the worst moment for extra heat. The video’s rule is short: pure nickel only, and cut the strips long enough to cover every parallel cell in the group.

Spot Welding: Settings, Technique and Common Mistakes

Welding is where the pack comes together, and the video walks through the technique with the welder set to 40 amps and a double pulse, the setting Micah always uses for this size of nickel. He lays each strip carefully, checks that both probes have good contact, and welds six to eight spots per strip — three or four weld passes per cell terminal — then completes the parallel connection across the pair.

Two mistakes are shown on camera and both are instructive. First, he once misses the cap and the spark jumps — the lesson is to watch the workpiece, not the camera, and stay right on top of the end cap. Second, he occasionally welds over air, which just puts a hole in the nickel; a couple of missed welds are not an issue as long as the good welds carry the current. He also doubles up the series connections with an extra layer of nickel strip on top, welded piggyback style, to reduce internal resistance and make current flow easier. Throughout, goggles are worn because sparks jump — and a spark in the eye is not cool.

Wiring the 7S BMS

The BMS is a 7-cell unit rated for 20A — about twice what the build needs, another deliberate safety margin. The video shows the three main pads: B- (battery negative), P- (discharge) and C- (charge). The charge connector is an RCA plug wired to C-, an Anderson connector goes on the discharge side wired to P-, and B- runs to the negative end of the first cell.

The sense wires are the part beginners dread, and the video slows right down here: eight sense wires for seven cells, with the first cell getting both a positive and a negative connection. The BMS board labels B1, B2, B3 and so on, and each wire must land on the exact correct cell junction — mixing them up means the BMS reads nonsense voltages and may refuse to run. Micah’s practical habits: tin the nickel strip before soldering, solder between cells rather than directly on a cell so heat stays away from the cell body, and cover finished contacts with heat-resistant tape so nothing shorts while you work on the rest of the pack.

Finishing: Foam, Heat Shrink and the Final Pack

The finished battery gets wrapped in a layer of 2mm EVA craft foam, cut to shape with a little overlap so the corners have the most protection, then sealed with heat-shrink. Micah’s sizing tips are worth copying: cut the perimeter strip about 11cm wide so it covers both sides and wraps around each edge, and add 10–20% extra length along the long axis because heat shrink contracts about 2:1 across its width and roughly 10% along its length. A hair dryer is enough for the job — a strong heat gun on high will melt the material.

The result is a 24V 5.8Ah pack — small, but perfect for a low-powered ebike, and the same method builds any pack you want by adding cells. Sealing the ends properly matters for rain and moisture: an open end is that much more exposed, and the video’s finish leaves no exposed nickel at all.

Safety and Practical Takeaways From the Build

Across the whole video, the safety rules are consistent and worth listing: remove jewelry and wear gloves before handling terminals, wear goggles while welding, use pure nickel to keep resistance (and heat) low, match cell voltages before paralleling, and keep a comfortable safety margin on both cell discharge rating and BMS current. One commenter with factory experience adds two field-tested details: work one cell at a time and keep a bucket of sand and a fire suppressant nearby — welding thousands of cells in production, those are the habits that prevent real problems.

If you would rather buy a professionally built battery than build your own, a custom 18650 or LiFePO4 pack is exactly what we make. Dajiu Energy is a Chinese manufacturer building lithium batteries for e-bikes, RVs, homes, golf carts and portable applications since 2017. Our product range covers LiFePO4 drop-in replacement batteries, EV and golf cart batteries, wall-mounted home storage, portable power stations, commercial energy storage and battery swap cabinets — explore the full lineup in our product center, or browse more buying guides. If you do build your own, we’d still suggest matching the video’s care — and if you’d rather not, tell us your voltage, capacity and compartment dimensions and we’ll engineer the pack for you.

What Viewers Are Asking (Top Comments on the Video)

Where the creator replied, we quote his answer verbatim; where he didn’t, we give our own practical answer — the way we’d answer a customer on the shop floor. We kept only comments with real practical value and dropped the pure thank-you notes.

@brunobruno9307 · 168 likes
"Friendly advice: Don't do it 4-5 times in a row. Check that video with thermal camera and comparison of spot welding and soldering. Even if you spot weld it gets some heat into the battery. It is better to spot weld once and then move to the next tab and do it in circles. This will give the battery chance to cool down a little bit."
Our take: This is the best safety tip in the thread, and it matches production practice. Spot welding does put heat into the cell even when done right, and a burst of 4–5 welds in a row on the same cell gives the heat nowhere to go. The habit we recommend: one good weld per tab, then move around the pack in a circle so each cell gets time to cool before it is touched again. It costs nothing, and it removes the exact failure mode the thermal-camera videos show.
@frozenprakash · 135 likes
"Power = Voltage x Current W = 3.7V x 20A W = 74 Energy = Voltage x Current x time W time = V x I x time W hour = 3.7V x [3000 mAh] W hour = 3.7V x 3 Ah Wh = 11.1 That simple. And for reference, 1000 Wh = 1 kWh [1 Electrical Unit], which is what our kWh energy meter uses in home ______________________________ mAh and Ah which are seriously flawed unit (which doesn't take voltage into account), which is normally used by manufacturers and marketers to misguide people !! Professional and universal unit for energy are, kWh or Wh. I mean, these all of us use kWh meter in home, kWh in Tesla car, and 1000 Wh = 1 kWh. (how else simple do you want ??) Still people use mAh and Ah, wonder how lame can they get !!! And for comparison (different rechargeable battery types): AAA [NiMH] = 1 Wh AA [NiMH] = 2.5 Wh AA [Li ion] = 3 Wh C [NiMH] = 5 Wh D [NiMH] = 10 Wh 18650 [Li ion] = 8 to 13 Wh (high drain to high capacity) 26650 [Li ion] = 14 to 18 Wh ____________________________ Average energy of Tesla battery are around 11 Wh [18650], and to make a Tesla P100D [100 kWh] Model S, = 100 kWh / 11 Wh = 100, 000 Wh / 11 Wh = 9091 batteries or in simple words, 9091 [18650 battery] x 11 Wh = 100,000 Wh = 100 kWh. ____________________________ So i would seriously recommend 18650 enthusiasts to use Wh and kWh [our universal unit] instead of flawed mAh and Ah which are way too childish unit for energy !!"
Our take: The math is correct and it is the right way to think about batteries. Volts × amps gives watts (instantaneous power); volts × amp-hours gives watt-hours (stored energy). The point about mAh and Ah being voltage-blind is worth remembering: two packs can both say 3,000mAh yet store very different energy if their voltages differ. For sizing an ebike or solar bank, always compare in Wh or kWh — that is the number that tells you how long the load will actually run.
@ElGatoLoco698 · 43 likes
"Ever try moving the spot weld electrodes a little closer together? Looks like they are too far apart causing minor issues."
Our take: Good observation, and electrode spacing does matter on some welder designs — if the two probes are too far apart, the current path through the nickel gets long and the weld quality drops, which can look like weak or inconsistent spots. On most hobby welders the probe spacing is adjustable, so it is worth testing on a spare strip: move the probes closer, weld a test strip, and check that the weld holds when you pry with pliers. The video’s own fix for a missed weld is simpler — stay on the cap and add another weld over the edge.
@rohanvija · 14 likes
"Hi, good content. I used to work for a company who manufactured battery Pack a good way to make sure the solder stays on nikel plate is to scratch it (nickel plate) with a blade, it helps solder stick better."
Our take: Factory tip, and it transfers straight to the home bench. Nickel develops a thin oxide layer that makes solder bead up instead of wetting; scratching the plate with a blade — or scuffing it with sandpaper — exposes fresh metal and the solder sticks properly. The video does the same thing by tinning the nickel strips before soldering the sense wires, so the two methods are consistent. Just keep the scratch light: the goal is surface prep, not thinning the strip.
@hatulflezet · 14 likes
"Hi Mike, Could you do a video about the various BMS's, (smart BMS vs regular etc) and tips about what to consider when searching for one, you know, kind of guidelines for selecting the best one suited to the battery we build? תודה מראש! 😉"
Our take: Great question, and the honest answer is that BMS selection deserves its own guide — which is why we cover it in our <a href="insights.html">buying guides</a>. The two-minute version: a smart BMS (Bluetooth, phone app, cell-level telemetry) is worth it for any pack over about 40 cells or any pack you cannot easily inspect; a regular BMS is fine for small packs where balancing current and cutoffs are all you need. The numbers to compare are balancing current (150mA–1A), continuous current rating, and whether low-temperature charging protection is built in — that last one matters if the battery lives outside in winter.
@exgenica · 13 likes
"Just a suggestion to look into using 21700 cells instead of 18650 cells. You get a lot more potential for higher capacity in almost the same physical space...just an increase of 3mm Diameter and 5mm Length for almost 50% additional capacity. Put another way, a 21700 cell stores almost as much energy as 1.5 18650 cells of similar construction. Plus, the 18650 cells can have a lower lifetime than the same capacity 21700 cell due to increased stress on the 18650 cell when talking about very high capacity cells. Using 21700 cells may also let you go to fewer batteries in parallel for the same performance. For example, you may be able to use 3p12s instead of a 4p12s configuration. In the 12s configuration that eliminates 12 cells right there for actually a slight increase in mAh capacity. So differences in cost between similar quality 21700 and 18650 cells may become a non-issue in a given application."
Our take: The 21700 suggestion is a fair one and the physics is right: a 21700 packs roughly the same capacity as 1.5 comparable 18650s in a barely larger can, which means fewer cells in parallel for the same pack — here, potentially 2P instead of 3P in a 12S layout, saving 12 cells. The trade-off to check before switching is cell availability and cost per Wh, which varies by market and brand. Both formats are perfectly buildable with the exact methods in this video — the layout drawing, nickel welding and BMS wiring are identical.
@luciferknight8224 · 12 likes
"would be good to show how to make a charger for home designed battery packs"
Our take: A good follow-up topic, and the short answer is that a proper charger for a DIY pack is a CC/CV charger set to the pack voltage and current you spec’d — for this 24V 7S pack, a 29.4V charger with the right connector. The important detail: never use a bare bench supply without a current limit, and never charge through the BMS’s P- port with an unrated charger. Most hobbyists use a matching CC/CV ebike charger with the correct Anderson or RCA plug, which is plug-and-play and has the overvoltage protection built in.
@filip3148 · 7 likes
"you should make more videos. this is incredibly helpful to people!"
Creator’s reply: I've got a video upcoming where I increase the voltage of a 24V 20AH battery to 36V 20AH by adding cells, hopefully that will be helpful for you!
@xxwookey · 7 likes
"Nicely done. Lots of useful detail from someone who's clearly done plenty of battery building before. I've been meaning to get a battery welder for a while now. Any particular reason to pick the 787A versus other hardware?"
Our take: Glad the detail level came through — that is the strength of watching a build from someone who has done it many times. On the welder question: the 787A is popular because it delivers a genuinely powerful pulse at a hobby price, and the 0.15mm pure nickel used here welds cleanly at 40A double-pulse settings. The honest advice is to pick a welder with adjustable pulse energy and a foot-trigger or reliable button — the specific brand matters less than having a machine you can dial in on test strips before touching real cells.
@miker8687 · 11 likes
"nah, I worked in a factory spot welding on these exact cells for four years straight in college. You just work on one cell and move one, never in four years was there a problem due to what you're describing. Few small issues were when the strap touched or welded in the wrong spot...keep a bucket of sand near by and a fire suppressant."
Our take: Factory perspective, and it is reassuring precisely because it is boring: four years of production welding on these cells, one cell at a time, and no heat-related failures. The two real-world failure modes were strip placement errors — a strap touching or welding in the wrong spot — which is why the video’s paper layout and careful placement matter. And his last line is the one to remember: keep a bucket of sand and a fire suppressant nearby. A battery build should be a calm, planned process — the equipment for the one-in-a-thousand moment is part of that plan.

Source video: EbikeSchool.com — “How to build a DIY ebike battery from 18650 cells” (youtube.com/watch?v=TY7FwffZ5vc). Comment excerpts are quoted verbatim from the video’s top comments; creator replies are quoted where they exist, and unanswered threads carry Dajiu Energy’s own answers. 1.5M+ views. Micah from EbikeSchool.com builds a 7S2P 24V ebike battery from Panasonic 18650 PF cells — layout on paper, voltage matching, pure nickel spot welding, BMS hookup and shrink-wrap finishing.