Building a 6S4P Samsung 30Q Pack for the X8 – Fish Paper, Spot Welds & No BMS Madness

Building your own battery pack is one of those things you decide to do once, swear you’ll never attempt again, and then instantly start planning your next one because it’s honestly addictive.

For the Project-X8 VTOL build, I needed something lightweight, solid, reliable and capable of giving the motors a proper kick when the VTOL system demands it. Ready-made packs are either too heavy, too expensive, or wrapped in shrink like a mystery sausage with no idea what’s actually going on inside.

So… I built my own 6S4P pack using Samsung 30Q cells, fish paper everywhere, proper cell spacers, and a custom 3D printed enclosure to keep everything tidy and safe.

And yes — I purposely did NOT use a BMS. And before anyone faints, I’ll explain exactly why.

Let’s get into the full story.

Why 6S4P?

I wanted the perfect combo of:

• High capacity
• High discharge capability
• Low voltage sag
• Not weighing enough to drag the X8 out of the sky

Samsung 30Qs hit the sweet spot:

• 3000mAh per cell
• 15A continuous discharge per cell
• Good internal resistance
• Proven reliability in the FPV and DIY battery world

A 6S4P configuration gives:

• 12Ah pack total capacity
• 6-series voltage (up to around 25.2V fully charged)
• Plenty of discharge headroom as four cells share the load in each series group

Basically: plenty of juice for long cruise, and plenty of punch for transitions.

Materials Used

• 24 × Samsung 30Q 18650 cells (genuine, tested, IR-matched)
• Fish paper wrap
• Fish paper positive and negative terminal rings
• Plastic 18650 cell grids/spacers (front and back)
• Pure nickel strip (not nickel-plated steel)
• Spot welder
• Kapton tape
• XT60 connector
• 7-wire balance lead
• PETG custom 3D-printed enclosure
• M3 hardware for the enclosure lid
• Heatshrink for wiring
• A strong cup of coffee for when things get stressful

Step 1 – Testing & Matching Cells

The very first job was testing every single 30Q cell. Even “brand new” cells can vary by:

• Capacity
• Internal resistance
• Actual cycle count (some sellers rewrap used cells)

So I:

• Checked the voltage of every cell
• Ran capacity tests
• Measured internal resistance
• Sorted them into groups so each parallel group was closely matched

Why bother? Because in a 4-cell parallel group:

• One weak cell becomes a parasite
• The others have to carry it
• You get imbalance under load
• You get more heat and more voltage sag
• You get a bad day in the air

Doing this step properly means your pack lasts longer and your flights stay predictable.

Step 2 – Fish Paper Everything

This is the step that separates a safe DIY pack from an accidental hand grenade.

Every cell got:

• A fish paper wrap around the metal can
• A fish paper ring on the positive terminal
• A fish paper ring on the negative terminal

Why fish paper?

• Nickel strips can rub through the cell’s plastic wrapper over time
• Packs flex under vibration, especially in aircraft
• Cell wrappers are thin and can nick easily
• Spot welds can leave tiny sharp points if you’re not careful

Fish paper makes the pack far less likely to short internally. It’s heat-resistant, electrically insulating, and physically tough.

Think of it as the bulletproof vest of battery building.

Step 3 – Plastic Cell Grids

The plastic cell grids do a lot more than just keep everything looking neat.

• They maintain a small gap between cells for airflow
• They keep cells rigid during vibration and handling
• They distribute pressure so cells don’t get crushed
• They stop the pack from twisting or “banana’ing” under stress

Once the 24 cells were dropped into the frames, it already looked like a proper factory-made module instead of a pile of pink chaos.

Step 4 – Laying Out the 6S4P Configuration

The core layout was:

• 4 cells in parallel per group
• 6 groups in series
• Simple, symmetrical, and easy to visualise for wiring

I used pure nickel strip for all the connections because:

• It has low electrical resistance
• It handles high current well
• It welds nicely without overheating the cells
• It doesn’t rust like nickel-plated steel

Each strip was welded with a decent spot welder – no soldering directly onto the cells because that’s just asking for heat damage and sadness.

I welded:

• All parallel connections first
• Then the series links between each group
• Then checked continuity and layout against the wiring plan

Nice clean welds, no burn marks, no hot cells – job done.

Step 5 – XT60 & Balance Lead

Since there’s no onboard BMS, the balance lead is the lifeline for managing this pack.

I installed:

• An XT60 for the main discharge connection (standard in RC land)
• A 7-pin balance connector for the six series groups plus pack negative
• Heatshrink and strain relief so nothing can pull loose under vibration

The wires were routed so they’d exit the pack neatly and line up with the openings in the 3D-printed enclosure.

Step 6 – Custom 3D-Printed PETG Enclosure

This was one of the most satisfying parts of the build.

I designed a PETG enclosure with:

• Internal channels to hold the cell grids snugly
• Rounded corners for impact resistance
• Ventilation slots so the pack can breathe under load
• Cable exit points for the XT60 and balance lead
• A lid that bolts down with M3 screws
• A snug “no-rattle” fit so nothing moves

PETG is a great choice here because:

• It handles heat better than PLA
• It has a bit of flex, so it absorbs vibration
• It doesn’t crack as easily
• It holds threads and screws nicely

Once the pack dropped into the enclosure, the whole thing looked OEM-level tidy – like something you’d pay good money for from a high-end FPV store, except you know exactly what went into it.

Why I Didn’t Use a BMS

This is the bit that usually triggers the “battery police”, but this pack is built for flight, not for a commuter e-bike.

BMS Cons for Flight Packs

Most BMS boards are designed for things like:

• E-bikes
• Power banks
• Portable tools
• Anything where user safety and idiot-proofing come first

They are not designed around:

• High discharge spikes
• High burst current
• RC aircraft where you want the full capability of the cells

A BMS can:

• Add electrical resistance in the main path
• Limit current output
• Add extra weight and wiring complexity
• Generate heat under high load
• Fail mid-flight and cut power completely
• Decide to “trip” to protect the pack and instantly end your flight

In other words: a cheap BMS gets to decide when the X8 falls out of the sky. I’m not a fan of that.

Why No BMS Works for RC & VTOL

Instead of a BMS, the strategy is:

• Use a proper balance charger for every charge cycle
• Use telemetry and voltage alarms from the flight controller
• Stay within safe voltage limits and C-rates
• Monitor how the pack behaves over time

This gives you:

• Full power delivery from the cells
• No surprise cutoffs from a cheap board
• Less weight
• Lower failure points in the system
• Better peak current handling for VTOL transitions

This pack is for a VTOL X8, not for someone’s Nan riding an e-bike to the shops. Different use case, different priorities. For RC flight, no BMS and proper external balancing is the better choice if you know what you’re doing.

Step 7 – Testing the Final Pack

Before closing it up, I tested:

• Total pack voltage
• Voltage of each parallel group
• Continuity on every weld path
• That there were no shorts between any series groups
• Overall resistance via the charger

Everything checked out, so I ran:

• A slow 1A balance charge
• An internal resistance check per series group
• A discharge test to watch voltage sag and recovery

The pack behaved exactly like a healthy Samsung 30Q pack should.

Step 8 – Buttoning It Up & Installing

Once testing was done, the enclosure lid went on with M3 screws.

No rattles, no flex, no movement inside – everything is tight and secure. The pack plugs into the X8 and sits low and central to help keep the CG where it should be.

The end result is a solid brick of power – in a good way. Strong, safe, rigid, and built for abuse in the air.

What I’d Do Differently Next Time

Every build teaches you something. For the next pack, I’d probably:

• Add some anti-vibration foam under the lid
• Print or add rubber bumpers on the ends of the case
• Use slightly thicker gauge silicone wire for extra headroom
• Add reinforcement ribs to the printed enclosure walls
• Try a CF-PETG filament for even more strength
• Maybe add a small external voltage display for quick checks

But overall, this pack came out very clean.

Final Thoughts

This wasn’t just another battery pack – it’s part of the whole Project-X8 ecosystem.

Building a 6S4P Samsung 30Q pack by hand means you know exactly what’s inside it. You trust it more, you understand how it behaves, and you control every part of its design.

Using fish paper, proper nickel strip, solid cell alignment, and a custom 3D-printed case turns a pile of pink cells into a reliable, safe, high-performance pack that you’d happily send up in the air.

And skipping the BMS? For RC use, with proper balance charging and voltage monitoring, it’s the right call.

Would I build another one? Absolutely. It’s weirdly satisfying.