The rest of this article is about when that trade works, which cells to pick, and the Betaflight settings that change when the pack can safely go much lower than a LiPo.
How Li-ion differs from LiPo in practice
Oscar lists three differences: energy density, discharge rate and the lowest safe voltage. Both chemistries charge to 4.2 V per cell. A LiPo should not go much below 3.5 V per cell, while Li-ion can go much lower, and Oscar gives 3.0 V per cell as an example.
The current limit is the one that decides whether a pack will fly a given quad. Before you put Li-ion on an existing build, Oscar suggests answering one question: how much current does it draw to take off, hover and cruise, and can the pack deliver that? If it cannot, the worst case he describes is that the quad simply will not fly well on it. It will not damage the stack. The comments under his guide show both ways to get there: one reader built a 6S pack and only then found the cells were rated at 2C, another's quad shut down a foot off the ground on cheap cells that Oscar thought were fake.
Two rules about current are worth knowing before you buy or build:
- Series does not add current. A 6S pack made from cells rated for 30 A can still deliver only 30 A. Oscar makes this point when a reader multiplies a cell rating by the cell count.
- Parallel does. A 4S2P pack has 8 cells and, with the same cells, twice the current, capacity and weight of a 4S1P pack at the same nominal voltage.
That also gives you a quick way to check a ready-made pack. If a 6S2P pack is rated for 45 A, each cell is contributing 22.5 A, half of what a Molicel P45B is rated for. Oscar's conclusion from that example was that the vendor did not use Molicel cells. If the cell type and the pack rating do not add up, something is wrong.
18650 or 21700
Both are the same cylindrical Li-ion format in two sizes; the number is the cell's dimensions. A 21700 is larger and heavier, with more capacity and a higher discharge rate. The 18650 is easier to find because so many devices use it. Oscar's view is that neither is the right answer for everyone.
Ready-made packs from Auline that Oscar tested show the difference:
| Pack | Cells | Capacity | Max continuous current | Weight |
|---|---|---|---|---|
| Auline V45 | 6S1P 18650 | 3000 mAh | 45 A | 314 g (about 50 g per cell) |
| Auline S70 | 6S1P 21700 | 4500 mAh | 70 A | 428.7 g (about 68 g per cell) |
For a single 21700 cell, Molicel's datasheet for the INR-21700-P45B gives a typical capacity of 4500 mAh (4300 mAh minimum), 3.6 V nominal, 4.2 V charge voltage, a 2.5 V discharge cut-off, 45 A continuous discharge with an 80°C cut-off, and a standard charge current of 4.5 A with 13.5 A maximum.
For 18650 cells, Oscar measured capacity by discharging at 2 A from 4.2 V to 2.9 V per cell, and voltage sag at 12 A over the same range. His capacity results:
| Cell (advertised) | Measured to 2.9 V |
|---|---|
| Ampace JP30 / NBD Nitro Nectar Gold 3000 mAh | 2827 mAh |
| Sony VTC5A 2500 mAh | 2415 mAh |
| Sony VTC6 3000 mAh | 2939 mAh |
| Molicel P30B 3000 mAh | 2851 mAh |
| Molicel P28A 2800 mAh | 2627 mAh |
| Molicel M35A 3500 mAh | 3263 mAh |
| Sanyo NCR18650GA 3500 mAh | 3265 mAh |
| Radiomaster 3200 mAh | 3058 mAh |
The two cells with the most capacity are not the ones he recommends for flying. For long range he picks the Ampace JP30 (sold by NewBeeDrone as Nitro Nectar Gold) for its capacity and low sag, with the Molicel P30B as the more widely available alternative and the VTC6 and P28A as good options too: the VTC6 gives slightly more flight time, the P28A a bit more punch. The M35A and NCR18650GA are his choice for low-current uses such as goggles and radios.
No 18650 in that table measured more than about 3265 mAh. When a reader built a pack from cheap cells labelled 4000 mAh, Oscar's answer was that a 4000 mAh 18650 is "just not a thing" and that the cells were probably fake. Buy from a seller you trust.
Building a pack
Oscar's 4S build uses 16AWG wire for the discharge lead, 20AWG or 22AWG for the balance lead, a 5-pin balance connector and an XT30 or XT60. He prefers the XT30 for its weight, since the current is low, and suggests an XT30 to XT60 adapter if your quad has an XT60. Check the balance lead order against a wiring diagram before you plug it into a charger.
Spot welding is the safer way to join Li-ion cells. If you have to solder, Oscar's tutorial is about keeping heat out of the cell:
- Discharge the cells to about 3.0 V first. Less stored energy means less fire risk.
- Roughen the terminals with fine sandpaper so solder bonds.
- Use an iron of at least 60 W, ideally temperature-controlled, at around 400-450°C with a thick tip, and leaded rosin-core solder. Do not use acid flux.
- Tin each terminal in a couple of seconds and let the cell cool. If it gets too hot to touch, stop and let it cool completely.
- Solder one terminal at a time on multi-cell packs, cover every joint with Kapton or electrical tape, add insulation between cells and wrap the pack in heat shrink.
If you have no soldering experience, Oscar's advice is to buy a ready-made pack. He also tested several ready-made 6S packs and found none that matched the performance of Molicel cells, which is why pilots chasing every minute still build their own.
Betaflight: cell count and voltage alarms
Betaflight's voltage alarms are set per cell, so they only work if Betaflight knows how many cells are connected. By default it guesses when you plug the battery in: it divides the pack voltage by the Maximum Cell Voltage setting (4.30 V by default) and adds one. A LiPo is never plugged in low enough to fool that. A Li-ion pack can be. A 6S Li-ion plugged in below 21.5 V, which is about 3.58 V per cell, is counted as 5S, and the OSD then shows each cell much higher than it really is. Oscar's example is a 6S pack at 18.0 V (3.0 V per cell) showing 3.6 V per cell, a reading that tempts you to keep flying.
The fix is to tell Betaflight the cell count in the CLI:
set force_battery_cell_count = 6
save
Next, look at the alarms on the Power & Battery tab. "Warning Cell Voltage" triggers the low battery warning and "Minimum Cell Voltage" the critical one. They are warnings only: Betaflight does not cut the motors at either value. The defaults are 3.50 V and 3.30 V, and the Betaflight documentation recommends 3.6-3.5 V for the warning and 3.3 V for the minimum. Those numbers are written for LiPo. On a Li-ion pack they go off while a large part of the capacity is still unused, and a reader of Oscar's guide landed nervously when his 4S pack alarmed below 14 V.
There is no single correct pair for Li-ion, so start from the sources:
- The cell datasheet sets the floor. Molicel measures the P45B's rated capacity down to 2.5 V, and that is the cut-off in its datasheet.
- Oscar normally lands at 2.8 V per cell. He calls flying down to 2.5 V "a bit risky".
- The warning has to leave time to fly home from wherever you are, which on a long-range flight can be minutes.
For example, if you want to land where Oscar does, set Minimum Cell Voltage to 2.8 V and the warning some way above it. Keep in mind that voltage sags under load and recovers at rest, so the number on the OSD during a climb is lower than the pack's resting voltage.
From Betaflight 2026.6 you do not have to choose between LiPo and Li-ion settings. The Power & Battery tab has up to three battery profiles, and each one stores its own name, minimum, maximum, full and warning cell voltage, capacity, forced cell count and capacity alert percentage. You can keep a LiPo profile and a Li-ion profile, switch in the CLI with battery_profile followed by the profile number (0, 1 or 2), and put the profile name on the OSD so you can see which one is active before take-off. On older firmware there is one set of values, so change them whenever you change chemistry.
Charging and storage
Most current LiPo chargers have a Li-ion mode, and the pack connects the same way as a LiPo. Oscar charges at 0.5C to 1C with the charger set to Li-ion and the correct cell count, and checks the temperature often; if the pack gets warm, he takes that as a sign the current is too high. For the P45B, the datasheet's standard charge is 4.5 A, which is 1C, and the maximum is 13.5 A.
For storage, Oscar's answer to a reader was the same as for LiPo: around 3.8 V per cell. Use the same cells throughout a pack. Oscar advised against combining packs made from different cells.
Quick checklist
- Measure or estimate the cruise current. If the pack's continuous rating cannot cover it with margin, stay on LiPo.
- Pick known cells from a trusted seller and treat anything above about 3500 mAh in an 18650 as suspect.
- Prefer spot-welded packs. If you solder, discharge to about 3.0 V first and work fast.
- Set
force_battery_cell_countto the pack's real cell count. - Lower the warning and minimum cell voltages, no lower than the cell's datasheet cut-off. On Betaflight 2026.6 or newer, keep them in a separate battery profile.
- Charge in Li-ion mode at no more than 1C and store at around 3.8 V per cell.