Charge current: start at 1C
"1C" means charge amps equal to the pack capacity in amp-hours. Divide mAh by 1000:
| Pack capacity | 1C charge current |
|---|---|
| 850 mAh | 0.85 A (often set to 0.8-0.9 A) |
| 1300 mAh | 1.3 A |
| 1500 mAh | 1.5 A |
Oscar Liang, iFlight's charging guide and the FPV Handbook all treat 1C as the default safe rate. At 1C an empty pack takes roughly an hour to fill. Many packs advertise higher charge rates (2C, 3C, 5C). Use those only when the manufacturer states them on that pack; the big discharge C number on the label is not a charge rating. HobbyKing's charging notes put it bluntly: a "100C" 1500 mAh pack is not inviting a 150 A charge.
If the pack gets more than mildly warm, stop. Oscar Liang's rule: a healthy pack should stay cool while charging. Heat means the rate is too high or the pack is faulty.
Some modern cells allow a faster charge rate on the label. Even then, repeated high-rate charging shortens life and adds heat, so iFlight and Oscar Liang still point you at 1C when you have the time.
Always balance charge
A multi-cell pack needs both the main discharge lead (XT30/XT60 and similar) and the balance lead (JST-XH). Balance charge is the mode that watches every cell and keeps them from drifting past 4.20 V while others lag behind.
Without the balance lead, a charger that still allows a non-balance charge can push one high-IR cell over 4.20 V while another sits under it. WARG's LiPo procedure and Oscar Liang both call balance charging the default; if a cheap charger lets you charge without the balance plug, replace the charger.
Standard LiPo full charge is 4.20 V per cell. LiHV packs that the maker specifies as high-voltage can go to 4.35 V per cell - only when you select the LiHV profile on the charger. Do not charge a normal LiPo as LiHV.
For a single pack on the charger, Oscar Liang says either lead can go on first. On a parallel board the order matters (see below).
Before you start the charge
- Confirm chemistry (LiPo vs LiHV) and cell count on the charger match the pack.
- Let a pack cool to room temperature after a flight before you charge it again.
- Skip damaged, swollen, punctured or crash-crushed packs. Charge those alone never; retire them.
- Charge on a non-flammable surface. Oscar Liang prefers a metal ammo box (seal removed so pressure can vent) over cloth LiPo bags, which tests have shown do not contain a fire. Keep a fire extinguisher nearby.
- Stay in the room. Oscar Liang and iFlight both list unattended charging as a common factor in LiPo fires. Warmth, swelling or an odd smell is your cue to stop and isolate the pack.
Parallel charging: useful, but stricter rules
Parallel charging ties several same-S packs together through a parallel board so the charger sees one larger pack at the same voltage. Six 6S 1500 mAh packs look like one 6S 9000 mAh pack. Oscar Liang's parallel guide is the checklist most FPV pilots follow.
Same cell count only
Never mix 4S and 6S on the same board. The higher-voltage pack will dump current into the lower one and can overcharge it. Same S-count for every connector you plug in.
Match voltage before you plug in
When two packs at different voltages share a parallel bus, the fuller one charges the emptier one hard through the board. Oscar Liang keeps the difference within about 0.1 V per cell (0.4 V on a 4S pack, 0.6 V on a 6S). The FPV Handbook uses the same 0.1 V per cell limit. Outliers charge alone. A cheap balance-port voltage checker makes sorting piles by voltage fast.
Main lead first, then balance
Always plug the XT30/XT60 into the board before the balance plug. Equalization current at connection can be large; balance wires are not built for that surge. After the mains are on, connect balance leads and check polarity - a reversed balance plug on an unfused board can melt traces in a second.
Set current from the sum of capacities
At 1C, charge amps = (sum of mAh of every connected pack) / 1000. Three 1500 mAh packs at 1C need 4.5 A. Six 1500 mAh packs need 9 A, and the charger also needs enough watts (for 6S full voltage, about 25.2 V × 9 A ≈ 227 W). If the charger is watt-limited, lower the amps; that is fine, it just takes longer.
Prefer packs of similar capacity on one board. Oscar Liang allows a small capacity spread with common sense; a much smaller pack on the same bus can take a harder share of current than you intended.
Use a fused board when you can
A board with main-port and balance-port fuses (Lumenier ParaGuard, HGLRC Thor-style boards and similar) limits damage when someone reverses a balance plug or a pack faults. Budget boards without fuses work until the first wiring mistake.
Do not parallel a bad pack
Damaged, puffy or high-IR packs belong out of the parallel group. One bad cell can drag healthy packs with it.
Multi-channel chargers as the quieter option
A dual or quad charger gives each pack its own channel. Packs never share a bus, so you can mix voltages, capacities and even chemistries in one session. Oscar Liang calls that the safer option when the budget allows it. A parallel board is still the cheap way to fill a stack of matching packs from one strong channel.
Short checklist
- Cool pack, correct chemistry and cell count, balance lead connected.
- Charge at 1C unless that pack's datasheet says otherwise; stop if it runs hot.
- For parallel: same S-count, voltages within ~0.1 V/cell, main plugs first, current = sum of capacities at 1C, fused board preferred, never leave it alone.