LiPo charge rate describes charging current relative to battery capacity. At 1C, a 1,300mAh pack charges at 1.3A; at 2C, it would charge at 2.6A, but only if its manufacturer permits that rate. Start with the battery's charging instructions, then check whether your charger, power supply and leads can support the resulting amps and watts.
The HOTA D6 Pro and VIFLY WhoopStor 3 illustrate two different limits: available power when charging larger packs, and selectable current when charging small 1S batteries. Neither charger's maximum setting tells you what is safe for a particular pack.
Featured gear
HOTA D6 Pro Dual Battery Charger
The HOTA D6 Pro is a dual-channel AC/DC balance charger for conventional FPV and RC battery packs, with two outputs and support for multiple battery chemistries. Best for: Pilots managing several 2S–6S FPV batteries.…
The HOTA D6 Pro is a dual-channel AC/DC balance charger for conventional FPV and RC battery packs, with two outputs and support for multiple battery chemistries.
- Best for
- A versatile dual-channel AC/DC charger for conventional FPV and RC packs; buyers must verify…
- Product type
- Battery Chargers
- Best for
- A versatile dual-channel AC/DC charger for conventional FPV and RC packs; buyers must verify…
- Product type
- Dual-Channel Balance Charger
For small 1S batteries, the WhoopStor example below shows why the lowest selectable current can matter as much as maximum power.
Featured gear
VIFLY WhoopStor 3 1S Battery Charger
The VIFLY WhoopStor 3 charges or storage-charges as many as six 1S LiPo or LiHV tiny-whoop batteries through independent PH2.0 and BT2.0 channels. Best for: Pilots managing multiple 1S tiny-whoop batteries. Not ideal for:…
The VIFLY WhoopStor 3 charges or storage-charges as many as six 1S LiPo or LiHV tiny-whoop batteries through independent PH2.0 and BT2.0 channels.
- Best for
- A specialized six-channel charger and storage discharger for 1S PH2.0 and BT2.0 tiny-whoop batteries;…
- Product type
- Battery Chargers
- Best for
- A specialized six-channel charger and storage discharger for 1S PH2.0 and BT2.0 tiny-whoop batteries;…
- Product type
- 1S Battery Charger and Storage Discharger
Convert the battery's charge C-rate into amps
Use this calculation for the charging rate for LiPo batteries:
Charge current in amps = capacity in mAh ÷ 1,000 × charge C-rate.
The discharge rating printed prominently on an FPV pack describes current leaving the battery. Find the separate charge-rate instruction on its label or documentation. A large discharge C-rating is not permission to use the same number when charging.
Horizon Hobby's lithium battery safety guidelines say to follow the pack's rated charge current and not exceed 1C unless the manufacturer specifies otherwise. A lower specified limit still controls. If the battery's identity, chemistry or safe charging limits cannot be established, leave it disconnected.
These hypothetical capacities show the arithmetic. The 2C column is a calculation, not a recommendation to fast-charge an unidentified pack.
| Battery capacity | At 1C | At 2C, if expressly permitted |
|---|---|---|
| 300mAh | 0.30A | 0.60A |
| 450mAh | 0.45A | 0.90A |
| 1,300mAh | 1.30A | 2.60A |
| 1,500mAh | 1.50A | 3.00A |
| 5,000mAh | 5.00A | 10.00A |
Cell count does not multiply this current. A 4S 1,500mAh pack and a 6S 1,500mAh pack both calculate to 1.5A at 1C. Their voltage, and therefore the charger power required, differs.
Check watts as well as amps
Output power in watts = pack voltage × charge current. For charger sizing, use the full-charge voltage as a conservative calculation point. iFlight's charging guidance specifies 4.20V per cell for standard LiPo, giving 16.8V for 4S and 25.2V for 6S. LiHV has a different permitted endpoint; never select it simply to increase capacity in an ordinary LiPo.
For the two hypothetical 1,500mAh packs at 1C, the calculations are 16.8V × 1.5A = 25.2W for 4S, and 25.2V × 1.5A = 37.8W for 6S. Two of those 6S packs require 75.6W of combined output capacity at that sizing point. These are calculated requirements, not measured wall consumption.
The distinction becomes clearer with two hypothetical 6S 5,000mAh packs, each approved for 1C charging. Each needs 25.2V × 5A = 126W at the same sizing point; together they need 252W. A charger with a shared 200W AC ceiling cannot sustain both requested currents through the entire constant-current portion as voltage rises, even if its amp setting allows 5A per channel.
Input power must also cover conversion losses and the charger's own consumption. Check the supply's actual voltage and power capability, the charger's configured input limit, and the budget available with both channels operating. For the wider purchase decision, the 6S LiPo charger guide connects those requirements to channel count and power-source choices.
Apply the limits of your actual charger
HOTA D6 Pro: AC power and DC power are different budgets
HOTA's D6 Pro specification graphics list 0.1–15A per channel, 200W on AC with automatic distribution, and up to 325W per channel on DC at an input voltage above 24V. The stated DC input range is 6.5–30V. A supply within that range does not automatically deliver the full DC rating.
For two 1,500mAh 6S packs at an authorized 1C rate, the calculated 75.6W output requirement is below the AC ceiling. For the two 5,000mAh examples, reduce the requested rate or establish a suitable DC setup. Buying more wattage cannot raise the batteries' permitted charge current.
The HOTA D6 Pro review covers its broader ownership tradeoffs. For operation, use the D6 Pro operating instructions, which explain channel selection and task parameters. The manual's generic battery table does not establish fast-charge approval for a specific FPV pack.
WhoopStor 3: check the minimum setting and every connected pack
VIFLY lists WhoopStor 3 charging current from 0.3A to 1.3A per port, with six independent 1S channels. It supports PH2.0 and BT2.0 batteries, conventional LiPo at 4.20V and LiHV at 4.35V. VIFLY's general suggestion of 2C does not override the battery manufacturer's instructions.
A hypothetical 300mAh pack approved for 1C fits the 0.3A minimum exactly. For a 450mAh pack limited to 1C, the ceiling is 0.45A: choose an available setting at or below that value, rather than rounding up. If a battery requires less than 0.3A, this charger's specified range does not fit it.
The WhoopStor 3 manual shows common current and target-voltage controls. Choose settings suitable for every connected battery, and use only one socket in each numbered PH2.0/BT2.0 pair. Six channels do not mean twelve batteries.
VIFLY specifies at least 40W input power. The manual warns that a USB-C source limited to 9V caps charge current at 0.6A. A USB-C plug alone therefore does not establish full charging capability. Its XT60 input supplies energy to the charger; it is not a multi-cell charging output.
Check firmware without changing the battery's limits
On September 9, 2026, the D6 Pro download from HOTA's support page contained a file named HOTA D6 Pro V1.0.53.prg. The VIFLY Download Center listed WhoopStor V3 firmware V1.17 separately from V2. Match update instructions to the exact model; neither listing establishes permission to increase a battery's charge rate.
Make the settings match the battery before starting
Use the charger manual's connection sequence and perform these checks on each charging session:
- Inspect the pack, insulation, leads and connectors. Do not charge a damaged or swollen battery. Let a hot pack cool to the manufacturer's permitted charging temperature.
- Confirm chemistry, cell count, endpoint and permitted current from the battery documentation. Select a charge task, rather than a storage or discharge task.
- Check connector fit and polarity. On a multi-cell balance charger, connect the main and balance leads to the same channel. Confirm the displayed cell count before starting.
- Check the power source and current setting. For the WhoopStor, recheck both saved settings before attaching a different batch.
- Charge in appropriate fire-resistant containment away from combustible material, with the charger ventilated. Stay present and monitor the readings. Stop safely if the pack becomes abnormally hot, swells or shows other abnormal behavior.
These precautions follow the charger manuals, Horizon Hobby and iFlight guidance. A low current setting cannot make a damaged pack or the wrong chemistry setting safe. Do not bypass a low-voltage rejection by pretending the battery is a different chemistry.
Why actual current falls below the selected rate
The set current is a limit, not a promise that the display will hold that number until completion. Texas Instruments explains constant-current and constant-voltage charging: current is controlled first; as the battery reaches its voltage target, the charger holds voltage and current tapers.
That is why 1C does not guarantee an exactly one-hour session, and 2C does not guarantee a half-hour session. Starting charge, the taper and multi-cell balancing affect completion. HOTA's manual also explains that balancing time depends on the cell-voltage difference.
When charging seems slow, look at where it slows. Near the correct voltage endpoint, tapering can be normal. Low current early in the session calls for checking input power, shared channel demand and the selected task. The WhoopStor's documented 9V USB limit is one specific example. Do not raise the voltage endpoint, disable safety limits or keep restarting the task to force the initial current back.
Choose a rate you can justify from the pack label
Calculate the pack's allowed amps first, select a setting within that limit, and then check voltage, connector fit and available watts. More charger capacity is useful when a verified charging requirement exceeds the present setup. If your existing charger already supports the required current and power, a larger rating alone does not give that battery a safer or faster charging instruction.
Sources
- Horizon Hobby lithium battery safety guidelines: Manufacturer instructions for charge-current limits, inspection, chemistry, connections and safe operation.
- FPV LiPo Battery Charging, Storage & Safety Guide: Manufacturer guidance for standard LiPo voltage, LiHV distinctions, cooling and charging precautions.
- HOTA D6 Pro official specifications: Official specification graphics for AC/DC power, input-voltage conditions and channel-current ratings.
- HOTA D6 Pro Operating Instructions, Ver 1.1.8: Manufacturer manual mirrored by a retailer, covering task setup, channels and balancing.
- VIFLY WhoopStor 3 specifications: Manufacturer specifications for current range, 1S chemistry, connectors and input power.
- VIFLY WhoopStor 3 manual: Manufacturer manual mirrored by a retailer, covering paired sockets, controls and the 9V USB limit.
- HOTA firmware and manual downloads: Official download location; the D6 Pro archive supplied the named firmware file on the check date.
- VIFLY Download Center: Official V3 firmware listing and separate V2 download.
- Constant-current and constant-voltage charging explanation: Technical explanation of constant-current/constant-voltage charging, used for the taper mechanism.
Last checked: September 9, 2026.
