Charge a new NiMH or NiCd (often called NiCad) RC pack with a charger mode that matches the chemistry, cell count, capacity, and the pack manufacturer’s instructions. Inspect the pack and leads first, then use the specified current or a compatible terminated charge program. A C/10 charge can be a useful slow-charge example for some nickel packs, but it is not a universal break-in rule for every assembled RC battery. LiPo, LiFe, and Li-ion packs require their own lithium charging programs.
This page is adapted from the original Dave Thacker Radical RC guide and updated September 14, 2026. The practical inspection routine and his field examples remain useful; product names, prices, and fixed charging claims from that older article have been removed or updated.
First identify the pack and charger
Before connecting anything, read the battery label and charger manual. Confirm:
- Chemistry: NiMH and NiCd are nickel chemistries. LiPo, LiFe, and Li-ion are different lithium chemistries.
- Cell count and nominal voltage: for example, a four-cell NiMH or NiCd receiver pack is nominally 4.8V and a five-cell pack is nominally 6V. Confirm that the receiver, servos, switch harness, and regulator can accept the freshly charged pack. Our guide to 4.8V or 6V receiver batteries covers that equipment check.
- Capacity: use the pack’s stated capacity in mAh when setting a current or estimating a charge time. Series cells increase voltage; they do not add the cells’ mAh capacity together.
- Connections: check polarity, plug fit, insulation, and wire condition. The RC connector and wire chart can help identify a connector and its current limits.
If the chemistry or charge rate is unknown, stop and identify the pack before charging. A charger that can physically plug into a connector is not necessarily the right charger.
How to charge a new NiMH or NiCd RC pack
- Inspect before charging. Look for crushed cells, a split wrapper, corrosion, a loose lead, damaged insulation, or a connector wired backward. Do not charge a damaged pack.
- Use the nickel mode for the actual chemistry. Select NiMH for NiMH and NiCd for NiCd when the charger provides separate modes. NiCd and NiMH can have different charge detection and rate requirements. Energizer’s NiCd application manual says nickel-cadmium packs should use the specified charger and charging conditions; do not substitute a guessed setting.
- Set the cell count and current from the pack documentation. Do not copy a rate from a loose cell data sheet onto an assembled pack unless the pack maker says it applies to that pack. Pack construction, cell model, temperature, wiring, and charger termination all matter.
- Supervise the first charge. Keep the pack where you can check it. If it becomes abnormally hot, swells, leaks, smells unusual, or the charger behaves unexpectedly, stop the charge and disconnect it when safe to do so. A mild temperature rise near the end of a nickel charge can occur, but rapid or excessive heating is a reason to stop.
- Verify the result. Let the pack settle, then check pack voltage and the connector. For a transmitter or receiver battery, perform the equipment’s normal range, switch, and load checks before flying. A charger display cannot prove that a switch harness, solder joint, or cell will carry the model’s load.
What does C/10 mean, and how long will charging take?
C means the pack capacity. For a 1650mAh pack, C/10 is 165mA; for a 720mAh pack, it is 72mA. A rough planning equation for a compatible constant-current nickel charge is:
Ideal hours = missing capacity in mAh ÷ charger output in mA.
That division is only the ideal electrical time for replacing the charge used; a partly charged pack needs less added charge than an empty one. A nickel battery does not accept every milliamp-hour perfectly: heat, charge efficiency, the starting state, current regulation, and the charger’s termination method affect the real time. The actual charge may therefore take longer than the ideal calculation, and a timer alone may be unsuitable. Use the battery and charger instructions to choose the current, termination, and supervision method. Do not turn the arithmetic into a universal overnight time or apply a generic loose-cell rate to an assembled RC pack.
Manufacturer guidance varies by cell and use. Energizer’s NiMH handbook describes a moderate-rate smart charger as preferred and says a 0.1C charge for 12–14 hours is well suited to NiMH batteries. Panasonic’s NiMH handbook documents terminated rapid-charge methods around 0.5–1C, a semi-constant-current method up to 0.1C, and separate trickle methods. Those are manufacturer examples for specified cells and applications, not a universal prescription for every RC pack.
New-pack break-in and cycling
A new nickel pack does not automatically require the same break-in routine. Some packs and chargers are designed for a slow first charge; others specify a terminated charge or a normal charge-and-use cycle. Follow the pack maker’s instructions. If you cycle a new pack to check it, record the charge and discharge settings and do not judge the pack from an unexplained first capacity reading.
Dave’s original field notes are still helpful as context: he reported using 720mAh and 280mAh NiMH packs in combat models with three to five servos, and a 2700mAh pack in a 1/3-scale Extra with nine JR coreless servos. Those examples show how capacity, weight, cell size, and model load interact. They are experience reports, not a current specification for a replacement pack. Our separate cell soldering guide provides construction background; follow the pack maker’s service instructions before any connector or lead work.
Radical RC’s four-point pack inspection
The original shop checklist below records the four checks Radical RC’s battery technician used before shipping assembled batteries. For a consumer, use the safe measurement steps with the charger and model disconnected; follow the pack maker’s service instructions for any damaged connector or lead.
1. Polarity and pack voltage: with the charger and model disconnected, use a voltmeter to confirm polarity and total pack voltage. Never use a meter’s continuity mode across a live battery.
2. Lithium cell readings: for LiPo, LiFe, and Li-ion packs with a balance connector, use the charger’s cell-read function or a meter as directed by the battery maker to check each cell before charging.
3. Discharge lead: with the charger and model disconnected, check discharge-lead polarity, connector condition, and pack voltage. Use continuity mode only on an isolated, disconnected, unpowered lead or harness.
4. Supervised first charge: if the battery maker calls for a commissioning check, connect the correct leads to the correct charger and follow that maker’s brief, supervised first-charge procedure before a full charge. Recheck cell balance and pack voltage. Do not make a five-minute test a universal rule.
NiMH and NiCd charging is different from LiPo charging
Never use a NiMH or NiCd program for a LiPo pack. Use a charger designed for LiPo, select the labeled cell count and voltage, and use balance charging when the pack has a conventional balance connector. The Reedy LiPo safety instructions require a LiPo-specific charger, balance charging, correct cell-count selection, supervised charging, and immediate removal from service for a damaged, swollen, leaking, or abnormal pack. They also specify that the maximum charge rate is a battery-specific limit; do not transfer a rate from one LiPo model to another.
Charge a conventional LiPo outside the model, after it has cooled, in the isolated fire-resistant setup specified by its manufacturer. Check the individual cell readings through the balance connector before charging. LiFe and Li-ion packs also need their own labeled chemistry and voltage settings. Some smart LiPo systems balance through a data connection instead of a separate balance lead; for example, Spektrum Smart G2 documentation describes that system-specific exception. Follow the battery and charger instructions for the system in hand.
After charging
Disconnect the pack from the charger when the charge is complete. Check the connector and leads for heat or looseness, then install the pack only after the model’s receiver, servos, switch, and regulator have passed their normal checks. If the pack is for a transmitter or receiver, capacity and runtime matter more than a no-load voltage reading. A cycler or suitable tester can reveal a weak cell before it becomes a flight problem.
For broader battery-care questions, see Radical RC’s battery FAQs. For current options, see receiver NiMH packs, TX NiMH and NiCd packs, NiMH single cells, and RC battery chargers.