Short Answer: Use the NiMH Program and the Pack Maker’s Instructions
Charge a new or stored NiMH RC pack with the charger’s chemistry-specific NiMH program, using the current, cell count or nominal voltage, termination method, and safety limits specified for that exact pack and charger. Do not use lead-acid (Pb) mode as a general NiMH workaround, and do not disable time or capacity protections just to make a charger continue.
A low-rate forming or conditioning cycle may be appropriate for a particular pack, but there is no universal recipe. The original answer below is valuable historical troubleshooting from the chargers available at the time; the current safety guidance is the manufacturer’s documentation for the equipment on your bench.
What Was Matt’s Original NiMH Charging Question?
Matt wrote after buying a 1,650mAh, eight-cell, 9.6V NiMH transmitter pack. He briefly connected it to his transmitter and saw the voltage start at 8.9V, then settle near 8.5V. He then put it on a Triton 2 at 0.1A with a thermal probe. The pack started at 79 degrees, the cutoff was set to 88 degrees, and the charge ran for 16 hours before the temperature sensor ended it after 1,670mAh had been delivered. He asked whether he should expect a higher measured capacity.
What Was Dave’s Original Answer?
Dave’s answer made several useful points. In the original reply, he estimated that a completely empty pack could require substantially more charge input than its rated discharge capacity because charging is not perfectly efficient. The 1,670mAh reading therefore did not prove that the pack had reached its full usable capacity, and the Triton’s low-current measurement accuracy was another unknown. That historical estimate is not a charging recipe; use the pack maker’s current rate, time, and termination instructions.
He also warned that an initial peak charge is unreliable. A new pack can show several voltage peaks as cells with unequal states of charge fill. In his experience, a false peak could fool a charger about 60 percent of the time at ordinary rates from roughly C×0.5 to C×2; he had not tested the much slower rate in Matt’s example, but expected it to perform poorly. One cell can trigger the charger before the rest are full, while the temperature rise may be too small or too variable for dependable termination. His practical rule was never to use peak detection on an initial charge or on a pack coming out of storage.
For regular service, Dave preferred enough current to give his older peak charger a clear termination signal rather than relying on a very low-current peak. His explanation was that a slow peak charge can hold a full pack in overcharge longer before the voltage drop becomes obvious. The exact current and termination behavior depend on the cells and charger, so this observation should not be turned into a universal setting.
Dave then described a workaround that made an older computerized charger behave like a simple forming charger. It used the charger’s lead-acid mode and defeated normal safety limits. That method is preserved here only as historical context; its settings and steps have intentionally been omitted because they should not be copied on current equipment.
One caution from the original answer still matters: a pack coming out of long storage may contain cells at unequal states of charge, which can make peak-based termination misleading. The safe response is to use the pack maker’s current conditioning procedure—not to recreate the old workaround.
Why Is the Old Pb-Mode Procedure Historical Only?
The Pb-mode workaround was an attempt to make an older computerized charger behave like a simple slow charger. It is not current universal NiMH guidance. NiMH and lead-acid batteries have different charging behavior, and modern chargers normally provide a dedicated NiMH program with chemistry-appropriate termination.
Current manufacturer handbooks may describe a low-rate NiMH charge for a specified time under specified conditions, but the exact rate, time, and endpoint depend on the cell, pack construction, temperature, and charger. Energizer and Panasonic both emphasize following the particular battery’s charging instructions. Never use a different chemistry mode or defeat charger protections to imitate an old procedure.
What Is a Safer Current NiMH Checklist?
- Confirm the chemistry, cell count, rated capacity, connector polarity, and condition of the pack.
- Select NiMH, not Pb or LiPo, and use the exact charger settings recommended for the pack.
- Use only a current that the pack and charger documentation support. A capacity number alone does not establish a universal safe current.
- Keep the charger’s timer, capacity cutoff, and temperature protections enabled unless the manufacturer’s instructions say otherwise.
- Charge on a stable, heat-resistant surface while remaining present. Stop for unusual heat, swelling, leakage, odor, or an unexplained charger error.
- After long storage, use the pack maker’s conditioning or cycle procedure if one is specified. Do not peak-charge it simply because the pack has been sitting.
What Does the 1,670mAh Reading Tell You?
It tells us what that Triton 2 reported under that charge, temperature, and termination event. It does not establish the pack’s complete capacity. The 100mA setting supplied 1,600mA in 16 hours before the thermal cutoff, and the charger reported 1,670mAh; losses, initial state of charge, measurement accuracy, and the exact termination behavior all matter. A controlled capacity test with the current pack and analyzer instructions is more meaningful than comparing one charge counter with the label.
Related Radical RC Resources
See Radical RC’s RC battery chargers, NiMH and NiCad charging guide, battery configuration chart, and battery parts.
- Energizer NiMH application handbook
- Panasonic NiMH handbook
- Horizon charger manual — chemistry and charger-setting examples
Dave