On the above curve you can see the red voltage line has a small drop at the end, it is the -dv/dt
and signals the battery is full.
The RD60xx with the “n” firmware has experimental support for this, via CutOff -dV/dT, Due to
the low resolution of the ADC, it is best to combine this with CutOff temp., in order to improve
the reliability and safety.
Previous firmwares will not allow you to automate this. Also note that the ORP delay and
ORP set settings work differently, and are not suited for this type of cutoff detection.
21.4.6. Float Charging (aka Trickle Charging)
This is the simplest method of charging, but it requires some care. It is normally reserved for
Lead Acid or, with precaution, for Lithium-ion batteries. It is not suited for NiMH or NiCd
batteries. It consists of applying a constant voltage charge at a rather low current, and can be
left on for lengthy periods, without significant damage to the battery.
As lithium-ion batteries do not support overcharging, they can only be float charged at a voltage
equal to or slightly lower than the cell voltage, resulting in 0 charge current after the cell is full. If
a charge current remains, you will damage the battery.
Lead acid batteries can be float charged with a small charge current remaining when full. That
small current is only meant to compensate for the self-discharge of the battery. Therefore, if you
set the voltage too high, you will damage (gas out) the battery.
Ideally, the float voltage is determined by the exact battery chemistry and the battery
temperature. The latter is not possible with the RD60xx (except when controlled from a PC for
example), as the temperature is only used for logging and cut off, not for controlling the charge
current or voltage.
If you want to use this method, set a low max current and a precisely chosen voltage.
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