Xantrex RV Series Inverter/Charger Owner’s Manual

Battery Charger

Theory of Operation

Inverter to Charger Transition

The internal battery charger and automatic transfer relay allows operation as either a battery charger or inverter (but not both at the same time). An external source of AC power (such as shorepower or a generator) must be supplied to the inverter AC input in order to allow it to operate as a battery charger. The RV series charger will always charge when there is AC power present, even when the inverter itself is turned off (by the on/off switch). When operating as a charger, the AC output is powered by the external source (such as a generator or public power).

The inverter automatically becomes a battery charger whenever AC power is connected to its AC inputs. There is a minimum 20-second time delay from the time the inverter senses that AC is present at the input terminals to when the transfer is made. This delay is built in to provide time for a generator to spin-up to a stable voltage and avoid relay chattering. The inverter will not transfer to generator until it has locked onto the generator’s output. The inverter’s AC input is internally connected to the inverter’s AC output while in the battery charger mode.

Transfer Switching Speed

While this inverter is not designed specifically as an uninterruptible power supply (UPS) system, its transfer time is normally fast enough to hold up most computers. The transfer time is typically 16 milliseconds.

Several PC magazines have run tests indicating a transfer time up to 100 milliseconds will normally hold up the present generation of PCs.

When switching from inverter to charger, the inverter waits a minimum of 20 seconds to ensure the AC source is stable (as the generator gets up to speed).

Battery Terminology

Describing the battery charger’s operation requires the use of terms with which you may not be familiar. The following terms will be referred to in the description of the battery charger operation.

•Electrolyte: Typically a mixture of water and sulfuric acid, it is commonly referred to as battery acid.

•Plates: Originally made of lead, they are now made of lead oxide. Plates are the part of the battery that collects current and are connected to the battery terminals. There are several plates in each cell, each insulated from the other by separators.

•Sulphating: As a battery discharges, its plates are progressively covered with lead sulfate. During recharging, the lead sulfate is removed from the plates and recombines with the electrolyte. If the lead sulfate remains on the plates for an extended period of time (over two months), it hardens, and recharging will not remove it. This reduces effective plate area and the battery capacity is diminished.

•Stratification: Over time the batteries’ electrolyte (liquid) tends to separate. The electrolyte at the top of the battery becomes watery while at the bottom it becomes more acidic. This effect is corrosive to the plates.

•Deep Cycle: A deep cycle occurs when a battery has been discharged such that less than 20% of its capacity remains (80% discharge).

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