Ambient temperature differences between the charger and battery have little effect during battery charging (bulk mode or absorption mode). If, however, the temperature difference is greater than 10C during float charging, the charger's output voltage may no longer be correct for long-term battery charge maintenance.
The charger is designed to be mounted inside an enclosure or equipment rack. There are four press-in standoffs in the bottom of the chassis. These have a minimum of 0.187 inch of available 6-32 threads to be used for mounting. Also, there are two 0.201 mounting holes in the side and the bottom of the chassis suitable for #10 hardware.
Heat Considerations The charger dissipates approx. 40 watts under worst-case conditions (full current at high line and low battery voltage). Most of this heat is transferred to the charger's chassis, which acts as a heatsink. Sitting on a bench, the chassis becomes quite warm at full output current. The charger is not damaged by this.
If the enclosure is metal and the charger is bolted to it, the enclosure acts as an extension of the heatsink and transfers much of the heat to the outside. It's highly recommended to utilize a metal enclosure this way. When using a small enclosure - especially a non-metalic one, a small fan is recommended to keep the enclosure temperature within the 60C maximum. This is more important for the battery than for the charger. With a large metal enclosure and/or with adequate ventilation, a fan should not be needed. The maximum ambient temperature spec. (60C) refers to the temperature inside the enclosure. Inadequate ventilation invites disaster.LED Signals The charger has two signals available to power customer-supplied LEDs. The LEDs should be standard (non-resistor). The "PWR" (power) signal indicates that the charger is being powered. If the power to the charger is interrupted, the "PWR" signal goes off. The "CHG" (charging) signal indicates that the charger is in bulk or absorption mode (part of the charging cycle). When the charger switches to float mode this signal goes off (the charging cycle is finished).
The "CHG" signal is supplied from a 5V source via a 200 ohm resistor and may be fed directly to non-resistor LEDs or TTL inputs. This 5V source has little pull-down capacity so a pull-down resistor may be needed for TTL interfaces. The "PWR" signal is supplied from the unit's raw DC power (approximately 12V) via a 1K resistor. This may be fed directly to an indicator LED.While the line voltage is on, the "CHG" (charging) signal indicates that the charger is in bulk or absorption mode. When the charger switches to float mode this signal goes off. During a line power failure, this signal serves a different purpose - see the power-fail section below.
Input Power The charger is designed to be powered from a 115VAC or 230VAC 50/60Hz line. The line input should be externally fused at 2.0A(115VAC) or 1.0A(230VAC). The four power transformer line terminals should be connected as follows. It is important that both primary windings be used. Do not use the charger with just one winding connected.
Mode 1 - Bulk Mode: The charger is in current-limit and delivers its maximum rated current (3.0A) to the battery. The "CHG" signal is on. It is in this mode that the battery receives most of its recharge. When the battery voltage rises to approximately 14.7V, the battery is at a 75% to 90% recharged level and the charger switches to absorption mode.
Mode 2 - Absorption Mode: The charger is in a constant-voltage mode delivering approximately 14.7V to the battery. The "CHG" signal remains on. It is in this mode that the battery is brought to a 100% recharged level. The charger's microprocessor calculates how long to keep the charger at the elevated absorption mode voltage. It doesn't matter if a load is across the battery during charging. The charger compensates for any current stolen by the load and completely recharges the battery.
When the battery is at a 100% recharged level, the "CHG" signal goes off. However, the charger may remain at an elevated voltage for several more hours before switching to the float mode voltage. This is to help equalize the charge level in each of the battery's individual cells.
Mode 3 - Float Mode: The charger is in constant-voltage mode at a lower voltage than in absorption mode (approx. 13.8V). This allows the battery to draw just enough current to make up for its internal leakage current. When the charger is in this mode, the battery may remain connected to the charger for all of the battery's service life with no damage to the battery.
Toggle the AC power (off - on) to initiate a charging cycle if just recharging multiple batteries.
Battery Connection Connect the positive battery terminal to the charger's "+BAT" terminal. Connect the negative battery terminal to the charger's "-BAT" terminal. When off, the charger draws very little leakage current from the battery (100uA) and so may be permanently connected. The load does not have to be disconnected when charging the battery (provided it doesn't consume all of the current).
Do not overtighten the terminal screws. The proper torque is 50 inch-ounces (0.4Nm).
The charger is not damaged by a short circuit at the battery terminals. However, in the event of a short circuit, even though the charger is not damaged, the battery may deliver a very large current that may melt wires or cause a fire. The battery should be fused close to one of its terminals. polymeric fuses work well. Size the battery wires and the fuse according to the current draw of the application.The charger is designed to be connected to a battery. Without a battery, a 1000uF/35V (or larger) capacitor may be needed across the charger's battery terminals to maintain stability.
LED Connections Connect the anodes (+) of the user-supplied indicator LEDs to the "+CHG" and "+PWR" terminals. Connect the LED cathodes to the battery negative terminal. Use LEDs or LED assemblies that do not have series resistors unless it is desired to reduce the LED current further.
Load Connection Connect the optional load to the LOAD terminal. The LOAD terminal is normally connected by the charger to the +BAT terminal. In the event of a line power failure, the charger maintains the connection of the two terminals while constantly monitoring the battery voltage. If the battery voltage drops to a level that may damage the battery, the charger disconnects the LOAD terminal from the +BAT terminal. When line power is restored, the charger reconnects the LOAD terminal to the +BAT terminal.
It is permissible to connect the load directly across the battery if the charger's battery-disconnect feature is not desired. It is also permissible to use the unit as a stand-alone battery charger with no load connected.
Load Current The load may draw up to 6A (RMS) at room temperature. The charger will supply up-to its maximum output current with the battery supplying the rest. The load current terminal is fused on-board with a polymeric fuse (Raychem RGE300 or equiv) which alone dictates the maximum allowable RMS load current. Short-term load currents may be considerably higher - refer to the fuse specifications
Recommended Battery Size 9Ah or larger
Note that some batteries can not be charged at a C/3 rate (this corresponds to a 9Ah battery charged at 3.0A). Check with the battery manufacturer. It may be necessary to use a larger battery.
Power Failure Operation: When the charger's line voltage drops to a level too low for proper battery charging, the charger switches to power-fail mode. The charger will not disconnect the +BAT from the LOAD terminal unless the charger is in power-fail mode and the battery voltage drops to the disconnect level.
In power-fail mode, the charger maintains a connection between the LOAD terminal and the +BAT terminal. The charger also constantly monitors the battery voltage. During this time, the charger uses the CHG terminal to report the level of the battery voltage by providing a series of on-off pulses. The values of the pulse widths were chosen to allow easy visual pulse counting when an LED is connected to the CHG terminal.
There follows a series of from zero to five 62mS pulses, with a 250mS spacing, followed by a second 500mS off time. The pulse train repeats this pattern continuously. The pulse-width tolerance is +- 5%.
The number of 62mS pulses is determined by the battery voltage.
5 pulses: Voltage = 12.60V and above (approx 80% - 100% charge level).
4 pulses: Voltage = 12.15V to 12.60V (60% - 80%)
3 pulses: Voltage = 11.70V to 12.15V (40% - 60%)
2 pulses: Voltage = 11.25V to 11.70V (20% - 40%)
1 pulse : Voltage = 10.80V to 11.25V (00% - 20%)
0 pulses: Voltage below 10.80V, battery-disconnect within 60 minutes.
If the battery voltage drops to 10.80V, a 60 minute timer is started. Should the battery voltage rise above 10.80V during this time, the timer is reset. The voltage must remain below 10.80V continuously for 60 minutes for the battery to be disconnected from the LOAD terminal.
If the battery voltage drops to 9V, the battery is disconnected immediately.
When line power is restored, the charger reconnects the LOAD terminal to the +BAT terminal and restarts a battery charging cycle.
Once the charger disconnects the battery terminal from the load terminal, it will remain disconnected until the AC line power is restored. This is true even if a fully recharged battery is swapped for the discharged one during the power failure. The charger can, however, be fooled during a power failure (if need be). After swapping a recharged battery for the discharged one, briefly connect a jumper (or perhaps a push button) from the +BAT terminal to the LOAD terminal. This will allow the charger to start operating again in normal power-fail mode.
