Ibex Battery Systems

Operation Manual

Mounting The output voltage of the charger is temperature compensated to match the requirements of a sealed lead-acid battery. The charger and battery should be mounted in the same enclosure so they experience the same ambient temperature.

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 a chassis 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.

The charger dissipates approx. 20 watts under worst-case conditions (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. If the enclosure is metal and the charger is bolted to it, the enclosure acts as an extension of the heatsink and transfers some of the heat to the outside. When using a small, non-metallic enclosure, a small fan may be necessary to keep the enclosure temperature within the 60C maximum. This is as important for the battery as for the charger. With a large enclosure and adequate ventilation, a fan should not be needed.

LED Signals The charger has two signals available to power customer-supplied LEDs. 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. When the charger switches to float mode this signal goes off.

The "CHG" signal is supplied from a 5V source via a 300 ohm equivalent resistance 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 18V) via a 1.8K 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. This signal is supplied from a 5V totem-pole source via a 470 ohm resistor and may be fed directly to an LED or TTL input. 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 1.0A(115VAC) or 0.5A(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.

low temperature 24V sla battery chargers
Charging Cycle: When AC power is turned on, the charger will begin a charging cycle (described below). This will occur even if the battery is fully charged. A fully charged battery will draw a miniscule charging current and will not be damaged by the charging cycle. This charging cycle will last for at least 2 hours. A charging cycle will also be initiated if the charger goes into current limit. This may be because the load has drawn more than the maximum current capability of the charger.

Enhanced 3-Mode Charging: This unit automatically charges the battery in three modes (bulk, absorption, and float charging). Because the charger is controlled by a microprocessor, it has the "intelligence" to determine whether or not a load is connected across the battery as it is being charged and to compute the ideal charging time for each charging mode. Because of this, the charger can be used to charge stand-alone batteries or as a combination charger/power supply. In either application, the charger properly charges the battery, using each of the three charging modes, with no danger of the charger locking itself into the absorption mode.

Mode 1 - Bulk Mode: The charger is in current-limit and delivers its maximum rated current (1.0A) 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 29.4V, 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 29.4V 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.

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.

If the battery is removed while being charged (the "CHG" signal on), the charger attempts to continue charging the (now-disconnected) battery. It automatically resets itself to the float voltage after an hour or two. If the battery (or a different battery) is connected to the charger during this time, the charger figures things out and re-calibrates its charging times to properly charge whatever battery is connected to it.

Battery Connection Connect the positive battery terminal to the charger's "+BAT" terminal. Connect the negative battery terminal to the charger's "-BAT" terminal.

The -BAT terminal is the return for everything - the battery, LEDs, and the application load.

Because there may be a considerable number of leads that need to be connected to the -BAT terminal, consider using a separate Jones type barrier terminal strip mounted within the enclosure to multiply the number of -BAT returns available. It's recommended that all battery and load connections be made with 18AWG wire or heavier.

When off, the charger draws very little leakage current from the battery (<20mA) and so may be permanently connected. The load does not have to be disconnected when charging the battery.

Do not over tighten the terminal screws. The output terminal block is plastic. The proper torque is 50 inch-ounces (0.4Nm).

Caution: Although the charger portion of the unit is current limited at 1.0A and is thus short-circuit proof, there is no current limit for the battery. A short circuit at the "LOAD" terminal will cause a huge battery current surge which will damage the battery-cutoff circuit.

Although there is a polymeric fuse at the +BAT terminal, it's response is too slow to protect the MOSFET battery switches. Before connecting the battery, check the application's resistance to ground at the LOAD terminal.

The battery should also be fused close to one of its terminals - this to protect wiring in case of a fault. Polymeric fuses work well. Size 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 is 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. The application's load returns 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 3A (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 RUE300 or equiv) which dictates maximum RMS current at higher temperatures - refer to the fuse specifications

Recommended Battery Size 4.0Ah or larger

Note that some batteries can not be charged at a C/4 rate (this corresponds to a 4.0Ah battery charged at 1.0A). 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.

-40C 24V lead acid battery chargers
The first 2000 millisecond pulse signals the start of the pulse train. This is followed by a 500mS off time.

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 = 25.2V and above (approx 80% - 100% charge level).
4 pulses: Voltage = 24.3V to 25.2V (60% - 80%)
3 pulses: Voltage = 23.4V to 24.3V (40% - 60%)
2 pulses: Voltage = 22.5V to 23.4V (20% - 40%)
1 pulse : Voltage = 21.6V to 22.5V (00% - 20%)
0 pulses: Voltage below 21.6V, battery-disconnect within 60 minutes.

If the battery voltage drops to 21.6V, a 60 minute timer is started. Should the battery voltage rise above 21.6V during this time, the timer is reset. The voltage must remain below 21.6V continuously for 60 minutes for the battery to be disconnected from the LOAD terminal.

If the battery voltage drops to 18V, 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 battery's positive terminal to the load's positive input. This will allow the charger to start operating again in normal power-fail mode.