W4ZT Repeater

Union City, Georgia

Batteries and Charger

The repeater has emergency backup power in the form of four 60 AH sealed lead acid batteries. Thanks to Eddie, K4UN (ex K4QFF), for the batteries. The charger is a commercial multi-mode charger from http://www.ibexmfg.com which provides a relatively low bulk charge to the batteries until they reach about 85% of their capacity and then it switches to a very low power trickle charge which tops off the battery charge and maintains it for extended periods. The total repeater current consumption is about about 11 amps. Tests have show normal operation in excess of 2 days of constant use on emergency power.

For now, the immediate indication that the repeater is running on emergency power is the voice message saying that the repeater is on emergency power. I also changed CW identification so that it says: "de w4zt/rep". The courtesy tone changes also to a "bee boop". The change over occurs automatically and as soon as commercial power returns, the repeater switches off of the batteries.

Click here to see the charger for the other batteries.

Your comments and suggestions are very welcome.

Tony - W4ZT

Here I am holding the battery charger board which is an IBEX Manufacturing model L12-3.0/16AC 12 volt charger. I have already drilled the panel and attached the metal standoffs used to mount the board.
Caught in the act of mounting the companion transformer.
The charger mounted to the panel is functional now. Two LEDs are wired through the panel on the left and a small toggle switch is on the right.
The charger board close up.
View of one of the batteries connected to the charger while checking the charge limits. Interestingly enough, the batteries specify a float voltage of 2.5 to 2.7 volts per cell. There are six cells in a battery so that adds up to 13.5 to 13.62 volts. The charger manufacturer recommends using 13.8 volts. After discussions they agreed that floating at manufacturer's specifications would be best but error on the high side would be better than on the low side. The final set voltage will be around 13.7 volts I think.
The connecting cables are all made up and ready to connect the four batteries together.
The batteries are all in their plastic boxes resting on top of the repeater cabinet. The jumpers are connected and the battery bank is ready for charging. Each battery is a sealed lead acid battery rated at 60 AH and they are all paralled using #12 wire.
The charger panel can be seen just below the monitor receiver which is the grey panel, third from the bottom in this picture, with the speaker grill and two knobs. The charger panel has an on/off switch and two LEDs. The LEDs indicate two conditions from the charger board. The lower LED is a green one indicating that the charger is powered and a battery is connected. The top LED is bright red and is the indicator that the charger is in mode 2, bulk charge. The red LED goes off when the charge limit voltage is reached and the charger switches to mode 1 providing critical float charge current to maintain the batteries at full charge for prolonged periods.
Here you can see the battery boxes and the cables coming out of them and going into the repeater cabinet. The blue cable goes to the repeater and the red cable goes to the charger. Two pin mating molex connectors are used to provide a cable disconnect. I have used these connectors for years as a "standard" 12 volt connector for mobile rigs and other 12 volt uses around the shop. A digital volt meter is attached with small jumper clips to the blue high current battery connector which is hanging out of the battery box. The high current connector which is capable of currents in excess of 75 amps is wired to the parallel batteries with #10 wire and is there for emergency use only.

The battery supply is isolated from the internal repeater power supply with a relay battery switch. Click here to see details.
The W4OVH repeater also uses the Ibex charger: http://www.dcm-va.com/W4OVH/

Last update was on November 20, 2006 5:04