PLC Battery Backup

[Paul555]

Hi all,

I have a Keyence KV16 controller and would like to employ some type of backup battery scheme to takeover when my DC power supply loses AC power. What is the simplest, most cost effective way to do this? I was thinking about two 12V lead acid batteries in series, but I'm not sure how to keep them trickle charged, nor how to switch them in/out of the circuit properly. It seems silly to me to add a small PC UPS and feed the DC supply. Any help? Thanks.

 

[cbarn24050]

a rechargeable battery of a suitable voltage connected to the dc bus via a diode.A resistor accross thediode would provide trickle current to charge the battery.

 

[buzzp]

You could use a transistor circuit to detect when to switch the power supply over. I would monitor the 12VDC and switch when this dropped to 9V or whatever your controller needs to operate. I have successfully implented this circuit but it was for powering down an OEM control and was used to write some data to an EEPROM before all power was lost.