Battery Backups

DeepThought · Feb 17, 2012

Hi All,

Just a quick question on battery backup's a have a few systems here and I would like to know what the average time is for renewing batteries in the following systems

Siemens S7 300 and 200
Allen Bradley SLC500
TI 505 systems
mitsubishi A and Q and FX series

I am trying to create a preventative maintenance schedule so we can change these at regular intervals.
Thanks for your help.

Clay B. · Feb 17, 2012

Everywhere I have worked we changed PLC batteries once a year. I have seen them last much longer than that but for the cost it was easier to make it an annual event.

FYI...The S7-200 does not use a battery backup. It uses a holdup capacitor with an E-prom.

Also, only order your batteries within a month of changing them. A battery sitting on a shelf for several years will probably be as useless as the one your changing.

DeepThought · Feb 17, 2012

Hi thanks I will take that advice as it was the time frame i was thinking about.
Ref s7-200
not to criticise however the 200 does have a battery part no.
SIEMENS - 6ES7291-8BA20-0XA0. - MODULE, BATTERY but as stated before i will change this yearly.

regards

deepthought

PS webstie for battery is
http://uk.farnell.com/siemens/6es7291-8ba20-0xa0/module-battery/dp/3783376

Clay B. · Feb 17, 2012

Yes you can buy a battery module for the S7-200 but it is not required to save the program. I should have been clearer

A battery is not required for an S7-200 to prevent the loss of the program.

Steve Bailey · Feb 17, 2012

I don't know for sure whether this applies to the S7-200, but in many cases where you don't need a battery to back up the PLC program, you may need one to back up the PLC variable values.

For example, if a timer's preset can be changed from an HMI panel, following a power interruption longer than the capacitor's limit the program gets restored from non volatile memory, but the preset may revert to its default or initial value, not necessarily the value it had prior to the interruption.

That's generally the reason why you might want to purchase a battery for a PLC whose spec sheet says you don't need one to preserve the program.

Ned_Flanders · Feb 17, 2012

DeepThought said:
Hi All,

Just a quick question on battery backup's a have a few systems here and I would like to know what the average time is for renewing batteries in the following systems

Siemens S7 300 and 200
Allen Bradley SLC500
TI 505 systems
mitsubishi A and Q and FX series

I am trying to create a preventative maintenance schedule so we can change these at regular intervals.
Thanks for your help.

We also change annually - I keep all the RS part numbers on a spreadsheet, along with make/model and BACKUP info so when the planned maintenance system churns out a reminder, I order them.

We have a right mixture of S5, S7 and 200's along with Hitachi and a few Bespoke systems (With 3.7v soldered cells).

Don't forget your HMI batteries!

Clay B. · Feb 17, 2012

Steve Bailey said:
I don't know for sure whether this applies to the S7-200, but in many cases where you don't need a battery to back up the PLC program, you may need one to back up the PLC variable values.

For example, if a timer's preset can be changed from an HMI panel, following a power interruption longer than the capacitor's limit the program gets restored from non volatile memory, but the preset may revert to its default or initial value, not necessarily the value it had prior to the interruption.

That's generally the reason why you might want to purchase a battery for a PLC whose spec sheet says you don't need one to preserve the program.

With the S7-200 that is almost correct. Presets for timers and counters are saved but other data values will be lost once the Capacitor loses its charge (usually around 48 hours). This is one of the reasons we use the S7-200 in our smaller machines. The data that will be lost on an extended power loss can be reloaded via a HMI.

daba · Feb 17, 2012

No-one has mentioned that you should be monitoring the state of the battery programmatically as well as performing a scheduled replacement. I'm certain that all the systems you mentioned have some sort of status bit that flags up a low battery voltage.

On A-B PLCs, SLCs, and earlier Logix5000 processors, the battery is drained during power-off time. The longer the system is powered off (cumulatively), the shorter the battery life. Of course you can't monitor the state of the battery if the system is turned off, and that is when it is being drained.

From Publication 1747-um011_-en-p....

Back-up power for RAM is provided by a replaceable battery. The lithium battery provides back-up for approximately five years for the 1747-L511 processor and two years for the 1747-L514 and 1747-L524 processor. A red BATTERY LOW status indicator alerts you when the battery voltage has fallen below a threshold level.

Once the BATTERY LOW status indicator goes on, do not remove processor power or your program may be lost. Replace the battery as soon as possible. You can replace the battery while the processor is powered.

and...

Your SLC 5/03, SLC 5/04, or SLC 5/05 processor provides back-up power for RAM through a replaceable lithium battery. This battery provides back-up for approximately 2 years. A BATT status indicator on the front of the processor alerts you when the battery voltage has fallen below a threshold level.

and...

The SLC 5/03, SLC 5/04, and SLC 5/05 processors have a capacitor that provides at least 30 minutes of battery back-up
while the battery is disconnected. Data in RAM is not lost if the battery is replaced within 30 minutes.

Battery Backups

DeepThought

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Clay B.

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DeepThought

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Clay B.

Lifetime Supporting Member

Steve Bailey

Lifetime Supporting Member + Moderator

Ned_Flanders

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Clay B.

Lifetime Supporting Member

daba

Lifetime Supporting Member

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