Could I run a small compactlogix off two 9V batteries ?

passwordg · Nov 3, 2015

I have a Compactlogix L24ER QB1B PLC. No additional PLC cards or logic is running. The PLC has its embedded digital IO.
Is it possible for two 9V batteries in series to power it for 2-3 hours ?
This is a one time run only and not part of a process.

There is one laser sensor connected to it which has its own battery.
A wall outlet is not possible, because the PLC is on a moving cart.

Is there a better solution than this ?

Dravik · Nov 3, 2015

I'd use a UPS and a 120V-24V power supply.

Simple and once the cart comes back to home base you just plug the UPS back in to the wall to recharge.

mk42 · Nov 3, 2015

passwordg said:
I have a Compactlogix L24ER QB1B PLC. No additional PLC cards or logic is running. The PLC has its embedded digital IO.
Is it possible for two 9V batteries in series to power it for 2-3 hours ?
This is a one time run only and not part of a process.

There is one laser sensor connected to it which has its own battery.
A wall outlet is not possible, because the PLC is on a moving cart.

Is there a better solution than this ?

I would think that 3x9V (27V) batteries would be closer to 24V than 2 (18V), but neither one is particularly good. Electronics don't typically like to be that far off from their desired voltage.

The UPS is the "correct" solution. The batteries might happen to work without destroying the electronics, but I have no idea how long they would last, or if they would at all.

RoTaTech · Nov 3, 2015

I would think you would get a few hours life from a pair of typical gel-cells; the sort used in children's ride-on toys, or emergency EXIT light batteries. They will be available in 6V or 12V, maybe even a 24V . . .

You just gave me an idea for one of my projects . . .

passwordg · Nov 3, 2015

RoTaTech said:
You just gave me an idea for one of my projects . . .

Share with us !

Ken Roach · Nov 3, 2015

Your basic 9V transistor radio batteries are designed for very low current draw. You could probably get up to an ampere (roughly the draw of the CompactLogix) out of one, but for a short period of time.

A little Googling suggests that a typical 9V alkaline battery drawing 1000 mA will have a capacity of only about 0.09 amp-hours, so that means it could run for about 0.09 x 60 = 5.4 minutes. A rechargeable one would probably do less.

For this application, you want a properly sized 24V battery backed UPS.

Dravik · Nov 3, 2015

Or something like a electric scooter battery maybe.

Firejo · Nov 3, 2015

The typical 9 volt battery is capable of about 400 mAh (400 milliamps for one hour). The L24ER QB1B at 24VDC is rated at 0.95A so even with three batteries in series you probably wouldn’t even power the processor up (and the batteries would get hot fast). Get a couple of UPS batteries connected in series. You can get 7Ah batteries for $30 which should power the processor for 7 hours.

mk42 · Nov 3, 2015

RoTaTech said:
I would think you would get a few hours life from a pair of typical gel-cells; the sort used in children's ride-on toys, or emergency EXIT light batteries. They will be available in 6V or 12V, maybe even a 24V . . .

You just gave me an idea for one of my projects . . .

Along those lines, a car battery is 12V. 2 of those puts you right in the ball park, and I'd have to imagine they'd have some good life to them.

Doug-P · Nov 3, 2015

mk42 said:
Along those lines, a car battery is 12V. 2 of those puts you right in the ball park, and I'd have to imagine they'd have some good life to them.

Or, motorcycle batteries if size/weight is a consideration. Plus, they'd be useful after the test!

Helliana · Nov 3, 2015

mk42 said:
Along those lines, a car battery is 12V. 2 of those puts you right in the ball park, and I'd have to imagine they'd have some good life to them.

Use Deep cycle marine if they are going to recharged often. The radio repeaters for the volunteer fire department i was a member of used deep cycle marine batteries with an A/C battery charger to power them. That way, if the power went out, the repeater would continue to work for several days. I don't see a compactlogix drawing down two deep cycle marine batteries in series very quickly.

RoTaTech · Nov 3, 2015

battery powered project

Mine is an easy one - I'm scrounging my parts bin: I'm going to try to use a light sensor from a motion-sensitive floodlight to a 24V LOGO!, to pop a 12V car door lock to open our chicken coop door at dawn so we don't have to get up so early. I'll also put in an LED lamp to keep them lit a while longer in the winter, so they lay more eggs. I'll put a pair of those cheap auto solar panels in series to keep the batteries charged up. I might put in a thermostat and one or two 12V 40 or 50W incandescent bulbs to take the chill off on a cold night.
I was going to run an AC extension cord out and do it with a AC-DC converter, but I'd rather grab a couple batteries and do it that way.

Could I run a small compactlogix off two 9V batteries ?

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