Question

Can you give me an estimate of power consumption in Amp-hours of a D05 CPU using a 12 V supply?

Answer

You need to first define the loads that you want to operate and how long you want to run them between battery charging cycles for the specific application in question. Your questions can be answered using this information and the Ohms law:

(W)WATTS = (E)VOLTS X (I)AMPS

The more amp hours the more run time. Run time is always dependent on work load and demand. Because most of us demand a lot from our batteries (e.g. cordless tools, head phones, flashlights), a 12v portable drill will always outperform a 9.6v unit, regardless of the amp-hour rating. And there is a major drawback to higher amp-hour batteries: the higher the amp hour rating, the shorter the life cycle (total amount of charges per battery) because there is less fluid in the cells.


EXAMPLE:

If you want to use a VCR and watch TV for 5 hours every night. A TV typically uses 60-100 watts and a VCR about 30 watts. Let's call that a total load of 120 watts. It has a draw of 10 amps (120/12 = 10) for 5 hours or 50 amp-hours. Adding up the loads, we get:

50 TV/VCR total

To run this load, you should have a 100 to 150 amp-hour battery bank (50 x 2). This assumes, of course, that you recharge each day.

D0-05DD-D EXAMPLE:

You need to plug in your usage to yield an amp hour rating like the above examples:

· 1.6 amps (Current depends on the I/O usage and com port usage. If no I/O and the comport is not used, then nominal current is <1amp. We recommend 2 amp fuses for the 12 vdc level, in this calculation 1.6 amps is the conservative estimate.)
· 20 watts maximum
· Hours you are running this PLC.

If you ran this PLC 1 hour, then the amp-hour rating is 32.

---

FAQ Subcategory: None

This item was last updated on 2002-08-01
Document ID: 931

---

The information provided in the AutomationDirect knowledge base is provided "as is" without warranty of any kind. AutomationDirect disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall AutomationDirect or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if AutomationDirect or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion of limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.