First some information on the sites that may be useful. We have remote sites running CR800 and CR1000 that transmit data via cellular modems and are powered by batteries (PS100 and PS200 I believe) and solar panels. The modems are run through the SW12 and cycled nightly. We collect data every 10 minutes.
There have been some issues lately concerning keeping the batteries charged. Thus I have a couple questions:
1. What is the threshold for battery voltage before we should suspect the associated mesurments as "bad"? (we have wind and temp sensors)
2. We record both the Average Battery Voltage (BattV_AVG) and Minimum Battery Voltage (BattV_MIN) every 1 minute. Strangely I have seen serveral instances where BattV_MIN > BattV_AVG. How can this be? Which one should I be looking for?
3. What should the voltage be for the logger? In general our "good" sites see voltage between 12-13 volts.
Answers to any or all would be very helpful and also any other best practices would be appreciated.
Thanks in advance!
* Last updated by: geoffm on 6/20/2011 @ 5:00 PM *
The operating voltage for the CR1000 is 9.6 - 16V. The datalogger will stop executing its program at 9.6V to avoid making bad measurements. When this happens, a counter will be incremented in the datalogger's Status table (low12Vcount). As you have noted above, in general 12-13 volts is good. Recording a minimum battery voltage as you have done is a good idea -- many people just look at a 24 hour period.
When the battery voltage is nearing its bottom limit, it may be unable to make a good battery voltage measurement. I'm not certain if this could be the case for the anomaly #2 above.
Dana W.
Related you might also check for something called a Low Voltage Disconnect that saves your batteries (lead acid I assume?) from being over discharged.
Most solar chargers have this included in their load ports where you connect the logger and sensors. But sometimes the chargers don't come with it or you have another setup (running purely from 'mobile' lead acid batteries in the forest for example).
In that case you can build your own LVDs or buy them (be aware most offered products are made for cars and the amperage switched is way over-powered for a small suit of sensors + logger).
As for which exact voltage level your site should shut down to protect the batteries you should contact the manufacturer of the batteries. For lead acid this value normally is around 10.8V to 11.2V.
I just built myself LVDs devices for some of our sites, that's why I know ;-)
When we install a remote site with a solar panel, we use a 12 volt deep cycle marine battery. We have had some out for 3 years before having to replace the battery. The solar panel has enough output to maintain the battery. I also monitor the battery voltage on the loggers to know when the battery needs replacing.