Basically, everything to be measured breaks down into 2 categories, production and consumption. Production refers to every regular source of electricity, in this case only the solar panels. Consumption refers to anything and everything on the boat that uses electricity. Once production and consumption are measured, overall flows can be calculated for each of a number of circumstances. These flows allow us to determine how long our batteries would hold out in any unfortunate situation, and whether or not we can support any changes in our current situation.
Production, as mentioned above, is solely from the solar panels. Solar panels will produce different amounts of power for different weather conditions, but will generally fall between a minimum and a maximum. My task concerning the panels is to determine these minimum and maximum values, and also discover what the normal daily production is.
My method for measuring production is fairly simple, but rather time consuming. Over several days (the spreadsheet currently has only one free space, but I will add more as they are needed) of varying conditions I take readings every 15 minutes, starting with the first usable light and ending when there is nothing left to measure. At each reading I check and record the current from the panels to the controller/booster and the current after the boost, and enter those numbers into the spreadsheet.
Once the numbers are in the spreadsheet, I calculate the average amps (total and per panel, before and after boost) at each time of day over several days and the total over each individual day. The numbers for the total over each day are then multiplied by the usable light per day (11 hours) to find how many amp-hours are produced in that day.
Determining consumption is a rather different process. There are three different types on consumers. Some are always on (satellite phone, for example) drawing a constant amount of power per day. For those, I simply measure their amp usage and multiply by 24 hours. The other two types are those that are used in varying amounts each day, and those that vary not only their usage time but their amp consumption.
The largest of the three types of consumers is the second, those items that use a consistent amount of power, but have variable usage times. For them, I first measure their amp consumption, then attempt to determine how much they are used each day. Since the time is variable, I get three different usage numbers. One of them, 'Normal,' simply refers to the average usage each day, basically what I expect it will be. The other two, 'Min' and 'Max,' indicate the least and the greatest number of hours the item is likely to be used. Minimum refers to a time when we would be on very stringent power controls, sacrificing some comfort for the sake of the batteries. Maximum is the most we would ever use the item in question. On the watermaker, for example, we might run it a lot if we needed more water because our water level was lower than usual.
The third type is the hardest to measure. These consumers use different amounts of power at different times. For these, it is not sufficient to simply produce a number (or 3) on how often they are used. First, each different consumption level must be measured, after which usage must be computed for each different consumption value. The best example of this is the 'Computers' category, with four computers and each could have several different consumptions. Indeed, if there is one category I am suspect could use some updating, it is that one. Fortunately I have not found anything else with significant variation in consumption.
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