We decided to allow our 50Volt battery packs to run more empty by changing the lower threshold point that they are allowed to discharge down to before cutting off and we left them to run overnight.
On the morning, we discovered that both battery packs had switched themselves off and upon examining the status of each pack, found that Pack One has discharged down to the minimum voltage threshold as expected but for Pack Two, we discovered that one particular cell, number 6, had drained to the cut-off threshold faster than its siblings and the the computer is programmed to disconnect the whole pack if it discovers any of its sixteen cells has fallen below the safe voltage levels, which is exactly what has happened. This is very useful to know this weakness and we are planning to swop out this cell for one of the 12Volt cells as we are unlikely to put the 12Volt pack through such heavy demands as we will be putting the two 50Volt packs.
But, in the meantime, we programmed the Solis Inverter to go into deliberate charging mode, using the Grid supply, to boost the charge levels back up to more useable levels. We also had a glorious sunny day on Thursday and we had collected 16kWh of energy and all of it was pushed into our battery packs, along with about 7kWh of Grid electricity before we told the Inverter to halt the charging operation at 6pm when we finished work.
We decided that we won’t allow the batteries to drain so far down to that shutdown threshold again so we reprogrammed the Inverter to stop drawing on the batteries when the voltage dips below 48Volts, which should allow the batteries to provide a tickle of power to the Inverter which will continue to monitor what our household is using and keep a record of our electricity usage at every 5 minutes intervals. The batteries look a bit better now that they had a good charge but we will wait and see and probably will deliberately discharge the two packs again and see what happens, especially to cell number 6 again.
We had another lovely day on Friday and we collected almost another 10kWh of energy but we will have to continue in our designed implementation of providing night-time grid charging and sign up to those off-peak tariffs to take advantage of loading our battery packs full of cheap electricity and run the household fully from the batteries instead, because even though we collected nearly 10kWh from the Sun, we actually consumed 25kWh for our whole 24hour period. It is going to get worse as the Sun moves around into the Winter cycle so we definitely will need to tap into the cheap electricity being offered during those off-peak hours.
Even with the second string of Solar Panels that we are currently installing, may give us another 5kWh on this particular day but of course, it could go much lower than that on a very dreary cloudy day, but also generate a load during a very good sunny day. This is why we are going to be building a Green Computer system that will monitor the weather for the next 24 hours, also monitor the electricity prices (so we can take advantage of those special cheap rates, even negative rates where they will pay YOU money to use the Grid electricity) and manage the whole battery packs, its chargers and the various solar inverters too. We will even eventually include the Thermal Solar arrays that we will have on our Garage roof, heating up water from the sunshine, and have that source of Solar Energy incorporated into the Green mix.
50V-Battery-displays