Circuit (Wiring) Description
We won’t discuss here regarding the specifications and power (AH) delivering capacity of the units (solar panel, inverter, battery, generator etc.) involved in the set up as it would be better to leave it to the experts (dealers and manufacturers). They will be in a better position to exactly judge the approximate power requirements of a particular house and do the installations appropriately. Moreover, if the installation specifications are optimized as per your calculations, it may become difficult to get a refund or a reinstallation done in case you miscalculate the parameters.
The circuit operation may be understood through the following explanation:
Referring to the adjoining figure (Click to Enlarge), let’s assume initially, one battery to be fully charged and the other partially discharged.
Let the charged battery be connected to “Battery #1” position and the discharged one to “Battery #2” position.
Now, according to the shown position of the 4-way switch, two things will instantly start happening: the inverter will be switched ON at once, powering the entire house, and, if it’s quite sunny outside, the battery #2 (partially discharged) will start getting charged through the PV set up.
If, unfortunately, the climate is not on your side, simply switch ON the diesel generator until the battery #2 is fully charged. The Ammeter will give you an instant indication of the charging status. The charging process may take as long as 10 hours; keep a watch on the ammeter, once it approaches the zero mark, you may switch OFF the Alternator. This procedure has been purposely kept manual for safety reasons.
T1 along with R1, D1, and P1 form a self regulating automatic battery charger circuit. It will strictly monitor the charging voltage of the uncharged battery and will restrict any voltage from the PV or the generator once it gets fully charged. So, the battery is ultimately always safe from over charging.
The 4-way switch will need a manual toggling every time the low voltage indicator comprising of T2, P2, R2 and LD1 becomes active. The toggling would mean an instant changeover of the discharged battery with the charged one, so that the cycle may start all over again.
The next page will teach you everything about the construction and the set up procedure for this off the grid generator battery home backup system.