Wiring Batteries and Solar Panel in Series-Parallel Configuration
You may think what is the purpose of this weird combination of series and parallel connection of both solar panels and batteries instead of simple series or parallel configuration. Well, it depends on the system needs i.e. increasing both charging voltage and battery storage capacity in Amp-hour (Ah) by connecting both solar panel and batteries in series/parallel combination according to the system requirement.
This unique design is needed when both the charging and storage energy needed to increase using solar panels and batteries. This is due to currents add up in parallel connection and voltage add up in series connection. In other words, current remains the same in series connection while voltage remains the same in parallel connection. This way, we get the advantages of both series and parallel connections by connecting PV panel and batteries in combo of series-parallel configuration. Let’s see how we do that.
Series Connected Solar Panels & Batteries
We may connect two solar panels or batteries by connecting their Negative Terminal “-” to the Positive “+” Terminal and vice versa. This way, two 6V (or 12 or 24V) 150W, 12.5A solar panels and 12V, 100Ah batteries connected in series would have the following values.
I1 = I2 ….. = In
i.e. current is same in each branch
12.5Amp = 12.5Amp
Current in series Connected Batteries
100Ah = 100Ah
As voltage are additive in parallel connection, this way,
V1 + V2 …… + Vn
i.e. voltage will add up in parallel connection. (suppose we have 12V PV panels and batteries).
12V + 12V = 24V.
PV Panels & Batteries in Parallel:
A solar panel or battery can be connected in parallel by connecting the Negative Terminal “-” of first one to the Negative Terminal “-” of second one and Positive Terminal “+” of second one to the Positive Terminal “+” of first one. In simple words, similar terminals are connected by jumper wires. This way, two 6V (or 12 or 24V) 150W, 12.5A solar panels and 12V, 100Ah batteries connected in parallel would have the following quantities.
Current from solar panel to the charge controller:
I1 + I2 ….. + In
12.5Amp + 12.5Amp = 25A
Similarly, Ah capacity of batteries in series would have:
100Ah + 100Ah = 200Ah.
Voltage for solar panel and batteries remains same in parallel connection:
V1 = V2 …… = Vn
i.e. voltage remains the same for both PV panels and batteries.
12V = 12V.
PV Panels & Batteries in Series-Parallel Combination:
The next part is interesting where we will utilize the maximum efficiency of 12V solar panels and batteries by arranging them in series-parallel combination to increase both the charging power from solar panels and storage capacity of batteries. This way, the more power will charge the battery quickly with extra power storage. We can use this system in tiny projects like 6V batteries and PV panels for 12V systems or residential applications like 24V or 48V and so on.
Suppose we have the following rated devices.
- 4 Nos. of solar panels each having 12V, 150W, 12.5A
- 4 Nos. of batteries each having 12V, 100Ah
We need to connect them for an efficient 24V green energy system.
To do this, connect the first 2 solar panels in series and do the same for the rest two solar panels. In simple words. make two pairs of two series connected solar panels. Now, connect these two sets of series connected PV panels in parallel as shown in the following fig. Do the same for batteries to arrange the same series-parallel connection of batteries. This way, you will get:
Voltage & Current in Series Parallel Connected PV Panels
A set of two series connected solar panels will have=
12V + 12V = 24V
12.5A = 12.5A
if we connect these series pairs in parallel, you will have to get:
24V = 24V ( from previous series (12V + 12V = 24V) and now they are in parallel)
12.5A + 12.5A = 25A (from previous series 12.5A = 12.5A and now they are in parallel).
You can see that we have increased the solar panel voltage from 12V to 24V as well as the charging power from 12.5A to 25A.
Voltage & Current in Series Parallel Connected Batteries
Likewise, the series-parallel combination of batteries would have the same impact as mentioned above for solar panels e.g. the batteries bank voltage would increase from 12V to 24V and storage capacity from 100Ah to 200Ah.
Voltage in a set of two parallel connected batteries:
12V = 12V = 12V
12.5A + 12.5A = 25A.
If we connect these two sets of series connected batteries in parallel, we will get;
12V + 12V = 24V
25A = 25A
You can see that we achieved 24V from 12V and 200Ah from 100Ah at once and it is according to our designed 24V system. So we can wire them through a solar charge controller and connect to the load equipment.
Wiring PV Panels & Batteries in Series-Parallel Combo for 24V System
The following simple wiring shows that four 12V solar panels and 12V, 100Ah batteries are connected in series-parallel combination. PV panels are connected to the batteries and DC load through a charge controller. The 120V or 230V AC load is connected through Inverter. The load can be powered up during normal sunshine/day and operate via backup power stored in the batteries during shading/night. This whole 24V system will work automatically as we have used the uninterruptible power supply (UPS) / inverter i.e. we have used automatic UPS wiring. It means no need to use additional auto or manual changeover or auto transfer switch for automatic operation.
Good to know:
- Series connection of batteries or solar panels will increase the level of voltage e.g two 12V, 5A PV panel or 12V, 100A battery in series will provide 24V. Where current is the same in both devices i.e. 5A in panels and 100Ah in batteries.
- Parallel connection of PV panels and batteries will add up the current and ampere hour rating of battery (storage capacity) e.g. two 12V, 5A PV panels in series will provide 12V, 10A. Similarly, two 12V, 100Ah batteries in parallel will provide 12V, 200Ah storage capacity. Where the voltage remain same in both equipment i.e. 12V.
Make sure the battery as well as solar panel voltage rating is the same while connecting them in series, parallel or series-parallel. In other words, a 6V battery should not be connected in series/parallel with 9V, 12V or other voltage rated batteries. Same rule is applicable to solar panels e.g. do not connect a 12V solar panel in series/parallel with 6V or 24V PV panel.
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