To store electricity one or more batteries come in handy. There are special ‘solar’ batteries, but also regular deep cycle (marine) batteries are usable, easier to acquire and a lot cheaper.
Regular car batteries with just a CCA (Cold Cranck Amp) marking are best to be left alone. These batteries, can deliver high amps over a short period, but do not store and discharge- recharge as well as deep cycle ones.
On thing we miss in a lot of tutorials on websites or youtube video’s is the use of fuses or breakers, this is important. Even a small battery like a 12V – 7Ah can have a short-circuit current of 50 to 100 Amps. Try to prevent this, way better for your nervs.
- Use the same batteries for the whole setup.
- This is just an example, can be more components.
12 Volt kits
Most common are so called 12 Volt solar panels or even complete kits. When specifics are read it usually turns out the PV-panel actually has an output of around 18 Volts and the Amperage seems lower, what is up with that ?
Actually, 12 Volt batteries aren’t 12 Volt at all, an empty battery will only hold upto 11.1 or 11.2 Volts, and a good full battery holds upto 13.3 or 13.4 Volts.
Charging means we need to have some level of current flowing into the battery, we can optain that by using higher voltages to charge. A car-battery for example can have a voltage of 12.8 Volt with the ignition in the off-position, as soon as it starts and the alternater kicks in, this will soon become upto 14.4 Volts.
Same in solar, we need a bit higher output of the panels just to help the charge-controller charging the battery. An 18-Volt panel does this even if it’s a bit cloudy.
Higher voltages of solar installations are usually a multiply factor of this 18-Volt panel, so we put two in series for a 24-Volt setup, and upto 4-panels on a 48-Volt installation. There is something better with higher efficiency, that is MPPT (Maximum Power Point Tracking).
Info: Additional charging
Info: Battery BCI groups
Info: Battery wiring
Info: Conductor sizing
The well know electric car manufacturer Testa introduces a new home-battery, the Tesla Powerwall. It’s going to be available in 2 versions, a 7kWh and a 10kWh. Large scale solutions are well within reach.
Powerwall 2 & solar roof
More info: www.teslaenergy.com