Designing a DIY Solar power kit
Choosing a leisure / solar battery
The Mastervolt battery on the previous page is probably a little too big for our solar power kit. Don't be tempted to over specify a battery because you'll have to fully charge it using your solar panels or wind turbine. Unfortunately solar panels aren't cheap (we like to think ours are very good value for money though!) so if you've a nearly empty monster of a battery, you'll need a lot of them to charge it in the required time.
Many different types of battery are used in solar power kits. Flooded lead acid batteries are the most common because they cost less and generally last longer than other types, largely because you can top them up. Other types such as Gel or VRLA (Valve regulated lead acid) batteries, can can be used in areas that don't have adequate ventilation, and because they are sealed with a valve there is less risk of you coming into contact with the acid.
If your requirements are going to be similar to our example application, then the two batteries below will work well. The more expensive version is a VRLA and the cheaper one is a normal lead acid.
Batteries also come in different voltages but are nearly always a multiple of 2V because they're constructed out of 2Volt cells. That's why there are 6 filling caps on a 12Volt car battery. One for each 2Volt cell.
Big batteries capable of storing and delivering lots of power are very, very heavy which is why we use 2 Volt batteries to make up very large 12 or 24 Volt systems.
A 3000 Amp hour 2 volt battery weighs nearly 250Kg, so six in series will weigh 1.5 metric tons. Difficult to move without a crane and specialist handling equipment. We recently sent a large solar home kit to one of the Comoros islands off the coast of East Africa. The kit contained twelve 2Volt 1000Ah batteries and each one was a two person lift. Our customer needed a lot of power and at 50% discharge he has 12,000 Watt hours, which is enough to run the lights in our example for 200 hours!
Charging batteries with solar panels