Choosing the Batteries for your Solar Cells

The choice of batteries is possibly the most important call to be made if arranging a solar energy system of any size. Unless you're looking at a very small system, potentially using a van battery, upgrading your battery capacity is likely to be difficult and costly. If you are employing a 24 volt battery and decide you want more storage, you'll either need to replace the battery for a bigger one or connect a second battery of the same size in level with the first.

When connecting batteries in parallel however , it is vital the batteries are similar. For this reason it might not be advisable to add to the battery after you have been using the system for a while, by which time there would've been some decrease in battery performance.

The capacity of a battery or cell is measured in amp hours. A hundred amp hour battery in theory can provide a current of one amp for 100hrs before becoming completely discharged ( although a battery shouldn't ever be discharged below twenty percent of maximum capacity, and on a consistent daily basis should not be permitted to go below 60 percent of maximum capacity ).

As the efficiency of a battery, and therefore it's an amp hour rating varies dependent on how quickly it is discharged, the standard discharge time is utilized when citing a batteries capacity.

If a battery is quoted as having a capacity of one hundred amp hours ( c10 ), that infers that the it will supply one hundred amp hours when discharged over a 10 period. A hundred amp hours ( c100 ) would imply that the battery will supply a hundred amp hours when discharged over a hundred hour period. For a specific battery, the c100 rating would be expected to be considerably higher than the c10 rating.

If 2 batteries are connected in series, the total amp hour rating will be same as each individual battery ( which should really be the same size ). If 2 batteries are connected in parallel, the total amp hour rating will be the total of that of the two batteries.

Don't underestimate the scale of battery required. It can be frustrating to have a system where the battery size does not give you enough stored electricity to get you thru a dreary day and also finding that your battery swiftly becomes completely charged on a sunny day and further output from your panels cannot be used.

Things to Consider : What is your daily use in Kw Hours. This is a little dreary to calculate but obligatory.

How trusty is your sunlight - do you typically get clear sun most days or is it far less reliable.

How long are you expecting your system to cope without sun.

Do you also have a wind turbine, and if that is so how reliable is the wind.

How efficient and convenient is your backup system. If you have an efficient diesel generator that starts mechanically when needed, this could reduce your requirement for battery storage.


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