SOLAR & BACK-UP BATTERIES
The typical car battery that we are all familiar with is designed to deliver a large current for a very short time to turn the starter motor and start the engine.In normal operation the car the battery will be fully charged, deliver a high current for a few seconds and then immediately be recharged again by the running of the car.
In delivering the current to start the engine it is only ever partially discharged (perhaps by as little as 5-10%) and was designed for this cycle of usage.We could call this a Shallow Cycle battery. As we know most car batteries typically last about 5 Years used in this mode.
Should the car battery be fully discharged every day for example, It would probably only last a few months.
THE DEEP CYCLE BATTERY.
In a domestic environment our electrical power needs to be available at as much at night as at any other time, thus the demand we place on the battery is to provide a low current but over a much longer period.
Without going into the detail of the technologies which have improved the performance of batteries to allow this to happen this is what the Deep Cycle does.
Deep Cycle Batteries then are optimized to perform in the reverse of the typical car battery. With regular discharging by 40% or even 80% before they are recharged. However even with Deep Cycle Batteries this may not be done continuously and batteries are rated as to how many cycles they are designed to withstand and at what level of discharge..
As with all things in life better performance means a higher price and the number of cycles of the battery you will buy should be known to you, as it is essential information in calculating the return on investment of your installation.
The below graph highlight the range of number of cycles of batteries on the market.
It is important then to design the back-up or solar system correctly and to use an appropriate number of batteries for the expected use of the system.
The guide line then is :-
Install as many as you can afford to increase the life expectancy.
Install too few and you will decrease the life expectancy dramatically and your return on the investment.