Batteries

In off-the-grid systems microhydro systems batteries are an essential component used to store the energy generated by the water turbine so it can be reused later as needed.  Batteries can also be used as part of a grid-connected microhydro system to provide battery backup in the event the grid goes down for a period of time. 

The batteries typically used in microhydro electric systems are 6-volt, deep-cycle, lead acid batteries.  These are different than the type of battery you use in your car.  A car battery is designed to provide a strong jolt of amps to get your car started but after that the discharge tends to fall off rapidly.  A deep-cycle battery provides less of a jolt but is instead designed to produce a steady discharge of electricity over a long period of time. 

A popular type of battery specifically designed for home energy systems is the Surrette battery.  They are large deep-cycle batteries with a larger form factor than a car battery and are designed to be used as part of a battery bank.

Consider carefully before choosing to use battery systems for electrical storage.  If you have access to the grid the grid itself can serve as your energy storage and you receive energy credits for every kilowatt hour you put back on to the grid.  Batteries require maintenance and can be fussy. If you have no grid access then batteries may be the only option you have.  If so, spend time to think through your approach to maintaining the battery bank and keeping the flow of electricity out of it stable.

Lead acid batteries operate best at around 70 degrees Fahrenheit or 21 Celsius.  At higher or lower temperatures their performance declines, sometimes dramatically. Therefore consideration should be given to storing batteries in areas that are at the appropriate temperature and which are well ventilated.  Batteries also tend to lose water when they are charged and so need to be refilled periodically.  In general, it is a good idea to check your batter bank every month in order to be sure that the lead plates don't run out of water.  It is best to use distilled water when refilling batteries in order to avoid residue buildup and to avoid compromising their efficiency.

Given the need to regularly fill and maintain batteries, make sure that they are located in a place that is easily accessible.  Avoid putting the batteries on to high a shelf which can make filling them awkward.  One useful gadget you might wish to consider are hydrocaps.  These are replacement caps for your batteries that contain a catalyst which reacts with the hydrogen and oxygen released by the battery in order to produce water.  They can cut the loss of battery water by as much as 90%.  There are also commercial batter filling systems which can be purchased which can refill multiple batteries from a central reservoir.