Battery Sizing

It is strongly recommended that you use a                                  12 volt, rechargable, deep-cycle, sealed lead acid battery! These batteries are designed to supply the amount of current needed  over a long period of time.  Other types of batteries such as automotive and some marine batteries provide high current for short periods of time which may damage some electrical components and result in a void of the manufactures warranties.

12 Volt, Deep cycle, sealed lead acid batteries are  widely available through battery suppliers all over the country. Deep cycle batteries are also widely available on the web in a variety of ratings, one of which should forfill your power requirements. There are also many  battery suppliers who should be able to help you with your battery selection. You can also check your local department stores that sell automotive batteries, they may also sell marine batteries that are also deep cycle batteries or your local marine supply.       With the growth in solar industry, there are also many companies on the internet from whom you can purchase batteries specifically designed to be used in solar photovoltaic systems.      Golf cart batteries, as they are called, are also widely available and usually have high amp-hour ratings. They are normally available in 6 volts, therefore two of these batteries must be installed in series (negative of first battery connected to the positive of the second) in order to obtain the desired 12 volts needed to operate the house correctly.

Batteries are usually listed based upon their amp-hour rating and time, with the standard being the 20 hour rate. This means that the battery will discharge down to approximately 10 volts over a 20 hour period of use at a specific current draw. Deep cycle batteries are designed to last and your battery should give you a minimum of 5-6 years of performance with minimum  maintenence. Some batteries have been known to last as long as 20+ years depending on the amount of discharge it has endured over the years.

The amp hour rating of batteries can seem a little confusing, this is because it is not an exact calculation. Many factors, such as temperature and discharge rate, can hinder a battery's performance and loads may vary, even if they are supposed to be steady. Recharging factors especially those associated with using PV with varying outputs, hopefully regulated by your controller, can also contribute to battery and system performance. So just as with any other power supply, the harder you push it, the less efficient it gets.

The following is an example of how to calculate how long a battery will last based on the                          power required for the Heated and Cooled Pet House.

First, you must determine the amount of time that your pet will use the pet house. Try to determine the amount of time that your pet will  actually be settled into the house. Overestimating this time is better than underestimating and will guarantee that there is enough power stored in the battery in times of no available sunlight. NOTE: This estimate does not take into consideration the amount of time that the unit will be off, once the thermostat is satisfied, while the pet is within the house, approximately 10-20 min/hr depending on heat losses. This will reduce the overall power consumption thus getting more time/power from your battery and allows for more battery charging time.

Second, you have to decide on how many days of storage you will want to have in your battery.  This depends on the amount of sunlight available to charge your battery. If you live in a location that may not get sun for several days then you would need a greater amount of storage capacity in your battery. FYI- photovoltaic panels will produce electricity even on cloudy days when there is very little sun. All they need is light.

Amount of time pet will use house

=____________    hours/day

=____________  watt-hours/day

multiply by 60 watts

then multiply by number of days of storage

=____________  watt-hours

divided by battery voltage  (12 volts)

=____________  amp-hours

*

x battery efficiency (90%)

= ___________ amp-hours

example:                If your pet uses the house for an average of 10 hours a day, and you would like to have enough storage  in the battery to last 3 days without having to being recharged, then you would require a battery with ...                               10 hours/day x 60 watts x 3 days = 1800 watt-hours                       then: 1800watt-hours/12volts = 150 amp-hours                        Thus you would need a battery with a minimum rating of 150 amp-hours.

* Most batteries have an efficiency associated with them of around 80-95% thus a battery    rated at 150 amp-hours will have a storage capacity of approxiamtely....                             150 amp-hours x 0.90 = 135 amp hours It is recommended that batteries only be discharge down to 20% of their total capacity to maintain their charging capacity. This also reduces amp hrs. available.                    in the example this would translate to 135 X 0.80 = 110 AH

We will gladly help you to chose a battery based upon your needs. Most recommended are the deep cycle, sealed, lead acid type. Then you can purchase the battery yourself or we can arrange for delivery at cost of battery plus shipping.

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