Windy Nation TrakMax 40 MPPT Solar Charge Controller - Manual (Page 20)

TrakMax 40 User Manual
Revision 1.0
batteries and are rated at 80 to 100 amp-hours at 12volts. Many larger systems use L16 batteries, which are
usually rated at 350amp-hours at 6-volts each. They are 17 inches high and weigh about 130pounds. 8D
batteries are available with either cranking or deep-cycle construction. Purchase only the deep-cycle version.
The 8D is typically rated at 220 amp hours at 12 volts.
7.1.4 Sealed Batteries
Another type of battery construction is the sealed gel cell. They do not use battery caps. The electrolyte is in
the form of a gel rather than a liquid, which allows the batteries to be mounted in any position. The
advantages are no maintenance, long life (800 cycles claimed) and low self-discharge. Absorbed glass mat
(AGM) electrolyte batteries are also acceptable. Their electrolyte is contained in mats between the battery
plates. Sealed batteries reduce the maintenance requirements for the system and are good for remote
applications. They are much more sensitive to the charging process and can be ruined in as little as a day of
overcharging.
7.2 B ATTERY S IZING
Batteries are the fuel tank of the system. The larger the batteries, the longer the system can operate before
recharging is necessary. An undersized battery bank results in short battery life and disappointing system
performance. To determine the proper battery bank size, compute the number of amp-hours that will be used
between charging cycles. Once the required amp-hours are known, size the batteries at approximately twice
this amount. Doubling the expected amp-hour usage ensures that the batteries will not be overly discharged
and will extend battery life.
7.3 E QUALIZATION C HARGING
Approximately every month, some batteries may need to be “equalized.” Since the individual cells of the
battery are not identical, some cells may not be fully charged when the charging process is completed. If the
batteries have been left in a discharged condition for long periods of time, the plates will have sulfates on
them from the electrolyte. If the sulfate remains on the plates for an extended period of time, it will harden
and seal off a percentage of the plate area, reducing the capacity of the battery. By equalizing the batteries
before the sulfate hardens, the sulfate is removed from the plates. Batteries with liquid electrolyte may
become stratified. Stratification concentrates the sulfuric acid into the bottom of the cell while the top
becomes diluted. This corrodes the lower portion of the plates, reducing battery life. Mixing of the electrolyte
by the formation of gas bubbles during the equalization process reduces stratification. Two methods can be
used to determine if a battery needs to be equalized. If possible, measure the voltage of each individual cell
while the battery is at rest (not being charged or discharged). A variation of 0.05 volts between cells indicates
an imbalance exists. If the battery construction prevents measurement of the individual cell voltages, use a
hydrometer. A variation of 0.020 in the specific gravity between cells is considered significant. Both
conditions can be corrected by an equalization charge. A proper equalization charge will not damage a
vented, liquid electrolyte type battery. It may, however, cause significant electrolyte usage and require that
the battery be refilled with distilled water to the correct level. This may be a problem with unattended systems
in remote areas which do not receive regular maintenance. Consult the battery manufacturer for their
recommendations.
7.3.1 Equalization Set Points (Non-Sealed Batteries Only)
Battery Type Bulk Volts Float Volts Equalizing Charge
Default Settings 14.0 VDC 13.5 VDC Disabled
Sealed Gel Lead Acid 14.1 VDC 13.6 VDC Not recommended; Consult battery manufacturer
AGM Lead Acid 14.4 VDC 13.4 VDC Charge to 15.5 VDC or per manufacturer.
Maintenance-Free
RV/Marine
14.4 VDC 13.4 VDC Limited Only if water level can be checked.
Deep-Cycle, Liquid
Electrolyte Lead Antimony
14.6 VDC 13.4 VDC Charge to 15.5 VDC or per manufacturer.
NiCad or NiFe Alkaline 16.0 VDC 14.5 VDC Not recommended; Consult battery manufacturer
Page 20 of 20 windy nation 03/06/2013