**1. Does it hurt the efficiency to have a higher input voltage?**

While it is possible to input 72 Vdc and output 12 Vdc, it is not the most efficient configuration for the controller. A system which had 36 Vdc input and 12 Vdc output would run more efficiently from the T80’s perspective. The most efficient configuration for the T80 is with 60 Vdc input and 48 Vdc output. Never-the-less, in many cases the savings in wire costs and the slight advantage of earlier wake up and shut down make the “inefficient” higher voltage to low voltage conversion the best system choice. Many systems input 72 Vdc for 24 and 48 Vdc batteries.

**2. What makes the Apollo Solar Charge Controller so efficient?**

The Apollo Solar TurboCharger is the most efficient PV battery charge controller available today due to 3 specific areas in the core design:

The use of Maximum Power Point Tracking (MPPT) makes the entire PV system up to 30% more efficient because it uses all of the output from the PV panels regardless of sunlight, latitude or temperature conditions. Our patent-pending MPPT system provides the quickest tracking to follow rapid changes in these conditions.

The use of Maximum Power Point Tracking (MPPT) makes the entire PV system up to 30% more efficient because it uses all of the output from the PV panels regardless of sunlight, latitude or temperature conditions. Our patent-pending MPPT system provides the quickest tracking to follow rapid changes in these conditions.

All the power circuit components are designed for very low resistance. The amount of power lost in any conductor is proportional to the resistance times the current squared. Since the output current can exceed 75 Amps, we have used special design techniques to keep all the resistances as close to zero as possible.

** 3. What is the maximum input voltage? Max VOC?**

The maximum operating voltage of the T80 is 140 Vdc. Above this, the unit will shut down to avoid damage. The absolute maximum applied input voltage the controller can accept without damage which is 150 Vdc. Each PV module has specific ratings for voltage and current at standard test conditions and temperatures, the manufacturers also publish current and temperature coefficients. The Voc for any PV module increases in cold temperatures. Modules are rated with an assumed cell temperature of 25o C, when calculated at 0o C there may be as much as a 25% increase in the rated Voc. The Voc voltage temperature coefficient for the specific location of the installation must be calculated from known weather data. Once the maximum Voc of the module is found a series string voltage may be determined.

**4. How can I reduce the amount of panels by using the T80/HV?**

The T80 & T80HV MPPT algorithm harvests up to 35% more energy than comparable units. This gets you more energy with less panels.

**5. Does the T80 automatically sense the battery size and type, and configure appropriately?**

The T80 & T80HV automatically sense the battery voltage, and prompts the installer to enter the battery type and capacity through an easy-to-use user interface.

**6. How does the T80/HV increase battery life?**

The T80 & T80HV incorporate precision charging. Through 4-wire measurement of battery terminal voltage; high resolution analog to digital conversion of critical inputs; and battery temperature compensation, the batteries are charged more efficiently. This equates to longer battery life.

**7. Can I mount the unit lying down or on its side?**

No, for highest efficiency, it must be mounted vertically to allow for proper airflow through the heatsink.

**8. How much mounting clearance is needed?**

At least 2” should be allowed on the sides to allow for proper airflow through the heatsink and vents. There should also be adequate spacing allowance at the bottom, around the wiring box, to provide for a proper bend radius for input and output cables.

**9. How loud is the fan?**

The fan at full speed runs at 35 dB/A. The output noise is further reduced by a variable speed control algorithm which only runs at high speed under the highest current and temperature conditions. In most cases, the fan is not noticeable.

**10. Do the relays click?**

The T80’s proprietary MPPT algorithm requires clicking the relays only once an hour during normal operation, when the unit drops below or above 5A out.

**11. What justifies a cost higher than the controller just about everybody is now using? Do I really need 80 Amps?**

In high power applications, the T80 provides 1/3 more power than our competitors. This saves using multiple units, thereby offering a lower cost per watt. Just what are the main advantages over the other controllers out there? Higher output current; Runs cooler; Built in Emeter function; 90 day energy harvest to name a few.

**12. Does the T80 come with a shunt?**

The T80 does not come with a shunt, but includes a printed circuit board (called the Apollo Shunt board) which mounts to a standard 500A-50mv shunt.

**13. What is the effect of high temperatures on the unit? Can I run my T80 in “desert like” conditions?**

The maximum recommended operating temperature is 40¼C (104¼F). The T80 monitors its internal temperature, and will fold back its output current if it is too high. The internal fan runs at 52 CFM (full speed), and moves air very efficiently across the internal components. There is also a provision to add an external fan controlled by an auxiliary relay. The T80 is currently being “proven” in desert like conditions.

**14. What input power should I use for a 12, 24, 48V battery system?**

The recommended array Vmp for a 12V battery system is 16 – 62 Vdc; for a 24V battery system, 32 – 102 Vdc. For a 48V battery system, 60 – 112 Vdc is recommended.

**15. Why don’t I have an option to Equalize?**

In order to enable the Equalization option, the T80 temperature sensor must be connected.

**16. Why does the Charge Controller not disply SOC data?**

Both battery voltage and current are required to calculate SOC. If either the shunt, or the battery sense cable is not connected, the T80 will not display SOC data.

**17. Can I chain together more than one T80?**

Yes, with a Network Option Card, which allows multiple units to act as one.

**18. How do I calculate the proper wattage of the PV array to get the most from my T80 Charge Controller?**

The T80 is capable of charging any battery at up to 80 Amps. The most power will be realized by using 48 volt batteries. The first pass at the math shows that 80 Amps X 48 Volts is 3840 watts. However, one can not charge a 48 volt battery with just 48 volts. There must be a higher potential to get the current to flow into the battery. In the case of a 48 volt battery the Absorb Set Point is that higher voltage, which can be set as high as 57.6 volts. So when we take 80 Amps X 57.6 volts we get 5608 watts. Since the T80, like all charge controllers has a small loss, one should add about 2% to the PV array to cover that loss. Adding another 2% for losses in the wire results in a maximum PV array size of 4792 watts.

The same theory applies to 24 volt and 12 volt batteries, but the numbers are cut in half or quarter. 80 Amps X 24 volts is 1920 watts. 80 Amps X 12 volts is 960 watts. One can connect multiple T80s in parallel to increase the output current such that a bank of up to 16 T80s will produce as much as 1280 Amps, which is sufficient to charge just about any battery system in the off-grid market.

If the batteries are the flooded type, they should be equalized periodically. Equalizing is carefully overcharging all the cells for a few hours so that even the lowest of the cells becomes fully charged. To cause the overcharge the voltage on a 48 volt battery needs to be as high as 64 volts. 80 Amps X 64 volts is 5120 watts. Adding 4% to cover losses, comes out to 5324.8 watts of PV array which is what the T80 and a flooded 48 volt battery can use.

One should not try to equalize GEL or AGM type batteries and the T80 will not allow it. In those cases, one only needs the maximum of 4792 watts. But, we all know that one can not buy a PV array in increments of 2 watts such that you end up with an exact amount of PV power, nor do you get the full output since the sun rarely yields exactly 1000 watts per square meter. The bottom line is that a great deal of rounding is normal and expected. The exact numbers given above are simply the theoretical maximums.

**19. What happens if the PV array can and does produce more power than the T80 can take?**

The main job of the T80 is to protect the batteries from being overcharged while filling the battery as early in the day as possible. The T80 measures the exact voltage at the terminals of the battery and then maintains that voltage very carefully to ensure that the battery does not get damaged. The MPPT (Maximum Power Point Tracking) algorithm in the T80 does a marvelous job of maximizing the power harvested from the PV array. It wakes up with first light and starts current flowing into the battery early in the day. This increases battery life since a lead acid battery deteriorates when left in the discharged condition. In many solar installations, the batteries are used during the dark hours and are most likely to be at their lowest state of charge in the early morning hours. The MPPT front end of the T80 takes advantage of the fact that the PV array is most likely to be the coldest in the morning and producing the highest voltage. The T80 is based on a DC to DC converter so all that extra voltage is turned into the optimum current and voltage product for charging the battery.

When the battery is full, there is simply no more need to charge it. Any extra power which is still available from the PV array will not be used for the battery. Any other load on the system such as an inverter can use that energy. If the battery becomes fully charged each day before noon, it may be that the size of the battery can be increased. The properly sized system will have more than enough battery to supply the loads for a number of days without sunshine. The PV array will be sized to fill the battery with a single day of sun if affordable. The popular alternative is to have a secondary means of charging the battery in the case of many days without sun. This could be a wind turbine, a micro-hydro turbine or, as a last resort, a fossil fuel generator.