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100: Why does the display of the FOX-D1 show -0.1 A or 0.1 A even when no current is flowing?

This is typical for electronic measuring instruments. The smallest value that can be displayed (here 0.1 A) may fluctuate.

110: What is the terminall “IN“ at my FOX-D1 for?

This terminal must be connected to the negative terminal of the battery (see instruction manual or printing at the back-side of the FOX-D1).

120: Is it possible to connect a wind generator to the FOX charge regulators?

No !
The FOX regulator is designed as a series regulator and once the batteries are nearly fully charged the regulator cutts of the connection between the solar module and the battery in fast alternation. When the batteries are charged now, the wind generator would operate without load. Accordingly the wind generator could be damaged due to dramatically increased rotational speed and very high voltage up to 100 V. The charge regulator could be damaged as well.
Hence wind generators need a special charge regulator that suits their technical specifications.

130: Can I run the motor resp. use a charger though the solar modules are connected and the FOX charge regulator is operating?

Yes, this is possible without any problems.

140: Which capacity of batteries do you recommend within a solar system of two pcs. of 70 Wp solar modules?

120 Wp nominal power do correspond to a charging current of approx. 8 A. According to this the capacity of the batteries should be between 80 Ah and 400 Ah. Please consider that a larger capacity of battery causes an extension of the battery life as it reduces the permanent charging/discharging cycles.

150: Sometimes the LCD Display shows a star like * on the display. Wwhat does this mean?

The regulator charges the batteries with a 3 step charging characteristic. When the star is shown, the battery is completely charged and the algorithm has achieved step 3. Now the battery will be charged up to 13.8 V to protect it from long term gassing.

160: Why does the LCD display never show ILoad = 0.0 A ?

The display never shows 0.0 A. Provided that the load current is below 0.5 A correspondingly the display shows the following: " ILoad < 0.5 A "
The measurement range is from 0.0 up to 16 A. According to the resolution of the FOX regulators it is difficult to measure any current below 0.5 A. To avoid the situation that a small load is switched on e.g. a radio (0.1A) and the display shows 0.0 A, the FOX regulators have been programmed in that way that if the current is less than 0.5A, the above message will be shown on the display.

170: How is the max. solarcurrent defined?

At solarpower you have generally 17V / 34 V voltage.
Example: FOX -350/E → 260W / 17V = 15,3A
520W / 34V = 15,3A
It results a max. current of 16A for this regulator.

180: Is it possible to load two different battery systems (12V and 24V) with one charge regulator at the same time?

No! You can only load batteries of the same voltage with one charge regulator.

190: Why does the charge regulator show no function (in connection with FOX-MD1)?

One reason could be that no battery (or one with a voltage below 8V) is connected to terminal B1 of the regulator or the pins are inverted. The internal fuse of the regulator could also be destroyed.

200: The FOX-D1 measures and displays the values of voltage or current not continuously. Between two readings there is always a certain delay (less than 1 second). So, if the values of voltage or current rise or fall dramatically during this time, for the viewer it seems as if the display jumps.

Check connections, all three terminals must be connected (see instruction manual or printing at the back-side of the FOX-D1).

200: What are the bulk and float voltages of FOX-220/320?

At 12V systems the bulk charging voltage at the default AGM setting is 14,2V while the float is 13,8V, at GEL it is 14,3V/13,8V and at Flooded it is 14,4V/13,8V. All charging voltages are temperature compensated with -20mV/K (@ 12V) (s. Datasheet).
At 24V systems the bulk charging voltage at the default AGM setting is 28,4V while the float is 27,6V, at GEL it is 28,6V/27,6V and at Flooded it is 28,8V/27,6V. All charging voltages are temperature compensated with -40mV/K (@ 24V) (s. Datasheet).

210: How is the charge curve of FOX-220 optimized?

The FOX-220 has an optimized (adjustable in conjunction with the FOX-MD1) charging algorithm in which you can set the type of batteries you want to use.

220: Up to what temperature the FOX charge regulators could be used?

The ambient temperature should not be higher than 50°C.

230: What is the right combination of modules to be connected to the charge regulator?

If modules are connected in series to the charge regulator the voltages of each are added (12V + 12V = 24V). So with two modules of 12V each you can also load a 24V battery.

If the modules are connected in parallel (combine all plus-poles and combine all minus-poles) to the charge regulator, the voltage of each module has to be equal. Both connections can also be combined (24V module parallel to 2x 12V module in series = 24V at the charge regulator).

240: Is it possible to charge 12V batteries with a 24V solar module?

Generally it is possible to charge 12V batteries with a 24V solar module, but the charge power is reduced to almost 50% of nominal charge power. The charge regulators recognize the 12V battery and tune the charge power.

250: Is it possible to charge lithium-ion battery systems with the Sunware solar modules?

Because lithium-ion systems are constructed very manufacturer-specificly, a manufacturer's surveyor should certify the combination of our modules and the li-ion system.

260: Why does even at night exist a voltage between the module connections?

The following is only be suitable with FOX-Regulators from SunWare!

At night a very low measurement current (~0,01mA) is required to detect whether the battery voltage is higher than the module's voltage (night operation).

270: Is it possible to connect two modules of different power, connected in series, to the charge regulator?

No! In a series connection the current of the more powerful module has to go through the less powerful one. That may cause an overload! So series connection only works with two identical (identical current) solar modules.

300: Why is it not possible to measure load currents ?

Check connections, all three terminals must be connected (see instruction manual or printing at the back-side of the FOX-D1).

10100: FOX-100 FOX-200 FOX-300 : What does the yellow LED indicate ?

The yellow LED is an indicator for the charging current. If there is no charging current, the yellow LED is off. When there is a charging current and the battery is not yet fully charged, the LED is permanently on. When the battery is nearly fully charged, the regulator reduces the charging current and the LED starts to flash.

10100: Can I use the FOX-100 in 24V systems ?

The standard FOX-100 is for use in 12V systems only. But certainly we can deliver special 24V versions on demand.

10100: FOX-200 FOX-300 : What does the red LED indicate ?

FOX-200 and FOX-300 prevent the battery of deep discharge. When the battery is empty, the load that is connected to the load-terminals will be turned off and the red LED will be on. As soon as the voltage of the battery is back on a normal level the load will be turned on and the red LED will be off.

10100: FOX-350 : Why does the display never show “Switch Battery”?

The display only shows this message when battery 2 is connected to FOX-350. In case that there is no second battery connected to FOX-350, the option of choosing between battery 1 and battery 2 does not exist accordingly.

10100: FOX-300, FOX-350 : Is it possible to connect the positive pole of the load to the regulator even when the negative pole is connected directly to the negative pole of the battery (or to the earth of the car body)

Yes, this is allowed. The regulator only operates the positive pole, the negative pole is internally connected to the negative pole of the battery.Thus the positive pole of the load can be connected to the regulator and its negative pole can be connected directly to the negative pole of the battery.

10100: Is it possible to connect different types of batteries to the terminals of FOX-300, FOX-350 (e.g. a lead/acid battery to terminal B1 and a gel battery to terminal B2)?

FOX-300 and FOX-350 are suitable for lead/acid batteries as well as for gel batteries. Thus it is no problem to connect two different types of batteries.

10100: Is it possible to check the functioning of the charge regulators FOX-100 to FOX-350 in case that only a solar module is connected and the battery is disconnected?

To operate perfectly, the charge regulator definitely has to be connected to a battery at terminal B1. In case that there is not any battery connected none statement of the functioning of the regulator can be inferred.

10100: FOX-150 FOX-250 FOX-350 : Why does the display sometimes show illegible signs?

Very rarely illegible signs appear at the display. But this appearance lasts at max. 20 sec. Subsequently the information at the display refreshes. By pressing the “ESC” button the display will be refreshed as well.

In case that the display fails and does not clear we recommend to RESET the regulator. For this purpose please disconnect the positive pole of the solar modules and remove both yellow fuses. Wait 1 min. and leave the regulator without any voltage. Afterwards replace both fuses and reconnect the positive pole of the module.

10100: FOX-300, FOX-350 : I have connected only the solar modules and one battery to the regulator. Can I use the negative pole of terminal B2 resp. LOAD to connect any consumer whose positive pole is connected directly to the battery?

Inside the regulator, the terminals and the negative pole of the battery are directly connected among each other. We absolutely recommend not to connect anything else but only a battery at terminal B2. Otherwise the charge regulator can be damaged!

10100: Why is there no current reading on FOX-150/E?

Please be sure that the negative pole of the solarmodules is not connected to the negative battery pole (chassis or ground) in any way as this short circuits the regulator.

10100: FOX-250 FOX-350: What does these icons mean IL, IS, B1 and B2?

IL = the current flowing from the battery to the consumer (current load).
IS = is the current from solar modules into the battery - the charging current.
B1 = the current battery voltage of battery 1
B2 = the current battery voltage of battery 2


Short explantions of the photovoltaic related terms.


Unit of the module performance under standard condition - maximum performance.


Kurzschlussstrom, der Strom der fließt wenn die Kabelenden eines mit Normbedingungen beleuchteten Moduls kurz geschlossen werden.


Short circuit current, the flowing current when the ends of the cables from a solar module are directly connected together and the panel is iluminated unter standard conditions.


Rated power, is the under standard conditions measured module performance. The module power must be specified by the manufacturer that way.

Solar modules are measured at 1000W/m² irradiation, vertical incidence, 25°C cell temperature and the color spectrum 1.5. In actual operation, a module can deliver only very rarely this performance. Neither the sunlight falls perpendicular to the module, nor is the cell temperature 25°C when the modules is in the sun.

Following relationship exists between P max, Imax and Umax:
Pmax = Umax * Imax.


the voltage of the module at the point of maximum power. This measurement is carried out under standard conditions.


the current generated by the module at MPP. This measurement is carried out under standard conditions.


Open-Circuit Voltage, open circuit voltage of the module. The open circuit voltage can be measured when the module is illuminated under standard conditions between the cableends of the module. For an 12V module the open circuit voltage should be greater than 20V and less than 25V.


Open-Circuit Voltage, Leerlaufspannung des Moduls. Die Leerlaufspannung kann gemessen werden, wenn das Modul unter Normbedingungen beleuchtet wird und am offen Kabelende des Moduls die Spannung gemessen wird. Bei 12V Modulen sollte die Leerlaufspannung grösser 20V und kleiner 25V sein.