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Frequently Asked Questions

Q: Is there a guide explaining the purpose of all of the LEDs and jumpers on the controller?
A: Here.

Q: What charge regulation method do Solar24 controllers use?
A: Maximum Power Set Point (MPSP) - the controller varies the charging current to maintain a predetermined PV input voltage; in our case, it is optimized for our panels' average VMPP of approximately 17.1 volts.

Cheap solar chargers use pulse width modulation (PWM), rapidly interrupting the connection between the PV input and batteries to regulate voltage. This is inefficient, and can reduce battery performance. It also tends to produce a lot of RF noise. On the other end, some controllers use Maximum Power Point Tracking (MPPT), in which the controller continuously tests the PV input to find its VMPP as illumination changes; however, this adds a great deal of complexity (and cost) to the system, for a gain of only about 3% over MPSP.

Q: How much current do Solar24 controllers draw from the battery when not in use?
A: The controllers we are currently shipping have an idle current draw of about 650µA (0.65 milliamperes). A fully-charged S24-Mini will take a bit over 6 months to fully discharge if kept in storage.

Q: Do Solar24 controllers produce any radio frequency interference (RFI)?
A: No. Our controllers were designed specifically with radio applications in mind, and do not produce any detectable RF emissions.

Q: How much load current can the S24-Mini or Model 1 controller handle?
A: We rate these products for a 20 amp load. However, they will handle pulsed loads in excess of this without triggering overload protection; you can use a transmitter which may draw 22-25A at peaks, for instance.

Q: What is the minimum and maximum PV input voltage for Solar24 controllers?
A: Open-circuit voltage in full sunlight (VOC) should be 21-22V, with a maximum power point (VMPP) of around 16.5-17.1V. Less than this will not be sufficient to power the charger, and more may damage it.

Q: What kind of batteries can be used with Solar24 controllers?
A: Our controllers are intended to be used with Lithium Iron Phosphate (LiFePO4) batteries. They can be configured, at the time of manufacture, for use with flooded lead acid batteries (such as a car or marine deep-cycle battery); this involves replacing some of the components on the circuit board, and changing the firmware. They will also work with Nickel Metal Hydride (NiMH) batteries. They are not intended for use with gel cells, Nickel Cadmium (NiCd), or Lithium Ion batteries.

Energy Partners LLC
MAREC Center
200 Viridian Drive
Muskegon, MI 49440
Email: info@solar24.pw