S24-Mini Solar Power Supply

This tiny, lightweight solar power supply features an integrated 40WH LiFePO4 battery, and offers plug-and-play convenience for QRP stations, camping, and anything else that needs a simple, reliable 12V DC power supply. It’s built into a rugged, water-resistant polycarbonate box.

Features

State-Of-The-Art Battery Technology

This power supply features a built-in 40 watt-hour Lithium Iron Phosphate (LiFePO4) battery, which will provide years of safe, reliable service.
External battery packs can be connected in parallel to facilitate longer operating times.

Plug-and-Play Convenience

The S24-Mini packs everything you need into a single, easy-to-carry package.
Just connect a solar panel and your 12V DC devices to the side-mounted screw terminals, and enjoy convenient, reliable solar power.

Expandable

If the integrated battery isn’t enough, it’s easy to attach extra external battery packs.

Made in Michigan

All of our products were designed in our lab at the Michigan Alternative and Renewable Energy Center in Muskegon, on the shoreline of Muskegon Lake.
Our printed circuit boards are manufactured by reputable supply partners in Holland, MI.

Requirements

Solar panel: 21-22 volts open-circuit (VOC), 16.5-17 volts at maximum power point (VMPP)
External battery (optional): 12.8V LiFePO4 (DO NOT use any other battery chemistry)
Load: 12 VDC nominal; maximum load 20A
Connections: Bare wire or spade lugs to screw terminals

Pinouts

S24-Mini
1	2	3	4	5
+	–	+	–	–
Load		PV in		Aux Batt

Pin 1 is common between load and external batteries.

S24-EXTBAT
Ø	1	2	Ø
	+	–

Battery Health

Charge your Mini when it arrives.
Open the top cover and disconnect the battery before long-term storage.

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 V_MPP 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 V_MPP 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 (V_OC) should be 21-22V, with a maximum power point (V_MPP) 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.

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