Schumacher sp-400

12v Solar Battery Charger

Solar battery chargers use the sun's energy to charge batteries. The technology behind the solar panels allows for up to 48V and 4000 Ah of capacity Lead-Acid or Ni-Cd battery charging. We will now dive into the more detailed outlook of solar battery chargers for 12V batteries. The batteries for most vehicles (like cars, boats, motorcycles, ATV, etc) are 12V. You will want a battery charger for your 12V battery if the vehicle has not been in use for some time. For example, the car's battery naturally drains because of the small electronic devices like onboard computer, alarm system, lock monitoring, etc. And you know that the battery life is shortened if it is not kept charged. Nowadays you have an option to charge your 12-volt battery with the power of the sun. Solar battery chargers are portable, lightweight, maintenance-free, eco-friendly and have no operating costs. A typical solar battery charger includes a waterproof solar panel, a charge controller, wires for attaching the charge controller to the battery via clamps or a cigarette lighter plug. The charge controller is in charge of the panel's output voltage regulation. The panel's output voltage will change depending on the sun's intensity at a given moment. A charge controller is required to modulate the voltage to, say, 12V and protect the battery from overvoltage.

Battery tenders, as the battery chargers are also known, help to maintain 12 V battery's charge when it's not actively used. You'd need one of those when you leave your vehicle not operational for several months. Solar powered battery tender operate just like regular battery tenders with a twist that you don't need an electrical grid. These devices come with a small and lightweight solar panel which makes them portable and not dependent on the grid. Solar battery tenders usually operate in outdoor conditions so they are bound to be waterproof and dustproof. Vehicles that would especially benefit from solar battery tenders are RVs and boats or cars that are not used frequently. 

How Does Solar Powered Battery Tenders Work?

The 2 main components of a solar battery tender are the solar panel and charge controller. The controller converts the Direct Charge produced by the solar panel into a "smart" charge fed to the battery. The microprocessor featured in charge controller limits the available voltage to prevent overcharging and maintains a healthy charge level for an extended battery life. Solar battery tenders activate as soon as the Sun starts to shine on them and the charging speed depends on the Sun's intensity and the angle of the solar rays relative to the panel's surface.

Battery Tender 021-1164 10W Solar Panel Charger & Maintainer

battery tender 021-1164

Main Features:
  • A built-in 3-step automatic microprocessor controller
  • Includes 10W solar panel
  • Output: 12 VDC, 540 mA, 5W max
  • Protection against
    • reverse polarity
    • water
    • spark
  • A built-in temperature compensation sensor
  • Dimensions: 14" x 28" x 1" (35.6 x 71.2 x 2.5 cm)
  • Weight: 5.5 lbs (2.5 kg)

The brand itself is called Battery Tender. They offer 3 variations of the solar panel: 5W, 10W, and 15W. It's a maintenance-free battery charger and maintainer with a built-in charge controller. The built-in intelligent microprocessor prevents overcharging and reverse polarity. The charge controller is mounted on the solar panel's frame for safety reasons. Both the panel and charge controller are waterproof and can operate in temperature conditions from -20°F to 120°F. The panel generates small but stable voltage even in an overcast weather. Wipe the panel once in a while to achieve a higher charging efficiency. Includes alligator clips and mounting hardware.

Pros Cons
Actually produces the rated power output Charging capacity is low
Has mounting holes for a permanent fixture LED status light can get covered after mounting
Easy setup

Schumacher SP-400 4.8W Solar Battery Charger

Schumacher SP-400 Battery Tender

Main Features:
  • Works with 12 V lead-acid batteries
  • Waterproof
  • SPC-7A charge is sold separately
  • Includes:
    • 4.8W solar panel
    • 12 VDC adaptor
    • clamps
    • mounting screws and manual

Schumacher charger has a rugged design to withstand the elements. It's compatible with 12 V lead-acid batteries. Starts the charging automatically after connecting to a batery. The water-resistant solar panel uses amorphous solar cells; charges even in a cloudy weather. Works with boats, cars, motorcycles, RVs, trucks. Using with a charge controller (sold separately) is recommended.

Pros Cons
Solidly built No status indicator light
Operates for years A charge controller is not included

Sunway Solar 12V Battery Charger

SunWay Solar 12V Battery Charger

Main Features:
  • Mounts to the windshield
  • 3W, 15V solar panel
  • ABS plastic housing
  • LED charging indicator
  • Weight: 23.2 oz (660 g)

Sunway solar 12V battery charger is shaped so as to attach to most cars' windshield with suction cups and charge the battery through the car's 12V cigarette lighter but it can also be used for charging the batteries of a boat, motorcycle, ATV, snowmobile, etc. The solar panel is covered with an ultra clear PV glass and has a durable plastic housing which makes it waterproof though not submergible. The solar panel comes in 2 variations: 1.5W amorphous silicon and 3W crystalline. The LED charging indicator keeps blinking if the battery is still in the charging mode or emits steady blue light is the battery is fully charged. The package includes a 14" x 5" (352mm x 128mm) solar panel, alligator battery clamps, 2.4 ft (8m) main cable, cigarette lighter plug, and 2 suction cups. NOTE: ensure the panels are clean and face the sun, make sure the battery is 12V and larger than 20Ah. This is a trickle charger meaning it will charge slowly, it's not intended for charging a fully discharged battery but rather to keep it from draining over time.

Pros Cons
Keeps a boat's trolling motor going longer No included charge controller
Keeps a car's, Rv's battery charged when not driving for a while suction cups don't hold tight
Good customer service

Suaoki 18V 12V Solar Portable Battery Charger

Suaoki 18V 12V Solar Portable battery Chanrger

Main Features:
  • 18W, 18V solar panel
  • Built-in blocking diode
  • Weight: 0.8 lbs (349g)

Suaoki portable battery charger has an 18W SunPower solar panel with a high efficiency of 22.5%. The panel's dimensions are 16.5" x 11" (42 x 28 cm). This is a trickle charger for a car through a 12V cigarette charger. it also works fine as a motorcycle, RV, marine, boat, snowmobile battery charger. The built-in blocking diode prevents the battery from backward discharge when the charger's voltage is lower than that of the battery's at night. Weighing less than a pound it is easily portable yet durable, made of water and heat resistant materials. If you leave your vehicle sit for weeks or months without using it then this charger will keep its battery at a proper storage voltage with no costs to you - it's solar. The package includes: 18W solar panel, crocodile clips (4.9ft / 1.5m), cigarette lighter plug (4.9ft / 1.5m).

Pros Cons
Good for sailboat's automatic bilge pump No included charge controller
Thin & flexible No indicator light
Short cables

Eco-Worthy 20W 12V Solar Panel Kit

Eco-Worthy 20W 12V Solar Panel Kit

Main Features:

  • Includes 3A 12V/24V charge controller
  • Good for DC loads
  • Waterproof panel with aluminum frame
  • Weight: 5.35 lbs (2.4 kg)

Eco-Worthy offers a versatile charging kit suitable as a 12V battery charger meanwhile supporting DC loads like a fan, LED light, etc., thanks to the supplied charge controller. In addition, the charge controller protects the battery from overcharging and over-discharging. The waterproof 20W panel with corrosion-resistant aluminum frame has over 20 years of life, it's dimensions are 20.5" x 14.4" (52 x 36.6 cm). Solar charging kit contains the solar panel with 3.2 ft (1 m) cable, a pair of battery clips with 6.5 ft (2 m) extension cable, and a 3A charge controller.

Charge Controller Specification
Nominal Output 12V / 24V
Operating Current 3A
1 min Load Current 6A
Max Solar Panel 40W / 80W
Over-Discharge Protection 10.8V / 21.6V
Float Charge 13.8V / 27.6V
PWM Charging Yes
Self-consumption 1.5 mA / 3 mA
Waterproof Class IP22
Pros Cons
The actual power of the PV panel is 25W The charge controller leaks in water
Works great for sailboat and gate opener battery The wires are easily disconnected
Good for large interstate deep cycle battery

12V Waterproof Solar Sealed Lead Acid Battery Charger

12V Waterproof Battery Charger

Main Features:
  • Trickle charge only
  • Overcharge protection
  • Waterproof
  • Rust/corrosive proof
  • Weight: 0.8 lbs (0.36 kg)

This waterproof solar battery charger is intended for sealed lead-acid batteries, that is, the most common type of batteries for outdoor activities like boating, camping, hunting & RVs. Has a built-in diode to prevent backward current at night.

Solar Panel Specifications
Power 1.2 W
Color Silver
Current 60 - 70 mA
Voltage 12V
Dimensions 6.89" x 6.26" (17.5 x 16 cm)
Weight 0.8 lbs
Warranty 1 year
Pros Cons
Small but efficient Alligator clips are small for car batteries
Does what it claims No indicator light
Withstand heavy downpour

HQST 100W 12V Polycrystalline Solar Panel

HQST 100W 12V Solar Panel

Main Features:
  • Corrosion-resistant aluminum frame
  • Pre-drilled holes for faster mounting
  • IP65 waterproof
  • Works in low-light conditions
  • Weight: 16.5 lbs (7.5 kg)
  • Warranty: 5 years materials, 25 years power output

HQST 100 W solar panel is different from the other battery chargers we saw above. This is not a trickle charger, it can charge your 12V battery rather quickly with 100W power. On the other hand, it's heavier and comes with pre-drilled holes for mounting so, surely, also less portable. It's covered with iron-tempered glass for enhanced stiffness and impact resistance. Besides, the frame is made of corrosion-resistant aluminum so, for instance, you can mount it on your trailer, RV, caravan or boat and be sure that it will withstand high winds, loads of snow, and moderate rains (IP65 waterproof - low-pressure water jets). The panel is designed with bypass diodes to make it shade- and low-light tolerant for charge availability in overcast weathers.

Panel Specifications
Power (Pmax) 100 W
Vmax 600V DC (UL)
Vmp 17.8 V
Imp 5.62 A
Voc 22.4 V
Isc 5.92 A
Dimensions 39.7" x 26.7" x 1.4" (100.8 x 67.8 x 3.6 cm)
Weight 16.5 lbs (7.5 kg)
Pros Cons
Similar quality with WindyNation but cheaper Doesn't put out full 100W (more around 80W)
Performs surprisingly well
Works great on a camper

If your battery charger does not work as expected check this out to troubleshoot and fix it.