Solar Project for School

[AlleghanySTEP]

Our school is in a competition that utilizes solar panels to charge RC car batteries. We currently have two 15W panels of different brands, and a smaller 3.2W panel. All panels are wired parallel to increase the amps to the charger. The charger is an AC/DC input charger. My question is, do we need to install diodes in the system, if so where should they be installed and what size diodes should be used? Additionally does anyone else have suggestions to make the panels more efficient?

Thanks

Jeff

[AlleghanySTEP]

Forgot to mention the charger is 110V AC and 12V DC

[Mike90250]

The PV panels need to be matched to Charger & the Battery you are charging.

The panels should have a sticker on the back , listing the Volts, amps and other specs.
The Charger should also have some specs, input voltage, output voltas & amps
The battery specs are also needed, then we can give you some feedback.


Is the car battery Ni-Cad, NiMh, Li-Ion ? What ? Voltage and amps too.


MikeSharp208_c.jpg

[AlleghanySTEP]

The PV panels need to be matched to Charger & the Battery you are charging.

The panels should have a sticker on the back , listing the Volts, amps and other specs.
The Charger should also have some specs, input voltage, output voltas & amps
The battery specs are also needed, then we can give you some feedback.


Is the car battery Ni-Cad, NiMh, Li-Ion ? What ? Voltage and amps too.


Mike[ATTACH=CONFIG]2009[/ATTACH]

The charger has multiple settings from 0.5 amps up to 5 amps. This is either with the 12V DC input or 110VAC input. The batteries are 7.2 V 3600mAh NiMh. One panel is a Sunforce 15W panel with the following specs from the website.

Power Output (Watts) 15.0
Mounting Hardware Required Yes
Panel Color Black
Frame Color Black
Number of Cells per Panel 1.0
UL Safety Listing No
CSA Safety Listing No
ETL Safety Listing No
Warranty 5 Year Limited
Color/Finish Family Black
Application 12-volt battery charger
Power Type DC
Solar Panel Technology Thin film
Length (Inches) 38.0
Width (Inches) 13.5
Thickness (Inches) 1.5
Weight (lbs.) 10.8
Adapters Included Yes

The other 15W panel is a Chicago Electric panel from Harbor Freight. The specs listed for it is below.

Description
Amorphous crystal solar panel provides superior performance in bright sun and in partial shade. Use this solar panel to power an appliance, light, small motor, or battery, but you must use a voltage regulator (not included) between them to prevent overcharging the battery and consequent damage.

15 watt solar panel gives you plenty of clean, quiet energy, no fuel required
Ideal for additional power and energy savings
Includes alligator clips, car lighter plug, bare wire end cable, and a 10 ft. standard lead with 2-way plug-end

Overall dimensions: 35-7/16" L x 11-7/16" W x 1" thick
Shipping Weight: 13.80 lb.
Specifications
Name 15 Watt, 12 Volt Solar Panel
SKU 96418
Brand Chicago Electric Power Systems
Shipping Volume 1.007
Max Output Watts 15

The third panel is one that was with my VW. The info for this panel is below.

Max Power: 3.2 watts
Voltage at max power:18.8 Volts
Current at max power: 170 MA

If there is any other info needed please let me know what it is. The way this part of the competition works is the students have just under 3hrs to charge a fully dead battery. If you set the charger for too many amps and a cloud passes over the panels, the charger will kick off due to insufficient voltage and require to be reset.

Any help and advice will be greatly appreciated.

[Mike90250]

your VW panel is the only one with useable specs. The 15w horrible fright panels are generally, junk. They may work a month or 3.

your battery will need 3.6Ah for full charge.

When clouds pass in front of the sun, ALL panels loose nearly all power. My 3,000 watt array, drops to 300watts. Your 30 watts of panel , would drop to 3 watts. If only a small cloud, a capacitor may help.

PV panels are CURRENT sources, not voltage sources, and behave differently than what most people are used to.

[Wy_White_Wolf]

.....PV panels are CURRENT sources, not voltage sources, and behave differently than what most people are used to.

AlleghanySTEP - Because of what Mike pointed out what you need to do is use the panels to charge a 12V battery (with a charge controller) and hook your RC charger up to that battery. Ineffiecent yes, but what needs to be done to change from current source to voltage source.

WWW

[Legacy]

the Sunforce panel has a maximum 1 amp output at 15volts
that is where they get the 15 watt rating from,that was on their
site