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Most portable solar chargers are designed to protect against natural battery discharge and electronic drain in RVs, boats, trucks, mobile homes or cottages.
They are helpful also to keep the 12-volt batteries charged and able to run small appliances such as fluorescent lights, coolers, small TVs, or laptops.
Charging a 12 volt battery with a solar panel requires a photovoltaic panel. It will produce an electric current when exposed to almost any sunlight (Even on overcast days).
Solar battery charger system 101
Keep in mind that Your panel will produce 100% full wattage output when placed on direct sunshine
Before buying a portable solar power system, it’s good to answer these questions:
- How long would the solar panel take to charge a 12 volt battery?
- What’s the ideal wattage for a solar charger?
- How can I control if it works fine?
- Will it fry my battery?
Most models have an illuminated LEDs that lets you know the panel is charging. Other have a built in controller to block the charge when the battery is full.
When You buy one, You’ll get quick connectors like cigarette lighter adaptors and battery clamps.
How to choose the right solar powered battery recharger
Solar is not the cure all for replacing spent energy
First start by the type of battery you’ll need to re-charge. In most cases one charger will work for all type of batteries, except for Gel Cell.
To calculate the wattage of the solar charger you’ll need to know the Amp/hours (Ampere per Hours) that your battery store.
To calculate the average charge time:
Take Amp/hour rating of the battery and Divide by the charger rating (in amperes) (*) and then add about 10% for the extra time to top off the battery,
(*) “Watt = Ampere x Volts” “Ampere= Watt/Volts” “Volt= Watt/Ampere”
I.e. Assuming You have a typical full size auto battery, it is about 50 amp hours.
To Calculate how much time You’ll need to charge the battery with a 15 Watt solar charger You’ll need:
- Calculate the Ampere per hour of the charger: 15 Watts /12 Volts = 1,25 Amperes
- Calculate the division: 50 amp hours / 1,25 ampers = 40 Hours of direct sunlight
- Add 10%: 4 hours
Result: Totally, with a 12 Volt solar powered car battery charger You’ll need 44 hours (nearly 2 days of sunlight) to charge a car battery with a 12 watt solar charger….this mean 7 days to full charge a dead car battery.
Note: Solar panels manufactures rate solar output in watts. As a rule of thumb rating of 15 watts delivers 1 amp per hour in direct sunlight.
Solar Battery Charging System & Accessories
Some panels are built with integrated battery that function as a power pack. You can charge the internal battery and then use to charge your batteries or devices.
When not included, You’ll need a converter. This converter is a switching power supply, and takes the nominal voltage of your panel and steps it up/down to the correct voltage for your battery.
The converter helps in eliminating these risks:
- If the maximum output voltage of the panel is too high, it can damage the battery.
- If the maximum output voltage is too low, it will never fully charge your battery.
- If the voltage output of the panel is less than the battery voltage, your battery will not charge.
The converter will take a certain amount of power from the panel and will convert it to the correct charge levels for the battery.
Solar Battery Controllers
In most case a solar charger controller is highly recommended. The Solar Controller will continuously monitor the charge and cut it off when charging is complete.
It helps in:
- Preventing overcharge
- Improve charge quality
- Prevent battery discharge in low or no light conditions.
Some solar panels are made with blocking diodes pre-installed they prevent battery discharge during low or no light conditions.
Once connected, you can charge your 12-volt battery nonstop for days without damaging the battery.
Inverters
Inverters turn DC (Direct current) power into AC (alternate current) power, the type of current that powers everyday appliances.
{ 6 comments… read them below or add one }
hashem 11.04.08 at 4:50 am
i would like to ask about time needed t discharging a 100 amperes per hour when a 60 watt of dc motor connected to the battery
admin 11.04.08 at 11:16 am
Do You mean a motor like this? http://www.samedaymusic.com/product–TCHPW60
Albert 12.11.08 at 9:09 am
how many 108 watt solar concentrator panels are needed to charge 120 12 volt batteries
admin 12.11.08 at 11:24 pm
Albert,
It depends on the Ampers Hours of the battery.
Have You tried for a bigger wattage?
108 Watt is good for 1 battery (i.e. for a car) and could charge it completely in 8-6 sun hours.
Enrico
Gord Cymbaluk 12.13.08 at 6:40 pm
I purchased a 1.8 watt solar panel charger to maintain my truck battery through the winter. I hardly drive it in the winter and the temperature sometimes dropes down to -30 to -40C during the night. Would it hurt the battery if I left the solar panel hooked up to the battery all the time.
admin 12.14.08 at 1:05 am
No Gord,
You’ll need to buy a solar charge controller.
Have a look here:
http://www.12voltsolarpanels.net/guide-buy-brunton-solar-controller-12volt-battery-charge-monitor
Thanks for the comment!
Enrico