# How long does it take to charge a 12v deep cycle battery with a 10 watt solar panel?

I want to also know if the 10 watt rating on the solar panel is 10 watts per day or is it constantly adding 10 watts? Is there a time which the 10 watts is being added like 10 watts per second or 10 watts per minute and so on?

### 13 Answers

- yankee_sailorLv 71 decade agoBest Answer
a 10w solar panel means at peak efficiency ( high noon, panel pointed flat at the sun, hitting it at 90 degrees), you will get 10 watts (at any given second).

Watts = volts x amps

a 12volt battery needs an "incoming" current of at least 13 volts to charge it; 13.5 volts is better.

so if the output VOLTAGE of the panel is less than 13 volts it wont do anything.

Even if it is, 10 / 13.5 = .74 amp.( three quarters). It will take forever and a day to charge a deeply discharged deep cycle battery..........

consider that a small 110v battery charger is putting out 3-5 amps ( or 3 x 110 =330 Watts) and the alternator on a car is putting out 20 to 50 amps at 14 volts ( 280 to 730 Watts).

- RamonaLv 44 years ago
You need more panel because it will take more than ones worth of sunshine to charge this battery so the battery will need to sit over night and wait to continue the charge. clouds will make the problem even worse. I use 24 - 100 Ah batteries with a 3500 watt system and I am using a 48 volt system. So my Ah = 24 X 100 / 4 = 600 Ah but this is at 48 volt so the watt hours are the same. But My computer puts the power where it is needed automatically. You have 125 watts for at best 10 hours per day = 1250 Watt hours per day. That battery needs at least 200 x 12 = 2400 watt hours that does not take efficiency of any of the systems into account. As you can see this battery may never charge completely.

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- 6 years ago
What is the open circuit voltage and voltage under load with the panel in full sun?

Assuming it is typical of many 10W panels, the open circuit voltage is 21V and the voltage under load is about 17V.

10W/17V is 588mA. A typical car battery is 40 Amp Hours. Amp Hours, or Ah, is the capacity of the battery. How much current a battery can delivery starting a car is called cold cranking amps.

A deep cycle marine battery will typically be more than 40Ah.

A 40Ah car battery at 50% charge will more than likely start your car in fair weather. Cold weather is another story.

So, to get a completely dead car battery to 50% - 20Ah - would be maybe two days of full sunlight - with only a 50% charge, or about 12.2 Volts.

Not a great battery charger - however - It makes a great supplement, and can offset the use of DC powered equipment in the vehicle while the engine is off. Things like low-wattage lights, cell phone chargers, tablets, and the like will drain the battery down that much slower.

I have a number of powered but low current items on in my truck all the time. A panel helps offset some of that drain if I don't drive for a few days.

- Anonymous5 years ago
There is a step-by-step video guide online right now that can show you how to reduce your power bill by making your own solar panels.

Take a look at it: http://tinyurl.com/Earth4EnergyRew

Why pay thousands of dollars for solar energy ($27,000 average cost) when you can build your own solar panel system for just a fraction of the retail cost. You can build a single solar panel or you can build an entire array of panels to power your whole house.

Some people are saving 50% on their power bill, some people are reducing their bill to nothing. But what’s most impressive is that just by following these instructions some are even making the power company pay them!

- 1 decade ago
Watts is a measure of energy per second. IE joules per second. 10 watts = 10 joules/second

Car battery capacities will be measured in mAH (milli-Amp hours)

capacities vary greatly although they will still take a fair while to get charged by such a tiny power charger.

- jleblanc42Lv 41 decade ago
It will put out 10 watts in full sunlight at noon, less at other times of the day. That means 0.83 amps, so just divide the battery capacity (in amp-hours) by 0.8 and you'll get an approximate charging time under full sun.

- JOHNNIE BLv 71 decade ago
Normal power is measured in kilo watts per hour. It sounds like 10 watts would be very small to do anything.