I have saw this question asked in other ways, but never have found an answer.
If I wanted to hook a solar panel up directly to a charger that has a 12 volt option, how many watts and or amps would be needed to make charger work?
Using a charger with 110 volts or a 12 volt battery would give it the needed power to work, but solar panels giving from a few hundred milliamps to maybe 2 or 3 amps might not be enough to be hooked directly to a charger, or would it?
Just substitute the power supply requirements. If a charger requires a 12V 1A DC supply then you need to be able to supply 1A consistently.
I don’t have any solar panel so I don’t know how stable the supply is and whether one would need to add additional regulation before the charger.
Regular charger circuitry works very poorly with solar panels. The charger needs to be able to implement MPPT (Maximum Power Point Tracking), else the efficiency of charging from a solar panel will be abysmal. Some chargers will even lock/latch up when supplied by a solar panel because they will naturally draw the panel down to a lower and lower voltage until the voltage is no longer sufficient to continue the operation of the charger.
Texas Instruments makes a very nice MPPT Chip - the BQ24650. Unfortunately, I am not aware of any hobby style or off-the-shelf charger that utilizes such a part. Most "Solar Chargers" sold on ebay or the china supplier sites are just regular old buck, boost or buck/boost converters that are really quite crappy for the job.
PPtk
Don’t bother hooking directly up to a charger it just wouldn’t work properly.
What you need is a solar charge controller. The SCC basically takes the voltage made by the panel changes it to wattage and amps and charges the bank of batteries or just a battery SAFELY. The best one to get is a Flexcharge NC25A it can take 120v and 25amps straight into it without melting down unlike alot! Of others.
This is what I was wondering. Thanks for the replies.
It all depends on the rating of the charger. For example my i4 requires 10 watts. 10 watts divided by 12 volts gives us 0.83 amps.
What I find works best for me is to have my solar panel charge a small lead acid battery from an old UPS (I was even using a motorcycle battery for a while) which acts as a buffer for when the panel isn’t producing as much as the charger needs. If your panel is smaller than what your charger needs you can have it charge the lead acid battery for a longer period of time and then use the charger once its full. For example, in order to run my 10 watt i4 for an hour a 5 watt panel would need to charge the lead acid for at least 2 hours.
Hope that helps