Recharging battery with solar panel.

Go To Last Post
6 posts / 0 new
Author
Message
#1
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

I am looking for some thoughts on a alternate lighting system for when the power goes out in my house. I am pretty much at the end of the electrical distribution grid in my town so I am prepared with an gasoline powered electrical generator to run my furnace. It's just an annoyance to get going. I can usually wait for a couple of days before I need to get it going. I have that problem solved.

The question I have is lighting. The resources I have on hand are: 1: 12V 17AH sealed lead acid batter in good condition, 1: Class 2 outlet powered battery charger with automatic cutoff, output 12V @ 1Amp, tested and it works. 1: scavenged solar panel, circa 2002, rated 10.3 watts, open circuit voltage 23.8 volts, max power 16.5 v @ .62 amps. Minimum blocking diode 1.5 amps. I will be driving 4 LED strips of about 10 LEDs that are really bright, current us unknown.

My question is if I want to recharge the battery from the solar panel do I need some sort of charge controller? I have no experienc in this matter. My instinct is to just hook the solar panel to the battery through a blocking diode for the few days I may be out of power. Does anyone have experience with charging a battery with a solar panel on a short term basis? Suggestion would be appreciated.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Harbor Freight and Northern Tool have small charge controllers. They taper off to 13.2V. Panel with no controller will just boil off the electrolyte. It will work if you watch it and cut it off before it starts bubbling. I think.

Imagecraft compiler user

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

SLA batteries can typically handle continuous C/3 overcharging (5 amps in this case) without venting gas but the internal recombination does produce heat. Your 700mA/10 watts maximum is unlikely to raise the temperature much. Probably the panel could be permanently connected without causing any damage.

Of course the overcharge only occurs after the overnight discharge is restored. If the usage was 2 amp-hours then only the extra amp-hour of charge would cause heating. So while a charge controller is probably not necessary, it would be a useful indicator that the battery is indeed fully charged. At those small power levels, chronic undercharge is more likely to damage the battery.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Just for general information, here is where you can buy the LED strips I am talking about. 24 LEDs at $1.80 with free shipping. They are not the perfect solution as they require some sort of mounting and connector wiring but I have that problem covered. www.tmart.com has some crazy cheap stuff that I have never been disappointed with. Your mileage may vary.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Quote:
My instinct is to just hook the solar panel to the battery through a blocking diode for the few days I may be out of power.

It all depends of you solar panel power and your battery. We are making some experiments with solar panel that has a higher peak of 16 V - 270 mA, 40 Ah Battery and a simple blocking diode. There is no bubbling as Bob said BUT if you increase the solar panel power you will see what Bob said.

Regards,

Bruno Muswieck

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

I have a 100Ah+5Ah battery and 2x60W solar panels connected through a CMP-12(or CMP-10 do nt know as I am hard at work at the moment) I use it to give me light and also it charges everything that can run from a car sigaret lighter outlet.
This now is going into its 3rd year of operation.
What you need to not forget is to put fuses in your system. I have also added an AVR circuit that disconnects the solar panels one by one if the battery voltage goes to high. For some reason the charge controller (cmp-12) every now and then keeps charging the batteries although it should cut of charging when the batteries are full.
I would put a charge controller in to maximize the efficiency from your panel, it also prevents discharging the battery to deep if you would use the load output of the controller.
Connecting the batteries directly to the solar panel can also be done if the panels do not have to much power, otherwise you will kill your battery as per Bobs remark.

for fusing I use car fuses. In a car shop I have bought a fuse box that can hold 6 fuses and connected that from the charge controller to the battery and from the battery to the 'load' effectively making a number of different systems each with its own fuse.