Last year I had a couple of Spartan go cameras setup on 6v 1.2a/h batteries with a 6 volt solar panel. I could get roughly 1.5 to 2 months out of them sending images after each detection (20 transmissions a day on average) before I had to swap out batteries. This year I am looking for something better. I am wondering what everyone does for their setups? I was thinking about buying a 6v golf cart battery this year and and rigging up a 2amp solar charger. My goal is to run 4-5 months on a charge of possible. If anyone has any expertise in this area, I am all ears.
My BEC Orions run off 6-volts. It is a bit of a challenge since most setups are 12 volt. I've used larger 33 ah AGM batteries. I found some 10 amp 6-volt solar panel charge controllers on-line. A panel advertised at 12-volt with a particular wattage delivers about half that wattage at 6-volts. I've been able to run 12-volt 50 or 60 amp panels with these 6-volt charge controllers. My Orions consume a lot more energy than your Spartans because they transmit full resolution images at 900 MHz rather than decimating them and transmitting thumbnails using the cell system. These large panels essentially keep my panels running until the batteries wear out which is 2 to 3 years.
The same general principles apply regardless of your power load. Here are some points to consider:
Battery size - Sulfation significantly reduces the life of an SLA battery. This occurs when an SLA battery get to around the 50% discharge level and stays there or lower for a period of time. You want to pick a battery large enough that given your load, it won't discharge this far before being recharged. The actual size depends on your load (pictures per day and amount of power required to take and transmit them), the amount of sunlight your solar panel gets each day on average, the size of your solar panel, and the efficiency of the charge controller. The battery needs to be large enough to account for several days of no sun during stormy periods which depend on your location. The average amount of sun also depends on that. There are sites on the internet where you can estimate you hours of sun per day per month based on zip code. This assumes full sun and no vegetation blockage.
Charge controller - Both PWM and MPPT controllers work well, but PWM are much less expensive. Don't try to charge the batteries directly from the panel. When charging SLA batteries you either need to measure the amount of discharge and then charge it at a fixed voltage for a fixed time period or you use a smart charger that essentially reads the battery and adjusts the voltage as needed to charge but not over or under charge the battery. A solar panel charge controller acts like a smart charger in that sense. Without it, the amount of voltage will vary as the amount of sun your panel gets changes.
I found that with SLA batteries that don't hit the 50% point, the life span is 1 to 3 years. When I have insufficient charging capacity and don't swap them for recharge before they hit 50%, the lifespan can be reduced to 1 month to 12 months.
Thanks,
Jack
