I have been using a Sun XTender PVX-340T battery with my solar system. During most days, the solar panel on my roof collects more than enough power to fully charge the battery, and once the sun goes down, the battery supplies power to 2 amps of my outdoor lighting - basically one of my tree beds. The tree bed has three LED spot lights (250mA each @ 12V) and one path light that uses one 11w incandescent bulb (1A @ 12V).
I'm writing this but fear I already know the answer. Since the system was put in, I've had current detection sensors installed on both batteries and the solar panel itself, measuring the amount of current flowing into and out of each battery, and from the panel itself. Only recently did I add a voltage measuring circuit to the VDAC in the garage connected with this setup, and began monitoring the voltage of the main battery I am concerned with, the PVX340T.
I've had the system operating basically on a photocell - when the ambient light level dropped outside below a certain threshold, a relay kicked on, turning on the outside lighting. Once the sun came up the next morning, the relay turned off, and the solar panel & controller took care of restoring charges to both batteries. I do keep mentioning a second battery, but it is not important to this conversation; it is not connected to this load in any shape or form, and the solar charging controller is configured to give 100% charging priority to the PVX-340T, and my measurements with the current sensors seem to confirm this.
We had a week of gloomy weather: Dim, rainy days and dark stormy nights. I was not paying attention, and the system essentially left the load attached to the battery throughout each night. The incandescent bulb in particular, just burned away every last electron that battery had within it.
All of a sudden it occurred to me that this was not good, so I built a voltage monitoring circuit and set up conditions in Venturii to drop the load if the battery voltage reached 10.5 volts, which seems to be the "empty" mark of a 12v battery. Venturii now logs the voltage and current for the battery, but I am finding that it is now dropping below 10.5 volts after only running for about 2 hours whereas before it seemed to last all night without any trouble. Does this mean that my battery is dead? It basically starts rejecting power very early in the day, and dies very quickly at night. Rated as a 34 amp-hour battery, it now seems to be a 4 amp-hour. Can anyone tell me what I already know?
