Having issues running the load in my solar system

JHarb14 · August 2017

Hello, I had just recently bought a small solar panel system so that I can learn more about solar, and to also run my small pond water pump. I got a small solar panel and a sort of cheap charge controller. I have 2 12 volt batteries that i was eventually going to wire up in either series or parallel. I have had these batteries sitting for a while, but both are in good shape.
The issue i am having is that when i hook up the solar panel, a battery and the load, the charge controller says the solar panel is charging the battery, but the load does not work. I have had it out in the sun for the past few days, and nothing has changed. The load light is on, but the arrow that means it is being powered is off. How can i fix this?

mike95490 · August 2017

Try connecting the Load to the battery, and not the terminals on the controller. Many controllers don't have very beefy outputs, and can't run a large load.

littleharbor2 · August 2017

Most inexpensive controllers with load control terminals are intended to power lighting at night They are configurable for different time durations and some have a 24 hour setting. The key here is for lighting they are triggered by darkness. If you want to use this feature during daylight hours you need to set it to do 24 hour output. One benefit to using the load connections on the controller is that the controller will shut down the load if the battery becomes dangerously discharged. These load terminals are really not designed to run any substantial loads.
As Mike95490 said, connect directly to the battery.

JHarb14 · August 2017

So for the past few days i had figured out why the load was not working; the pump was faulty. The issue i'm having now is the load won't stay on the whole time. I had set it to 24 hour mode, but after a few hours it shuts off. On the screen of the charge controller, the battery blinks, and if i want to turn it on again i have to hold down 2 buttons, then the battery bars come on again and the load works. This is annoying and i would just like the load to stay on all the time. The battery never gets below 11 volts. Thanks

littleharbor2 · August 2017

Sounds like you have battery problems. How old is your battery? Did you get it new? You mentioned they were sitting around a while, not good for flooded batteries especially. Were they fully charged before you hooked them up/ Have they ever been equalized? You should try to never go below about 12 volts.

Estragon · August 2017

11 volts is almost completely discharged. Any significant load at that state of charge is likely taking voltage below the controller's low voltage cut-off. The controller disconnects the load to protect itself from the low voltage, and to prevent permanent damage to the battery.

My guess is pressing the buttons resets the controller, which sees a voltage with no load above cut-off and starts working, which sucks voltage down again, and so on.

I suggest disconnecting the load, and fully charging the battery ASAP. Fully charged, the battery should stay at 12.8v if left sitting overnight with no charging source. While charging, battery voltage should get up to around 14.5v and stay there for 2-3 hours.

It would help if you could list the running current of the pump, the wattage of panel charging, and battery type and capacity.

JHarb14 · August 2017

I fully charged the battery last night and it is now at 12.8 volts. The solar panel is 20 watts. The power consumption is 5.0W@12V ~ 21.5W@24V (currently running 12v, but would like to run 24v if possible to get more power through my waterfall) and the battery is a 12v 7ah battery. It still shuts off during the night time. Do i need a larger battery?

Estragon · August 2017

Probably. 12v times 7ah is 84 watt-hours, but you generally can't use 100% of capacity. Using more than about 50% is hard on a true deep-cycle battery, which yours may not be. It quite likely has some degree of sulfation, so its functional capacity is likely lower than 7ah.

Assuming the 5w@12v load is correct (did you measure it, or is that a rating?), you would be under 50% charge after about 9hrs. My guess is the 5w is a minimum and the actual draw is higher, so 9hrs is probably optimistic.

The 20w panel, might produce about 1a charging current. Most locations get something like 4-5hrs of average daily full sun equivalent - less if the panel is not correctly angled or has any shade, so it would likely be borderline able to charge the battery some days, and not able to on others. It would not likely be able to catch up on charging the battery from a very low state of charge.

For your higher powered waterfall - roughly 1a@24v for a couple of cloudy days would be something like 48ah. You would want twice that to avoid drawing down below 50%, so roughly 100ah@24v. To recharge that you'd want enough panel to give you around 10a@28v so a couple of 100ish watt 12v panels in series, or a 250ish watt 24v panel.

fratermus · August 2017

littleharbor2 said:

One benefit to using the load connections on the controller is that the controller will shut down the load if the battery becomes dangerously discharged. These load terminals are really not designed to run any substantial loads.

For the OP's benefit: running a relay off the LOAD output would preserve the low voltage disconnect function while allowing higher current loads.

mcgivor · August 2017

fratermus said:

littleharbor2 said:

One benefit to using the load connections on the controller is that the controller will shut down the load if the battery becomes dangerously discharged. These load terminals are really not designed to run any substantial loads.
For the OP's benefit: running a relay off the LOAD output would preserve the low voltage disconnect function while allowing higher current loads.

Valid point, preserving low voltage cutout protection whilst allowing larger loads, perhaps installing a diode across the coil would be a useful addition to snub the collapsing reverse EMF from damaging the controller when the relay drops. Just a thought.

Having issues running the load in my solar system

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