Will I Need a Battery?

[LarryJ]

My project includes one solar panel, a charge controller, and a 12v submersible water pump. Originally I was planning to run the wires from the panel directly to the pump, but then I learned about charge controllers, so I ordered one with a load timer. Now I'm wondering if I'll need a battery to make the whole thing work.

[bob-n]

You haven't told us about your expectations for this pump or details on what you bought. But in general, charge controllers are meant to charge batteries, not directly run the load.

[LarryJ]

You haven't told us about your expectations for this pump or details on what you bought. But in general, charge controllers are meant to charge batteries, not directly run the load.

The question isn't about expectations for the pump, it's about circuitry. Let me rephrase. Will electricity flow from the panel through the charge controller to the load if a battery isn't attached. Does the absence of a battery create an open circuit. I purchased an, M10A LCD Solar Charge Controller Battery Regulator 12V/24V Auto Switch Timer.http://www.ebay.com/itm/402312718565

[Mike90250]

The absence of a battery usually means the charge controller is unable to work and will often be damaged without a battery to power itself to regulate the PV panel.

[Mike90250]

Most instructions for charge controllers begin with:
Always connect the battery before connecting the Solar Panel. ( after the 3 pages of when to where a hard hat and using insulated wire cutters )

[LarryJ]

The absence of a battery usually means the charge controller is unable to work and will often be damaged without a battery to power itself to regulate the PV panel.

Interesting. Is there no electronic device that could be put between the PV panel and the device drawing the load to ensure the device doesn't overheat or burn out when PV panel is outputting maximum wattage/voltage/amps....so there wouldn't be a need for a battery.

[SunEagle]

Interesting. Is there no electronic device that could be put between the PV panel and the device drawing the load to ensure the device doesn't overheat or burn out when PV panel is outputting maximum wattage/voltage/amps....so there wouldn't be a need for a battery.

The only load that will work wired directly to a pv panel is a DC load that has a voltage and amp rating that comes close but is higher then what the panel can output.

Some of those loads are pumps and fans but they do have DC motors. An AC motor or load requires a DC to AC inverter and an inverter requires a battery to work.

[Mike90250]

A zener diode of the desired voltage will limit the voltage, but wastes a lot of power, so they are seldom used. And again, only for DC loads, an inverter is extremely sensitive to it's DC input voltage, and it's amp consumption varys way too much for a single panel to power it, you would need 5x the panel, to allow for clouds and other solar variations that would be continuously shutting the inverter down.

[PNPmacnab]

Unless you have a bilge pump, many common fountain pumps .are AC with converters built in that can take a wide variety of voltage directly from a panel. It should state this in lit. Yes, there is a device to put between panel and brushed motor called a linear current booster. it is usually cheaper to get a pump with wide voltage range,

[Asterix]

My project includes one solar panel, a charge controller, and a 12v submersible water pump. Originally I was planning to run the wires from the panel directly to the pump, but then I learned about charge controllers, so I ordered one with a load timer. Now I'm wondering if I'll need a battery to make the whole thing work.

It all depends on the size of the solar panel.
You will also need to take into account a number of factors other than the amount of sunlight.

The spec for your 12V submersible pump would be nice to have, for this project, be it a pond pump or some sort of aquaponic/hydroponic application.

You really don't need a charge controller if you only want the pump to work when there is sun, but you do need a suitable pump and panel match. There is no use having a 50W panel if your pump is 50W, conversely there is little point in having a 100W panel for a 10W pump, although it would work fine in sun.

Any motor, no matter which type, always need a higher power than its rated power( usually an average power rating given) to start up. A motor has to overcome its pullout torgue, in other words it has to start its mass turning before it can work, which takes more current (power) to do so. A decent rule of thumb would be 1.5 to 2 times its rated power, but that is in air. A water pump also has the water mass acting as a resistance.

So basically if you have a solar panel rated at 2 to 3 times the rated power of your pump, it should be ok.

The next thing you have to consider is the speed at which the pump will turn, although some DC pumps have an in built regulator, which limits the power. Cheep Chinese pumps never, so the motor speed will vary, depending on what Voltage the solar panel is kicking out at any one time.

One thing about solar in this situation is your not worried about efficiency, however if you want a timed system, then you are talking about charge controllers and deep cycle batteries or lithium cells, all of which must be calculated for the pump and timer system.

I run fountain pumps and hydroponics system which is designed specifically for solar power.

[chrisski]

I think anything designed for solar hydroponics is better than what I looked into, but didn't build, with a voltage regulator or buck board instead of batteries.

Amazon has 8V - 40V tp 13.8 VDC 10 Amp buck converters. This particular buck converter says it can be used for solar. Some of the fine print on other voltage regulators, especially the higher amperage says NOT for solar.

I had thought about using this to run a 1000 GPH pump, 12 VDC, 7 amp bilge pump. It would be part of equipment I hiked in and a buck converter or voltage regulator is much lighter than hiking a battery in. Unfortunately for this project and what I was using it for, a small gas pump was so much more economical and lighter when you thought about hiking two or three fragile solar panels in. Just plugging this cheap bilge pump into a panel, others said it surged in the sunlight, so I'm not sure how long that bilge pump would last.

10 amps is not a lot of power, probably just enough to power the bilge pump and not much more.

It's a shame you can't buy a higher wattage DC regulator designed for solar to take the $1000 battery bank out of the equation for things you'd want to run on DC, but it just does not exist. I've seen a few years ago a company developed one, but seems not to have taken off. So many things can go wrong with that voltage regulator idea.

[LarryJ]

You really don't need a charge controller if you only want the pump to work when there is sun, but you do need a suitable pump and panel match. There is no use having a 50W panel if your pump is 50W, conversely there is little point in having a 100W panel for a 10W pump, although it would work fine in sun.

So basically if you have a solar panel rated at 2 to 3 times the rated power of your pump, it should be ok.

Thanks for all the info. Exactly, I only want the pump to run when the sun's out, and efficiency is not a concern.
The panel is a 100w, 5.5a, 12v. The pump is 12v, 3.8 amp. Don't know about watts. It's manufactured by Whale. Couldn't find specs on their website.

[chrisski]

The pump is about 45 watts. Watts = Volts X amps

[Asterix]

I think anything designed for solar hydroponics is better than what I looked into, but didn't build, with a voltage regulator or buck board instead of batteries.

Amazon has 8V - 40V tp 13.8 VDC 10 Amp buck converters. This particular buck converter says it can be used for solar. Some of the fine print on other voltage regulators, especially the higher amperage says NOT for solar.

I had thought about using this to run a 1000 GPH pump, 12 VDC, 7 amp bilge pump. It would be part of equipment I hiked in and a buck converter or voltage regulator is much lighter than hiking a battery in. Unfortunately for this project and what I was using it for, a small gas pump was so much more economical and lighter when you thought about hiking two or three fragile solar panels in. Just plugging this cheap bilge pump into a panel, others said it surged in the sunlight, so I'm not sure how long that bilge pump would last.

10 amps is not a lot of power, probably just enough to power the bilge pump and not much more.

It's a shame you can't buy a higher wattage DC regulator designed for solar to take the $1000 battery bank out of the equation for things you'd want to run on DC, but it just does not exist. I've seen a few years ago a company developed one, but seems not to have taken off. So many things can go wrong with that voltage regulator idea.

I would just use 18650 batteries with suitable charge controllers for the battery bank. Not that much weight compared to lead acid and could be carried to wherever you want. I wouldn't bother with Voltage regulators so much these days as they are power hungry, a buck converter is far more efficient.

I am surprised you cannot find a higher power DC regulator, maybe you are not looking for the correct thing.

A charge controller is a DC regulator, designed to give you a Voltage out which although may vary a little does work well. My Renogy mppt can take a large Voltage in and produces a regulated Voltage out. You don't have to have a large battery, In fact it can be pocket sized if all your intending to do is to use it during daylight.

[Asterix]

Thanks for all the info. Exactly, I only want the pump to run when the sun's out, and efficiency is not a concern.
The panel is a 100w, 5.5a, 12v. The pump is 12v, 3.8 amp. Don't know about watts. It's manufactured by Whale. Couldn't find specs on their website.

Actually your panel is not 12V, its more like 18.18V to give you a 100W output. As soon as you connect a load the Voltage will of course drop,ergo your Wattage goes down.
Just remember the Voltage and current on all but the newer panels state: Open load Voltage and short circuit current.
With a 40W pump it may work ok on sunny days, its a case of try it out, however if you have a meter, then use a battery and check real world statistics for the pump. Then you will know if the panel is suitable.

40W is a large pump with high flow rate, so it may be worth checking that you need a pump of that size.