Solar panel controller power dump

[Tammany]

Does anyone run anything off the solar controller power dump at all? I've got an extensive array of panels totalling nearly 150w to fit this year and was wondering if it's worth connecting anything to it as their is going to be quite a bit of excess charge most of the time. The only thing I can think of that might be of use is a fan?

 

[VicS]

Does anyone run anything off the solar controller power dump at all? I've got an extensive array of panels totalling nearly 150w to fit this year and was wondering if it's worth connecting anything to it as their is going to be quite a bit of excess charge most of the time. The only thing I can think of that might be of use is a fan?

Is it a Power dump. The load terminals may have one of several functions

To switch off a load when the battery volts falls to blow a set figure ( that can be useful for say a fridge ...... or garden shed )

To turn on lights when its dark for some predetermined period. Thats useful for street lights!

Some can be programmed for various functions.

What solar controller are we talking about

 

[lpdsn]

It's not a power dump in the sense of it being used to dump excess current from the solar panels. I can say this with confidence having made that erroneous assumption myself when I first started looking at solar power.

To get back to the question, I don't use it and I don't think many people do on boats. It's more for if you have a more simple arrangement with a standalone panel, battery and load, such as in a garden shed, where you want to use the controller to turn off the battery from the load when the battery voltage falls too far.

 

[elenya]

Hi

As stated it is a load rather tah dump. We run our domestic power through the load as this will then switch that load iff if battery voltage falls too low. Solar power requires no dumping of excess power. We run 600w of panels and have no power dump.

 

[FirstAway]

On my previous boat I wanted to do the same thing, and in the end set up a computer fan controlled by a light sensor, when the sun shone the fan worked. Maybe not the most elegant solution but it worked for me, keeping the boat noticeably drier.

Bob

 

[Tammany]

Instructions are a bit vague but it says it routes excess power to the terminals when the batteries don't need charging. Nothing connected to it at the moment though but vent fan seems best bet

 

[Hadenough]

That is my understanding ie; when the batteries are "full" instead of dumping the charge the load terminals become live. I have a vague plan to wire the fridge through a relay to use this surplus charge. Trouble is I'm not clever enough and my expert is continually busy.

 

[RichardS]

That is my understanding ie; when the batteries are "full" instead of dumping the charge the load terminals become live. I have a vague plan to wire the fridge through a relay to use this surplus charge. Trouble is I'm not clever enough and my expert is continually busy.

You might as well just run the fridge from the batteries as a fridge needs to be connected to the power source continuously. The power being used by the fridge will be fed back into the batteries by the solar panel. If there is any "excess" power then it doesn't matter, as long as the fridge is getting what it needs,

Richard

 

[VicS]

You might as well just run the fridge from the batteries as a fridge needs to be connected to the power source continuously. The power being used by the fridge will be fed back into the batteries by the solar panel. If there is any "excess" power then it doesn't matter, as long as the fridge is getting what it needs,

Richard

The trouble is at night when the solar panels are not producing any power.

If the load terminals are "programmed " to cut the load off when the battery volts falls to a set value then the fridge can be let running into the hours of darkness but the solar controller will protect the battery from excessively deep discharge by switching it off

The fridge will restart when the battery voltage is restored to some slightly higher set value.

I did ask the OP what solar charger he is using but he has not said so impossible to know exactly how these load terminals are programmed.

Many of the cheap far eastern MPPT controllers are designed for street light control. If you had one of those it would run the fridge for some predetermined period after dark!

 

[RichardS]

Post Deleted!

Was indeed talking nonsense as the controller that I ultimately bought does not have any "load" terminals ..... which is, presumably, why I have never used them. :ambivalence:

Richard

 

[Hadenough]

So what about during a sunny day when, say at 13.00 the controller decides that the batteries are full and diverts the charge to the output (I am assuming that this is what happens). If the fridge is drawing off the batteries the controller will cut in/out to compensate for the draw from the fridge. If the fridge was able to draw off the "excess charge" during this time then all of the solar charge would go on/ off to the batteries. So when the sun dies at say 16/17.00 and there was no "excess" charge the draw from the fridge would be starting from a higher stored amperage? Just asking?

 

[DavidGrieves]

I have a PWM solar controller, the type that is designed to control street lighting. It can be programmed to turn on a device when it gets dark, I can choose how long it stays on after dark or have it on constant.
I have mine connected to a navtex on constant, to keep the internal navtex battery charged.
I also thought about connecting it to an anchor light so it came on at dusk.

 

[RichardS]

So what about during a sunny day when, say at 13.00 the controller decides that the batteries are full and diverts the charge to the output (I am assuming that this is what happens). If the fridge is drawing off the batteries the controller will cut in/out to compensate for the draw from the fridge. If the fridge was able to draw off the "excess charge" during this time then all of the solar charge would go on/ off to the batteries. So when the sun dies at say 16/17.00 and there was no "excess" charge the draw from the fridge would be starting from a higher stored amperage? Just asking?

But that only works if, after dark when the panel stops producing, the battery power is sent back to the controller and down the load connection .... and that's not how it works I don't think but I might be wrong.

If you had some kind of changeover switch in a dual connection between the battery and the load terminal then that might work provided you remember to switch it over. Perhaps the switch could be automated with a gizmo of some kind?

Richard

 

[VicS]

I agree that the problem is at night which is why I thought that it was no good connecting the fridge to the load terminals. I think that my PWM controller just shuts off the "load" connection once night falls and there is no surplus power to be used (i.e. power still being supplied which is surplus once the batteries are fully charged)

Having said that, I've never actually used the load terminals on my controller so I could be talking nonsense.

Richard

MY understanding is that the load terminals allow the device connected to them to continue operating after dark , drawing power obviously from the battery , until the volts fall to some specified level. Then it shuts the power off to prevent over discharging the battery.

As I said though different controllers do different things. There is at least one more up market one which allows the operation of the load terminals to be programmed ( using a computer) to do almost anything you want.

I dont know what controller you have so cannot comment on its operation. Similarly dont know what controller the OP has ! You may be right in thinking yours will switch the load off once night falls but its not one I've previously come across

Some of the instructions, esp for the cheap far eastern imports are next ti impossible to understand so that does not help either

 

[VicS]

So what about during a sunny day when, say at 13.00 the controller decides that the batteries are full and diverts the charge to the output (I am assuming that this is what happens). If the fridge is drawing off the batteries the controller will cut in/out to compensate for the draw from the fridge. If the fridge was able to draw off the "excess charge" during this time then all of the solar charge would go on/ off to the batteries. So when the sun dies at say 16/17.00 and there was no "excess" charge the draw from the fridge would be starting from a higher stored amperage? Just asking?

I don't think you are right about it "diverting" the power to the load terminals. If its not a street light controller power will be available at the load terminals all the while the battery volts are above the cut off value.

If the load consumes more than the solar panel is producing the balance will be drawn from the battery. If the load is less than the solar panel output the balance will go towards charging the battery, if it needs it

 

[PaulRainbow]

Vic has covered a lot of what i'm about to type, but anyway ..................

I have a Victron controller, which is programmable. A lot of controllers are not programmable and will be hard coded to one of the variations. Amongst the possible settings are :

Load terminals permanently off. Self explanatory.

Load terminals permanently live. If all loads are connected to the load terminals the Victron software can monitor solar yield and consumption. With the Victron "Control" gauge or bluetooth dongle you can monitor this and keep a 30 day history.

Conventional or user defined algorithm. Switches off the load terminals off at a given battery voltage and back on at a higher voltage. This could be used to switch the load off at a low voltage, to protect the battery, but that's almost papering over the cracks in most cases, better to fit more batteries/panels or use less power. You could also use this for the fan that someone mentioned, fan comes on at a high voltage, goes off at a lower one, but that seems a bit daft, you fully charge your batteries then use some of the power to run a fan, lowering the battery, which might not get replaced as the Sun could go down as you reach the lower voltage. Using this algorithm for a fridge makes no sense at all.

Another option here could be to connect a relay to switch a mains charger on. When the voltage gets low, switch the charger on, switch it off when fully charged. This might be a better option than my idea of using the sunset option, i'll experiment and see. There is a two minute delay with this option to prevent the software reacting to quickly, such as a heavy load switching on/off.

Streetlight functions. There are a variety of settings here. Such as what to do at Sunset and Sunrise. IE ; become live at sunset and go off at sunrise, or visa versa. Or, at Sunset become live for a fixed time, live until midnight, on until Sunrise. Various possibilities here, i plan to set mine so the load terminals become live until midnight (or sunrise if need be) and connect a relay to the terminals that switches my mains charger on to keep the batteries topped up over night.

I don't consider any of those settings to truly make use of any "surplus" yield. Let's look at a fridge, as this has been mentioned. Let's say we have connected the fridge to the load terminals and set the algorithm to switch the load terminals on at a particular voltage. During the day, the Sun is shining and our preset voltage is reached, so the load terminals become live. The batteries may or may not be fully charged. If they are not fully charged the fridge will be using power that could have gone to the batteries. If they are fully charged the fridge will still be running and the batteries will remain charged. But what if the fridge was connected to the batteries as usual ? If the batteries were not fully charged the fridge will use some of the solar yield, as it would if connected to the load terminals. If the batteries are fully charged the solar yield will run the fridge and keep the batteries charged (if the yield is high enough). So no benefit in connecting the fridge to the load terminals. The downside is the fridge won't run at all if the preset voltage is not reached, in which case, warm beer and rotten food Better to connect the fridge to the batteries and if there is not enough solar yield fit more panels or turn on the mains charger or genny in the evening to top the batteries up.

It's also important to match the panels to the batteries. If you think there will be a significant amount of solar yield that does not get harvested, increase your battery capacity. If you don't get enough yield, add more panels.

My own setup consists of one 110ah engine battery and two 110ah batteries for the domestic bank. The two banks are totally isolated. I have a 60w solar panel on a pole at the pushpit and two 30w panels on the coachroof. The two 30w panels are wired in parallel and then wired in series with the pushpit panel to give 60 @ 24v. This is then fed to the batteries via a Victron MPPT controller. I stayed onboard from April to October and the solar panels almost kept up with my use. Fridge was on 24/7, FM radio on most of the time, lights, some use of the Eberspacher early on, pumped water and some use of nav gear. I used shore power for charging my laptop, some min or power tool use and topping the batteries up in the evening if the battery voltage looked low. Total cost of shore power for 7 months (excluding service charge) was £15.

Since October the solar yield has not been great so i have left the mains charger on 24/7. It doesn't appear to be working overtime. I'll know how much shore power i've used at the end of the month.

I am in the process of increasing the solar panels to 260w and have changed all of the lights to LED.