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Old 12-06-2022, 02:46 PM   #1
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Suggestions for using "wasted" solar power?

Looking for suggestions...

How would you use ~150-250w of power for 8-10hrs per day so it's not just "wasted" while RV is in storage?

I've got multiple RVs (Class C) and they each have 500w of solar panels, and 200AH of lead batteries. Most of the time, especially in the off-season, they are just sitting in uncovered storage (getting plenty of sunlight year-round). While in storage, the solar is on and the batteries are easily maintained at 100% by the solar (my RV standby draw with everything "off" is only about 0.3amps). The output from the solar charge controller goes to my batteries and a 2000w PSW inverter (which is always off unless needed while camping as it draws ~2amps in standby when on). The solar charge controller also has terminals for a load (pos/neg) such that the solar charge controller could power something else (in addition to maintaining the coach batteries) while it is collecting sunlight.

In order to maintain the coach batteries at 100% it probably only uses ~20w worth of the 500w of solar. Of course we all know it is next to impossible to actually get 500w out of 500w worth of solar panels, especially in the off-season. But certainly my 500w worth of panels must be generating 200-350w worth of power during off-season sunlight hours (I live in CA so most days even in winter are sunny).

It got me to thinking the other day... It sure would be nice if that "extra" solar power (not battery power) could be actually DOING something instead of just holding the batteries fully charged WHILE IN STORAGE. There is a load terminal (pos/neg) coming off the solar charge controller and I'm thinking about getting an inexpensive 300w inverter to connect to it. My understanding is it would only have power when it is coming from the solar panels, and NOT getting power from the batteries. So it is a way to harvest/use this "extra" solar power from my panels for probably 8-10hrs per day. The question then becomes, "What to do with this power?"

The RVs are not stored near my home, so there is no way to use the power on my home.

A couple ideas that come to mind, but just not sure if they are needed/worthwhile...

- Power a circulating fan. This would move air around in the RV to hopefully keep things fresh and dry. Not sure it is needed though (I haven't had any problems with smells, mold).
- Power a humidifier. This might help to keep moisture down inside the RV. I haven't had a problem with this, but seems like it couldn't hurt.
- Power a couple Ultrasonic pest (mice/rat/squirrel) plug-in repellents. I haven't had an issue with mice/rats/squirrel, but prevention is always a good idea. I did have one mouse about 3 years ago. Thankfully, there are a few outdoor cats near where I store my RVs.

Any suggestions on how you would use ~150-250w of power for 8-10hrs per day so it's not just "wasted"? Thought some of you might have some creative ideas.

Thanks!
Chris
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Old 12-06-2022, 04:41 PM   #2
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Suggestions for using "wasted" solar power?

I would run a dehumidifier, i have this one off Amazon and even though it runs off 120v, the unit itself runs on 12v @ 6 amps, just cut the cord before the inline power supply and wire to your 12v or put a cigarette lighter plug on it. Down here on TX gulf coast I have to empty once a week

https://www.amazon.com/Ivation-IVADM..._rpt_ba_s_1_sc
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Old 12-06-2022, 04:58 PM   #3
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Be sure that what ever " extra " power you draw does not let the batteries discharge.

How would you regulate that ?
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Old 12-06-2022, 07:10 PM   #4
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Suggestions for using "wasted" solar power?

Quote:
Originally Posted by twinboat View Post
Be sure that what ever " extra " power you draw does not let the batteries discharge.

How would you regulate that ?


He’s going to use the load output from solar ctlr, he says it will only run off the solar not batteries
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Old 12-06-2022, 07:52 PM   #5
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Security lighting and dedicated battery.
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Old 12-06-2022, 09:13 PM   #6
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Security lighting and dedicated battery.

That's a good idea! (adding security lighting) I don't know that I'd want to add a dedicated battery/etc for this. But your idea reminded me that at my HOUSE I recently added some wireless solar motion sensor lighting units around my house. Makes sense that I should add some around the RVs in the storage yard. Something like these:


https://www.amazon.com/AmeriTop-Wire.../dp/B07XLF6QHV


If someone enters or gets near my RVs, then they will get lit up with these lights. Enough to scare them off? Who knows...but couldn't hurt.



-Chris
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Old 12-06-2022, 11:10 PM   #7
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Some fans can help keep things fresher particularly in bedroom or areas with a lot of carpet and fabrics. Just having an inverter idle 24/7 will use up watts not to mention a dehumidifier . it would probably have to be on daily /weekly timer. What will be the temps during storage, will water freeze in dehumidifier.
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Old 12-07-2022, 12:18 AM   #8
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Some fans can help keep things fresher particularly in bedroom or areas with a lot of carpet and fabrics. Just having an inverter idle 24/7 will use up watts not to mention a dehumidifier . it would probably have to be on daily /weekly timer. What will be the temps during storage, will water freeze in dehumidifier.

I believe a small 300w inverter will only have a small power standby draw, but that doesn't matter as it would be connected to the LOAD port of the solar charge controller. That means, correct me if I am wrong, the 300w inverter will only be powered if the solar is providing the power (which means I don't need to worry about any power draw from the inverter on the house batteries).



The coldest the temps get in winter is about 30*F as a nighttime low.


-Chris
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Old 12-07-2022, 08:54 AM   #9
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Wasted Solar

Quote:
Originally Posted by SJ-Chris View Post
Looking for suggestions...

How would you use ~150-250w of power for 8-10hrs per day so it's not just "wasted" while RV is in storage?

I've got multiple RVs (Class C) and they each have 500w of solar panels, and 200AH of lead batteries. Most of the time, especially in the off-season, they are just sitting in uncovered storage (getting plenty of sunlight year-round). While in storage, the solar is on and the batteries are easily maintained at 100% by the solar (my RV standby draw with everything "off" is only about 0.3amps). The output from the solar charge controller goes to my batteries and a 2000w PSW inverter (which is always off unless needed while camping as it draws ~2amps in standby when on). The solar charge controller also has terminals for a load (pos/neg) such that the solar charge controller could power something else (in addition to maintaining the coach batteries) while it is collecting sunlight.

In order to maintain the coach batteries at 100% it probably only uses ~20w worth of the 500w of solar. Of course we all know it is next to impossible to actually get 500w out of 500w worth of solar panels, especially in the off-season. But certainly my 500w worth of panels must be generating 200-350w worth of power during off-season sunlight hours (I live in CA so most days even in winter are sunny).

It got me to thinking the other day... It sure would be nice if that "extra" solar power (not battery power) could be actually DOING something instead of just holding the batteries fully charged WHILE IN STORAGE. There is a load terminal (pos/neg) coming off the solar charge controller and I'm thinking about getting an inexpensive 300w inverter to connect to it. My understanding is it would only have power when it is coming from the solar panels, and NOT getting power from the batteries. So it is a way to harvest/use this "extra" solar power from my panels for probably 8-10hrs per day. The question then becomes, "What to do with this power?"

The RVs are not stored near my home, so there is no way to use the power on my home.

A couple ideas that come to mind, but just not sure if they are needed/worthwhile...

- Power a circulating fan. This would move air around in the RV to hopefully keep things fresh and dry. Not sure it is needed though (I haven't had any problems with smells, mold).
- Power a humidifier. This might help to keep moisture down inside the RV. I haven't had a problem with this, but seems like it couldn't hurt.
- Power a couple Ultrasonic pest (mice/rat/squirrel) plug-in repellents. I haven't had an issue with mice/rats/squirrel, but prevention is always a good idea. I did have one mouse about 3 years ago. Thankfully, there are a few outdoor cats near where I store my RVs.

Any suggestions on how you would use ~150-250w of power for 8-10hrs per day so it's not just "wasted"? Thought some of you might have some creative ideas.

Thanks!
Chris
Hi Chris, there are two methods that are very practical:

1) The beauty of the absorption fridge, it will run off of 120VAC or LP Gas, and it will automatically switch between the two. We made a controller that will turn the dedicated inverter for the fridge on, then test the solar output to see if there is enough amperage and voltage from the battery. This is our custom design that resides within our v5.11 controller.

2) If you have a residential fridge, then power the electric part of your hot water heater. Water is one of the best ways to store energy because of H2O heat capacity.

To answer another persons question on how to regulate the excess solar?
If the batteries are at let's say 13.7V (float), and you turn on a load that is 17A, then check the solar output, if it is 17A, then you are fine. Monitor the two variables. If the batteries go to say 12.8V AND/OR solar output goes below 17A, turn off the inverter that is powering your load. Simple if one is an embedded systems engineer

If there was enough interest, we would make a controller like this.

Happy Holidays
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Old 12-07-2022, 09:14 AM   #10
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What brand of solar controller? The ones I have seen with a “load” output don’t usually do what you expect….i.e. output power only when solar is active.

They instead will switch on the “load” as darkness approaches, and back off when sunlight returns…..a solar lighting type of usage.

Worth verifying before continuing the project
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Old 12-07-2022, 09:17 AM   #11
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Suggestions for using "wasted" solar power?

Since you store offsite, my priority would be powering a cellular hotspot device, so I could check temperature, and have security cameras active.

Another idea would be powering a computer mining cryptocurrency
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Old 12-07-2022, 03:48 PM   #12
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I had a big beautiful post prepared when either the website or my computer had a hick-up and said I needed to login. When this happens, everything is lost, has happened before and is irritating.

I'm going to jump to the punch line of my original post and say I think the OP is overthinking what is needed. The solar panel connection he wants to use won't run a fan, security light, dehumidifier or any other equipment without some extensive intervening electronic equipment to convert the solar power.

I would suggest using all the equipment you already have in the coach. Solar for power, batteries for storage of power and 12V source, and inverter for 120V power. All the things you want to do can be done as long as you understand the amount of power you're asking for compared to the capacity of the batteries and solar panels. No extra cost for additional equipment.

A security light should work off an electric eye and recharge the next day, a fan or dehumidifier, depending on size, could run for a couple hours a day from a timer and recharge for the rest of the day. I think you have all the equipment you need to do what you want, just utilize it properly.
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Old 12-07-2022, 03:55 PM   #13
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Quote:
Originally Posted by Jon_C View Post
He’s going to use the load output from solar ctlr, he says it will only run off the solar not batteries
And if he uses all of the incoming solar from the load side, there will be none to keep ahead of the parasitic loads on the battery.

If the batteries didn't need some solar, he wouldn't need any.
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Old 12-07-2022, 04:31 PM   #14
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Electric fence around the underside to protect your cat converter?

Mike in Colorado
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