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SJ-Chris's avatar
SJ-Chris
Explorer II
Dec 06, 2022

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"?

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
  • Cptnvideo's avatar
    Cptnvideo
    Nomad
    Dec 06, 2022
    Cheap 300 watt inverters likely have an output of modified sine wave. And that might not power a fan. Not sure, but I think cheap fans have pure inductance motors that won't work with modified sine waves.
    A different application since we live in our RV full time. But I sometimes turn on the electric side of the water heater when we boondock and the solar has fully charged the batteries - just to use some of that "wasted" solar power. I have tried to think of ways to use excess solar energy and I have mostly come up blank.
    BTW, I like the idea of plug in pest controls. Also, I don't know why you want to add a 2nd inverter - just turn your existing one on but turn off any high draw items.
  • MEXICOWANDERER's avatar
    MEXICOWANDERER
    Explorer
    Dec 07, 2022
    I powered an indoor garden set up on a dining room table. Cherry tomatoes, radishes and dill. I use a power supply 50 watt UV LED chip.
  • SJ-Chris's avatar
    SJ-Chris
    Explorer II
    Dec 07, 2022
    Cptnvideo wrote:
    I don't know why you want to add a 2nd inverter - just turn your existing one on but turn off any high draw items.


    There are a few reasons....

    As mentioned, this is for when the RVs are in STORAGE. The 2000w PSW inverter has a standby draw (...with NOTHING connected to it) of over 2 amps. That means 24+ amp hours per day that would be used by the 2000w inverter doing nothing, and the solar panels would need to put that back into the batteries each day. That's ~12% of the battery capacity and I wouldn't want the batteries discharging/charging back and forth EVERY day.

    I don't want to use the BATTERIES. I want to use the excess solar capacity. The solar charge controller has a "Load" output/connection. This is separate from the output that goes to the coach batteries. My understanding is that this "Load" output will draw ONLY from the solar charge controller (power from the solar) and NOT from the batteries. So, when the sun is shining and there is excess power coming from the solar panels, then the extra 300w inverter will have power and whatever is plugged in will have power. Then, when the sun goes down the 300w inverter will power off. It is this power I am trying to take advantage of.

    -Chris
  • pianotuna's avatar
    pianotuna
    Nomad III
    Dec 07, 2022
    SJ-Chris wrote:
    Looking for suggestions...

    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,

    The circulating fan would equalize temperatures inside the RV. I think that might be of use.

    I'm sure you meant a dehumidifier not a humidifier. Unfortunately dehumidifiers that actually work generally draw 1200 to 1500 watts. More than you have "spare".

    The ultrasonic pest units draw milliamps. Less than you have "spare". It may also be the reason they are not effective.
  • SJ-Chris's avatar
    SJ-Chris
    Explorer II
    Dec 07, 2022
    pianotuna wrote:


    Hi Chris,

    The circulating fan would equalize temperatures inside the RV. I think that might be of use.

    I'm sure you meant a dehumidifier not a humidifier. Unfortunately dehumidifiers that actually work generally draw 1200 to 1500 watts. More than you have "spare".

    The ultrasonic pest units draw milliamps. Less than you have "spare". It may also be the reason they are not effective.


    Yes, I meant dehumidifier.

    -Chris
  • valhalla360's avatar
    valhalla360
    Navigator
    Dec 07, 2022
    One issue is if you isolate the consumption away from the batteries, you don't have 8-10hrs of power. Output will start at a very minimal output mid morning, peak somewhere around noon and then fall off as afternoon progresses.

    So any use has to be able to handle a wide range of wattages. A cheap 12v fan would be doable but other than saying you used more of your solar generation, not sure what benefit it really would provide. A lot of small 12v fans use less than 1/2 amp, so probably simpler to just run it thru the battery bank.

    If you had them at home or your own lot (with existing grid power for an office or something), you could probably set up a quick connect system to back feed into the grid (ie: net metering), similar to a residential solar system. Obviously, needs to be done to code but say 6 rigs at 500w would be equivalent to a 3000w solar array and would likely generate somewhere around 12-15kwh per day. Assuming $0.25/kwh California rates, that would reduce your electric bill by around $90-100/month. But if they are just in a storage yard, that probably won't work.
  • dalej's avatar
    dalej
    Explorer
    Dec 07, 2022
    I have been using a dehumidifier. Its set up on a timer to only come on during the maximum solar time.
  • Chum_lee's avatar
    Chum_lee
    Explorer
    Dec 07, 2022
    An ozone generator/air filter/fan can discourage pests (rodents, insects, etc.) and minimize mold from growing inside your MH. It will help reduce that musty smell that forms after several months of storage. It won't kill mold once formed, but, it will reduce the associated smell. Many smaller ozone units have well under 100 watt electrical load. People have reported that ozone can cause certain plastics like PVC, ABS, vinyl, etc., to become brittle and degrade prematurely. Delicate electronics can also be adversely effected. Read any warning labels before you decide.

    Chum lee
  • Grit_dog's avatar
    Grit_dog
    Navigator
    Dec 07, 2022
    I’d say you’re trying too hard to find a solution to nothing.
    The libby EVers on this forum would tell you how you could sell it back to the utility company.
    Just don’t ask them to run the numbers as to whether it’s feasible….lol.

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