Adding more panels to RV?

[Isaac-1]

Thanks for the replies, sorry about being a little slow responding, been busy the last week with one thing after another breaking around here. Since starting this thread my likely timeline to do the upgrade has been pushed back a bit due to other upgrades I want to do to the RV first. I do tend to agree that the current setup is well sized to the current battery bank size and I will likely try to time my upgrade with the need to replace the current pair of batteries which I hope will last another year or so given the continuing drop in lithium battery costs.

As to the reason that I desire more solar power, my wife has a health condition where she needs to avoid getting overheated, and I would like the ability to run an air conditioner for at least a couple of hours at a time off of the battery system. The motorhome is equipped with a 13,500 btu roof top air conditioner / heat pump, but I also own a 9,000 btu water cooled marine air conditioner (that has been sitting in my shed for a few years), which I intend to add to the motorhome connected to a radiator mounted under the coach to dump the heat. This 9,000 btu air conditioner draws about 890 watts while operating (not counting whatever power the radiator fan will need), which I hope will allow me to keep the motorhome somewhat cool during the day without running the generator when stopped at tourist attractions, etc. while traveling. Therefore any solar capacity I can add towards that circa 1000 watt air conditioning load will help extend battery run time, and of course the highest need for air conditioning will also be during periods of bright sunlight.

[SunEagle]

Actually I currently have the solar powered food truck parked in my driveway in the cold dark long winter months of Western NY State and I am exclusively using this to power my off the grid home! So the "assignment" of the system now for the Food Truck is substantially and totally different from its original mission. Yet it works perfectly for BOTH applications!!! Amazing stuff this solar PV / battery based systems.

Out of curiosity what was your investment cost for the solar/battery system on that truck and what is the daily watt hour usage?

[Zoar]

I'm thinking along the same lines as White Wolf. With only a pair of batteries, I don't think you want to go with any more solar wattage as the batteries wouldn't want that much peak current anyway. Do you need more battery power to handle your usage? If not, then it seems like you're sitting pretty with 400 watts of solar matched to a pair of deep cycle batteries.

I love the solar food truck, there is an example of usage that I could see warranting all that square footage of panels since your peak power needs probably coincide with peak solar harvest times. So you need excess solar to even get any recharging to happen.

Actually I currently have the solar powered food truck parked in my driveway in the cold dark long winter months of Western NY State and I am exclusively using this to power my off the grid home! So the "assignment" of the system now for the Food Truck is substantially and totally different from its original mission. Yet it works perfectly for BOTH applications!!! Amazing stuff this solar PV / battery based systems.

[ewarnerusa]

I'm thinking along the same lines as White Wolf. With only a pair of batteries, I don't think you want to go with any more solar wattage as the batteries wouldn't want that much peak current anyway. Do you need more battery power to handle your usage? If not, then it seems like you're sitting pretty with 400 watts of solar matched to a pair of deep cycle batteries.

I love the solar food truck, there is an example of usage that I could see warranting all that square footage of panels since your peak power needs probably coincide with peak solar harvest times. So you need excess solar to even get any recharging to happen.

[J.P.M.]

I have some experience with Mobile Solar/ Battery Based systems.

I have done two.

The first was good and the second has been VERY VERY successful and VERY good.

First let me state a few things I recommend as baseline thinking:
1) I installed RAILS on the roof of my food truck. The same rails used for PV arrays used in residential market. They work better than anything else. It is also easy to screw and glue/seal the penetrations.
2) Use as large a PV system as possible, and use large panels, not the 100 watter little guys
3) Use a Lithium battery bank with as much storage as you can afford
4) Use quality, robust charge controllers ( I swear by OUTBACK)
5) If you cannot get enough panels on your roof consider an "awning" that can raise up when you park and fold flat against the side when you drive. (it is always picking up sun power by the way as long as it is day time and even when the panels are folded flat against the sides when driving especially when the sun is hitting it straight on or substantially so)


Pi Truck Solar Awning.jpgPi Truck 1c.jpg
Pi Truck Photo Two Goats Summer.jpgPi Truck 2016A.jpg

The lower left photo - close to south end of Seneca or Cayuga lake ?

[Zoar]

It has been almost a month, no one has any thoughts on this?

I have some experience with Mobile Solar/ Battery Based systems.

I have done two.

The first was good and the second has been VERY VERY successful and VERY good.

First let me state a few things I recommend as baseline thinking:
1) I installed RAILS on the roof of my food truck. The same rails used for PV arrays used in residential market. They work better than anything else. It is also easy to screw and glue/seal the penetrations.
2) Use as large a PV system as possible, and use large panels, not the 100 watter little guys
3) Use a Lithium battery bank with as much storage as you can afford
4) Use quality, robust charge controllers ( I swear by OUTBACK)
5) If you cannot get enough panels on your roof consider an "awning" that can raise up when you park and fold flat against the side when you drive. (it is always picking up sun power by the way as long as it is day time and even when the panels are folded flat against the sides when driving especially when the sun is hitting it straight on or substantially so)


Pi Truck Solar Awning.jpgPi Truck 1c.jpg
Pi Truck Photo Two Goats Summer.jpgPi Truck 2016A.jpg

[Wy_White_Wolf]

The missing part of the equation is the size of the batteries.

If the batteries are of the generic 75-100AH design then I would not recommend increasing the solar array until you can replace them. 400 watt array with a PWM controller is about the max limit you want to have.

If they are a larger battery in the 150-200 AH range then either of your options is possible and workable.

If you can find panels that match the existing panels I'd only look at adding 2 more and replacing the PWM with an MPPT controller. It's greater efficiency will offset the smaller array.

I wouldn't add a second charge controller unless it's the same as the present one so as to minimize problems between them.

WWW

[Isaac-1]

It has been almost a month, no one has any thoughts on this?

[Isaac-1]

First I would like to say that I have some experience with 12V battery solar installs in the 20-125 watt range over the last 10-15 years. (boats, remote wifi relays, remote security cameras, etc.)

I bought a used motorhome last month where the previous owner had started upgrading the electrical system, so I have been handed a partially complete project, which I intend to continue and perhaps alter a bit.

First let me describe my current situation which is basically as I bought it, but the addition of installing a 2000 watt pure sine wave inverter (Xantrex ProWatt SW which is a stand alone inverter along with its associated external 15 amp transfer switch and remote panel), Not my first pick of the way to do things, but the inverter came with the motorhome, just not installed.

Back to the current setup, I have 4, 100 watt panels for a total of 400 watts worth of panels on the roof feeding into a Schiender C35 (35 amp which seems kind of marginal to me) PWM charge controller, which seems to be a nice variable set point PWM controller, which charges a pair of 12V deep cycle batteries.

My goal is to aim for 800+ watts worth of panels on the roof if possible while mounting around various obstacles (vents, etc.), at a minimum I would like to get up to 600 watts worth of panels I would also like to switch to Lithium batteries (probably LiFePO4) when the current deep cells need to be replaced in a couple of years (they were installed in 2014). Ideally I would like to do this in stages as I get time and money for this project.

The catch is I want to do this without removing the existing 4 100 watt panels, as the motorhome has an Aluminum roof and I want to minimize the number of roof penetrations and being an Aluminum roof it is hard to patch the screw holes from the existing mounting brackets.

Now here is the question, what is the best way to achieve this, I know mixing and matching panels is usually a bad idea?

Some thoughts I have so far:

option A,
Add 4 more panels to the roof and wire them series / parallel with the existing panels and feed them into a MPPT controller so that each old panel would be wired in series with 1 new panel then let the MPPT controller handle the voltage reduction.

option B
Keep everything as is, and add separate circuit with the new panels and another charge controller, then adjust the voltage on the current charge controller so that it only operates for the bulk charge range, then have the new panels and their controller handle more bulk charging in parallel then let the new panels handle topping charge until I convert to Lithium. I am still researching al the special lithium charge controller issues, with the hope that more and better options will be on the market in a year or three.

option C ??????


thanks for your thoughts