How many Watts of Solar is enough?

[chessie4905]

Gary, if you are serious about trying solar, you could start with one or two of proper size that will work with future expansion in mind. Install with that in mind so you don't have to remove and relocate existing ones to make room for more. Do the wiring with that in mind also. This is where the recommendations of current users will be beneficial as far as routing the wiring and controller locations. I'm curious also about such things, also mounting, wind resistance, access to other items on roof, and also visual appeal or ugly monstrosity. This way you can get your feet wet. I suppose you could buy some from Harbor Freight to try, although some consider them junk, but I don't know if from actual use of that item or just a general bias against HF. Just some thoughts
BTW, does it hurt to have panels installed and in sun without being connected to anything? Sort of like when getting them first installed.
Also, do they usually have places on them for mounting or is this a personal need to fabricate issue.
Do you wire them like Xmas lights, or run all leads independently to controller.
Do these get wired to inverter in a specific location or how do you connect them to inverter/ generator/ house battery system. Just interested in general idea for now

[windtrader]

I considered the HF route but that is a throwaway and really not such a deal.

Victron MOPPT charge controllers are top notch, starting at 100 bucks for 75v/15amp.
https://www.amazon.com/Victron-BlueSolar-MPPT-Charge-Controller/dp/B00U3MK0CI

Just add a good 280/320 watt panel or two and you are off to the races with a solid foundation you can build on, no throwaway.

Get up on the roof and measure how wide a panel you can place without it being a visual eyesore from on the ground site lines. Some may not find this a concern but my bus is not going to have a bunch of panels hanging out. There should be plenty of room to place a few panels with relative ease.

[Iceni John]

Gary, if you are serious about trying solar, you could start with one or two of proper size that will work with future expansion in mind. Install with that in mind so you don't have to remove and relocate existing ones to make room for more. Do the wiring with that in mind also. This is where the recommendations of current users will be beneficial as far as routing the wiring and controller locations. I'm curious also about such things, also mounting, wind resistance, access to other items on roof, and also visual appeal or ugly monstrosity. This way you can get your feet wet. I suppose you could buy some from Harbor Freight to try, although some consider them junk, but I don't know if from actual use of that item or just a general bias against HF. Just some thoughts
BTW, does it hurt to have panels installed and in sun without being connected to anything? Sort of like when getting them first installed.
Also, do they usually have places on them for mounting or is this a personal need to fabricate issue.
Do you wire them like Xmas lights, or run all leads independently to controller.
Do these get wired to inverter in a specific location or how do you connect them to inverter/ generator/ house battery system. Just interested in general idea for now

1.   Don't waste you money and time with HF's solar panels.   They don't last.   Buy 'real' panels from reputable suppliers.   And don't buy flexible panels either.
2.   Panels don't care whether you're using the power they make, or not.   They won't last longer or shorter whether they're connected or not.
3.   PV panels are just a series of individual cells attached to a substrate with a glass front over them, and the entire shebang is mounted within an aluminum frame for protection.   Some folk directly mount the panels to the bus roof, but you have to careful you don't stress or bend them that way or they will crack.   I've mounted each of my panels inside a separate support frame made from 1.75" 6063 angle, with a half inch space all round in case I need to replace a panel in the future with one that is up to 1" larger.   These support frames are hinged to a walkway between my two roof hatches, and supported on their outside edges by stainless struts that can lift them up to 45 degrees above horizontal for winter insolation.   When down against the roof for travel they are at 21 degrees below horizontal due to Crown's curved roof.
4.   Panels can be wired in series or parallel.   Each panel has an output cable with MC4 connectors, and should be connected to a combiner box that then sends power to the charge controller.   I have my panels in parallel to minimize losses if one panel is shaded, and so the charge controllers are down-converting voltage (and boosting current) by a factor of only 2  -  if MPPT controllers have to buck greater voltage differences their efficiencies drop significantly and they get hotter.
5.   Charge controllers and inverters should be mounted as close to the batteries as possible, but not in the same compartment as them.   Cables should be as short and fat as possible, with correctly-crimped terminals (no hammer crimpers!), and copper busbars can be used wherever possible.

HandyBob has some good thoughts on RV solar systems:  https://handybobsolar.wordpress.com/
The gurus and experts at the Northern Arizona Wind & Sun forum always have sensible words of wisdom:  http://forum.solar-electric.com/

John

[chessie4905]

So they don't need connections to inverter and inverter isn't effected by their output directly to batteries through their controller? Do they or controller cause a drain to batteries if they aren't charging? For example, if coach is sitting inside garage for, say as month.
Thanks for the info so far. I'll check out those sites.

[Iceni John]

So they don't need connections to inverter and inverter isn't effected by their output directly to batteries through their controller? Do they or controller cause a drain to batteries if they aren't charging? For example, if coach is sitting inside garage for, say as month.
Thanks for the info so far. I'll check out those sites.

Solar is just one of several ways to charge batteries, so the inverter is connected to the batteries in the usual way.   Remember, solar is providing power, and the inverter is drawing power.   As the SmartGauge folk state, the inverter and loads are connected to the same location on the batteries as the charger and solar charge controller.   And if the sun isn't shining and the charge controller isn't sending power to the batteries, there won't be any drain from the batteries  -  the CC's output is protected by diodes (as are the solar panels themselves).   However, if the bus is unused for a long time, it's prudent to completely turn off the batteries to avoid phantom loads from slowly draining them, but it's still a good idea to have a small trickle charger on them to always keep them at 100%.

I have a Blue Sea 6006 switch for each battery bank's output (I have two separate house battery banks in parallel) to the inverter and DC load center, but the charge controllers are always connected to the batteries even when those load switches are Off.   I can turn off the PV inputs to the CCs, and the outputs from the CCs to the batteries, by separate Carling Type C circuit breakers.   The CCs and inverter/charger are in the underfloor storage bay, but only a few feet from the batteries themselves that are in their own separate vented compartment;  power is taken through the wall by VTE Power Posts and Power Bushings.   All cables between the batteries and the main DC positive busbar are 2/0, and from the busbar to the inverter is 4/0, with tinned copper lugs circumferentially crimped with a FTZ 94284 crimper tool.

John

[windtrader]

John,

However, if the bus is unused for a long time, it's prudent to completely turn off the batteries to avoid phantom loads from slowly draining them, but it's still a good idea to have a small trickle charger on them to always keep them at 100%.

Is there some issues with using the PV/CC to stay connected to the house bank and keep them topped off? What other options if the bus has no access to AC while stored?

[jcussen]

As had been said, buy as many as you can afford. And as many as you can fit on the roof. I believe solar panels will only go up in price in the future. I can only fit about 1000 watts, wish I could do 3000.

[Iceni John]

John, Is there some issues with using the PV/CC to stay connected to the house bank and keep them topped off? What other options if the bus has no access to AC while stored?

My CCs are always connected to the house batteries even if the batteries' load switches are Off.   I have to turn off the CCs' own circuit breakers to stop the batteries from being charged.

John

[silversport]

I have upgraded from 45 watts (PO) to 500 watts had to change/upgrade, charger and wiring. We will be in Quartzsite this month to see how it works. I do have LP on board.

[Dave5Cs]

Did the solar panels themselves go bad?  From what I have read it is extremely rare to have the panels themselves go bad.  There are panels still running from the 1970s when solar was just getting started.  It seems sort of silly that today's panels have a 25 year performance warranty, but many only have a 12 year warranty against other failures?  Isn't the panel performing at zero percent of original performance if it fails entirely?

I would like to put four 60 cell panels totaling around 1,000 watts on my bus, but they have to be cheap around $100 per panel to make it worth the effort.  The $750 total cost of the system could buy a lot of diesel for my generator.  I don't use the bus enough to make solar really pay off.  The additional four to six hours a day of not hearing the generator run might be worth it although my generator is pretty quiet.

Brian E. Yes the Panels 75% were going bad over time Slowly but surely. They came out twice and told us it was the inverters and that they needed to be replaced which they did for 2500.00 per unit. Turns out we called another company and had them check it all out and it turns out the panels were going brown at the edges and when they tested 50% of the panels were having trouble keeping up. Look at the edges from the frame in and see if they are brown and keep an eye on it and test some to see what they are putting out compared to what they are suppose to. We got new panels and inverters. This system we can monitor on our smart phones or computers and see what they are doing at any time. Part of the cost was covered by the state Solar fund.

[Gary Hatt - Publisher BCM]

Someone in Quartzsite told me yesterday, you should have 1.5x the amount of amps of solar panels than you have in your batteries. Never thought of relating battery storage to the size of the solar panels, but this makes sense, irrespective of what you have for power needs in your coach.  It is all about how many amps you have total in your batteries.  I would like to hear other opinions on this.

[thomasinnv]

Someone in Quartzsite told me yesterday, you should have 1.5x the amount of amps of solar panels than you have in your batteries. Never thought of relating battery storage to the size of the solar panels, but this makes sense, irrespective of what you have for power needs in your coach.  It is all about how many amps you have total in your batteries.  I would like to hear other opinions on this.

Did you mean that the watts of solar should equal 1.5x the amp hour capacity of your battery bank? That would make more sense. Actually, i would say that would be the upper limit so as not to charge above the batteries maximum charging rate capacity on good sunny days or you will drastically reduce thier lifespan. Again, as has been stated before, how much solar you need really depends upon your average power usage, not so much the size of the battery bank. If you have a battery monitor that tracks amp hour usage this would be a great place to start. Monitor your usage over the course of a week and do some math.

Sent from my SM-G930T using Tapatalk

[bobofthenorth]

Someone in Quartzsite told me yesterday, you should have 1.5x the amount of amps of solar panels than you have in your batteries.

As stated that doesn't make sense.  Maybe I could see some equivalency between watts of solar and AH of battery but amps are a current measure, not a power measure.  If you had 1000 AH of batteries for easy figuring then 1500 amps of solar even at 12 volts nominal would be 18,000 watts of solar which is not going to fit on your roof.  I could however understand 1000 AH of batteries and 1500 watts of solar.  

I don't think you should get too hung up on a rule but rather should think about balance and power use.  Don't go overboard on batteries while neglecting how you are going to charge them and conversely it doesn't make sense to have a bunch of charge capacity if you can't use it or store it.

[lostagain]

Gary, never mind the solar panels. Just go to a Tesla charging station, lol. I was reading how people do that, then use the power at home. Tesla might have to start charging money for plugging in...

JC

[richard5933]

I went through this calculation when deciding on the house batteries for our 4108. The Trojan dealer told me that they recommend a charging rate of approximately 10% of battery capacity. We're going to have about 780 Ah between our four L16 batteries (set up as a 12v system), and he said that a 70-amp plug-in charger would be the proper size. In setting up solar, ideally we would be able to charge the batteries at about the same rate.

Going with a formula of Amps=Watts/Volts, a 1000-watt solar setup would provide about 83 amps output under optimal conditions. Since there is no way to always have optimal conditions, bigger would be better. Seems like there are a lot of 'kits' available that include six 160-watt panels (960 watts total), which would be about the smallest we'd consider given our battery setup.