Solar Panels

[Fred Mc]

I just noticed a local ad for flexible solar panels. $389 for 100 watts and it got me thinking.(sometimes dangerous AND costly)

At any rate  could someone who either has, or understands ,the practical application of charging batteries with solar panels tell me what to expect.

My questions would be
1.Do you just hook up the leads from a solar panel to the battery and let it charge.
2. With a single 12v deep discharge battery of 800cca how long would it take the solar panel to charge the battery(assuming bright sunny day)

Thx

Fred

[windtrader]

HF has 100 watt kits for $150.

100 watt panel will output around 70 watts per hour if mounted flat for 5-6 hours, about 500 watts a day.

Batteries for house use should be of the deep cycle design. They are rated in Ah not CCA as that indicates a start battery.

The main components include the panel(s) and a charge controller, basically a voltage regular that ensure excessive voltage is not applied to the battery during charge.

[Iceni John]

Almost $4 a watt for a panel that won't last more than a few years is NOT a good deal.   Flexible PV panels are not like standard PV panels that usually have a 25-year warranty and will produce usable power for a lot longer than that.   They are simply not a cost-effective way to get solar power.   Don't waste your money with them  -  the most bang for your solar buck is by buying so-called "grid-tie" panels such as are used for residential and commercial installations:  they are often 60-cell panels that are rated at about 250W, and you can get them for well less than a dollar a watt, sometimes close to 50 cents a watt.   That will be for new Grade A panels with 25-year warranties from reputable manufacturers with UL-listings.   Grade B are cosmetic blems, but still are UL-listed.   PV panels these days are almost a commodity item, so you can buy on price.   Just avoid no-name panels from who-knows-where, sometimes with fake CE certifications and UL-listings, or panels without good frames and proper MC4 connectors.

I have Sharp panels, made in USA, UL-listed, with good strong frames (important for a vehicle installation), but Grade B because some cells are a slightly different shade of dark blue than others.   I paid 79 cents a watt a few years ago, when prices were higher than now.   If I had haggled and tinked around I could have got them for 10 cents a watt cheaper, but I'm happy with what I paid.

John 

[Iceni John]

Unless the panel and battery are both very small, you should use a charge controller to give exactly the correct charge to the battery.   Simple cheap PWM controllers are fine for smaller systems, but the better MPPT controllers are worth it for larger systems.

If your battery is rated at CCA, it is not a true deep-cycle battery, but instead either a start battery or a "marine" battery that is a start battery intended for slightly deeper discharges.   Start batteries need to be recharged quickly back to 100%, such as from an alternator;  deep-cycle batteries benefit from a slower multi-stage charge to maximize their long-term life, so chargers for them will be programmable to give different voltages and currents depending on what the battery needs.   If you habitually recharge a deep-cycle battery from a vehicle alternator, it will have a short life.

The general wisdom is that deep-cycle batteries should be charged at a 5 to 13% charge rate.   A 100W panel would be OK for charging a small battery, but any battery bank large enough to be useful for house loads will need a lot more than 100W, unless it is being Bulk-charged instead by a generator and using PV only for the Absorb and Float stages of charge.

John 

[ol713]

    Hi'
      Keep in mind also you will need a solar panel regulator so as
      to not damage your battery.
      I have had my solar panels for over 20yrs.  Best money i have
      put into the bus.   If you get a regulator,  try to find one that has
      a switch to select "battery #1"  or "battery #2".   Then you can
      elect which battery bank to charge.   (house or start)
                                             Merle.

[Fred Mc]

Hmmm, so not as simnple as I thought.

The battery I was mentioning is a deep cycle.I got the teminology wrong.

Thanks

Fred

[Zephod]

I have two 10W and one 15W solar panel. I can charge my phone and my tablet with ease and when I get the wiring sorted out and the real battery mounted under the bus then I should be way better off. I find my 25W of vertically mounted solar panels provides ample power for ventilation and device charging.

Harbor Freight panels are expensive. A 100W panel (saw one today) for $150 when they're $100 in Home Depot.


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[belfert]

I paid just over $100 per panel for 300 watt panels back in May.  They are grade B, but still UL listed and with warranty.  I had intended to use two for my bus, but one got broken in shipping.  The same company still has more of these panels, but shipping is pretty steep for small quantities.

Edit: To clarify, I bought a pallet of 22 panels intending to use 20 for my house and two for the bus.  One came broken so the bus idea went out the window.  I ended up changing the design for the house project and will use all 21 panels for the house after all.  The seller would not send me another panel as they claim the trucking companies often break just one or two panels on a pallet.  They did offer my money back for the broken panel.

[Slug]

We have had a lot of failure with flexible panels in Australia with them delaminating in short time frame. Might last longer in cooler climate, but have been loosing popularity here
I've got 2000watt glass panels on my bus roof added benifit keeps the sun off 
James

[Zephod]

We have had a lot of failure with flexible panels in Australia with them delaminating in short time frame. Might last longer in cooler climate, but have been loosing popularity here
I've got 2000watt glass panels on my bus roof added benifit keeps the sun off 
James

I will never understand why bus manufacturers in hot climates don't add a safari roof like on the land rover safari


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[Scott & Heather]

They did:


But that's off topic, OP, I have been toying with ideas on solar as I slowly build my battery bank...I've learned from the knowledgeable guys on here who have done big solar installs on their coaches that there are a few important and somewhat expensive ingredients to a solid solar system. A battery bank to store the energy for later use, the solar panels of course, proper solar panel placement on your roof for maximum sun exposure (some even use tilting and rotating panels to maximize this aka technomadias coach) a charge controller and a good inverter for 120 volt needs. This is definitely a road I want to travel soon, but i absolutely need a magnu hybrid inverter first and they are almost $2000, so I'm biding my time....


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[Lee Bradley]

Just went down that road.  Spent about $1400 for panels, combiner, controller, mounting hardware.  Had the system up and running for the Great American Eclipse. I was in western Oregon and the system's highest output was 19.5 amps 28.8 volts to the battery bank, 3.5 amps at about 8 am. It also shades 41 square feet of the roof.  


Hyundai-HiS-S350TI   Hyundai HiS-S350TI > 350 Watt Mono Solar Panel
2   $248.50   $497.00
Midnite-MNPV2-MC4   Midnite Solar MNPV2-MC4 > Pre-Wired Combiner Box
1   $149.31   $149.31
Midnite-Solar-Kid   Midnite Solar The Kid > 30 Amp 12 - 48 Volt MPPT Charge Controller
1   $324.26   $324.26

Shipping was $260

I could have probably used a lesser controller but I wanted an MPPT controller and this one will support two more panels if I want to add them.

[windtrader]

Lee,
Please post your component details? Specifically, the panel and controller rating and brand/model.

I'm getting close to doing it but still on fence whether to future proof the charge controller and buy up in size.

I can get used Kyocera 130w panels for 30 bucks and a Victron 75/15 MPPT controller for under a hundred. Figure a couple hundred bucks for a 500 watt system is a cheap experiment.

[Iceni John]

proper solar panel placement on your roof for maximum sun exposure (some even use tilting and rotating panels to maximize this aka technomadias coach)

Unless Technomadia have recently changed their PV system, I think they just have a simple tilting setup for half their panels.   As with most things, one has to decide how much visual impact is acceptable  - some here think that PV on a bus is "a freak show" and "crap for traveling", while others are happy to put function before appearance.   Le Corbusier said that a house was merely a machine for living in, so by extension a bus conversion is similarly a mobile machine for living in, and if it has the ability to generate useful free power from the sun doesn't that make it a more efficient machine?!   (And we all like efficiency, yes?)

I saw a photo once of an RV with 2-axis tiltable panels, and it seemed very complicated and potentially unreliable to me.   Simple 1-axis tilting panels are a good compromise between appearance and year-round solar harvest, especially on a vehicle that may not always be oriented ideally to the sun.

John

[windtrader]

John,

Tilt mounting. Unless you can freely orient the bus when parked, then two axis allows for more effective orienting. Just being able to tilt up would not be worth the effort to me. It seems you just need to mount the tilting mount on swiveling base, not that much more to incorporate that.