With a stock 2 panel PV system

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With a stock 2 panel PV system

June 19, 2020, 02:01:44 pm

115 watts per panel.

What can I expect for recharging times on stock battery set up?

Say from 50% drained.

Re: With a stock 2 panel PV system

Reply #1 – June 19, 2020, 02:16:40 pm

Since 50% drained will dangerously shorten battery life, a more reasonable expectation is to install a battery monitor to determine just what your typical overnite A-hr usage is, then decide how much solar you need, and get a good MPPT controller to maximize power transfer. If you determine your overnite average approaches 50% - considered full discharge for flooded cell technology - then either upgrade the batteries or improve your power consumption efficiency.

Steve

Re: With a stock 2 panel PV system

Reply #2 – June 19, 2020, 02:26:04 pm

Quote from: tedeboy - June 19, 2020, 02:01:44 pm

115 watts per panel.
What can I expect for recharging times on stock battery set up
Say from 50% drained.

What time of year, summer or winter? 50% of the coach battery is 110-amp/hours.
In the summer, two panels produce a total of 230-watts, it theoretically should produce around 18-amps but you will never see it, it will be in the 14-15-amp range max, mid-day. It will be lower early and later in the day.
You possibly could get close to a full charge on a mid-summer day if all 12-volt loads have been eliminated and the rig is parked in the open where the roof gets full sun all day long, just the thing most owners try to avoid in the summer's heat.

In the winter, it could take several days to fully recharge, with the short days and low sun angle, winter boondocking requires twice as much solar as what is needed in the summer. We occasionally run the batteries down mid-winter with a 400-watts of solar. I'm thinking of adding another 100-watt panel for a total of 500-watts.

I have never met anyone who thought they had too much solar.

Larry

Re: With a stock 2 panel PV system

Reply #3 – June 19, 2020, 03:03:59 pm

Will Lazy Daze forgo installing the PV system if I want AM Solar to install one for instance?

Re: With a stock 2 panel PV system

Reply #4 – June 19, 2020, 04:47:21 pm

Quote from: tedeboy - June 19, 2020, 03:03:59 pm

Will Lazy Daze forgo installing the PV system if I want AM Solar to install one for instance?

Only LD can answer this question. If thinking about a future solar upgrade, I would install one panel so the cable run and the box for the solar controller are built-in.
Steve probably wouldn't do it but you could ask that the lead-in cables be upgraded to much larger ones, to eliminate having to remove and replace the Factory cables during the upgrade. This would make the upgrade much easier and less expensive, it would be worth paying Steve extra to do so.
In most floorplans, the cables from the controller to the panel can be removed and replaced with larger cables, to match the upgraded solar array needs during the upgrade. I would verify this is possible before ordering.

Larry

Re: With a stock 2 panel PV system

Reply #5 – June 19, 2020, 04:49:51 pm

Quote from: Larry W - June 19, 2020, 04:47:21 pm

Only LD can answer this question. If thinking about a future solar upgrade, I would install one panel so the cable run and the box for the solar controller are built-in.
Steve probably wouldn't do it but you could ask that the lead-in cables be upgraded to much larger ones, to eliminate having to remove and replace the Factory cables during the upgrade. This would make the upgrade much easier and less expensive, it would be worth paying Steve extra to do so.
In most floorplans, the cables from the controller to the panel can be removed and replaced with larger cables, to match the upgraded solar array needs during the upgrade. I would verify this is possible before ordering.

Larry

Thanks Larry.

Re: With a stock 2 panel PV system

Reply #6 – June 19, 2020, 07:26:19 pm

Standard solar panel recharge time

device watt hours / solar panel watts = solar recharge times

for example a 13 watt solar panel will charge a 50 watt hours battery pack in 3.84 hours
50/13 = 3.84 hours.
or
Lifeline AGMs 12v 220 a/h comes to 2640 watts at 100% charge. At 50% that's 1320 Watts. Soooo the math would say at 20 watts an hour solar panel (very very optimistic) it would take 1320/20= 66 hours to go from 50 to 100%.

BTW no battery is ever 100%. On day 1 the capacity starts to drop. Without very expensive equipment capacity is just a guess.

glen

Re: With a stock 2 panel PV system

Reply #7 – June 19, 2020, 07:52:52 pm

Quote from: colddog - June 19, 2020, 07:26:19 pm

Standard solar panel recharge time
device watt hours / solar panel watts = solar recharge times
for example a 13 watt solar panel will charge a 50 watt hours battery pack in 3.84 hours
50/13 = 3.84 hours.

Unfortunately, the situation is more complicated for many reasons. The 13 Watt solar panel is rated in lab conditions, about 72 degrees (maintained) and under one sun illumination - roughly midday at the equator. Over the course of a summer day in North America, you can expect perhaps 10 watts midday and less before and after. You might get 50% of that in Winter... There are insolation charts for various parts of the country to help calculations.

Next, batteries can accept a good charge rate when significantly discharged, but this decreases as the state of charge increases. A good MPPT controller can do the job of maximizing power to the battery, but once the battery voltage reaches about 14.4V or so, the charger will clamp the voltage there, and the battery will accept less current as its state of charge increases. The solar panel may be able to put out full power to run lights and appliances, but current to the battery will slowly drop, extending the time to full charge for hours.

Steve

Re: With a stock 2 panel PV system

Reply #8 – June 20, 2020, 09:30:14 am

Quote from: Steve - June 19, 2020, 07:52:52 pm

Unfortunately, the situation is more complicated for many reasons.

Steve

<smile> yup. I agree. In experiments with my setup I found in the 'real' world nothing like the claims on various companies web site and literature. In fact the only thing I can say for sure is that when the sun is out you will get some production of electricity but nowhere near what is claimed. The best I ever got was 9 Amp per hour. For a 100 Amp recharge that would take around 10 hours of so.

glen

Re: With a stock 2 panel PV system

Reply #9 – June 20, 2020, 09:55:34 am

Steve makes a very good, and often overlooked, point: lead-acid batteries (including AGMs) can't accept a high charging rate right up until they're full. The more charge they have, the slower they accept charge. So you can't just say "I have x watts of solar panels and y amp-hours of batteries" and do the math.

This is one of the major advantages of LiFePO4 batteries: they charge at a high rate right up until they're full, so a full charge is achieved in much less time than with a lead-acid battery. But LiFePO4 batteries are still quite expensive compared to lead-acid batteries, so most RVers continue to use the older, more cost-effective technology.

Re: With a stock 2 panel PV system

Reply #10 – June 20, 2020, 11:17:12 am

Not to be nit-picky, but it helps for all to keep electrical units straight in these discussions to avoid confusion:

-The definition of an Ampere (A) is one Coulomb of charge per second. The Ampere is a unit of charge flow rate.
-Ampere-hour (A-hr) is the most convenient measure of charge when we talk in RV groups, so that is one Ampere flowing for 3600 seconds, or 3600 Coulombs.
-Energy flow is expressed in Watts = Amps X Voltage.
-Energy is expressed in Watt-hrs, so Watt-hr = Amp-hr X Voltage.

With a little luck, I haven't confused myself here.

Steve

Re: With a stock 2 panel PV system

Reply #11 – June 20, 2020, 11:34:21 am

The more I learn the more I think that even with the 2 panel option the stock PV system just isn't powerful enough to be anything other than a glorified battery maintainer while in storage.

Is that too cynical?

Re: With a stock 2 panel PV system

Reply #12 – June 20, 2020, 11:47:35 am

And, a coulomb is "the quantity of electricity transported in one second by a current of one ampere."

I looked that up, of course; I have just enough "wire savvy" to avoid frying the rig and/or killing myself. I hope.

YMMV.

Re: With a stock 2 panel PV system

Reply #13 – June 20, 2020, 12:00:50 pm

Quote from: tedeboy - June 20, 2020, 11:34:21 am

The more I learn the more I think that even with the 2 panel option the stock PV system just isn't powerful enough to be anything other than a glorified battery maintainer while in storage.

Is that too cynical?

I think so.

I've read a rule of thumb that your watts of solar panel should be about equal to the amp-hours of battery storage. 2 panels matches very well with the factory battery configuration.

I have 200 watts with the standard 2 6-volt golf cart batteries. On a sunny summer day, I can go from 60% to full. Often, I don't discharge the batteries below 80%.

That sort of system isn't going to be a full time boondockers, run the microwave and a desktop computer kind of system. It does work really well for a large number of people.

The only time I feel limited on the 12V side is when we're camped for a few days in full shade.

Everything in a RV is a tradeoff. Electrical independence via solar costs $$$. Running the generator for a couple of hours is A LOT cheaper.

LED lights and iPads and lightweight laptops have really reduced the power consumption for a lot of daily tasks.

Rich
'03 MB in NC

Re: With a stock 2 panel PV system

Reply #14 – June 20, 2020, 12:10:23 pm

Quote from: rich - June 20, 2020, 12:00:50 pm

I think so.

I've read a rule of thumb that your watts of solar panel should be about equal to the amp-hours of battery storage. 2 panels matches very well with the factory battery configuration.

I have 200 watts with the standard 2 6-volt golf cart batteries. On a sunny summer day, I can go from 60% to full. Often, I don't discharge the batteries below 80%.

That sort of system isn't going to be a full time boondockers, run the microwave and a desktop computer kind of system. It does work really well for a large number of people.

The only time I feel limited on the 12V side is when we're camped for a few days in full shade.

Everything in a RV is a tradeoff. Electrical independence via solar costs $$$. Running the generator for a couple of hours is A LOT cheaper.

LED lights and iPads and lightweight laptops have really reduced the power consumption for a lot of daily tasks.

Rich
'03 MB in NC

I called AM Solar and spoke with them.
They recommend 2 watts per amp-hour.

Do you have the stock Lazy Daze installed system?

Re: With a stock 2 panel PV system

Reply #15 – June 20, 2020, 12:16:04 pm

Quote from: tedeboy - June 20, 2020, 12:10:23 pm

I called AM Solar and spoke with them.
They recommend 2 watts per amp-hour.

Do you have the stock Lazy Daze installed system?

I have a stock battery system; the batteries themselves have been replaced of course.

My 2003 was ordered by the original owners without solar. Electrical hookups were their style. I added a single 200 watt panel around 2011.

Rich
'03 MB in NC

Re: With a stock 2 panel PV system

Reply #16 – June 20, 2020, 12:20:13 pm

Quote from: tedeboy - June 20, 2020, 11:34:21 am

The more I learn the more I think that even with the 2 panel option the stock PV system just isn't powerful enough to be anything other than a glorified battery maintainer while in storage.

Is that too cynical?

200-watts of solar is fine for modest electrical usage and will work fine in the summer as long as you do not spend hours each day watching satellite TV, then more solar will be needed.
Living in SoCal, you can enjoy year-round camping and travel, it's the mid-winter where most solar charging system fall flat on their faces, producing less than half of their summertime output.
In the winter, we tend to use more power for lighting and electronic entertainment, due to the shorter, cooler days.

Your needs and lifestyle determine how power production is needed.
Does your existing LD have solar, if so how much and are you satisfied with its capacity for your usage?
Do you have plans to increase your electrical consumption in the new rig?

Larry

Re: With a stock 2 panel PV system

Reply #17 – June 20, 2020, 12:55:57 pm

Quote from: Larry W - June 20, 2020, 12:20:13 pm

200-watts of solar is fine for modest electrical usage and will work fine in the summer as long as you do not spend hours each day watching satellite TV, then more solar will be needed.
Living in SoCal, you can enjoy year-round camping and travel, it's the mid-winter where most solar charging system fall flat on their faces, producing less than half of their summertime output.
In the winter, we tend to use more power for lighting and electronic entertainment, due to the shorter, cooler days.

Your needs and lifestyle determine how power production is needed.
Does your existing LD have solar, if so how much and are you satisfied with its capacity for your usage?
Do you have plans to increase your electrical consumption in the new rig?

Larry

All great questions.
Our current rig does not have PV and it's not like I really missed it too much although if I could avoid running the generator for a couple of hours that would be nice.
I am leaning towards getting the second panel option. It is still less expensive than getting an entire system change and for our modest electrical needs it may work out fine.
Thanks for all the help.

Re: With a stock 2 panel PV system

Reply #18 – June 20, 2020, 03:06:52 pm

"I think that even with the 2 panel option the stock PV system just isn't powerful enough to be anything other than a glorified battery maintainer while in storage."

That's probably overly pessimistic. It very much depends on your camping style and where you camp. Stay in full-hookup parks most of the time? Two 100 W panels and two 225 Ah batteries will probably do fine. Like to boondock? Unless you're careful with your power usage, you may want more panels.

Camp in the southwest? You'll have plenty of sun on your panels for most of the year. Camp in the Pacific Northwest or in heavily wooded eastern campgrounds? You'll want more panels to make up for getting less sun.

"I called AM Solar and spoke with them. They recommend 2 watts per amp-hour."

Good example of what I was just saying. Springfield, Oregon (where AM Solar is located) averages 158 sunny days per year. The US average is 205 sunny days, and Quartzsite, Arizona averages 305 sunny days. In short, AM Solar gets less sun, so they need more watts on the roof to get a decent charge on their batteries. Their advice is right for their area, but may be overkill if most of your camping is in Arizona, New Mexico, or southern California. You get the idea.

Re: With a stock 2 panel PV system

Reply #19 – June 20, 2020, 03:17:22 pm

Quote from: Andy Baird - June 20, 2020, 03:06:52 pm

"I think that even with the 2 panel option the stock PV system just isn't powerful enough to be anything other than a glorified battery maintainer while in storage."

That's probably overly pessimistic. It very much depends on your camping style and where you camp. Stay in full-hookup parks most of the time? Two 100 W panels and two 225 Ah batteries will probably do fine. Like to boondock? Unless you're careful with your power usage, you may want more panels.

Funny, back when I had my '85 TK, I could easily go 4-5 days simply by conserving power. This was with no solar, no generator, no LED lights. Trojan T-105's. Ya'll are power hungry!

Re: With a stock 2 panel PV system

Reply #20 – June 20, 2020, 03:55:17 pm

Quote from: HiLola - June 20, 2020, 03:17:22 pm

Funny, back when I had my '85 TK, I could easily go 4-5 days simply by conserving power. This was with no solar, no generator, no LED lights. Trojan T-105's. Ya'll are power hungry!

And back in the dark ages, when you owned an LD, big-screen TVs, satellite dishes and computers were not commonly used in RVs.

Larry

Re: With a stock 2 panel PV system

Reply #21 – June 20, 2020, 04:01:14 pm

Quote from: Larry W - June 20, 2020, 03:55:17 pm

And back in the dark ages, when you owned an LD, big-screen TVs, satellite dishes and computers were not commonly used in RVs.

True, Larry. We called it "camping!"

Re: With a stock 2 panel PV system

Reply #22 – June 20, 2020, 04:03:31 pm

Quote from: HiLola - June 20, 2020, 04:01:14 pm

True, Larry. We called it "camping!"

Camping is sleeping in a tent, using a Coleman stove and gas lantern.
RVing is closer to condo camping.

Larry

Re: With a stock 2 panel PV system

Reply #23 – June 20, 2020, 05:01:11 pm

Quote from: Larry W - June 20, 2020, 04:03:31 pm

Camping is sleeping in a tent, using a Coleman stove and gas lantern.
RVing is closer to condo camping.

Depends on your point of view, I guess. I follow the Wikipedia definition.

Camping - Wikipedia

Now back to our regular scheduled programming! 😉

Re: With a stock 2 panel PV system

Reply #24 – June 20, 2020, 05:12:07 pm

Quote from: tedeboy - June 20, 2020, 11:34:21 am

The more I learn the more I think that even with the 2 panel option the stock PV system just isn't powerful enough to be anything other than a glorified battery maintainer while in storage.

Is that too cynical?

Resource conservation + efficient battery charging = happy campers. Full LED lighting, and just what is needed turned on; catalytic heater provides most heat instead of watt-hungry furnace; 200W solar with efficient multi-stage MPPT charge controller; 12V LED/LCD TV and media player instead of disc player; etc. This is what we have, and discharge is rarely more than 20% down, and batteries fully charged well before nightfall.

Steve

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