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-   -   Max. watts solar roof panels 25ft. Safari? (https://www.airforums.com/forums/f448/max-watts-solar-roof-panels-25ft-safari-124744.html)

HCR 09-01-2014 07:39 AM

Max. watts solar roof panels 25ft. Safari?
 
My friends w/ 5th Wheels (and their large roofs) have sufficient panels to create 600 watts, and more.

I'm wondering if anyone with my length AS has information on how many panels with how many watts it's possible to install.

As always, thanks in advance.

lewster 09-01-2014 08:36 AM

Quote:

Originally Posted by HCR (Post 1504240)
My friends w/ 5th Wheels (and their large roofs) have sufficient panels to create 600 watts, and more.

I'm wondering if anyone with my length AS has information on how many panels with how many watts it's possible to install.

As always, thanks in advance.

400-600, depending on the panels that you use, whether you replace your existing TV antenna with a Jack digital antenna from King Controls and of course, who plans and executes the installation. :D

HCR 09-01-2014 08:43 AM

Hadn't considered removing antenna--good idea as I use a portable Dish receiver and don't use the roof antenna.

Thanks for responding!!

lewster 09-01-2014 08:53 AM

PM me if you have more specific questions.


Lew Farber
RVIA/RVDA Nationally Certified Master Tech
Master Tech Energy Systems, Inc.
AM Solar Certified Installation Center
Lifeline Batteries**Magnum Inverters
541-490-6357

Flht2k 09-01-2014 11:45 PM

Hello

New to forum, visited an AS store today. Getting ready to buy, I am interested in using solar for everything. Noticed your a solar specialist. Is it possible to have such a system to run the a/c, microwave and such. I do a lot of dry camping. I do have a Honda gen 2000. What do you suggest. If this has been requested before, please direct me to the correct thread.

Thanks

richinny 09-02-2014 07:20 AM

https://www.airforums.com/forums/f240...es-122512.html

lewster 09-02-2014 09:11 AM

Thanks Ricky,

Here is my tome on Peukert's Theorem, which is the underlying principal that restricts batteries from being used for A/C operation.

Here's a little blurb that I wrote some time ago with reference to a Yeti inverter/battery system. When discussing battery capacity for very large loads like an air conditioner running thru an inverter, this little bit of information should go a long way to realizing the extreme limitations of large DC loads, even if you have a very large battery bank and inverter to match.

PM me if you have any specific questions.

PEUKERT:

Sorry to shoot down your aspirations, but your Yeti 1250 is simply a small AGM battery bank coupled to a small (1250 watt) pure sine wave inverter in one very expensivepackage. This is coupled to 60 watts of solar for charging? If it will take 24 hours to charge from a 60% depth of discharge, you are probably looking at batteries with a capacity of about 200 amp/hours (which, BTW, they conveniently omit from the specifications).

I calculate this by using their 60 watt solar array (5 amps max.) during 4 peak charging hours (10-2:00) and the residual for the rest of daylight hours yielding 40 amps to the batteries, 24 hours (3 days) gives you 120 amps of charging.....probably a 200 amp/hour battery pack.

That won't even come close to touching a roof A/C's 120VAC requirements, especially with only a 1250 watt inverter. Then there is a little thing called the Peukert effect:

Peukert's law, presented by the German scientist W. Peukert in 1897, expresses the capacity of a lead–acid battery in terms of the rate at which it is discharged. As the rate increases, the battery's available capacity decreases.
Manufacturers rate the capacity of a battery with reference to a discharge time. For example, a battery might be rated at 100 A·h when discharged at a rate that will fully discharge the battery in 20 hours. In this example, the discharge current would be 5 amperes. If the battery is discharged in a shorter time, with a higher current, the delivered capacity is less. Peukert's law describes an exponential relationship between the discharge current (normalized to some base rated current) and delivered capacity (nomalized to the rated capacity), over some specified range of discharge currents. If the exponent constant was one, the delivered capacity would be independent of the current. For a lead–acid battery however, the value of k is typically between 1.1 and 1.3. It generally ranges from 1.05 - 1.15 for VRSLAB AGM batteries, 1.1-1.25 for gel, and 1.2-1.6 for flooded batteries.[1] The Peukert constant varies according to the age of the battery, generally increasing with age. Application at low discharge rates must take into account the battery self-discharge current. At very high currents, practical batteries will give even less capacity than predicted from a fixed exponent. The equation does not allow for the effect of temperature on battery capacity.

Simply put, the capacity of any battery bank decreases exponentially with the increase in the draw from that battery bank. You would need a minimum of an 800-900 amp/hour battery bank coupled with at least a 2800 watt sine wave inverter. To keep this charged properly with solar, you would also need 800-1000 watts in your solar array. I have placed 800 watts on a newer 27' Airstream in the past, but that was about the limit. A 30-34' trailer could get 1000+ watts using the proper panels (AM Solar GS-100 to be precise).

Still, from all of this, you will still only be able to run a roof A/C for less than 2 hours after doing the Peukert calculations. PM me for the actual calcs. if you like, but basically you reduce a 900 amp/hour battery bank (6 Lifeline GPL-6CT AMG golf cart batteries) to 50% depth of discharge maximum draw. This give you a usable battery capacity of 450 amp/hours.

At a 16 amp draw (for the compressor and fan of a 15K BTU roof A/C), you would expect that you could run that A/C (not even counting inverter loss) for 450 amp/hours divided by 16 amps =28 hours. But because Peukert shows an exponential drop in battery capacity based on the higher amp draw, you actually will reduce the capacity of this 900 amp/hour battery bank to a mere 30 amp/hours, giving you less than a 2 hour run of your A/C.

Class dismissed!

PS: I've tried it and it works out pretty closely to the formula!!!

ghaynes755 09-02-2014 10:19 AM

HCR I have a 25FC Rear Bed, did not take off the antenna and have 705 watts (3-135 and 3-100). Probably room for one more 135w if I change out the antenna.

HCR 09-03-2014 01:09 PM

Ghaynes755

Thanks for reply and can you pls. post here how many batteries (6 or 12 v) and where you placed them.

thanks in advance.

ghaynes755 09-03-2014 10:00 PM

1 Attachment(s)
4 - 6V Lifeline GPL-4CT's. 2 in the original battery box (AMSolar made a frame to raise the cover original cover up) and 2 in the front roadside interior storage space, the one under the bench seat closest to the front window. That kept the wire runs very short. Worked out great.

Attachment 220732

lewster 09-03-2014 11:05 PM

Quote:

Originally Posted by ghaynes755 (Post 1505666)
4 - 6V Lifeline GPL-4CT's. 2 in the original battery box (AMSolar made a frame to raise the cover original cover up) and 2 in the front roadside interior storage space, the one under the bench seat closest to the front window. That kept the wire runs very short. Worked out great.

Attachment 220732

Gee Gary, you should have replaced the crank-up TV antenna with a Jack digital antenna mounted in the center of the trailer just between the sky-lite and the Fantastic Fan. Could have added another 135 watts!!!! :bb:

HCR 09-04-2014 08:57 AM

Gary, thanks for posting the photo and answers!

ghaynes755 09-04-2014 09:24 AM

Lew, yeah I thought about either the Jack or the disk Winegard that is on the 2015 AS models. Unfortunately I thought about it to late. Will see how it goes through the winter and put that on the list of further improvements.


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