Do I Need A Solar Panel?

Ratkity

I love it when Jenn geeks with charts!! My hero! Rock on, girl.

jkjenn

ScottG said:

Thanks for the chart, Jenn. Did you derive those usage figures yourself using your monitoring system, or are they from published sources? If from published sources, do you have a sense (again, from your monitoring system) how they compare to real world use?

I frequently do multi-day trips without shore power, so have the same questions as Jiro. However, being lazy and a little cheap, I don't want to fiddle with any more equipment than is absolutely necessary. Knowing what I can actually get from my battery based on specific usage is really helpful.  

A little bit of both. I indicate in the notes column (not in screen shots.) You can access the entire workbook, here.

I think mileage could vary, as it seems kitchen galley light and shower lights may differ in different T@bs and in all likelihood, your battery no longer recharges to the full amp hours, but it is a decent general guide.

Nomad

"mileage could vary" <- Yep, it does. So many variables.

jkjenn

PXLated said:

"mileage could vary" <- Yep, it does. So many variables.

But t should be relatively close if you have a healthy battery.

Nomad

Maybe :-)
I've just found that none of the specs ever live up to real life - They're all just theories.

jkjenn

PXLated said:

Maybe :-)
I've just found that none of the specs ever live up to real life - They're all just theories.

Not when you measure them yourself.

Nomad

They change over time though - so, are you constantly monitoring/measuring - and then there are those anomolies that pop up for a day or two for no explainable reason ... like, why is my fridge condenser fan running a lot today when it hasn't for days and nothing has changed?

ScottG

I understand there are always confounding variables, but this sort of data (particularly when derived from real-world testing) is a good starting point.

We treat the T@B more like a tent, and are very conservative with our battery use, but multi-day boondooking (not to mention general neglect…) have pretty much toasted the original battery. My reading here and elsewhere have me thinking a 120W solar suitcase will probably do the trick. Maybe a larger battery, too, since I'll need a new one anyway.

Thanks for the research and info!

Nomad

ScottG - Ya, the data's a good base reference point ... The 120 has worked well for me - A slightly bigger battery is in my future at some point.

ChanW

So, does a higher wattage setup make up for numerous generally cloudy days? Or are all cloudy days always useless, and does solar need direct sunlight? (Buffalo is having a pretty solid string of heavy clouds these days, so I'm a little sensitive about it )

Nomad

You get some charge no matter the sky unless it's just miserably black (I've even had a little charge showing under a full moon). A dank, rainy day is not good. I get a full charge under bright, solid overcast.
The more direct the sun the better though. That's why I prefer the suitcase vs a permanate install. Can move the panels around. Park under the trees but still have the panels out in the bright sun (that's my setup right now)
Note: All my experience is north in the summer, south in the winter.

jkjenn

PXLated said:

They change over time though - so, are you constantly monitoring/measuring - and then there are those anomolies that pop up for a day or two for no explainable reason ... like, why is my fridge condenser fan running a lot today when it hasn't for days and nothing has changed?

Part of the reason I got a fancy battery monitor.

ChanW said:

So, does a higher wattage setup make up for numerous generally cloudy days? Or are all cloudy days always useless, and does solar need direct sunlight? (Buffalo is having a pretty solid string of heavy clouds these days, so I'm a little sensitive about it )

Yes... we have too and solar is poor in our neck of the woods on a sunny day in January, not to mention multiple cloudy. I forgot to turn on the battery switch off after my camping trip over New Years and you know we have had maybe 1-2 sunny days since then. With my 50w charger I was still at over 80% charge.

PXLated said:

You get some charge no matter the sky unless it's just miserably black (I've even had a little charge showing under a full moon). A dank, rainy day is not good. I get a full charge under bright, solid overcast.
The more direct the sun the better though. That's why I prefer the suitcase vs a permanate install. Can move the panels around. Park under the trees but still have the panels out in the bright sun (that's my setup right now)

Solar in the NE in the heart of winter, even on sunny days is poor. It starts to improve in March. Cloudy days are almost worthless this tine of year. In the other 3 seasons it is OK, but not winter. I would like to go back and compare amount of days with cloudless skies between last year and this year. It seems like last year had more.

Someone share a solar power calculator that takes latitude into account. Their calculations seem consistent with my win experience.

ChanW

Jenn, I agree, re more clouds this winter. But the weather in November December was mild, in either case. It might be just the last few weeks, which have been extreme everywhere, that are clouding our memories, so to speak.

good weather history app: WeXplorer (Android, dunno if otherwise).

jkjenn

I need to bundle up and go remove the snow from the panel, tonight, lol.

jkjenn

This thread motivated me to write up a post on some guidance for answering @JiroTX's original question. If you are interested, you can find it here.

JiroTX

Thanks Jenn! Very nice guide for all T@B users. I think I'm just going to make this trip as a test trip without solar and see how it goes. Since the weather changes a lot at the Chisos Mountains, I probably should not depend on solar. Plus, getting the battery is way cheaper than the solar panel. Yes, I am still trying to decide, but I will probably just go there without any additions and test it. For the worst case, I can just drive the trailer around to charge.

Nomad

It's always a good idea to get some travel time under ones belt to figure out ones needs - Can't begin to tell you how many of my plans thoughts changed after a couple months on the road.

jkjenn

JiroTX said:

Thanks Jenn! Very nice guide for all T@B users. I think I'm just going to make this trip as a test trip without solar and see how it goes. Since the weather changes a lot at the Chisos Mountains, I probably should not depend on solar. Plus, getting the battery is way cheaper than the solar panel. Yes, I am still trying to decide, but I will probably just go there without any additions and test it. For the worst case, I can just drive the trailer around to charge.

Good idea. If the off grid use is primarily 1x a year, I wouldn't put a lot of money into it.

Ratkity

jkjenn said:

This thread motivated me to write up a post on some guidance for answering @JiroTX's original question. If you are interested, you can find it here.

Jenn, you are amazing! I so love it when you geek and pull out the spreadsheets!!

Right now, I'm "cobbled" by using the group 24 battery (80ah) that came with my T@B, but am saving to invest in your golf cart battery set up. I think I can find a welder to add the new battery set up to my tongue (using extra front box space for an additional propane tank). TV can handle the extra weight - no worries there. I promise I'll see how the setup handles first before doing any long trips.

I have one flexible permanently mounted 100W panel with controller and monitor - Trimetric - but not as awesomely installed as yours! Kudos!.  I set up the solar system to expand - I will be doing that by making an extra 100W flex panel to "float" around and be strategically placed towards sunlight. The group 24 is fine for me right now. I'm currently a weekender boondocker and haven't retired yet to my dream of stalkin... er, um... following in PXL's footsteps and going where the heat goes during the year.

I've bookmarked your wonderful page. Thank you again! If I haven't told you that you are awesome lately, I shall tell you again! You're an inspiration to this old lady who is more than ready for the road. *hugs*

jkjenn

That was way too generous, @Ratkity, but thank you.

As an FYI, I did not need to have any welding done. I simply bolted two pieces of stock angle from Lowe's to the frame. When I mounted the box, I use those giant disc-like washers to help reduce the stress placed on the battery box as the T@b ambles down them road. (fender washers) I also use a lockable ratchet strap, although that is probably more helpful for my piece of mind than actually holding the box down.

Joe

Jenn -

Very well written and I admire your innovative approach to solving the problem.  You've given me something to think about.  Well done!

~ Joe

sbutzen

We've done three nights with the fridge and Alde running on battery and propane.  Had no issues.

JiroTX

Thanks sbutzen,
I tested for about 31 hrs (I think I'll be using Alde shorter than that in three days) and the voltage meter was still showing 12.40v. I concluded 3 nights would be just fine, but that depends on the weather condition during the day time (Chisos Mountains can get 85-90F in March, and that would run the fridge more).

leenscottfl

I agree with jc. What is a battery box cradle insert?

ScottG

leenscottfl said:

I agree with jc. What is a battery box cradle insert?

Check out this thread a little further down. I asked the same question--RZRBUG gave a good description of how he fitted a group 30 battery in the standard plastic tub. I plan to do something similar before the next camping season.

http://www.tab-rv.com/forum#/discussion/2387/fitting-a-group-27-battery