Do I Need A Solar Panel?

JiroTX · January 2016

I have started preparing for the trip to Big Bend in March. The campsite has no connections. I went there with a rental T@G last year and had a wonderful time for three days.
Now, I got a T@B, I was wondering if I should get a solar panel or not. I will be using the T@B mostly just for sleeping and keep the food in the fridge. I will be running the fridge off propane and occasionally heater if needed (It can be in 30's at night time, but I do not think I will need the heater). I can use lamps if that helps the battery. Cooking will be outside with a portable grill and stoves.

Since we will have at least four people, we won't take a shower in the T@B (tank won't be big enough). We will need to drive 45minutes to get to the store to take a shower everyday, and I can drag my T@B when we go there to charge.

I was initially thinking about getting a solar panel like HQST 100 Watt flexible panel ($190 on Amazon).

or maybe two of them to charge during the day while we are gone for hiking.
(I know Zamp would be easier, but I do not want to pay too much money for it...)

If I am using the fridge and heater at night time only, do I need to get a solar system? Or is it going to be okay if I just drive/charge for about 2 hours everyday (can fridge and heater run off propane/battery without charging for a day or two)?

I have a 2015 Outback M@x S. It is not going to be the same situation in March, but since it is pretty cold in East Texas today, I just unplugged my T@B in the driveway (should be fully charged) and started the fridge and heater to test. The voltage meter shows between 12.28-12.35 depending on what I am using (just cutting the lights on drops the voltage for about .04-.05. I will see how it goes, but I wanted to get some input from y'all.

Image: https://us.v-cdn.net/5021717/uploads/editor/x4/0ljo1tkamn0p.jpg

Thanks,

Jiro

Nomad · January 2016

What size battery do you have?
I've been in upper 30s at night since I got SW so the Alde runs quite a bit thru the night. I have just a Group 24 and if it's fully charged at sundown I'll wake up to anywhere between 11.9 and 12.2 with fridge and Alde.

JiroTX · January 2016

PXLated,

I am not familiar with batteries... but I still got the battery that came with the T@B. It says SRM-24, so I am guessing it's the same one you have?
I started the heater with temp setting "3" and fridge at 3 at 2:30pm. It's been almost 3 hours, and the fridge is down to 25 degrees/room temp is 70. Outside temp is 41.
The battery monitor now says 12.51.

Maybe it's more practical to get a bigger battery than getting a solar panel since I usually go to campsites with electric hookups? I don't know if two hour driving would recharge the battery good enough or not...

Image: https://us.v-cdn.net/5021717/uploads/editor/cs/8d9lwbntz7ws.jpg

Image: https://us.v-cdn.net/5021717/uploads/editor/1p/e8p6x1rr8lui.jpg

Nomad · January 2016

From my experience, with the fridge on battery while traveling, it maintains the charge you started out with - but that depends on your TV and how much your alternator puts out. I live off solar and my 24 does fine but at some point I'll change it out for a 27 so I have some margin.

JiroTX · January 2016

Thanks PX. Maybe I should go ahead and order a solar panel (hopefully 100W is enough) if it only maintains the charge and not charging (I can always turn the fridge off or put it on propane and charge while we are taking shower, but I think it is safer to get a solar panel).

What about propane? How long does it last with fridge 24/7 and Alde only at night? Big Bend can get over 90 in March and usually below 40 at night time.

jkjenn · January 2016

It's pretty tough to know for sure, but you will likely need a solar panel or to increase your battery capacity. I think you battery is a 100ah. That might last you a couple lf days if you are really judicious, but I think it will be tough.
I upgrade my battery to 2 golf cart batteries (6v.) It gives me a lot more leeway, at 225ah.
You will likely get decent sun in March at Big Bend. Solar in the northeast, right now, is pretty weak.

Nomad · January 2016

First off - Jenn's setup is totally overkill for me even though I do a lot of boondocking. I have 120 watt solar and the whimp battery and do fine as long as there is solar - Even overcast. The only way I'd ever do a setup like hers (sorry Jenn) is if I wanted to spend a month in isolation - I don't - The only thing I'd chage in my setup is a group 27 :-)
As far as propane usage - 7-10 days a tank when running the fridge and the Alde running at night.
I do have a generator for bad days but one could just hit a campgrounds with hookups on those days.

jkjenn · January 2016

PXLated said:

First off - Jenn's setup is totally overkill for me even though I do a lot of boondocking. I have 120 watt solar and the whimp battery and do fine as long as there is solar - Even overcast. The only way I'd ever do a setup like hers (sorry Jenn) is if I wanted to spend a month in isolation - I don't - The only thing I'd chage in my setup is a group 27 :-)
As far as propane usage - 7-10 days a tank when running the fridge and the Alde running at night.
I do have a generator for bad days but one could just hit a campgrounds with hookups on those days.

100ah is fine if you don't really want to use the lights, fan, pump, TV, or radio or charge your electronics.

In all seriousness, if you don't have solar, a 100ah battery isn't going to you much extended dry camping. You will need to look at either solar, a different battery, or generator.

mash2 · January 2016

The lifeline has a 20 hour rating of 84 amps. Means that you really have about 42 amps or less before you start impacting the battery life (most say that going down below 12.2 will reduce your battery life - and anything below 11.6 will shorten battery life significantly. At 11.9 you would be draining your battery down to about 40% charge (not great over the long run).

If you switch to a good group 27 you should be able to get up to 110 amps (20 hour rating), which would add about 30% capacity ... if Pxlated is getting down around 11.9 -- he's using about 50 amps daily (84*60% of battery capacity. At 110 Amp rated battery, the same battery would not 60% on a daily basis. No knock on PxLated, but I'd try not to let battery get below 12.2 so would want the additional capacity of a larger group 27 battery. 120 solar generally appear enough to recharge 110 AMPs in decent weather. If not, you could augment by driving around for the day, hit a campground with hookups or use a generator to augment.

BTW, I'm as overkill as Jenn, but would not recommend that you go wild. The 120 watts solar seems quite adequate (I'm generally running with 136 watts myself.) My other overkill is because I have so far resisted using a generator and prefer the 12 v frig which is a bit more power hungry. With a generator and lower requirements of the 3-way, I'd have upgraded to larger group 27 battery with my solar and called it a day.

Unlike Pxlated, I've done months at a time, never not full time, so I bow to his knowledge on the greater depth in managing a system. Just some observations.

Nomad · January 2016

Just to be clear - I rarely hit 11.9, that's worse case where the Alde is running almost constantly all night. I'm usually sitting at 12.2 with the Alde heating, fridge on propane and the two back lights running till midnight. No multimedia other than my iPad. - Charging all my gizmos during the day.
Should add - This is over 15 months of daily use. I could probably kill my battery every 6 months and still come out cheaper than you two - Mash2/Jenn :-)

jkjenn · January 2016

PXLated said:

I could probably kill my battery every 6 months and still come out cheaper than you two - Mash2/Jenn :-)

My set up was under $400. How much was your Zamp?

JiroTX · January 2016

Thanks everyone for the input.
I am driveway camping tonight to test . The heater/fridge have been running for about 10 hours now. Battery monitor is showing 12.53V.
Outside temp: 37F, room temp: 70F, Fridge: 35F. I am using a lamp instead of the LED lights in the T@B.
The temp settings on Alde is "3" and fridge "3.5." The outside temp drops to 26F tonight.
I am lowering the room temp setting to "2." I'm getting boiled in here...

At Big Bend, I will use the heater for 8-10 hours max at night and the fridge for 24 hours. I may not use the heater at all. I didn't think it was cold last year in a T@G with no heater.

I will probably order a 100W flexible panel ($189) and a charging controller ($30-40) from Amazon. I might upgrade the battery to SRM-29 (about $150). Buying both the solar system and battery is still cheaper than 120W Zamp.

mash2 · January 2016

Plated, that's why I bowed to your knowledge.

I used 11.9 because you said that was in your range and wanted to point to potential issue of smaller battery (voltage that low is definitely stressing the battery).

I also agree with your assessment of 120 watt with a single battery (though a think a larger battery would buy some comfort in range - which I thought you indicated may be in your future). 3-way frig buys more freedom for you as well as the generator. (I won't quibble about what is cheaper, though like Jenn, my setup was under $400 as well and I haven't invested in a generator and my propane use is much lower than yours so there is a tradeoff there as well).

In the end, I was just saying that think that a 30% increase in battery storage might be a good investment...and that any extended time requires solar or generator (or as you said, more cushion). Seems to be worth 12-15 AMP additional capacity daily.

I think I've always been clear, make incremental improvements as you need them, and try to choose a direction that allows you add if you feel it is necessary.

And JiroTX, your plan seems very reasonable to me (though not sure if you have a generator as well).

Nomad · January 2016

Jenn - How much were your batteries and that whole setup? My battery cost me nothing extra, came with the T@B :-) -- Say nothing of all the time I saved by buying the Zamp and just plugging it in :-)

Nomad · January 2016

Mash2 - "11.9 - 40% - not good over the long run" --- Is that consistantly down to 11.9 and what's the long run? You'll shorten the overall life of your battery by X months/years?

The battery chart that gets posted here (see pic) implies that 11.9 is A-Ok Green.

This morning is a good example of how it normally goes... Woke up before sunup, monitor is at 12.2 (fridge/Alde overnight), crank the heat up from 2 to 3, Alde kicks in to take the chill off, monitor drops to 11.9. It may stay at 11.9 or may rise back to 12.2 depending on how often the Alde kicks in at the higher temp setting. Sun comes up, monitor rises back to fully charged over the course of the morning.

Obviously, if I don't want the morning heat kick or don't need heat at all I rarely go below 12.2. There are unexplained anomolies every once in awhile. A day here or there where it drops for no apparent reason and then the next day is back to normal - gremlins.

Note: My iPhone & iPad are usually plugged in all night also.

Ratkity · January 2016

Ok stupid solar/shore power story of the day..... tl;dr (skip to last 3 lines)

There I wuz (all beginning stories have to start with those words).... camping wif my other tiny trailer peeps at a wonderful state campground with shore power, waterway views, fishing, kayaking, pot luck, good food, and tall tales around the campfires.

This fabbo Airstream Bambi owner had shown me the camper-TV cord "short" you can do (non-blinking) that would turn on your running lights of your camper instead of using that overly-bright white LED porch light that not only beckons you home at night, but calls out to every moth, insect, arthropod within a half mile as well. Well, I went to my camper-TV 'lectrical cord and used a sold piece of insulated wire (ain't dumb.. no shocking event happened) to short the two female inputs. In mah excitement to connect the 2nd of the two inputs, I brushed against the metal of one of the other inputs. Coupla sparks.. nuthin major. Running lights were on and beautiful, not overpowering to neighbors and quite pleasant. I did NOT unplug the shorting wire during the day. Was just a 3 day weekend, and pffft, I was on 30A shore power.

The weekend weather was cold, rainy and nasty, but spirits were high (some were drinking said spirits) and much fun was had by all. End of the gathering: drove home (less than 2 hrs), parked (I call it "threading the needle" as I have to back thru 2 fence posts while missing my Harley Softail), hauled in dirty clothes bag, grabbed backpack and went inside.

Next day after work, I went to make sure all was spotless and to replenish some staples in mah sweet T@B. Automatically checked the voltmeter installed in the cabinet under the sink. 12.1v??? Wha??

Guess what those widdle bitty sparks did at the beginning of the weekend? Blew the converter's inline-fuse on the battery PLUS the one to the solar charge controller. Oops.

What didn't happen - the trailer converter was fine - it just never charged the battery during the weekend, the inside electronics were protected, the solar controller (100W flex panel - permanent install) was protected, the permanently installed voltmeter runs on a dedicated fused line and wasn't affected, I didn't drop the battery below D.E.A.D. and was slightly surprised I didn't run the battery any lower - battery specs - 80 Ahr (20 hrs), group 24.

Moral of the story - don't randomly hit other metal objects when shorting those two inputs on your trailer-TV cord to light up your way! I also took a bit of "wite out" and marked which inputs on the camper-TV cord to short if I want to do that again and promised mahself I will be extra careful while connecting the two inputs.

When all is said and done, always double-check to see if your battery is charging whether via solar, generator or shore power. Make sure said battery is healthy, add distilled water if it's flooded even if it's a little thirsty, and don't make things spark unnecessarily (carry extra fuses - for HHGTTG fans, remember a towel too).

ChanW · January 2016

Ratkity said:
.......
When all is said and done, always double-check to see if your battery is charging whether via solar, generator or shore power. Make sure said battery is healthy, add distilled water if it's flooded even if it's a little thirsty, and don't make things spark unnecessarily (carry extra fuses - for HHGTTG fans, remember a towel too).

And that 42 is probably the answer to everything...

Verna · January 2016

@Ratkity, use a fuse on the 7-pin connector. It's safer than bare wire. Just a 7.5 or 5 amp fuse like the 30 amp battery fuse. It will work just fine.

Ratkity · January 2016

^^^ Thanks Verna! At the time, it was a redneck fix for the weekend. I'll totally use the fuse next go-round. Still makes me laugh at myself since I am always preaching about fuses to the point where I'm teased as being Dr. Fuse (my other persona is Dr. Obvious).

JiroTX · January 2016

Ok, both Alde and fridge has been running for 20 hours now. The meter is still saying 12.43. When the Alde kicks in, it drops to 12.35. Since I will be using Alde for less than 10 hours a day, I think I can do it without charging for at least two days.

I am still getting a 100W flexible panel + controller. I do not think I am getting a new battery (I still might).

Why everyone's considering SRM-27 instead of SRM-29? SRM-29 is only 20 dollars extra, and it has RC: 210 instead of 160 of SRM-27. It's not much bigger either.

TnMtnCmper · January 2016

Very interested in the answers to that last question! Why not go big if you upgrade the battery? I hope to do this myself this spring.

Nerdy1 · January 2016

We just got our 120W Zamp setup this week, so I haven't had a chance to really try it out yet (suffering the cloudy, snowy El Nino weather here in New Mexico...still haven't been able to move my brand new baby because of all the snow from a storm 2 weeks ago). Purchased the panels through Amazon, got them fast (~1 week) and I thought at a pretty reasonable price. It is nice to have everything self-contained - no worries about leaving anything home.

Nomad · January 2016

JiroTX - Not so much the cost - It's all about size I believe. What you can make fit in the propane cover without major mods like welding a new frame, etc. - Every inch counts.

JiroTX · January 2016

From the chart Interstate has on their website, SRM-29 is only 1/4" longer and 1/2 taller than SRM-27.
Upgrading SRM-24 to SRM-27 gives you only 15% extra capacity.
SRM-24 to SRM29 can give you 50% extra.
On their website, suggested retail price for:
SRM-24 is $113.95-$120.95
SRM-27 is $121.95-$128.95
SRM-29 is $141.95

Looking at 5amp Hour of Ampere Load for SRM-24, it's 15.5hrs. I think Alde+fridge is less than 1 amp, so If you use Alde only for night time, you can probably go without charging for at least 3 days with SRM-24.

Image: https://us.v-cdn.net/5021717/uploads/editor/a2/1aetycgebm50.png

Nomad · January 2016

JiroTX - I know there's an easy way to fit a 27 (make a battery box cradle insert). Haven't seen anyone do a 29 yet though. Agree that a 29 gives you more for little extra money. Have looked at the same charts but haven't dug into the area and done any measurments for fit though.

JiroTX · January 2016

Thansk PXLated. I was just curious why everyone was talking about 27.

Now it has been 25 hours since I turned on the Alde and fridge. The highest outside temp since then was 43, and the lowest was 26. It is still showing 12.40v.

Now, I have one more question. When I turned up the heat and some lights, 12.40v dropped to 12.19. Am I supposed to look at the 12.19 to determine how much battery I have left or 12.40? I just turned them back off, and now it's 12.39v.

jctangney · January 2016

What is a "battery box cradle insert"?

Nomad · January 2016

JiroTX - Not sure :-) ... If you left the lights on, it'd probably stay at 12.2 for a long time. For instance, I start at sundown at 12.8 with Alde, fridge and lights on. It will gradually end up at 12.2 till I shut off the lights at midnight and it will usually still be 12.2 when I get up - if the Alde has to run alot, it may drop to 11.9 in the early morning hours but seems to stay there till the sun comes up again.

JiroTX · January 2016

Just let y'all know. I stopped the Alde/fridge after 31 hours (the battery monitor said it still had 12.38v) and plugged it in. It was fully charged (the charging fan stopped) in about 2 hours. During this period, high temp was 43 and low was 26. I kept the room temp around 70 (I lowered it to "2" but it was too cold at 60F, so I turned it back up to "3.") and fridge to "3.5." It was a cold day in East Texas.

It looks like the battery lasts for at least three days without charging, but I will still get a 100W solar panel and see how it works. I will probably get the flexible one (HQST) and stick it on the roof with Command strips only when I want to charge. If I get a regular panel (Renogy-about $50 cheaper than the flexible), I will try to make a bracket to put it on the Yakima roof rack (probably not permanent/only when I need to charge).

Thanks everyone for all the info!

Jiro

jkjenn · January 2016

Jiro, the one thing about the battery monitors that plug in is that they do not give you the actual state of charge. They give you the state of charge, plus or minus what you are adding or using. To get an accurate read, you have to disconnect anything that is drawing or adding power to the battery. By turning everything off and removing anything that is charging the battery, you can get a pretty good idea.

Based on you using the fridge 24 hours a day and the Alde for 8 hours a say, here is what you can expect:

Assuming these numbers ring accurate for you, you could expect about 3 days. 3 might be a stretch because it is unlikely you actually reach 100 ah when you recharge as battery life diminishes. I like to account for a 10% loss as a buffer.

I am not saying you should do this, but if you have a 225ah battery, you could probably go 5-7 days. This should give you an idea of how amp hours plays its part in the equation.

Image: https://us.v-cdn.net/5021717/uploads/editor/fl/u7wzukndxiaw.png

ScottG · January 2016

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.

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