1st Solar System Reality Check

[JohnJack]

This is my first foray into solar and battery powered camping. I have to consider my wife and two toddlers now. So, I have to ease them into truly roughing it. Someone's signature line I saw about knowledge without experience defines me in the solar/electrical area. I'm looking for a gut check. Thanks in advance for helping us out.

The major concern is running a heater for a couple of nights in a row in Minnesota with minimal hours of light. Lights (not yet LEDs), small radio, charging some batteries (camera, laptop, etc.). and small refrigerator and box fan in the summer, are less important items I'm worried about.

I'm planning to add to my 2002 Coleman Sedona popup camper:
A new battery box and battery, http://www.oreillyauto.com/site/c/detail/SSBL/AGM31T/N0056.oap?ck=Search_deep+cycle+%26+marine+batteries_-1_3253&keyword=deep+cycle+%26+marine+batteries . I know it is probably not the best quality battery, but I like the idea of being able to replace it at any retailer wherever I decide to go in the U.S.A. Am I a complete idiot for considering this? I can procure it for 211 dollars so it is an especially economical to alternatives.

I am thinking something like this solar panel setup, http://www.solarblvd.com/Solar-Panels-&-Systems-12-Volt-Solar-Panels/c1_269/p2755/W-Solar-100-Watt-Foldable-12-Volt-Solar-Panel/product_info.html

If you look at the solar panel setup above... Should I consider whether or not to purchase a charge controller that is capable of more panels (A higher amp rating, correct?)? My current thought is to use whatever comes with it and see how it performs. I am just concerned with what failure looks like... No power when you need it most. It seems like a cheap voltmeter is the best solution to preventing failure, correct?

I already have a cheap detachable 400W inverter that I am planning to wire into the 120V system. Any watch outs there?

So, battery, solar panels, charge controller are reviewed. I've read up enough to know that full charge/voltage is extremely important. I'll worry about wire sizes when I get there. Anything else that I'm missing?

Thanks for all your past and future help!
JohnJack

 

[pappawheely]

Solar blvd has good prices but don't expect them to help with technical issues.

 

[zelatore]

Any time I hear somebody say they want to run a heater off an inverter/battery power I start to get worried. It seldom works very well.
First, I see that is a 100 amp/hour battery. So that sets the base-line of your available power. The next question is what sort of heater are you trying to run and for how long? I won't even get into the lights or other things as they will likely be minimal demand compared to an electric heater.
If this is a typical 120v home space heater, they are usually around 1500w. That works out to (v*a=w, so 120v x 12.5a =1500w) 12.5 amps. You have 100 amp/hours in that battery, but in reality you can only use about half that before dropping below usable voltage. So that's about 50 amp/hours of usable power. So that means you can run your 12.5 amp heater for about 4 hours.
But wait, there's more!
That assumes a 100% efficient inverter to power the heater. This doesn't actually exist. In reality, let's figure it's more like 90% efficient, so that's less than 4 hrs.
And then let's throw in whatever power you draw for you lights or other items. Now we're down to maybe 2.5-3 hours of power.
Yes, your solar system will put 400w, but that's assuming full sun. You specifically said this would be used with minimum hours of daylight, so your charging capacity will be very limited.
In short, I don't think you will have good luck trying to run a heater off a single gp31 battery. Heating elements of any kind are just power hogs. A microwave for a few minutes, a TV, lighting, even refrigeration are good inverter/battery loads, but heaters are a tough nut.

FWIW, I'm not a solar guy but I do install inverters and battery systems fairly regularly on boats and yachts. So I may not be 100% on your charging capabilities with the panel, but I still feel pretty comfortable saying it's just not great to run an inverter to power a heater. I'd think a small Honda 2KW generator might be a better/more cost-effective solution, or a fuel powered heater of some sort.

 

[java]

Lets assume the pop up has a forced air heater (most do right?) so your only running the fan and ignitor.

But I don't think that battery will do. I have 170AH's worth of batteries in my RV, running a few fluorescent lights (18W) for a couple hours, the fridge and heater overnight drain the batteries all the way. The sticker on the fridge says 4 amps IIRC.

My 200W of solar will charge it back up over the course of a sunny day, but the controller sucks and only gets them to 12.6V. I have been impressed with how little light it actually takes to make some power with the panels. It might not be much but its some.

 

[HenryJ]

Your best investment in power comes from conservation. The money spent to change all your lights to LED is a good investment. It can be done reasonably too. I was under $50 to do all of my E1. Hopefully your fridge is propane. That will help. If it is 12v , it will still be "doable". I have one of those onboard too.
Consider a deeper lake. Two six volt golf cart batteries will offer twice the reserve power. You are going to need all that.

I am just north of your latitude and we have done fine with 40w panels. This season we added a 12v fridge to the mix and upgraded to the 100w panel you have linked above.

I think you are on the right track. Go for it.

BLT Offroad E1

 

[zelatore]

6v 'golf cart' (in this case simply meaning a deep cycle) AGM batteries would be considerably more expensive, particularly in AGM, but would provide substantially more power than even the best group 31 battery. You could find 400 amp/hours from a pair of quality 6v L16 batteries. Of course, you'd have a lot more weight to deal with as well as the physical size to find a place for. And the cost of both the batteries, wiring, and battery box(s) would be higher as well. It is a far better solution though.
I think the key question is what sort of heater you want to run and for how long over how many days. The bigger battery bank would prolong the amount of run time, but you would certainly still be drawing power faster than you can replenish it. So once back from your trip you would need a way to top up the batteries before departing again. I typically install large inverter/chargers on boats and use the engine alternators in a similar manner to your solar charger - they provide power back to the system (considerably more than solar) but only for a short time, perhaps a few hours of running time a day, then they boat sits at anchor for a day or more. It's still a net-lose over all but the alternators, or your solar panels, prolong the time before reaching critical depletion. In my case, once the boat is back to dock it is plugged in and the inverter will switch automatically to a high capacity (say 50-100 amps) charger to top up the batteries before the next trip. You would be able do to the same. I don't know if a solar charge controller will produce the right voltage to fully top off an AGM bank even if left with no drain for days, so I'll leave that to those with more expertise in solar. Do keep in mind though that those big battery banks that take longer to drain take correspondingly longer to re-charge as well.

 

[kenn_chan]

long post, sorry Solar panels, charge controllers and inverter chargers.

We have similiar issues in that we have two young daughters (2 1/2, and 4) that we plan on hauling around on our trips.

I just finished my purchases for our solar system and after researching for several months this is what I came up with.

If the panel puts out more than 18 volts (say like 26~30ish) then you can use a MPPT charge controller which will allow you to properly charge AGM's and deep cycles, though the MPPT controlers cost more than the PWM style.

I have two QPower pro g240's running through a morning star MPPT30 charge controller into two (2) 200 ah 12 volt deep cycles.

so panels spces are 240 watts each @ 7.9 amps @ 30.2 VDC. as the MPPT charge controller converts the voltage form 30.2 to 15ish (adjustable to match batteries) amps goes up in relationship making a pretty descent amount of juice. the pig about this is the cabling is almost as expensive as the other components.

after mocking the system up in my driveway I was able to power two sawafuji-engel 12 volt fridges, led lights and a 4000 BTU a/c for about 4 hours on the batteries (no solar as I was simulating night use by dissconnecting the panels) before the inverter/charger shuts down at the 11.5 VDC (low voltage cuttoff for inverter) that I chose.

This still left enough volts/amps for the 12 volt fridges to run for another 5 hours before I stopped the experiment. This gives me the entire night for the fridges, and 4 hours of the a/c running continuous. My next plan is to put a thermostat on the a/c so that it will cycle off and on. currently it only has off/on with a hi low setting for the fan. If it cycles off and on I am hoping to extned the a/c through most of the night.

for heating I am considering the Mr. Heater Big Buddy propane heater. anybody tried them?

worse case I have a yamaha inverter genset that is really quite that I can use to recharge the batteris with or to power the whole camper with if necessary. though my goal was to use it only when absolutely necessary or if possible to eliminate it entirely.

ken

 

[HenryJ]

6v 'golf cart' (in this case simply meaning a deep cycle) AGM batteries would be considerably more expensive...

True, however flooded cell "golf cart" batteries may be an affordable option.
I am just about to the point of returning to the flooded cell batteries. AGM is nice and clean, but the finicky charge issues and inability to refill lost fluid / expelled gases, could be a real deal breaker in the end. It just seems like the old lead acid flooded cell batteries might actually be a better solution if properly maintained. More forgiving. Able to be serviced. Cheaper to replace when the time comes. If I get 75% of the life and at 50% the cost am I winning?

 

[Bbasso]

I've been using the buddy heater for years in my vans, if you have insulation it can keep you very warm. Without insulation it will keep you comfortable.
Just be sure to get the hose to use a 20lb propane tank. Worthy investment.

 

[CaliMobber]

Ken are you really advising this guy to buy a MPPT charge controller for his 100w single battery solar setup? lol it would cost more than everything else combined.

Check out handy bobs page for some true no BS solar info. In the end you just need to figure out how much power everything is going to use and go from there.

Its a lot of reading but will open your eyes to the real world of rv solar

http://handybobsolar.wordpress.com