15 replies to this topic

[Taku]

Putting together a solar package for a new build. I have looked at many of the solar/battery posts and think I have it figured out but want to run it by the folks that know what they are talking about (I am definitely not an electrician and am surprised my wife is letting me even do this since I nearly killed myself doing some house wiring years ago).

 

Will need to power full time:  TF65 Fridge  2 Amps

 

Will need power less than full time:

 

- 3 LED Light Panels @ 1.2 Amps total

- Fantastic Fan: 2 Amps

- Charging computers: 3 Amps/Hr

- Charging camera batteries: 2 Amps

- Occasional phone charging, etc.

 

Looking at a 200 Watt panel and a 100 Amp lithium battery and a 20 Amp MPPT charge controller

Will also have this wired to the truck for charging.

 

Does this sound like a correct interpretation of the Amps required for the various needs and enough solar package to work?    Thanks for your thoughts. 

[Jon R]

Perhaps your wife has a plan?

Just kidding.

Your estimate of battery capacity needed seems correct, and your panel sizing should be adequate for camping in mostly sunny conditions. You might consider more panel if you are going to be in cloudy conditions a lot. I’m installing 400w of panels for that reason.

I’d also suggest you consider a 30 amp mppt controller, which will give you more margin for growth. Depends on the voltage your panels operate at, though. You might be fine.

[Vic Harder]

Taku, to get a full picture, we kind of need to know when/where you camp and how long you stay "out" for, or how long between extended length drives or being parked and on shore power.

 

You don't mention a furnace, so I assume you are camping in warm places?  If so, then the estimate of "full time" power draw by the fridge becomes more reasonable than otherwise.  

 

I see an estimate of an "average 2A per hour".  Does that mean 48AH in a day?  That seems high.  My 130L TruckFridge uses about 36AH on a hot day/night.

 

Likewise for your LED panels and everything else... how many hours a day will they be on?  Add all that up to get a guesstimate of AH used in a 24 hour period.

 

Say it ends up being 50AH used in a day/night.  With a 100AH Lithium battery you will have less than 2 full days without charging in between.  Does that work for you?  If you are parked in full shade, will you go for a long drive to charge up?

 

And to charge up 100AH in a good day of solar you will need the equivalent of 100A for one hour, or 10A for 10 hours.  You will not get that from a 200W panel.  Or if driving using one of the 30A DC2DC chargers on the market, you need to drive for more than 3 hours. 

 

I'd be more inclined to want 3x the solar Watts as AH of battery, so 300W in your case.

[ri-f]

I agree with Vic, that you will need to increase your solar to at least 320W or more, and with JonR regarding the Victron 100/30 mppt controller. And with your estimate of daily electrical loads, it seems to me that you would be consuming upwards of 75 amp/hrs/day. It depends on how long you're running or charging electrical appliances and how energy efficient those appliances are. Climatic conditions will be a factor, too. I don't think you will be able to go longer than a day or two between charges with your proposed set up. If you move around frequently and drive a few hours when you do move around, you might  be ok, but really, you will need to cut back on your electrical useage unless you plug into shore power occasionally, or drive a lot, and often, while your DC to DC charger is running, or you'll need to increase your solar signifcantly. Running a Fantastic fan at 2 amps/hr is a drain, but it doesn't have to be. Your FF can be modified to run at 0.25 amps/hr (see the link below to do the mod, inexpensively). Anywhere you can shave amp/hrs will help. A sunny moderate climate will help. If you are in a cold climate you can use a Wave 3 heater;  it doesn't have a fan and therefore no electrical load. Your fridge running at an average of 2 amp/hr full time will consume half your 100AH LiFePO4 battery each day, all by itself. Maybe it can run at a more efficient setting to save amp/hrs. A lot depends on your useage patterns, how long you're out on your excursions and how energy independent you hope to be while your out there. Bottom line: double your solar, get a 30 amp DC to DC charger, and use energy efficient equipment to increase your off grid time between charges.

 

Rich

[rando]

As Vic mentioned, it all depends on where you wander.   

 

Most of our wandering is in the very sunny Rockies and South West.   We have a similar set of loads to what you describe, and have never had an issue with 160W of roof mounted solar through an MPPT 100/20, and a 150Ah lithium battery.   I can't recall the battery going below 50% (except for testing), so a 100Ah would be fine as well.  We do have a 120W foldable panel which we have used a handful of times when parked in one place for multiple nights in the dead of winter to improve our collection angle, but it is more a novelty than a necessity.   

 

Charging from the truck is normally just straight from the alternator (which yields 5-10A), but I recently cobbled together a DC-DC charger, but again more a novelty than a necessity as solar is almost always enough. 

 

Now if you spend a lot of time in the PNW, the upper mid west, or the Maritimes, then more solar, and a beefy DC-DC charger may be required.  

[ri-f]

Putting together a solar package for a new build...Will need to power full time:  TF65 Fridge  2 Amps

 

With 2 160W panels, a 100AH BB, a 100/30 mppt, and a 30amp dc-dc charger, Engel 45 fridge (consuming 0.75 amps/hr average, full time), an efficient 10-inch tablet for watching a movie, two phones that need to be topped up, a camera battery, and occasional fan use (overhead or furnace - summer or winter), we've never been below 75% soc overnight in sunny places (hot or cold), and we're topped up to 100% by noon next day; and we don't need to run the dc-dc at all. We can even go 4-5 days without any charging source at all if the panels were sitting under a tree canopy in the forest and received no meaningful charge. That said, in winter, completely off grid, under heavy cloud cover in the PNW or anywhere for that matter where incident light levels are very low, we might only receive 10-20 amps/day, which will leave us with a deficit that will grow over time and eventually force us to use the dc-dc charger to top off, which will take a few hours of driving. The point is, you most likely won't always be in an ideal climate. That's the reason for having a well-rounded energy system that will work in your favor in almost any climate or region at any time of year. Okay, you may not have a problem in, say, Arizona. And you might have an over abundance of energy during the sunny summer months, but you will definitely need more charging capacity if you intend to roam around in places that are climatically challenged. I wouldn't want to be limited to having to drive my truck or run a generator a few hours to recharge a battery that is < 20% soc after only 1-2 days, if I were out for longer than a couple days. Just saying, less is more, depends on the circumstance.

Rich

 

 

[Taku]

Thanks for the replies, greatly appreciated. We will be camping for 1 - 3 months at a time (retirement looms!) in the west so sun should not be too much of an issue. I was trying to estimate power needs on the high side and can easily reduce the amp hours (computer/phone/camera batteries will only be every few days if that and in the past have taken "town days" on longer trips and use the public library/coffee shops for extra charging). Using some of the notes from above I would say below 50 AH/day is reasonable. We will be carrying a canoe or kayak many times, so limited to one panel on the roof, so will add in a folding panel for extra wattage as was suggested. Upgrade the MPPT too - better to have it than to upgrade later. For the furnace question: we have a Propex in our current Ocelot and like it - for this build we are going to try a Buddy heater. A friend has been using that in his Cougar for the past five years (about 8 months/year out) and really likes it - so it that works, no power needed. Foot pump for water so no power there either. So will look at something like this:

 

- 300 - 400 Watts of solar panels (plus the DC charging too)

- 100/30 MPPT

- 100 AH battery (likely to get something bigger though)

 

Thanks again for the help

[ri-f]

Thanks for the replies, greatly appreciated. We will be camping for 1 - 3 months at a time (retirement looms!) in the west so sun should not be too much of an issue. I was trying to estimate power needs on the high side and can easily reduce the amp hours (computer/phone/camera batteries will only be every few days if that and in the past have taken "town days" on longer trips and use the public library/coffee shops for extra charging). Using some of the notes from above I would say below 50 AH/day is reasonable. We will be carrying a canoe or kayak many times, so limited to one panel on the roof, so will add in a folding panel for extra wattage as was suggested. Upgrade the MPPT too - better to have it than to upgrade later. For the furnace question: we have a Propex in our current Ocelot and like it - for this build we are going to try a Buddy heater. A friend has been using that in his Cougar for the past five years (about 8 months/year out) and really likes it - so it that works, no power needed. Foot pump for water so no power there either. So will look at something like this:

 

- 300 - 400 Watts of solar panels (plus the DC charging too)

- 100/30 MPPT

- 100 AH battery (likely to get something bigger though)

 

Thanks again for the help

Sounds like you are on the right track now. One suggestion would be to subsitute the Buddy for a Wave3, which I think will be more efficient. I've used both and in retrospect I'd go with the Wave3. Either one will require venting. Also suggest you mod your Fantastic fan - it will be quieter and wildly efficient. Good luck with the new build.

 

Rich

[pvstoy]

"...We will be carrying a canoe or kayak many times, so limited to one panel on the roof, so will add in a folding panel for extra wattage as was suggested.... "

Watch location if you will get shading on the panel.

[Wallowa]

"...We will be carrying a canoe or kayak many times, so limited to one panel on the roof, so will add in a folding panel for extra wattage as was suggested.... "

Watch location if you will get shading on the panel.

 

 

I would think that anywhere you carry a canoe/kayak on the top will shade some part of a solar panel mounted between the Yakima rails...remember interference with roof vents...