Yet another solar question

[climbing coastie]

I read all the "How much solar do you need" thread and am a little more confused than before I read it. My needs are slightly different as I will be chasing winter quite a bit looking to ice climb and ski.

I have a set amount I'm going to spend on my electrical set up. After reading up it seems like the best battery life is to keep them topped off as much as possible, so here is my question. Would it be smarter buying a bigger battery bank so I don't drop it down so low, or a smaller bank with more solar to get it back up to full quicker? Seems to me this could be a never-ending loop (bigger battery, more solar, bigger battery, ect.)

I've figured out that a 150ah battery should work for me and I shouldn't get that down below 75-80%. Should I go with 150ah and 400w solar or 200ah with 300w solar? Would hooking it up to my van's alternator change the answer? I'm guessing my morning drives (45min max) wouldn't be long enough to get much charge out of it. Does every little bit help or would it be a good idea anyway so when I do drive 6-8hrs it would top off my battery.

 

[Optimistic Paranoid]

How long do you anticipate doing this?

Solar panels have an assumed lifespan of 20 to 30 years.

I would not expect more than 6 to 7 usable years out of lead acid batteries.  This is based on years of observing engine starting batteries, which ordinarily are only depleted to 95% before being fully recharged.

So strictly on the basis of best bang for my buck, I would prefer to invest my money in panels rather than batteries.

 

[Almost There]

Would hooking it up to my van's alternator change the answer? I'm guessing my morning drives (45min max) wouldn't be long enough to get much charge out of it. Does every little bit help or would it be a good idea anyway so when I do drive 6-8hrs it would top off my battery.

It won't change the answer about solar/batteries but its' still a good idea anyways. The short morning drives won't do much but driving to the ski slopes in winter where you  have less sun anyways and at a higher latitude will certainly  help keep the batteries happy.

What I'm concerned about with solar is that if you're chasing winter, you're not chasing the sun. The amount of solar power available to be harvested by the panels varies considerably by latitude and season. Northern Arizona Wind and Sun had a big chart of North America on the wall when I was there and it was quite amazing as to the percentage of solar power available or not available between say AZ and WA states so unless you're skiing in the high sierras you might be needing a whole lot more solar panels to be able to harvest enough power. You might want to run the question past them giving them your location and season.

 

[tx2sturgis]

You are a prime candidate for tilt-able roof panels, or portable panels that you can deploy at an angle, and move, to catch the maximum amount of sunlight. If you flat mount the panels, you will probably see much less than half of their rating.

On the other hand, cool or cold panels tend to put out a bit more power than panels that are hot.

On my old motorhome, I had one large tilting panel that did very well in the summer when it was tilted towards the south. Of course, on short, and cloudy days, it struggled, but was quite productive on sunny days.

 

[Putts]

Northern Arizona Wind and Sun had a big chart of North America on the wall when I was there and it was quite amazing as to the percentage of solar power available or not available between say AZ and WA states

Got curious, Googled a map. 

It's for homes, but it should work for a van.

1. 
   
   1. Find your city in the map and match it to the numbered area.
      Let’s start with our home, Portland, Oregon. Our city lies within the 1,400 band, so 1,400 is our number.
      
   2. Multiply the number of kW your system is rated for (we get 4.77 from above) by the number of the map color in your area. For us it’s: 4.77 x 1,400 = 6,678.
      
   3. Next, multiply that number by 0.78. Why 0.78? It represents the percentage of electricity you can expect to capture, based on inverter efficiency, panel performance, and losses from wiring. We calculate: 6,678 x 0.78 = 5,209 kWh generated per year.
      

 

[John61CT]

Would it be smarter buying a bigger battery bank so I don't drop it down so low, or a smaller bank with more solar to get it back up to full quicker?

You really should start with how many peak AH you use per day, or at least a high average, call that number X.

This gives you a minimum bank size of X times four, in a winter scenario I would say six, so you can go 2-3 days without letting your bank go down below 50%.

I've figured out that a 150ah battery should work for me and I shouldn't get that down below 75-80%.

Assuming you mean SoC, you only plan to draw the bank down by 20-25%.

If 80% DoD, a SoC of 20%, that would murder even a quality bank pretty darn quickly.

So only planning to use 25AH per day?

So figure you need solar to produce ** in real life ** not STC ratings 30-35AH per day in normal winter conditions.

Another way is put in 300w minimum for a 150AH battery, for winter maybe go up to 400w.

Would hooking it up to my van's alternator change the answer? I'm guessing my morning drives (45min max) wouldn't be long enough to get much charge out of it. Does every little bit help or would it be a good idea anyway so when I do drive 6-8hrs it would top off my battery.

Every bit helps, especially with a good external VR like MC-614, but very unlikely will you ever actually get to 100% full, the "low amp long tail" really needs shore charging or lots of solar.

The ideal would be an hour high-amp Alt charge in the early morning, followed by a full day of solar.

 

[tx2sturgis]

On my old motorhome, I had one large tilting panel that did very well in the summer when it was tilted towards the south.

TYPO!

That should have said WINTER.

Sorry for the error.

Damn movable keys!

 

[akrvbob]

Get more panels to capture the small amount of sun.

To extend the life of your batteries, use less power. One of the most important things in solar is conservation, and yet we hear little about it. Simply use less electricity. One summer a group of us went 16 days without seeing the sun in Flagstaff AZ, everyone ran out of power but me. I watched the weather and when I saw that storm coming I stopped using power and went to emergency conservation.

Plus I had bought all the solar I could afford and everyone else had bought what they thought they "needed." Obviously, they needed more, they just didn't always need it.

Buy solar for the worst situation, not the "normal."

 

[Weight]

I bought the most solar that would fit my roof area.

 

[climbing coastie]

So I bought 4 100w panels and a 200ah AGM battery. After driving from the lower 48 to Alaska during continuous cloudy weather I really need to hook it up to my alternator! Either my heater draws WAY more power than stated or my battery wasn't full when I installed it (even though my charge controller assumed it was)

What's the difference between the MC-614 mentioned above and the ASR-5? Reading info on these you can program a delay into them will I still need a battery isolator or will one of these units replace that?

 

[Trebor English]

Those Balmar regulators replace the regulator in your alternator to make better charging.  You have a regulator already.  Your engine computer may be intimate with your alternator.  These products may be hard to get working correctly in a van if you want to keep all the computer functionality.  You still need an isolator unless your 200 amp hour AGM is your starter battery.

 

[John61CT]

Did I understand correctly that you are using your battery electricity to produce heat?


MC-614 is more adjustable, has more features to be compatible with different batt types and prevent overcurrent demands overheating the alt.

Standard alt setups are not designed to put out high amps for more than a few minutes, and often just stop working when they get hot.

Powerful charging direct from alt may not be feasible with modern very fuel-efficient vehicles.

Then need to go to a DCDC charger like Sterling's batt2batt series.

 

[speedhighway46]

We have our “Sternwake” electrical expert back in the person of John61CT.

Thanks!

 

[John61CT]

Puhleeze!

SternWake's forgotten more real-world hands-on knowledge than all of us left here have put together.

He does live on if you really need him, just not here.

 

[climbing coastie]

My Wabesto gasoline fired heater is what is producing the heat. Litature says it draws 2.5a but after three nights my charge controler cut off power.

So do I not need one of those regulators?? Just go straight from alt to battery with an isolator? This won't kill my battery?


On a side note: my battery says 60a max for charging and 20 or 30 reccomended. The cheapest 25a charger I can find locally is $275. Will I hurt my battery to use a less expensive 7.5a charger designed for AGM batteries?

 

[John61CT]

> So do I not need one of those regulators?
First question is, could your vehicle even be adapted to use one?

Only worth pursuing (with lead batts) if you see the alt as being a major charge source for you, i.e. you usually spend many hours per day driving.


> Just go straight from alt to battery with an isolator?

The purpose of those latter is to keep House loads from running Starter batt down, nothing to do with charging per se.

> This won't kill my battery?

Running the batt down will kill it faster than any alt.

Purpose of a better VR is to protect the alt from the bank, at least as much as improving charging.

> On a side note: my battery says 60a max for charging and 20 or 30 recommended.

IMO can be safely ignored with a lead batt. But you need heavy wiring, quality crimping, fuses etc infrastructure to handle those rates.


> The cheapest 25a charger I can find locally is $275. Will I hurt my battery to use a less expensive 7.5a charger designed for AGM batteries?

If it's a cheap battery that you're already abusing, no difference, other than taking lots longer to recharge.

But a quality AGM bank should be charged at .4C or higher for maximum longevity. That's 40A per 100AH bank capacity.

Note that this sort of infrastructure expense will amortize over a long time, often longer than your vehicle.

Batteries are a consumable.

 

[climbing coastie]

Thanks John!! I think you just saved me quite a bit of money.

My van is my daily driver right now. I usually don't drive more than an hour or two a day, but when I go on climbing trips it's not uncommon for me to drive 12-16hrs a day for 2-4 days then back to short drives. Sounds like replacing the alternator every so often would be cheaper than the charge controller and chancing it screwing up my electronics.

 

[John61CT]

You are drawing the wrong conclusions.

No one is saying a situation that might break your alt is an acceptable solution. It won't just wear out sooner like a battery, it either will work or not.

Yes you may be fine, but you need to either find a professional or learn how to figure out the details, with some support from here.

Step one, buy a decent DMM and ammeter, and learn how to use them.

Once we figure out that you can safely use your alt - and we need full details on your setup, lots of variables there,

Get your House battery well installed with proper connections to the alt/starter circuit.

And realize doing it right costs money, if you invested in a Webasto you obviously can afford, it.

And just getting this alt-charging bit set doesn't mean you won't need other sources, it will take some evolving, trial and error until your systems balance your usage and supply.

PS are you running the Webasto while driving?

 

[climbing coastie]

Thanks for the clarification. Should have known nothing was that simple.

I'm quite familiar with Fluke meters as we had them at work, though I only own a cheap one. What readings do I need to take?

Details of my system: Renogy 400w premium kit (https://www.renogy.com/products/kits/premium-kits), wired in series, a Vmax charge tank 200ah battery (XTE4D-200).  

Electrical draws are/will be: truckfridge TF-130, Wabesto heater, LED lights, maxxair fan, and possibly a water pump. All calculated to be well under 60ah a day. No inverter needed. Of course if I find I have plenty of power left I might add stuff. 



No I'm not running the Wabesto while driving. I have an aux heater that heats with engine coolant while driving. With it and my dash heater going I was sweating in a t-shirt when it was -25°F out.

 

[John61CT]

What make, model and year vehicle?