How to Live on 100 watts of Solar

[tx2sturgis]

I found out today I do not have a solar controller or inverter for the 100w panel.  I have a converter and the panel wires go directly to the house battery.  If I get my genny fixed, can I boondock indefinitely?

This is what I suspected, and probably explains the short lifespan on the house battery.

Someone installed the panel with no knowledge of needing a controller. If there is no blocking diode, then current is free to flow from the battery at night back into the solar panel, causing a loss of energy from the battery.

Plus, during bright sunny days, with little use of the interior systems, the battery can easily get over-charged and it will overheat, outgas, leak, dry out, or a combination of these.

Was your inspection guy able to check the fluid levels in the batteries?

 

[jonsun]

man we should've told her to get the spec off the panel

 

[duckwonder]

Was your inspection guy able to check the fluid levels in the batteries?

He did not check the batteries as part of the PDI but I requested it.  He kindly demonstrated how to use my multimeter when I asked.  The levels were low but he said they're fine and I ran in and got some distilled water.  I thank people in the forums who have shown me some basic level info that has benefitted the overall health of the van.

 

[duckwonder]

man we should've told her to get the spec off the panel

I would have but the info was on the underside of the panel and un-mounting was not part of the guy's timetable today, but yes, I wish I had that.

 

[highdesertranger]

maybe if you gave us the dimensions of the panel we might get a better idea of how many watt it is. a 100 watt panel with no controller I don't believe it. when you got a reading of 13.5 volts was the sun out? was the panel shaded? did both batteries read the same voltage? we need pics of the wiring on both batteries. is the wire from the panel exposed on the inside of the van? what's the battery voltage in the morning before the sun comes up? highdesertranger

 

[duckwonder]

maybe if you gave us the dimensions of the panel we might get a better idea of how many watt it is.  a 100 watt panel with no controller I don't believe it.  when you got a reading of 13.5 volts was the sun out?  was the panel shaded?  did both batteries read the same voltage?  we need pics of the wiring on both batteries.  is the wire from the panel exposed on the inside of the van?  what's the battery voltage in the morning before the sun comes up?  highdesertranger

Thank you.  Going back to the Solar and Batteries thread.  It's more about my particular situation and I'm confusing people including myself, lol.  This one is more general for what can be run/expected with 100w of solar per day.  Will answer this in the other thread.  Thanks.

 

[Gideon33w]

You wont run anything with a setup which fries batteries ...
Anyways, it's about needs and wants. So, what are those for you?
We can tell you what can be run but if it doesn't apply to you how is that helpful?

There's people on here who run the basics plus a 12v fridge on 100w.
The fridge cuts it a bit close though and you need to watch things.

Also, battery capacity plays a major factor.
Depending on your needs, 50w solar + 200ah battery might be > 100w solar + 100ah battery.

 

[John61CT]

re MPPT advantage

> The real question is this:  is it worth 2x-3x the money to get the benefits?

The Victron MPPT has almost all the adjustability and features you'd want, and even their 75/15 gives lots of flexibility for $100.

Those lousy cheap Chinese units and IMO kit-included SCs aren't worth bothering with, we're talking about the cost of a takeaway meal for a small family for something that will last longer than your vehicle.

 

[Trebor English]

I have one of those lousy cheap Chinese units.  At $10 the price multiplier isn't 2 or 3.  The $100 unit is 10 times the price.  It has all the adjustability and features I want.  

It is now in the second year of service.  By mistake I disconnected it from the battery (panel still connected) one morning and didn't notice till the sun went down.  The controller didn't fry and is still in sevice.  Durability seems adequate.
 
I don't bother with the controller.  It keeps the battery charged.  It displays the voltage.  

When I go to Burger King it costs less than $4 for a Whopper Junior and a salad.  To upgrade to the $100 controller would be 25 meals.  

[sarcasm] My first wife still likes toll roads.  They must be better than those other roads otherwise they wouldn't charge for them.  If you don't spend enough the product must be poop.  Higher price will make a product better.  [/sarcasm]

 

[frater secessus]

The Victron MPPT has almost all the adjustability and features you'd want, and even their 75/15 gives lots of flexibility for $100.

That's my point;  the 75/15 ($90) is 2.5x the cost of Victron's own PWM ($35).  WIth the BT dongle ($50) for programming it is 4x the price of the PWM.

Those lousy cheap Chinese units and IMO kit-included SCs aren't worth bothering with

I object to this characterization;  I think it is FUD and not based on experience or good faith research.  I also think it denigrates the practical choices forum members have made here on Cheap RV Living.  Recently Bob made a similar point with fierce conviction when another thread got judgemental.

The 75/15 is great and would handle 100W of solar nicely.  So could a Tracer 2210A w/MT50 display.  Just as configurable and has a higher voltage limit (100v).  The 75/15 setup costs 75% more than the Tracer setup. It is obviously worth 75% more to Victron owners, and I respect their decision.

Thought experiment:  why doesn't a 75/15 owner spend yet another 75% more to get an industrial grade controller like the Morningstar Sunsaver MPPT 15A for $240?
My guess:  they can get what they need without overspending.  <-- same for Tracer/Renogy owners

 

[John61CT]

Apologies for overstating the case, I've not considered buying PWM for a long time (other than Bogart's), and had plenty of dud Chinese cheapies.

 

[jonsun]

when you can get MPPT for $100-150 and it comes with full adjustability its worth it. when they were morningstar, outback, etc for $400 yeah no thanks. the value is in the adjustability which is absolutely crucial for a full timing system.

if the victron PWM is fully adjustable and at least 15A for $35 yeah that's fine too. just make sure you get the components to hook it up to external controls.

 

[TechScott]

Wow, this thread has been going round and round. The issue with a system with a single 100-watt panel isn't necessarily just usage (read: discharge) it is often the rate that the system's battery can absorb a charge. It's not uncommon to find mobile living folks with many hundreds of watts of solar and extremely frugal electrical usage fighting to keep their batteries charged due to limited sunny hours. The challenge isn't the panels ability to provide electricity to the batteries, but the battery's ability to absorb it. Lithium batteries bar outstrip standard lead acid and AGM battery's ability to absorb a charge. In addition, a lithium battery can be safely discharged 30-50% more than a standard lead-acid or AGM battery (hence more capacity). If you use more electricity during peak charging hours, a battery that recharges faster is more likely to be fully charged at the end of the (charging) day if the battery is able to absorb all residual electricity not being used.
Of course, lithium batteries cost more...

 

[jonsun]

100w aint shaby without a fridge

 

[Boyntonstu]

Wow, this thread has been going round and round. The issue with a system with a single 100-watt panel isn't necessarily just usage (read: discharge) it is often the rate that the system's battery can absorb a charge.  It's not uncommon to find mobile living folks with many hundreds of watts of solar and extremely frugal electrical usage fighting to keep their batteries charged due to limited sunny hours.  The challenge isn't the panels ability to provide electricity to the batteries, but the battery's ability to absorb it.  Lithium batteries bar outstrip standard lead acid and AGM battery's ability to absorb a charge.  In addition, a lithium battery can be safely discharged 30-50% more than a standard lead-acid or AGM battery (hence more capacity). If you use more electricity during peak charging hours, a battery that recharges faster is more likely to be fully charged at the end of the (charging) day if the battery is able to absorb all residual electricity not being used.
Of course, lithium batteries cost more...

Not too expensive:

[video=youtube]

 

[user 15722]

He's got a nice VW transporter powered by those cells... and a vid about the trip on his channel. It's interesting.
It seems he got it in a wringer over a bulk by on those batteries... kinda too bad. wheels

 

[duckwonder]

Wow, this thread has been going round and round. The issue with a system with a single 100-watt panel isn't necessarily just usage (read: discharge) it is often the rate that the system's battery can absorb a charge.  It's not uncommon to find mobile living folks with many hundreds of watts of solar and extremely frugal electrical usage fighting to keep their batteries charged due to limited sunny hours.  The challenge isn't the panels ability to provide electricity to the batteries, but the battery's ability to absorb it.  Lithium batteries bar outstrip standard lead acid and AGM battery's ability to absorb a charge.  In addition, a lithium battery can be safely discharged 30-50% more than a standard lead-acid or AGM battery (hence more capacity). If you use more electricity during peak charging hours, a battery that recharges faster is more likely to be fully charged at the end of the (charging) day if the battery is able to absorb all residual electricity not being used.
Of course, lithium batteries cost more...

The sun has been going round and round awhile.  So glad it does that, lol.  This is all Greek to me so it takes me awhile!  Thanks for further explanation of the batteries.  The manufacturer whether knowingly or unknowingly created a space for a single lead acid battery so that is what I'm limited to, at least for the time being.  I like the idea of AGMs because I have so much to learn and anything I can maintain less is a good thing.  Lithium is too new and too expensive for me but sounds very promising.

 

[frater secessus]

The challenge isn't the panels ability to provide electricity to the batteries, but the battery's ability to absorb it.

Yes, Li chemistries would be better.  But a person living on 100W of solar is unlikely to be running a lithium bank.

So how does the 100W 'dweller deal with the realities of Absorption?  By getting to it as soon as possible  then running loads during that stage.

 

[lenny flank]

 It's not uncommon to find mobile living folks with many hundreds of watts of solar and extremely frugal electrical usage fighting to keep their batteries charged due to limited sunny hours.  

I don't use much electricity. During the summer I have no trouble keeping things charged. In winter when the days are shorter and the sun is less intense, I often need to recharge the laptop in a fast-food or mall or something to keep up. Of course, today I could buy a 200w system for the same price I paid years ago for my 100w system.

Lithium batteries are superior in many ways to lead-acid. Alas, they just cost too damn much. In the future if the price on them comes down, I think they'll quickly replace lead-acids.

 

[John61CT]

Demand is growing, I doubt price will come down on LFP.

But properly cared for, even paying 7x the price per 100AH, just the greater **usable** capacity, plus the longevity, make it cheaper than lead long-term.

The lower weight and space requirements are a big bonus for mobile use as well.