Insufficient Solar?!

[boywonder]

Originally Posted by B350

And yes, the solar charger is the Renogy 20 Amp Commander MPPT solar charge controller.

I guess the lack of overhead sun at this time of year plays a big factor too which I didn’t consider. So maybe that is playing a significant role in the equation?

Of course the lack of sun is playing a big factor this time of year.....

As far as problems go, being a bit light on panels and having lots of battery capacity is better than the other way around....IMO

And you have relatively high output compact panels on the roof now (I have 2 of these same panels paralleled with a 120W polycrystalline Kyocera and 350AH of batteries).

Is there any way that you can squeeze another 100W eclipse panel up there? That would be my first choice......

What has been the max amperage that you have seen with two panels?

[B350]

Originally Posted by boywonder

Of course the lack of sun is playing a big factor this time of year.....

As far as problems go, being a bit light on panels and having lots of battery capacity is better than the other way around....IMO

And you have relatively high output compact panels on the roof now (I have 2 of these same panels paralleled with a 120W polycrystalline Kyocera and 350AH of batteries).

Is there any way that you can squeeze another 100W eclipse panel up there? That would be my first choice......

What has been the max amperage that you have seen with two panels?

Ha! I’m glad to be on the positive end of a problem!

The lack of sun in the PNW definitely contributed to the low state of charge the batteries are at now. It seems that with the dwindling overhead sun trying to get these batteries fully charged again will be nearly impossible.

Unfortunately, the rooftop space is right with the existing 2 panels, a Maxx Air fan and Yakima storage box on the ass end. I measured about 15” of usable space but that’s far off the 21” needed for anothe 100W panel. Another panel would mean needing a new 40A MPPT controller too...

I actually don’t know what max amperage the panels have produced. I just know that before we left home in August the charge state was always around 14+V.

I happen to have a pic of the readout from June. And the second pic is from tonight after a good day of sun on the Oregon coast.

[Scalf77]

A couple of questions,
Is it possible that either of your panels gets shaded by the by the max air and or Yakima box?
The negative of panels in series is the effects of shading.

Have you calculated your total current usage for a normal day?
That should be the driving factor in your sizing requirements of solar.

How much space between panels and roof, recommendation is 1.5". The effect of temperature can reduce panel output. It probably won't solve your issue, but any gain is gain.

A big problem when charging with solar, is having enough to support the absorption charge. Many times if we have depleted our batteries, we spend the best solar time of the day getting the bulk charge done, but don't have enough time to complete the Absorption phase of the charge cycle

I think someone else mentioned splitting your batteries. It could be possible to have solar connected to the disconnected battery maximizing the output of the solar controller to charging the battery. Then you switch back to the other battery the next day.

In general I think you will find you need more panels, not sure how old your panels are, but panel efficiency is growing every year, I recently replace a 140 watt panel with a 180 panel of the same size.

Also, if your staying parked in one location, then you may want to look at being able to angle the panels. That means the van would need to be parked in the correct direction. It would be a pain, but would provide more charge with a limited system.

First thing is to get a good reading on your amp usage.

-greg

[Flux]

And sorry for the silliness on the series vs parallel. It was more of a question if your controller is setup with the best situation for your batteries and I am not familiar with that controller. I spent a good amount of time researching the correct settings for the Lifeline battery. Luckily my controller has a built in profile for that battery.

Will you have access to 120V all that often??

[1der]

The pics of the display help a bit.

The one taken during the day looks right. 36v coming in from the series connected panels, battery banks looks like it is in float (full) since the 1.1A is all that the batteries needed and there was no load /draw. The float voltage of 14.4v seems high for float, so this should be looked at.

The one from last night looks correct as well. 12.6v after resting for 4 plus hours and a little bit of draw?? 12.6 is full charge, why do you think you are not getting full charge?

What are your draws? What is the voltage in the morning? Do you have any temperature sensing charge compensation?

You may or may not be under paneled depending on what your usage is. if you have only a fridge and some lights, then you may only be drawing 15 amps or so over night on a cold night. Add a heater, radio, water pumps and it can pop up to 50 amps over night. Your 200w should provide you with 40 to 50 amps of charge during the day. But remember you have loads which are drawing during the day so the amount left to replenish the batteries is less than the total available amps from the panels.

I like Scalff77's recommendation of looking for higher wattage panels for the same foot print. You can get a 360w 60 cell panel that measures 66x39. Adding another 100w panel and connect them in parallel would eliminate the need for a new controller since your voltage down from the panels would be 18v. IMPORTANT: if you were to add a 140 watt panel to your two 100w panels, you will not get 140 from the new panel, it will be limited by the 100w panel rating. The panels need to be the same watt rating.

What gauge wire is coming in from the panels?

[REF]

I just added one of these to my system to be deployed as needed or when parked for longer periods of time, can be angled as needed towards the sun, or when parked in the shade. There are others out there, but these seem to be from a trusted brand and the price was lower than others.

https://www.renogy.com/renogy-100-wa...-o-controller/

Also comes in a version with a controller, this might be needed in your case because of the limitations of your 20 amp controller.

https://www.renogy.com/renogy-100-wa...olar-suitcase/

I built a shelf below the rear platform to store it and added the plug to the rear of the van with 25' of cable

[MountainBikeRoamer]

Like arctictraveler is saying --- 12.7 volts is indeed a pretty healthy "full battery" resting charge. So based on that number alone, wouldn't your impression be that the batteries ARE fully charged?

If 12.7 volts is the highest voltage you see at the battery's terminals **while they are actually being charged,** then that might be a different story....

On the line of dialogue that Scalf77 is indicating ---
---- and having read a good number of posts here on the forum about the most accurate means of measuring the actual "state of charge" of a battery (as well as a good bit of the exhaustive write-ups by solar/battery guru "handy bob" at his website), it seems that measuring amp-hours in vs amp-hours out is the only way to truly conclude with any reasonable certainty that a battery is fully charged or not.

Does your Renogy charge controller have this function? Or do you have a battery meter (like a Bogart Trimetric 2030, for instance), that utilizes a shunt to precisely measure amp-hours in/out to the battery bank?

If I'm learning anything (and I am most decidedly a slow learner when it comes to a lot of this electrical voodoo), it is clear that voltage is a poor measure of a battery's actual state of charge. A significantly-depleted (or partially damaged) battery can show a high surface charge voltage for instance, but that charge voltage can sag almost immediately when a load is applied.) 12.7 volts as a resting charge does indeed sound pretty darn good.

Again, if you are indicating that 12.7 is the max voltage at the battery terminals while the panels are feeding charging voltage, then I'd be indeed concerned. Even a basic "maintenance voltage" for a topped-off battery (supplied by a charger, not the actual resting voltage of the battery itself) ought to be around 13.2 volts.

My main curiosity is trying to learn exactly what "metric" you have been using to determine that your batteries aren't getting fully charged, so I think I'm still on the same page with arctictraveler.

[Flux]

Page 19 has the Absorption and Float Voltages at Temperature Chart for your lifelines. If you can alter your chargers settings to better match these, you will get better charging efficiency.

http://lifelinebatteries.com/wp-cont...cal-Manual.pdf

For Example, at 70°F your absorption voltage is 14.4 and your float voltage is 13.4

[boywonder]

Originally Posted by Scalf77

The negative of panels in series is the effects of shading.

I think someone else mentioned splitting your batteries. It could be possible to have solar connected to the disconnected battery maximizing the output of the solar controller to charging the battery. Then you switch back to the other battery the next day.

Good point on the series wiring.....a little shading on one panel hurts...

Switching batteries in and out may end up leaving some juice on the table, if a single battery gets topped up by noon or so....but perhaps better for battery care and feeding.

As Greg mentioned, a big question is how many AH are you consuming per day roughly?....

Originally Posted by 1der

I like Scalff77's recommendation of looking for higher wattage panels for the same foot print. You can get a 360w 60 cell panel that measures 66x39. Adding another 100w panel and connect them in parallel would eliminate the need for a new controller since your voltage down from the panels would be 18v.

What gauge wire is coming in from the panels?

The eclipse 100W panels are roughly 20" x 40" so two of them is 40" x 40"......So if B350 has 15" of extra space that =55" total.....11 inches short of 66".....assuming the eclipse panels are side by side.

Wiring the three panels in parallel increases current and reduces voltage....so perhaps pushing the 20A current rating of the existing controller. However, I'm assuming that since an MPPT controller doesn't waste much power when the panels are wired in series then the output current from the controller to the battery is still going to be lots of amps....with series wired panels it has to be that way, or there is no point.

[ShuttlePilot]

I agree with what Greg suggests ^^^^.

But just for some back of the envelope math. Lets assume your system is working great to see if your experience is close.

Your battery bank is 400Amp hours (Ah) to dead. Lets assume your batteries are 100% by late afternoon and you have used 20% of that by next morning.

400 Ah x 0.2 = 80 Ah removed from batteries by morning.
or
80Ah x 12.7 volts = 1,016 Watt hours that need to be replaced by solar. In addition to what is used through the day like refrigerator running.

Now for solar generation. Again let's assume everything is working great including full sunny day. Which is where solar installers, manufacturers, and many owners greatly exaggerate the math. Here is just a ball park calculation.

200 watts of solar, averaging 70% efficiency (maybe a stretch), between 10 am and 2 pm, add an additional hour for the cumulative morning and afternoon off peak time. So 5 hours of generation.

200 Watts x 70% = 140 watts average
140 watts x 5 hours = 700 watt hours for the day.

So in this dirty calculation the solar isn't keeping up with the energy used by 316 Watt Hours. Don't forget this is on top of the energy used during the day like refrigerator so the deficit would be what ever that is too.

So my suggestion is that if your seeing a gradual decrease over several days your set up is probably working as designed. I believe your full timing out of your van. I would suggest what some off grid folks do that just can't add any more solar but have a large battery bank. A small Generator. They run their generator after a few days when the bank gets to around 60%. But here is the smart part. They only use the generator for a Bulk charge and in the morning. Then, letting the solar on "Charge Day" finish the Absorb charge. This is a more efficient way of using the generator time and when the noise is OK.

There is often ways to improve the efficiency of a solar system. Watts made by the panels to watts stuffed into the batteries and appliances. These will improve your system but I don't think it will make your setup meet your expectation.

-Eric