Why does my solar not charge to 100%?

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Southdowns

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Hi Guys,
I have just come back from a lovely weekend at the Beaulieu pop up campsite, with bags of hot sunny weather. My question is why does my solar not charge my battery to 100%
Every day the monitor was dropping slowly and on the final day it was around 85%.
I am not complaining about the lack of solar, we had as much as we needed, running the Maxair, some lighting, charging phones etc. I just don't understand when we were out for the days with nothing on why it would seem from the shunt monitor that we were not putting power back into the batteries.
On one day we had a yield of 410 WH's with a P max of 183W and a V max of 68.04, the battery had a max of 14.58V with a min of 13.00V.

The controller very quickly went through it different phases from bulk to float
When I checked the app on my phone the more things we had on the more watts we were generating but with things turned off the watts went down to 1 or 2

Am I expecting too much and is the above normal?
I was hoping that the solar would keep pushing the percentage back up especially over such a sunny weekend.

We have 3 X 175 watt panels, 3 X 125ah gel batteries and the controller is Victron Energy SmartSolar MPPT 150/35

Thank you
Ian
 
Sounds like the controller needs recalabrating to the battery.
I would say the battery is fully charged hence no input from solar when nothing turned on.
Switch stuff on and put a drain on the battery which is then being charged by solar.
 
Agree with John looks like the controller is set up wrong.
For a start 14 58v is too high you normally only charge Gels to 14 2 - 14.4v, I think the default absorbtion phase on the Victron is 4 hours for Gel.
So it should rise to 14.2 - 14.4v then hold at that for 4 hours then drop to 13.8v float.
Without the absorbtion phase the batteries will only be 80% charged.
 
Last edited:
Are the 3 x 175W panels wired in series? If so that voltage seems about right for the maximum power point, assuming they are 36-cell (9 x 4) panels. You should have plenty of solar power, enough to whizz the batteries back up to 100% in this weather. The drawback of series wiring is that any small amount of shade on one panel drastically affects the whole string. Such as the shadow of an aerial, or a large leaf.

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On the day mentioned above, the bulk charge took 2h 59mins, 21%, absorption 1h, 7% and float 10h 23mins, 72%
When I set up the controller I downloaded the data sheet, which I have attached, but I could not work out what information I needed from it. So I used a default setting of AGM spiral, there did not seem to be another option for AGM. This has an absorption of 14.7v and a float 13.8v with something called an equalisation voltage of 16.5v

The panels are wired in series.
 

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Southdowns said:
On the day mentioned above, the bulk charge took 2h 59mins, 21%, absorption 1h, 7% and float 10h 23mins, 72%
When I set up the controller I downloaded the data sheet, which I have attached, but I could not work out what information I needed from it. So I used a default setting of AGM spiral, there did not seem to be another option for AGM. This has an absorption of 14.7v and a float 13.8v with something called an equalisation voltage of 16.5v

The panels are wired in series.
Click to expand...
Why would you use an AMG setting when you have Gels?
 
Sorry my fault I have AGM as per the data sheet, don't know why I wrote gels. Probably still had my brain on holiday time
 
Would have loved lithium but beyond the depth of my wallet

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OK 14.7 is correct, asorbstion phase 1 - 4 hours not that critical, switch off the equalisation only really used on knackered Lead Acid batteries.
 
Okay, just tried that, not been able to turn if off completely but its gone down to 8v and will not go any further. The setting changed from AGM spiral to user defined and the battery went into absorption phase and the panels started producing watts
Does that sound okay?
 
Hi , how do you know it doesn’t fully charge? Do you have a shunt or battery monitor and the charge is on deficit?

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Hi Raul,
Yes I have a Victron shunt with I think its the 712 monitor, not the smart one though.
And yes the percentage reading goes down slowly even though the vehicle has been in good sunlight all day.
 
autorouter said:
Are the 3 x 175W panels wired in series? If so that voltage seems about right for the maximum power point, assuming they are 36-cell (9 x 4) panels. You should have plenty of solar power, enough to whizz the batteries back up to 100% in this weather. The drawback of series wiring is that any small amount of shade on one panel drastically affects the whole string. Such as the shadow of an aerial, or a large leaf.
Click to expand...
Does that mean anyone with only one panel will suffer this drastic loss of output if a small shadow is across the panel? Not a dig, just cannot see how two small panels in series would be affected more than one large panel. Perhaps someonr can explain it.
.
 
Southdowns said:
Hi Raul,
Yes I have a Victron shunt with I think its the 712 monitor, not the smart one though.
And yes the percentage reading goes down slowly even though the vehicle has been in good sunlight all day.
Click to expand...
Forget the percentage for the moment, does the shunt re set to 100%? How much Ah amorphous is missing if not resetting?
 
Yes it does reset to 100% after we have driven it or we are on EHU, sorry do not know what Ah amorphous is?
 
It’s the count down with minus displayed on monitor, representing you discharged amps. As you charge, they come down to 0. As you discharge, they increase.
If it does re set by other means of charging, you may not have enough solar for your needs, or, solar controller not set up right, and drops in float to soon.

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Yes, as more demand increases the minus Ah goes up and conversely as each item is turned off the minuses comes down. My wife has said I am becoming addicted to the monitor and I keep checking it with things turned on and off.
I would have hoped that 3 X 175 watts would have been more than enough, we are not heavy users and I am guessing the maxair is probably our biggest draw of energy the rest is a mix of lighting and some charging or phones and kindles.
Would resetting the controller be the first thing to try? Having said that I am not sure what I would do differently, the battery data sheet was difficult for me to decipher so I picked the default AGM spiral setting but following Lenny HB's advice I tried to turned off the equalisation setting but only got that down to 8v
 
68c said:
Does that mean anyone with only one panel will suffer this drastic loss of output if a small shadow is across the panel?
Click to expand...
Yes, that's what happens. In one panel, all the cells are in series, in your case 9 x 4 = 36 of them. A shadow causes a high resistance in one cell, which reduces the amps through the whole line of cells.

If the panels are in parallel, the amps from the other panels are not affected. Panels on a house roof are usually out of any shadow, so it's not a problem normally. On a motorhome there's more potential shading problems, including aerial/satellite dish, so they are usually wired in parallel for that reason.
 
autorouter said:
I guess it's one of these spellcheck errors, and was meant to be amp-hours.:rolleyes:
Click to expand...
No, that’s the actual term used by victron representing the amps gone out of a full SOC battery.
 
Personally, for that reason I would have the 3x175 in parallel, you have no need for high voltage for a 12v system. It’s a short run and 22v is plenty. If it was 4x 175 then I would done 2S2P

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Your batteries were fully charged, but the battery monitor wasn't detecting this and resetting to 100% like it should have. Concentrate on setting up the battery monitor.
 
He said IS reseting to 100% when it drives or ehu.
 
Raul said:
He said IS reseting to 100% when it drives or ehu.
Click to expand...

This could happen if the battery monitor is set up to reset on a specific voltage for a period and some of the chargers (i.e. the B2B and mains) will absortion at a higher voltage (or for a longer period) and activate the 100% reset, whilst the solar chargers has a fractionally lower absorbtion voltage, or shorter period. Also, some profiles (i.e. Lithium) will have no float, which can also confuse a battery monitor by dropping voltage more than a full absorbtion phase.
 
Raul said:
Personally, for that reason I would have the 3x175 in parallel, you have no need for high voltage for a 12v system. It’s a short run and 22v is plenty. If it was 4x 175 then I would done 2S2P
Click to expand...
Thats interesting I went with series as it seemed to be the majority way of fitting it (YouTube videos)
If I change this to parallel my amps will go up, would need to check what the amp rating is for the panels, also instead of a cumulative 3 X 175 watts I will only get a single 175amp I am currently running 6mm cables from the panels to the controller, would I need to beef these up?
 
Southdowns said:
Thats interesting I went with series as it seemed to be the majority way of fitting it (YouTube videos)
If I change this to parallel my amps will go up, would need to check what the amp rating is for the panels, also instead of a cumulative 3 X 175 watts I will only get a single 175amp I am currently running 6mm cables from the panels to the controller, would I need to beef these up?
Click to expand...

The trade off is that series connection will be much better in low light/off season and have reduced resistive losses due to lower currents. Parallel tends to have better performance in partial shading, although this depends on the design of the bypass diodes. In reality, all panels are a combination of series and parallel connections.

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