Is my solar setup faulty?

[monsteruk]

Hi All,

First post, so please be kind!

We have a 150W solar panel with an MPPT controller, and a 110ah leisure battery (all fitted by a camper converter, both brand new). Based on a couple of short trips without electric hookup, I don’t think the panel / MPPT are charging the leisure battery correctly - but have never had a solar panel before so want to get some other opinions as to whether what we are experiencing is “normal”. We are going back to the converter with this, but it would be really useful to see how others with a similar setup are getting on, as this will aid us in our conversations with the converter.

To make things easier, we decided to perform a controlled test to get some specific data and evidence (our MPPT controller has a Bluetooth connection to an app, so we can see current readings, and also download data for 30 days).

Panel: FLEXi SUN – 150W Flexible Solar Panel | CampervanCulture.com
MPPT: Midsummer Energy

The test we performed is as follows:

• Start with leisure battery 100% charged.
• CRX50 fridge turned on at 7AM (middle setting, and full of cold food).
• No other electrics turned on.
• Camper parked in / facing the sun for the entire day. The test day was 17th September, which just happened to be the best day we had in September: Conditions on test day were as follows:
  • Wall to wall sunshine (no clouds at all)
  • Outside Temperature: 18 to 22 degrees
  • Camper time directly in sun (upwards of 10 hours).

Test checks:
Check MPPT Bluetooth readings at 07:00, 13:00 and 17:30
Check MPPT data for the entire 24 hour period

Test results – individual readings:

Date / Time	Solar Watts	Solar Voltage	Solar Current (amps)	Battery Volts	Battery Current (amps)	Battery State	Battery % charge	A/H remaining
17/09/2020 07:00​	0​	20.25​	0​	12.65​	0​	bulk	100.00%​	110​
17/09/2020 13:00​	0​	13.03​	0​	12.38​	0​	not charge	75.00%​	82.5​
17/09/2020 17:30​	0​	12.6​	0​	12.24​	0​	not charge	60.00%​	66​

For that 24 hour period, the MPPT controller recorded the following key points:

• Max battery charge (start of day): 13.27v
• Min battery charge (end of day): 12.09v
• Time in Bulk (when its actually charging): 4 hours, 28 mins.
• Total produced Watt Hours: 50wh (which I am assuming is just 4 Amp Hours, so very very low!)

Conclusions:
Even with the van parked in good sun, at 22 degrees or so for 10 plus hours - the leisure battery was down to 60% charge (from 100% at 7AM), in a little over 10 hours. Over that period, the Bluetooth app reported a total output of 50 watt hours from the solar setup (which seems ridiculously small to me - adding just 4ah, back into a 110ah battery).

We based all our calculations of which panel to buy on this article: Solar Power - The Camping and Caravanning Club. In there is suggests that 150w panel should produce up to 1,000wh on a summers day, and 120w or so on a winters day. Lets be kind and say our sunny test day was in the middle of those points – and even based on that assumption, our setup should still have produced around 600wh or so in the day, as opposed to 50wh as it did?

Question:
What experience do others have with 150 watt panels? Is what I am seeing “standard”? My expectation was that on a lovely sunny day, the solar setup should run a fridge (on medium setting, full of cold food) for 10 hours without consuming 40% of the leisure battery’s charge? If what I am seeing is right, I cannot for a second understand why anyone (including me) would every buy one!

Comments and thought much appreciated.

 

[Phil_G]

Sounds like a faulty panel, or a bad joint between the controller & the panel. The panel voltage should never drop as low as 12.6 during the day, under full load (ie flat battery) the MPPT function should vary the current it pulls to hold it at its maximum power point which wanders around 17-18v ish. With less load (ie full a battery) the panel will float higher, but never down to 12.6 even on a dull day. Try to repeat the panel=12.6 situation, then measure at the panel by sticking a couple of pins into the cable inside the van but as near as poss to the source. If the panel reads 12.6 in daylight, I'd say its goosed.
Cheers
Phil

 

[monsteruk]

Sounds like a faulty panel, or a bad joint between the controller & the panel. The panel voltage should never drop as low as 12.6 during the day, under full load (ie flat battery) the MPPT function should vary the current it pulls to hold it at its maximum power point which wanders around 17-18v ish. With less load (ie full a battery) the panel will float higher, but never down to 12.6 even on a dull day. Try to repeat the panel=12.6 situation, then measure at the panel by sticking a couple of pins into the cable inside the van but as near as poss to the source. If the panel reads 12.6 in daylight, I'd say its goosed.
Cheers
Phil

Hi Phil,

Really appreciate you taking the time to reply - most useful.

I have updated the main post with details of the specific panel and MPPT controller we have (just in case that makes a difference).

I will ask the converter to do the test you have recommended. I am reluctant to start messing with the wires etc. (I am not electrically minded). If I manage to do something wrong, it all becomes my problem rather than theirs - if you see what I mean.

I guess my main question would be, in those sunny conditions, roughly how many watt hours of generation should I expect from my setup? I am assuming 50wh in those conditions is very low, and indicates there is an issue somewhere? This is my main concern - that the converter looks at the panel and says, "yeah, thats all fine". Just looking for some opinion on whether those figures I have posted are lower than one would expect and indicate a problem with the setup (then I can hold my own a little in the conversation with the converter). If that makes sense.

Cheers,

Roy

 

[Skyliner33]

I know its not quite what you are asking, but was anything else drawing power during the test? Im surprised a compressor fridge drains your battery from 100 to 60% in 10 hours.

Mine runs down a 110Ah battery about 6 -7% overnight. Its always above 90% in the morning and thats even in the last few days running the fridge empty so at its most inefficient.

 

[T6Jay]

No, your experience is not "standard", you definitely have a fault somewhere.

We have a fairly similar setup, 50L vitrifrigo fridge, 160W panel, Renogy MPPT (DCC50S), 95Ah AGM battery. On a fairly average september night/day, overnight the fridge takes around 15Ah out of the battery, by lunchtime it's back up to 100%.

Best case - on a bright day in September, I've seen the solar fully charge the battery from ~87% to 100% by 10am
Worst case - The last few days have tipped it down all day, and the system can't keep up, the panel puts around 5Ah (60Wh?) back in the battery each day. Gonna need the EHU if the van's not driven.

Can you measure a) the voltage from Panel+ to MPPT+ and b) the voltage from Panel- to MPPT-, a+b will be the voltage drop. This should be <1V, and ideally <0.5V, if it's not, then you could have a bad connection somewhere, or the cable could be too small.

 

[monsteruk]

I know its not quite what you are asking, but was anything else drawing power during the test? Im surprised a compressor fridge drains your battery from 100 to 60% in 10 hours.

Mine runs down a 110Ah battery about 6 -7% overnight. Its always above 90% in the morning and thats even in the last few days running the fridge empty so at its most inefficient.

Hi, thanks for your response.

The figures above were for a test undertaken during the day. However, I did actually run the test for 48 hours so do have the figures for overnight - and I can confirm that the power usage overnight was actually quite low (pretty much as you have indicated. I am suspecting that the reason the fridge drained more power during the daytime, is that the camper was parked in the sun during the test (to maximise access to solar), but this would obviously have the affect of heating the inside of the camper, meaning the fridge needs to work harder to keep the temperature at a low level. At night (as there is no sun), the inside of the camper would have been far cooler, so the fridge would not have had to work as hard. That is what I am guessing is the difference.

My key question I guess, is about whether in 24 hours a total of 50w/h of power from the solar setup (in seemingly ideal conditions) is ok, or whether it indicates a problem with the setup.

Many thanks,

Roy

 

[t0mb0]

I'm confused about the 50wh the controller claims it's put in given on the three occasions you spot checked it it was producing zero amps. How is it telling you it's put in 50wh?

 

[Loz]

I just quickly looked at my controller output with the partially cloudy and sun not directly over, with a 100W panel I'm seeing 20W and 1.5 amps going in.

 

[Skyliner33]

Hi, thanks for your response.

The figures above were for a test undertaken during the day. However, I did actually run the test for 48 hours so do have the figures for overnight - and I can confirm that the power usage overnight was actually quite low (pretty much as you have indicated. I am suspecting that the reason the fridge drained more power during the daytime, is that the camper was parked in the sun during the test (to maximise access to solar), but this would obviously have the affect of heating the inside of the camper, meaning the fridge needs to work harder to keep the temperature at a low level. At night (as there is no sun), the inside of the camper would have been far cooler, so the fridge would not have had to work as hard. That is what I am guessing is the difference.

My key question I guess, is about whether in 24 hours a total of 50w/h of power from the solar setup (in seemingly ideal conditions) is ok, or whether it indicates a problem with the setup.

Many thanks,

Roy

Hi, you're welcome.

OK, to add to my informations, I stated the overnight values as that is the lowest that my battery drops.

To give an indication at the T6forum fest in early September my battery was fully charged every day before 9:30am.
I have a 180W solar panel and a redarc dc-dc charger. Also my panel is on the fixed OEM roof, so its not angled towards the sun in any way.

I will see if I can get some screenshots for you.

 

[monsteruk]

I just quickly looked at my controller output with the partially cloudy and sun not directly over, with a 100W panel I'm seeing 20W and 1.5 amps going in.
View attachment 87448

Thanks for that, this is mine as of now...

I dont really understand electrics. You battery is showing as 13.41v (which I thought was 100%), but the state is still "bulk" (which I understand to be charging). Mine shows as "state: off", which is not charging? In any event, your voltage seems to be higher than mine, even though yours is a 100w panel and mine a 150w.

 

[Skyliner33]

Just taken these 2 screenshots. As an idea of conditions its raining when I took these:



From the forum meet at Sibbertoft

 

[monsteruk]

I'm confused about the 50wh the controller claims it's put in given on the three occasions you spot checked it it was producing zero amps. How is it telling you it's put in 50wh?

Hi,

On the phone app, there is an option to export the data for the last 30 days. Its not hour or hour in the export, its just daily totals. I got the 50wh from those daily totals (see attached image). As you say, for those 3 spot checks, it was not doing anything, but I did observe a small amount of charge at other spot checks (again, image attached).

The real weird thing is there seemed no consistency. I would check it in the middle of the day (sun at its highest in the sky), and not charging at all (even though battery needs charging). I would check again, when sun lower in at it was (very slowly) charging!

Images below:

Roy

 

[monsteruk]

No, your experience is not "standard", you definitely have a fault somewhere.

We have a fairly similar setup, 50L vitrifrigo fridge, 160W panel, Renogy MPPT (DCC50S), 95Ah AGM battery. On a fairly average september night/day, overnight the fridge takes around 15Ah out of the battery, by lunchtime it's back up to 100%.

Best case - on a bright day in September, I've seen the solar fully charge the battery from ~87% to 100% by 10am
Worst case - The last few days have tipped it down all day, and the system can't keep up, the panel puts around 5Ah (60Wh?) back in the battery each day. Gonna need the EHU if the van's not driven.

Can you measure a) the voltage from Panel+ to MPPT+ and b) the voltage from Panel- to MPPT-, a+b will be the voltage drop. This should be <1V, and ideally <0.5V, if it's not, then you could have a bad connection somewhere, or the cable could be too small.

Thanks for the response, really helpful!

Where you say:

We have a fairly similar setup, 50L vitrifrigo fridge, 160W panel, Renogy MPPT (DCC50S), 95Ah AGM battery. On a fairly average september night/day, overnight the fridge takes around 15Ah out of the battery, by lunchtime it's back up to 100%.

I am assuming that the fridge is still on the next day? I.e. when it is back to 100% at lunchtime, that is with the fridge still on - so the solar must be producing enough output to power the fridge AND still charge the battery back up to 100% by lunchtime?

Roy

 

[T6Jay]

I am assuming that the fridge is still on the next day? I.e. when it is back to 100% at lunchtime, that is with the fridge still on - so the solar must be producing enough output to power the fridge AND still charge the battery back up to 100% by lunchtime?

Yes, the fridge has never been off since the solar was fitted, months ago. Until the last few very rainy days the solar always got the battery back up to full, or almost full before evening, even on dull dry days.

For your information, the fridge pulls about 3A for about 10mins, then switches itself off for about 15 mins. This is when it's left empty, and closed.

 

[monsteruk]

Yes, the fridge has never been off since the solar was fitted, months ago. Until the last few very rainy days the solar always got the battery back up to full, or almost full before evening, even on dull dry days.

For your information, the fridge pulls about 3A for about 10mins, then switches itself off for about 15 mins. This is when it's left empty, and closed.

Again, really useful. What you say about the amount of time the fridge is on, means my initial calculation I did before I had the camper, were in the correct ball-park. See below.



It does 100% sounds like we have a problem!

Thanks

 

[t0mb0]

Hi,

On the phone app, there is an option to export the data for the last 30 days. Its not hour or hour in the export, its just daily totals. I got the 50wh from those daily totals (see attached image). As you say, for those 3 spot checks, it was not doing anything, but I did observe a small amount of charge at other spot checks (again, image attached).

The real weird thing is there seemed no consistency. I would check it in the middle of the day (sun at its highest in the sky), and not charging at all (even though battery needs charging). I would check again, when sun lower in at it was (very slowly) charging!

Images below:

Roy

Ah, I see. In that case I think it's almost certain your panel, or the connection to your panel, is faulty.

 

[T6Jay]

What size cables has the installer used? some cables have --AWG or --mm² written on them. If you can't see that, what's the diameter of the cables (if they used 2 or 3 core flex, what's the diameter of the flex?).
If you don't have a vernier, use an adjustable spanner and a ruler to measure it.
Also, what's the length of the cable?

 

[Phil_G]

Mine shows as "state: off", which is not charging?

No, 'state' on or off refers to the optional switched 12v output from the controller, which few people seem to use.
Its not related to charging. I dont go with the cable size theory, even a wet piece of string wouldnt drop 6 volts - to me thats either a bad joint, or a duff panel, maybe a blown blocking diode.
Cheers
Phil

 

[monsteruk]

What size cables has the installer used? some cables have --AWG or --mm² written on them. If you can't see that, what's the diameter of the cables (if they used 2 or 3 core flex, what's the diameter of the flex?).
If you don't have a vernier, use an adjustable spanner and a ruler to measure it.
Also, what's the length of the cable?

Will try and have a look later when home and get back to you (if not too dark to see it properly.

Cheers,

Roy

 

[T6Jay]

I dont go with the cable size theory, even a wet piece of string wouldn't drop 6 volts

I know you're are being tongue in cheek here, and I mean no disrespect, but I have seen 6V and more dropped on long cable runs in 24V systems, where the cable size is more than enough to carry the current.
And more specifically, I've seen VW transporter solar installs that use 1mm² flex, the thinking must be that if the panel puts out 10A, the cable will carry it. Yes it will, but volt drop could easily be 3V in this case. That'll definitely put a dent in the charge rate. Renogy say volt drop should be 5% (~1V) at the most, and this 5% will reduce charging efficiency by 10%.

to me thats either a bad joint, or a duff panel, maybe a blown blocking diode.

On this I agree entirely

In my opinion (I'm an electrical engineer), if you find a bad joint/duff panel, and fix it, and this improves your charging, you should still check the cable size is adequate. If an installer is not capable of jointing cables properly, you can bet they aint capable of sizing them properly either.