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ISSUE: (SOLVED) Low Voltage Output from MPPT

eric.sund

New Member
Joined
Nov 17, 2021
Messages
8
Hi!

In short:
I have issues with my MPPT that does not output sufficient voltage for charging. Solar panel seems to be working fine, but the MPPT does not up the voltage to more that 12.6-12.8. (See image, end of post)

What could be wrong, perhaps is the MPPT broken?

Background:
The system is built for my van 2 years ago. Learned a lot from Will with his videos and book!

Everything has been working flawlessly the past time until recently when I installed an inverter. I did the stupid mistake and forgot to disconnect the panel before disconnecting the batteries. I realised 30s later and plugged out the panel. I don't think the panel had much light, it was autumn in Sweden. I think it wasn't outputting more than 5W probably less.

I baned my self for the mistake but reinstalled everything and nothing seemed to have happened. Everything working as far as I could tell, though it's hard to troubleshoot when you don't receive much sunlight.

Fast forward to now, I'm in Spain with much more sun, and I have noticed that my batteries keeps draining. So I continuously check the MPPT and notice that the voltage never have gone up above 13v even tough the panel are producing over 100W. In any case far from boost (14.7V) or float (13.8V). I disconnected everything again and checked the cables, and also reseted the MPPT to default "Sealed" without success. At the moment idle battery voltage is around 12.4V.

Im asking you kindly for your assistance. What could be wrong? I guess the last resort is to buy a new MPPT.

The system contains:
- 300w single solarpanel (Vmp 33V, Imp 9.12A)
- EPEVER Tracer 3210AN 30A
- 2x 130AH Leoch AGM 12v (SLCA-12130 DT)
- EPEVER Inverter 500w pure-sine (recently installed)

mt50-battery.jpg
 
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what model MPPT? Tracer BN xx?

what battery type has been selected?
What are its settings?
1637155252671.png
 
Type of battery (LFP or Lead-acid)?
SCC settings for bulk current, absorb voltage and float voltage, and absorb time limit if timer based absorb exit?

Picture says panel is putting out 31v x 3.3A = 102.3 watts and battery taking 12.6v x 8.2 amps = 103.3 watts (should be less than 100% but high 90's% is possible) This is just poor accuracy on monitor.

Battery is taking all the PV power available so this says battery is not fully charged yet.

The 102 watts of PV power may be just panel illumination conditions. Check what it is when battery needs charging at mid day with sun directly facing panel. It should produce more PV power although not likely 300 watts. 250 watts would be good number at max sun illumination on panel because of panel heating.
 
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what model MPPT? Tracer BN xx?

what battery type has been selected?
What are its settings?
View attachment 72566
Sorry I accidentally published the post to early, please check back for the edited version.

It's an EPEVER Tracer 3210AN (A series 30a) While troubleshooting I have reseted MPPT to default "Sealed". I can't remeber the exact settings before, but I had increased the boost charge to better suite my batteries. around 14.7v.

The mppt settings:
Screenshot 2021-11-17 at 14.38.52.png
 
Type of battery (LFP or Lead-acid)?
SCC settings for bulk current, absorb voltage and float voltage, and absorb time limit if timer based absorb exit?

Picture says panel is putting out 31v x 3.3A = 102.3 watts and battery taking 12.6v x 8.2 amps = 103.3 watts (should be less than 100% but high 90's% is possible) This is just poor accuracy on monitor.

Battery is taking all the PV power available so this says battery is not fully charged yet.

The 102 watts of PV power may be just panel illumination conditions. Check what it is when battery needs charging at mid day with sun directly facing panel. It should produce more PV power although not likely 300 watts. 250 watts would be good number at max sun illumination on panel because of panel heating.
It's an AGM 12 battery (Data sheet).

SSC settings:
Screenshot 2021-11-17 at 14.57.47.png

What I don't understand is why the voltage is so low? Should it not be around the "boost charing voltage" 14.4v, when it get sufficient power from the panel and the battery is not full?

The panel is mounted flat on my roof so I never get full power, hence why I sized up the PV more than I need.
 
It's an AGM 12 battery (Data sheet).

SSC settings:
View attachment 72571

What I don't understand is why the voltage is so low? Should it not be around the "boost charing voltage" 14.4v, when it get sufficient power from the panel and the battery is not full?

The panel is mounted flat on my roof so I never get full power, hence why I sized up the PV more than I need.

No. The charge controller can't force a battery to a given voltage unless it provides enough current to do so. When your MPPT can provide 13A of current, your AGM won't read 14.4V until it's about 80% charged. Then it has to hold 14.4V for at least a few hours with continually reducing current to completely charge the battery.

Fun with math:

2 * 12 * 130 = 3.12kWh

ASSUMING YOU GET FANTASTIC SUN WITH NO SHADING AND PERFECTLY TILTED/SOUTH FACING PANELS, you'll need TWO FULL DAYS OF UNSHADED SUNSHINE TO COMPLETELY CHARGE YOUR BATTERY IF YOU USE NO POWER WHATSOVER.

Your inverter has a continuous power drain just by being on. It's probably not huge, but even a 7W drain 24h/day is over 10% of your usable battery capacity. And with this new feature, you are probably using more loads.

  1. It's winter.
  2. Your panels are flat on your roof.
  3. You have a new load allowing you to use more loads than you did before.

Conclusion: you are using more power than your system can resupply in a given day, thus you are continually driving your battery voltage lower, and the solar can't keep up.

In your original post, you show a battery at 12.6V while receiving 8.2A of charging - this indicates your battery is at a horrifically low state of charge.

Solutions:
  1. Use less power (probably a tiny fraction of what you currently use).
  2. Get more solar (get some flexible panels you can temporarily hang vertically on the south facing side of the van. They will outperform your roof panel by about 50% this time of year).
  3. Supplement with AC-DC charging from shore power.
  4. Supplement with DC-DC charging from the vehicle.
Please know that you have likely damaged your batteries from 1) excessive discharge and 2) rarely charging to true 100%.

EDIT: Using Madrid's location/weather, your panel is only capable of producing 30% of the power that it would produce in July at the same location. About the same relationship in southernmost city of Malaga.
 
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No. The charge controller can't force a battery to a given voltage unless it provides enough current to do so. When your MPPT can provide 13A of current, your AGM won't read 14.4V until it's about 80% charged. Then it has to hold 14.4V for at least a few hours with continually reducing current to completely charge the battery.

Fun with math:

2 * 12 * 130 = 3.12kWh

ASSUMING YOU GET FANTASTIC SUN WITH NO SHADING AND PERFECTLY TILTED/SOUTH FACING PANELS, you'll need TWO FULL DAYS OF UNSHADED SUNSHINE TO COMPLETELY CHARGE YOUR BATTERY IF YOU USE NO POWER WHATSOVER.

Your inverter has a continuous power drain just by being on. It's probably not huge, but even a 7W drain 24h/day is over 10% of your usable battery capacity. And with this new feature, you are probably using more loads.

  1. It's winter.
  2. Your panels are flat on your roof.
  3. You have a new load allowing you to use more loads than you did before.

Conclusion: you are using more power than your system can resupply in a given day, thus you are continually driving your battery voltage lower, and the solar can't keep up.

In your original post, you show a battery at 12.6V while receiving 8.2A of charging - this indicates your battery is at a horrifically low state of charge.

Solutions:
  1. Use less power (probably a tiny fraction of what you currently use).
  2. Get more solar (get some flexible panels you can temporarily hang vertically on the south facing side of the van. They will outperform your roof panel by about 50% this time of year).
  3. Supplement with AC-DC charging from shore power.
  4. Supplement with DC-DC charging from the vehicle.
Please know that you have likely damaged your batteries from 1) excessive discharge and 2) rarely charging to true 100%.

EDIT: Using Madrid's location/weather, your panel is only capable of producing 30% of the power that it would produce in July at the same location. About the same relationship in southernmost city of Malaga.

Thank you for your very instructive answer, I learned something new! My knowledge in this area is very limited.

I checked in to a campground this evening for shore power. I guess I will have to be more careful with my usage, for some reason I thought the system would have no problem keeping up. Will start using my DC-DC charger every time I drive from now on as well.

Hopefully the batteries are not too smoked.
 
Looks like you have a power meter below the MT50. Can it measure kWh or Ah? If so, it would be very helpful to know how much your batteries take on when you can get them fully charged.

AGM batteries LOVE to be fully charged. Charging them to full after each discharge is key to prolonging their life. Any time they are not fully charged, they are degrading. Any time they are below 70-80% charged, that degradation accelerates, and they sustain damage that reduces their capacity even if unused. ANY time you have an opportunity to charge your AGM batteries, you should take it. Hopefully, the addition of the DC-DC (coupled with sufficient driving) will resolve the issue.

If you're ever looking at your battery voltage, and it's been resting at or below 12.4V (no or negligible current in or out), it's time to charge it. It might be objectionable, but it's probably worthwhile to idle the vehicle just to get some charging. 26A of charging for an hour will get you 10% capacity.
 
Looks like another example of under sized system for the load.

What’s your daily KWhr usage?

When this was commissioned we’re the batteries always getting to >13.8 daily?

My guess is the batteries are toasted. They need to be fully charged and load checked to verify how much damage has already been done.
 
Looks like you have a power meter below the MT50. Can it measure kWh or Ah? If so, it would be very helpful to know how much your batteries take on when you can get them fully charged.

AGM batteries LOVE to be fully charged. Charging them to full after each discharge is key to prolonging their life. Any time they are not fully charged, they are degrading. Any time they are below 70-80% charged, that degradation accelerates, and they sustain damage that reduces their capacity even if unused. ANY time you have an opportunity to charge your AGM batteries, you should take it. Hopefully, the addition of the DC-DC (coupled with sufficient driving) will resolve the issue.

If you're ever looking at your battery voltage, and it's been resting at or below 12.4V (no or negligible current in or out), it's time to charge it. It might be objectionable, but it's probably worthwhile to idle the vehicle just to get some charging. 26A of charging for an hour will get you 10% capacity.
Yes it power meter can measure how much the system is using. I've just been very naive, since before installing the inverter it has never been a problem. So I have not looked much at the power meter. I'll have to calculate how much power I use per day. I study out of my car now and use a display together with my laptop. So the usage is indeed a lot more than before.

The DC-DC is 30A so it helps a bit. I'll research how I could implement additional portable flexibel panels that I can incline towards the sun.

Hopefully I can get them charged up fully by tomorrow afternoon with the help of shore power.

How would one check the batteries for damage? By damage/degrading you mean that their maximum capacity is decreasing?

Once more, thanks your helpful information!

Looks like another example of under sized system for the load.

What’s your daily KWhr usage?

When this was commissioned we’re the batteries always getting to >13.8 daily?

My guess is the batteries are toasted. They need to be fully charged and load checked to verify how much damage has already been done.

Earlier I noticed that the voltage was much higher during charge. Either around Float 13.8v or bulk 14.6v. But I guess I never really drained the batteries as much then.
 
Yes it power meter can measure how much the system is using. I've just been very naive, since before installing the inverter it has never been a problem. So I have not looked much at the power meter. I'll have to calculate how much power I use per day. I study out of my car now and use a display together with my laptop. So the usage is indeed a lot more than before.

Definitely keep an eye on that. 130Ah/1.56kWh is your max before you exceed the 50% discharge rule.

The DC-DC is 30A so it helps a bit.

Good number. An hour of charging is about 10%.

I'll research how I could implement additional portable flexibel panels that I can incline towards the sun.

Given your panel's 33Vmp, 2X 100W 12V flexible panels (about 17Vmp each) could be placed in series and then that string put in parallel with your 300W. Essentially, add parallel MC4 connectors at the MPPT and then plug a 2S 100W/12V panel vertical array into them when you need it. You'll still get what you get from your 300W, and the 300W won't impeded the 200W vertical array. There will likely be ~5% losses due to the panel's not being perfectly matched, but you'll still get a big benefit from the additional 200W.

Might be a bit nutty, but a vertical mirror reflecting onto your roof panel could noticeably improve yield. Might be very impractical given the size of the roof panel.

Good conversation starter if you're lonely, though. :)

Hopefully I can get them charged up fully by tomorrow afternoon with the help of shore power.

I should hope so. What's the amperage of your AC-DC converter?

How would one check the batteries for damage?

Without conducting detailed testing, you'll need to go by voltage and estimated state of charge. Every 13Ah is 5% of your capacity. After you fully charge it, use X amount of Ah (at least 52Ah) and then completely cut off all charge/discharge from the battery for two hours. Check resting voltage and compare to AGM voltage chart.

state-of-charge-chart-for-agm-battery.png


You can then calculate your estimated total capacity.

By damage/degrading you mean that their maximum capacity is decreasing?

Yes.

Earlier I noticed that the voltage was much higher during charge. Either around Float 13.8v or bulk 14.6v. But I guess I never really drained the batteries as much then.

Those sound like good numbers for a fully charged AGM. If you're not observing that on a mostly daily-basis anymore, you're definitely over-utilizing their capacity.
 
Another take-away from the chart above is that if you notice your battery at a low voltage while you're pulling loads, say 11.8V - a pants-pooping level - fear not. If you remove the loads and observe the battery voltage to rebound upwards (without charging), that rebound voltage is more indicative of state of charge than the loaded voltage.

A battery monitor that reports true state of charge would do you good. :)
 
Do you have any loads running while you are seeing about 100W of power receiving and going out?
 
Given your panel's 33Vmp, 2X 100W 12V flexible panels (about 17Vmp each) could be placed in series and then that string put in parallel with your 300W. Essentially, add parallel MC4 connectors at the MPPT and then plug a 2S 100W/12V panel vertical array into them when you need it. You'll still get what you get from your 300W, and the 300W won't impeded the 200W vertical array. There will likely be ~5% losses due to the panel's not being perfectly matched, but you'll still get a big benefit from the additional 200W.

Might be a bit nutty, but a vertical mirror reflecting onto your roof panel could noticeably improve yield. Might be very impractical given the size of the roof panel.

Good conversation starter if you're lonely, though. :)
Hmm.. Interesting! So I could just disconnect the extra array by the MC4 parallel connector and the 300W will work on its own? Will look more in to this.

Hahah yea would be a pretty big mirror and I am already short of space in the car! Also imagine hoisting it up on my roof ?

I passed this place few weeks ago, maybe I can ask them if I can park my car in the center.
Solar furnace in Font Remeu
solarfurnace.jpg

I should hope so. What's the amperage of your AC-DC converter?

Only 8A, so it will take a while. At the moment the battery sits around 14V, when I started it was around 13V.
The max voltage of the charger should be 14.7V for for bulk/absorption. Might need to spend another night at the campground.. ?
Without conducting detailed testing, you'll need to go by voltage and estimated state of charge. Every 13Ah is 5% of your capacity. After you fully charge it, use X amount of Ah (at least 52Ah) and then completely cut off all charge/discharge from the battery for two hours. Check resting voltage and compare to AGM voltage chart.
Another take-away from the chart above is that if you notice your battery at a low voltage while you're pulling loads, say 11.8V - a pants-pooping level - fear not. If you remove the loads and observe the battery voltage to rebound upwards (without charging), that rebound voltage is more indicative of state of charge than the loaded voltage.

A battery monitor that reports true state of charge would do you good. :)
Okay! Does voltage charts between AGM batteries vary much? From my battery spec I calculated which is quite different from your chart. (I just assumed that there is 6 cells per battey)
SOC:
100% 13V
90% 12,78V
70% 12,54V
50% 12,36V
40% 12,3V
Screenshot 2021-11-18 at 12.53.22.png

Yes a battery monitor with true SOC would be very helpful. Either I'm drawing from the batteries when it's dark or the solar is charging, so its hard to get an accurate reading. I guess a battery monitor like this Renogy that Will recommends would do the job? How can they measure SOC? Calculate Wh in/out?
 
Hmm.. Interesting! So I could just disconnect the extra array by the MC4 parallel connector and the 300W will work on its own? Will look more in to this.

Yep.

Hahah yea would be a pretty big mirror and I am already short of space in the car! Also imagine hoisting it up on my roof ?

I passed this place few weeks ago, maybe I can ask them if I can park my car in the center.
Solar furnace in Font Remeu
solarfurnace.jpg

that would help! :)

Only 8A, so it will take a while. At the moment the battery sits around 14V, when I started it was around 13V.
The max voltage of the charger should be 14.7V for for bulk/absorption. Might need to spend another night at the campground.. ?

8A * 12V = 96W, so yeah... not much. If you're still using power, you're taking away from that. There is no harm in adding an additional charger in parallel with that one.

Okay! Does voltage charts between AGM batteries vary much? From my battery spec I calculated which is quite different from your chart. (I just assumed that there is 6 cells per battey)
SOC:
100% 13V
90% 12,78V
70% 12,54V
50% 12,36V
40% 12,3V
View attachment 72676

Plate formulation and electrolyte concentration can vary, so go with Renogy's numbers.

Yes a battery monitor with true SOC would be very helpful. Either I'm drawing from the batteries when it's dark or the solar is charging, so its hard to get an accurate reading. I guess a battery monitor like this Renogy that Will recommends would do the job? How can they measure SOC? Calculate Wh in/out?

Will recommends a few:


You program them with the battery capacity, and they count current in and out and compare it to the capacity. The SmartShunt is crazy accurate. It allows you to program in temperature effects (cold batteries deliver less capacity), and it takes into account Peukert's effect, i.e., your 130Ah batteries only have 130Ah when you're pulling 6.5A (for 20 hours). If you pull more, you will have less than 130Ah capacity. The Victron unit factors this into its calculation.
 
Other points to consider. The batteries may have lost capacity or have partially failed. The Leoch batteries suffer accelerated ageing and loss of capacity if not fully charged at 0.2C inital charge current and have a high, 14.7 volt, absorbtion voltage, with 3 to 4 hours of absorbtion time. Your solar panel and solar regulator will not meet these conditions.
The Leoch130 Ah batteries have this capacity at the 100 hour rate, at the 20 hour rate its capacity is 107 Ah. At new install this is the capacity value needed for battery monitors.
I have reciently replaced two Leoch 130 AGM in a motorhome that had lost 40% of their capacity in two years due to non ideal charging.

Mike
 
Thank you for the help!

The batteries have definitely been exposed to non optimal charging. Living in variable climate, and winter far north, it's hard to get them charged fully everyday. I will evaluate how the system manages from now on with different charging/usage behaviour. Then see what upgrades needs to be done. I guess there is many advantages with Lithium batteries, especially that they seem to be fine not charging up fully everyday.
 
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