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diy solar

Why aren’t my batteries charging under a bright sun?

LithiumCanuck

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Jan 3, 2022
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First full weekend after having changed my batteries a few weeks ago.

I replaced my acid-lead batteries with 3 SS EG4-LL and every time I get to my cottage, they are always fully charged. This is the first time I have the time to spend the weekend there and do some testing. On Friday, I discharged my batteries to 68% and when I woke up on Saturday, it was very cloudy. I noticed some charging during scattered periods of sun but decided to go do something else waiting for the sun to come out.
In the afternoon, now under a bright sun, I went down to look at my batteries. They were still below 70% and discharging (a little) while my solar charger was only giving a couple amps, just what’s needed for my iternet and some other stuff…. I decided to shut everything down and when I powered up my gear, the batteries were charging with the 20 amps given by my charger (ok, maybe not full sun…)….. Saddly, I had to go and didn’t have time to check anything else.

What am I missing?

My charger is an Epever 4215BN with these settings (partial list):

Charging Limit Voltage: 28.8v
Overvoltage Reconnect Voltage: 28.8V
Equalize Charging Voltage: 28.8V
Boost Charging Voltage: 29.2V
Float: 27.2V
Boost Duration: 180
 
Do you remember what the voltage of the arrray was when you had that trouble. my array is on my rv roof and I’m usually parked in the shade and my controller frequently gets stuck at low voltage. With my configuration getting stuck reduces my output to half of my typical output in full sun. Disconnecting the PV and reconnecting it fixes the issue once I am In good sun. Here is a tread where this was discussed a little bit.

 
Do you remember what the voltage of the arrray was when you had that trouble. my array is on my rv roof and I’m usually parked in the shade and my controller frequently gets stuck at low voltage. With my configuration getting stuck reduces my output to half of my typical output in full sun. Disconnecting the PV and reconnecting it fixes the issue once I am In good sun. Here is a tread where this was discussed a little bit.

I should have noted ?. I am more interested in amps than volts I have to correct this. Thanks for the info, I will gather more info if it happens again.
 
I should have noted ?. I am more interested in amps than volts I have to correct this. Thanks for the info, I will gather more info if it happens again.
The MPPT does it’s magic by finding the maximum power point of the solar panels. This is the point where the panels produce the highest amperage output at present sun conditions. In heavy shad or overcast this will be at the lowest voltage required to send charge to your batteries. If you have a max v open circuit voltage of 100 volts from your panels and the charger is holding the voltage down to 30 volts you could possibly get less than a third of your possible output. Hopefully it’s just a fluke and it will never happen again.
 
The MPPT does it’s magic by finding the maximum power point of the solar panels. This is the point where the panels produce the highest amperage output at present sun conditions. In heavy shad or overcast this will be at the lowest voltage required to send charge to your batteries. If you have a max v open circuit voltage of 100 volts from your panels and the charger is holding the voltage down to 30 volts you could possibly get less than a third of your possible output. Hopefully it’s just a fluke and it will never happen again.
If it does, I’ll look at the panels voltage and I’ll just disconnect the array instead of shutting down everything.
 
Also remember that when most people do their solar-insolation calculations the early morning and late afternoon hours are typically considered "throw away".

In other words, it can be very bright, but the light energy is low because the sun at an angle is further away, and photons have a lot of atmosphere, not just clouds, to pass through losing energy.

See if you can find the solar-insolation chart for your area and see what are the usable hours. Even more critical during the winter, which is what many use when they do the overall power-budget calculations..
 
Also remember that when most people do their solar-insolation calculations the early morning and late afternoon hours are typically considered "throw away".

Thank you. I sized my installation taking this fact under account and it has been running very well until that day with my flooded lead batteries (I replaced them a few weeks ago). I experienced that bug for the first time last week and I was wondering if it was because of one of my parameters...
 
Do you remember what the voltage of the arrray was when you had that trouble. my array is on my rv roof and I’m usually parked in the shade and my controller frequently gets stuck at low voltage. With my configuration getting stuck reduces my output to half of my typical output in full sun. Disconnecting the PV and reconnecting it fixes the issue once I am In good sun. Here is a tread where this was discussed a little bit.


Mine does the same thing from time to time - Xtra 3210N. PV input voltage drops in half, charging is limited. Switch off the panel disconnect and back on, they bounce back up to normal and charging current doubles.

Seems to happen if there is other charge current coming in, like the dc to dc charger, then the SCC needs to get reset.

I would like to figure out why it does this, but simply resetting it gets it going again. I think it's a bug in their software.
 
would like to figure out why it does this, but simply resetting it gets it going again. I think it's a bug in their software.
Ya

I bought an MPPSolar AIO because I was fed up with the Epever bug. Now a few months in I just bought a new 4215N to double up with my original 4210.

I decided to decommission the AIO because the non-AIO system is 1/3 of the idle consumption. I love the thing but I need less draw 24/7 than I’m experiencing now.

The Epever product is awesome but the ‘skating’ bug you mentioned and the higher-volt cutout bug are quite annoying to say the least.
 
If the Tracer becomes a problem with keeping correct parameters I'd probly swap it out for a Victron controller. I just don't think they have the same issues.

If the Tracer SCC is the only charge source it seems to keep up - everything stays right. Over our trip when I had the dc-to-dc going when we drove, and some unintentional converter charging (cats hit the on-switch TWICE when we were plugged in) that is when the PV input voltage would drop off and have to be reset. I would just switch off the input breaker from the panels, wait a couple of seconds and switch them back on - volts would go from 18+/- to 43, where it's supposed to be. It's weird that the SCC could limit the input voltage - I'm just not getting that. I need to put a DMM on the terminals when it does that, see what the panels are really doing. Maybe there's a diode feedback to the panels or something.

I haven't had problems with it over-volting though, but then you wouldn't really know it unless or until the pack or cells got over-volted on the bms.
 
I'm a newb so take my advice for what it's worth. But . . . I had a similar problem at my cottage. I couldn't seem to get more than 22w in the sun and 65w in "full" sun. A soft cloth and a bucket of soapy water later, and I was charging at 250w. A fine layer of pollen had accumulated on the panels. Worth a try.
 
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