Need help with my system

[cstairs]

I built a solar setup in my camping trailer that was fine for two years,but now every once in a while it stops charging the battery.
I have 4 80w panels installed on the roof. Two of them slide under the other two for travel. So they are set up in 2 pairs in series then the pairs in parallel. I have a 24v lipo 8 cell battery with an Overkill bms. My charge controller is an hqst MC2420N10.
So sometimes it just isn't changing the battery, full sun part sun doesn't matter. The green light on the controller indicates "battery full charge" which I have never seen it not green. Even though the BMS tells me the battery may be at 50% or 60% . Then randomly it will start charging like normal.
I can't find any loose connections. I checked with a meter once when it wasn't charging and it showed 43v coming into the controller. My best guess is that the controller is bad, but before I spend the money on a new one I thought some may having more knowledge than me might have an idea what's going on.

 

[ScrodusGargleRotten]

I would trust the controller over the BMS. Its probably doing what you told it too.

One way to know is take a volt meter to each cell. if any cell is 3.48 + that means your pretty charged up. Could be 97% if on the charger at the time of measurement. If any cell is more than 0.02v away from any cell in the range of 3v-3.35v you may have a nasty cell imbalance that will limit the usefulness of the battery.

Your BMS may have bluetooth and may give you the individual voltages.

I imagine you have your charge voltage on the low side and the BMS soc(not really accurate) drifted way down over months.
If you notice reduced capacity look into cell imbalance on this site.

By the way. That ANL fuse should be replaced with a class T.
That anl fuse will always heat up more than most like and its amp interrupting ability is not good enough.
If you had a nasty shorty, the anl fuse would blow and then possibly arc until it burned itself and its surroundings.

Get a class t fuse.

That ratchet strap probably needs to go as well if its compressing the cells. House have burned down from stuff like that.

Looks like you have spacers between cells. That would make compression useless and bad.
You should have cell separating sheets.


What is your pack charge voltage set too?
If this is a 24v system, you need a class t fuse between the 2 8 seies strings and an additional BMS for the now separate 8S string.

 

[DC_Ripple]

From the manual:

Please connect the battery first, and then the solar panel.

Since your MPPT is auto sensing, it might get confused on choosing the correct voltage.

Try turning everything off. Open disconnect for solar panels.

Measure your battery voltage + to - on the battery terminals to ensure you are close to 24V.

Close the breaker and ensure you are getting close to 24V on the mppt terminals.

Then close the PV breaker.

The manual mentions setting the battery type and how to use the Keys.

It also explains how to reset the device to factory default.

SRNE Solar MC2420N10 MC Series MPPT Solar Charge Controller User Manual

SRNE Solar MC2420N10 MC Series MPPT Solar Charge Controller User Manual

device.report

not sure if you have the external bluetooth.

 

[Mattb4]

The HQST solar charge controller (IIRC) is not really set up for LiFePO4 battery charging. If your batteries BMS disconnects either on High cell voltage or low battery voltage it is going to confuse the heck out of this SCC. There is also what the SCC has in it for boost, absorb and float settings.

 

[DC_Ripple]

Seems like it can handle LiFePO4, but you may be on to something with the bms disconnect

 

[cstairs]

I would trust the controller over the BMS. Its probably doing what you told it too.

One way to know is take a volt meter to each cell. if any cell is 3.48 + that means your pretty charged up. Could be 97% if on the charger at the time of measurement. If any cell is more than 0.02v away from any cell in the range of 3v-3.35v you may have a nasty cell imbalance that will limit the usefulness of the battery.

Your BMS may have bluetooth and may give you the individual voltages.

I imagine you have your charge voltage on the low side and the BMS soc(not really accurate) drifted way down over months.
If you notice reduced capacity look into cell imbalance on this site.

By the way. That ANL fuse should be replaced with a class T.
That anl fuse will always heat up more than most like and its amp interrupting ability is not good enough.
If you had a nasty shorty, the anl fuse would blow and then possibly arc until it burned itself and its surroundings.

Get a class t fuse.

That ratchet strap probably needs to go as well if its compressing the cells. House have burned down from stuff like that.

Looks like you have spacers between cells. That would make compression useless and bad.
You should have cell separating sheets.


What is your pack charge voltage set too?
If this is a 24v system, you need a class t fuse between the 2 8 seies strings and an additional BMS for the now separate 8S string.

Thanks for the info on the fuse. I haven't told the controller to do anything, just connected it and chose the battery type. Don't see any other options.
Last time it wasn't charging my BMS told each cell was just over 3.2. I moved it to full sun ,turned everything off and on a couple of times,still no charging. Moved it back to our campsite which was shadier and still nothing. I checked about a half hour later and it was charging. According to the BMS the cells are always very closely balanced. The ratchet strap isn't all that tight, it's just to keep the battery from moving around while traveling. The 2 plastic straps came on the battery.

 

[cstairs]

From the manual:

Please connect the battery first, and then the solar panel.

Since your MPPT is auto sensing, it might get confused on choosing the correct voltage.

Try turning everything off. Open disconnect for solar panels.

Measure your battery voltage + to - on the battery terminals to ensure you are close to 24V.

Close the breaker and ensure you are getting close to 24V on the mppt terminals.

Then close the PV breaker.

The manual mentions setting the battery type and how to use the Keys.

It also explains how to reset the device to factory default.

SRNE Solar MC2420N10 MC Series MPPT Solar Charge Controller User Manual

SRNE Solar MC2420N10 MC Series MPPT Solar Charge Controller User Manual

device.report

not sure if you have the external bluetooth.

I've done all that and a factory reset.

 

[cstairs]

Seems like it can handle LiFePO4, but you may be on to something with the bms disconnect

This is correct

 

[cstairs]

This is a screenshot of my BMS readings. Everything is working right now. Also the settings of the BMS.

 

[ScrodusGargleRotten]

This is a screenshot of my BMS readings. Everything is working right now. Also the settings of the BMS.

Id move the cell undervoltage stop to 2.8 from 2.5

 

[mikefitz]

class t fuse between the 2 8 seies strings and an additional BMS for the now separate 8S string.

The OP has 8 cells and a 8s BMS, just one battery. The classT fuse would be an improvement.

Also the settings of the BMS.

Suggestions.
Start balance 3400
SW circuit enable is set to on if you don't have a hardware switch connected to the BMS, set to off
Charge under temp reset is 10 suggest 4
Discharg under temp, suggest trig -20, reset -15
Cell under volts trig 2500, reset 2750

4 80w panels installed on the roof

Suggest you check each panel for OC volts and SC current, this is possible with a multimeter.
If the panels are flexible type then its very possible one or more has failed.
With intermittent collections in the MC4 or within the solar panels, its still possible to measure a voltage but have no current into a load.

charge controller is an hqst MC2420N10

Ensure the charge voltages are not two high. With the low charge currents , 24 volts absorbtion, (boost), with 13.5 float.

 

[cstairs]

The OP has 8 cells and a 8s BMS, just one battery. The classT fuse would be an improvement.

Suggestions.
Start balance 3400
SW circuit enable is set to on if you don't have a hardware switch connected to the BMS, set to off
Charge under temp reset is 10 suggest 4
Discharg under temp, suggest trig -20, reset -15
Cell under volts trig 2500, reset 2750


Suggest you check each panel for OC volts and SC current, this is possible with a multimeter.
If the panels are flexible type then its very possible one or more has failed.
With intermittent collections in the MC4 or within the solar panels, its still possible to measure a voltage but have no current into a load.


Ensure the charge voltages are not two high. With the low charge currents , 24 volts absorbtion, (boost), with 13.5 float.

I will try to check these things tomorrow, it's been a rainy day.
Thanks

 

[cstairs]

The OP has 8 cells and a 8s BMS, just one battery. The classT fuse would be an improvement.

Suggestions.
Start balance 3400
SW circuit enable is set to on if you don't have a hardware switch connected to the BMS, set to off
Charge under temp reset is 10 suggest 4
Discharg under temp, suggest trig -20, reset -15
Cell under volts trig 2500, reset 2750


Suggest you check each panel for OC volts and SC current, this is possible with a multimeter.
If the panels are flexible type then its very possible one or more has failed.
With intermittent collections in the MC4 or within the solar panels, its still possible to measure a voltage but have no current into a load.


Ensure the charge voltages are not two high. With the low charge currents , 24 volts absorbtion, (boost), with 13.5 float.

I've made the changes in the 2nd paragraph. Only thing I'm not sure of is if I have a hardware switch connected to BMS. I don't think I do. It's only connected to the battery. It's raining and cloudy again today. Hopefully tomorrow I can check the panels voltage. They are not flexible panels . I'll attach a picture.

 

[cstairs]

The OP has 8 cells and a 8s BMS, just one battery. The classT fuse would be an improvement.

Suggestions.
Start balance 3400
SW circuit enable is set to on if you don't have a hardware switch connected to the BMS, set to off
Charge under temp reset is 10 suggest 4
Discharg under temp, suggest trig -20, reset -15
Cell under volts trig 2500, reset 2750


Suggest you check each panel for OC volts and SC current, this is possible with a multimeter.
If the panels are flexible type then its very possible one or more has failed.
With intermittent collections in the MC4 or within the solar panels, its still possible to measure a voltage but have no current into a load.


Ensure the charge voltages are not two high. With the low charge currents , 24 volts absorbtion, (boost), with 13.5 float.

So I checked the voltage today. The panels are in indirect sun. I got 21v from 3 of them and 22v from the 4th. Checked amps coming from all 4 together and it was from .4 - .8 , at one point it hit one for a few seconds.
As far as I can see there aren't really any settings to change on the controller other than the battery type. Really nothing has changed for 2 years before this started happening.
It seems to be working fine for the past week but we are leaving soon for a 2 week trip and I don't really want it to stop on me again.
Any other thoughts would be appreciated.