Recent issue LiFePO4 low voltage solar setup

[AsRed]

Please any help to identify the source of my issue would be awesome

I have successfully being using a Bioenno Power Solar Controller – SC-122430T to charge and manage my LiFePO4 batteries since Dec 2020 without any issues.

Recently I have been getting repeated fuse burn outs on the solar panel feed-in side of the solar controller as soon a power is permitted to flow from the solar panels with the LiFePO4 cells connected.

If I disconnect the LiFePO4 cells from the SC122430T battery terminal (middle terminal) I can eliminate the fuse burning out.

When I disconnect the battery and keep the solar panel connected the SC122430T display reads L7 U8 P2 ie
L7: Solar Controller Always On
U8: Voltage from Solar Panel is 9.3V
P2: Battery Full: The charge on the battery is full

With the LiFePO4 batteries disconnected (I get no short fuse burnout) and at the respective terminals
- Solar feed in (left terminal) reads 13.96v
- battery (middle terminal) reads 13.96v
- load (right terminal) reads 13.96v

Is this normal for the SC122430T?

If I connect the LiFePO4 batteries I get the fuse burning out

I wanted to eliminate the SC122430T being the issue before I look at replacing either the BMS or any of the 4 Winston WB-LYP 100AHA cells

Also each of Winston WB-LYP 100AHA voltage measures are a follows
Cell 1 reads 2.428v
Cell 2 reads 2.504v
Cell 3 reads 2.890v
Cell 4 reads 2.938v

Does that look normal or could the short be on one of the cells or a failed BMS?

For the BMS I’m using the PCM-LO4S30-526
https://www.batteryspace.com/PCM-with-Equilibrium-function-for-12.8V-LFP-Battery-Pack-30A-limit.aspx

Any help or approach to isolate my issue would be very much appreciated.

 

[MisterSandals]

When I disconnect the battery and keep the solar panel connected the SC122430T display reads L7 U8 P2 ie

A solar charge controller should never have solar input without a battery connected first. You may have damaged the charge controller doing this.

Also each of Winston WB-LYP 100AHA voltage measures are a follows
Cell 1 reads 2.428v
Cell 2 reads 2.504v
Cell 3 reads 2.890v
Cell 4 reads 2.938v

This battery is near 0% charge. A BMS should disable this battery with a cell below 2.5V. Similarly, if the battery is so low that the BMS disconnects the battery having just solar attached may have damaged your charge controller.

Without a battery connected, the SCC has no idea what the operating (battery) voltage is, and maybe startup in a confused state, possibly with a voltage indicated by your array. This is a forbidden setup so what happens is dependent on the SCC robustness of design.

 

[AsRed]

Thanks so much for your reply.

So do you think I should replace the SCC, do they have a limited life?
I would not have normally disconnected the battery and still had solar feed-in but I was trying to isolate the source of the short.

As the short was happening before the battery was disconnected do you think I can rule out the BMS or the cells themselves as an issue?
The cells have had a constant drain on them so quite probable that the BMS has cut when they got to 0%

I’d be happy to replace the SCC but wanted to eliminate any other sources of my issue.

Finally would you recommend a particular SCC for my setup - all was good with the Bioenno until now?

 

[MisterSandals]

The cells have had a constant drain on them so quite probable that the BMS has cut when they got to 0%

This is a tricky condition to cut off solar. It “can” be the cause of your problem, especially if this damaged your SCC.

Solar feed in (left terminal) reads 13.96v

This sounds too low to ever work. Normally SCCs require about 5V over battery voltage to start charging.

What panels do you have? Voc and wattage?

What is max input voltage of your SCC.?

This one?

12V/24V, 30A Solar Charge Controller (MPPT) for LiFePO4 Batteries (SC-122430NE)

Click here to download the Material Safety Data Sheet for LiFePO4 (Lithium Iron Phosphate) batteries. Price: $169.99 The Bioenno Power SC-122430NE Series MPPT Maximum Power Point Tracking Solar Charge Controller is a top-of-the-line solar charger designed for installations requiring zero...

www.bioennopower.com

Input Voltage Range: 100VDC

If you have more than 1 panel, arranging it series will increase voltage and maybe provide better charging (does not address your fuse issue but may help charging).

I still do not see a pattern as to when the fuse blows. Does it ever blow when battery voltage is good and battery connected before solar?

 

[AsRed]

Thanks MisterSandals I’ve solved my problem thanks to your feedback!

So it turned out to be an intermittent fault/connection in my Anderson connectors going out to the battery from the SCC.
As this was intermittent it was hard to isolate/find and explains why my batteries got down to their minimum charge limit.
So I’ve charged the batteries and the BMS is working well, it levelled out the cells and I could eliminate that as an issue. A properly charged battery meant that the SCC was much happier
So I then reconnected everything in the correct order and the SCC is operating without any issues.
So thanks so much for your time taken!

 

[defed]

A solar charge controller should never have solar input without a battery connected first. You may have damaged the charge controller doing this.

i know you shouldn't have solar in to a c/c w/o batteries connected, but this brings me to something i had never considered until now...if the BMS shuts the batteries off, you essentially have this condition, correct? so in a scenario where your system is running along, and something happens...say you're admitted to the hospital and nobody is there to monitor it, there could be a case where the batteries are not getting charged due to several days of bad weather, the bms shuts the battery off for low voltage, and now you are suddenly left w/ nothing 'connected' to the c/c.

i guess this could happen ANY time due to the bms shutting it off for any reason - a minor side affect risk of using lifepo. again, something i had never considered and probably not a problem w/ FLA.

 

[upnorthandpersonal]

i know you shouldn't have solar in to a c/c w/o batteries connected, but this brings me to something i had never considered until now...if the BMS shuts the batteries off, you essentially have this condition, correct? so in a scenario where your system is running along, and something happens...say you're admitted to the hospital and nobody is there to monitor it, there could be a case where the batteries are not getting charged due to several days of bad weather, the bms shuts the battery off for low voltage, and now you are suddenly left w/ nothing 'connected' to the c/c.

i guess this could happen ANY time due to the bms shutting it off for any reason - a minor side affect risk of using lifepo. again, something i had never considered and probably not a problem w/ FLA.

To be fair, I think this is mostly an issue with extremely low quality/older charge controllers. I've never had issues with that, and even had confirmation from the manufacturer of mine that this is not a problem (and this is a lower cost charge controller). Victron and even some low cost alternatives start up on solar input only because they remember the voltage of the once connected battery - this allows them to charge a fully dead battery and thus don't have issues with no battery being connected.

 

[DVD]

Agreed. I haven’t seen a recent charge controller that required battery. A PWM unit with only LA capability was the last one I saw about 6 years ago.

 

[Pappion]

Post is missing information.
What is the Fuse Amps? Where is it located? The SCC user manual does not mention fuse.
What are your solar panels Current rating? Are they parallel or series?
How many batteries?

 

[defed]

To be fair, I think this is mostly an issue with extremely low quality/older charge controllers. I've never had issues with that, and even had confirmation from the manufacturer of mine that this is not a problem (and this is a lower cost charge controller). Victron and even some low cost alternatives start up on solar input only because they remember the voltage of the once connected battery - this allows them to charge a fully dead battery and thus don't have issues with no battery being connected.

possibly, but i believe that my xantrex mppt states that you should have the batteries connected 1st. it's older, maybe 15 yr old technology. will it damage it if you don't do it that way? i don't know, but just seems the potential is there.

 

[MisterSandals]

possibly, but i believe that my xantrex mppt states that you should have the batteries connected 1st. it's older, maybe 15 yr old technology. will it damage it if you don't do it that way? i don't know, but just seems the potential is there.

Yes this issue has been debated quite a few times. Will Prowse did some experiments where he actually tried to kill several different SCCs without success. Yet every manual that i have seen indicates that you MUST connect the battery first and disconnect the battery last.

The number of killed SCCs "with just this issue" is very low if any, reported here.

The issue that I have seen and luckily caught involved an accidental battery disconnect and reconnect. The SCC somehow, without a battery connected momentarily assumed the battery voltage was more like my array voltage (~25V) and started charging my 12V battery to 24V. I caught it at around 16V. Had my SCC had a setting (not auto battery voltage detect) i would have set it to 12V this may not have been an issue. This was a "once" occurrence so largely speculation on what saw and what the SCC did.