Fire or Explosion eminent? SCC allowing high voltage to battery!

[WorldwideDave]

I have a fuse between the solar charge controller and battery. I also have a kill switch between the SCC and the battery. I also have breakers on the PV side between the panels & SCC.
There was no load running on my inverter (2000 W) or the battery (12V LiFePO4 Chins 200Ah). The sun charged up my battery to over 14.2 Volts, and the inverter was making noise (overcurrent alarm - renogy product).
I went outside, and turned on a 12V load. I looked at the SCC and it said 19 V, which is what the solar array (300 W, 2 panels) brings in to the SCC.
I looked at my battery monitors that connect to the PV input and side of the SCC, and the one on the negative battery terminal. Both read 19.1 V!
I immediately killed the breakers on the PV side, and killed the connection between SCC and Battery as well. Voltage dropped down to 14.5.
I started up a 12V load (small - 50 watts max) and the beeping of the inverter stopped and voltage relaxed down.
So a few things:
1. - pretty sure I have a bad solar charge controller
2. - if the shunt and monitor on the battery side said 19 V, why didn't the battery internal BMS stop it at 14.6 or something?
3. - Was my battery monitor just showing that 19V was coming INTO the battery, but the battery itself was not more than 14.5 V? Battery does not have bluetooth.
4. - Did the battery BMS actually prevent the 19V, but I could not see that? Asking because why when I killed the SCC power line to the battery (after PV was killed) did the battery drop from 19V down to 14.5 so quickly?
5. - If the SCC doesn't prevent more than 14.4 or whatever voltage from going to the battery, what is supposed to do that?
6. - Is the SCC junk now, or can I add a victron battery smartconnect or whatever its called to kill it instead of the SCC?
7. - I have had something similar to this happen on another SCC with a different battery. I threw that SCC away. The battery was fine, however I was scared. I think sending 19 V - like straight from a panel - to a battery can make things go boom or catch fire.
8. - The glass fuse I had did not blow - it blows based on amps, not volts I guess.
9 - I need to get a kill switch between the positive or negative battery cable, not the SCC and the battery. I am using 4/0 wires, so finding a kill switch that is affordable may be a challenge.
Thank you all SO MUCH for reading! SCC and PV still disconnected; battery running a small DC load to drain it down just to be safe.

 

[Rocketman]

What SCC do you have?

From your description this is what I think happened…

I think the SCC started charging the battery too high - (the 14.5v when the solar was cut off indicates it was this high - which is too high), at 14.5 or 14.6v the BMS quit accepting power. When some SCC’s have the battery cut-out (or they die) they keep increasing the voltage to their max - hence the 19v.

When you killed the solar source - the battery was ready to discharge- so it did. Thus the immediate 14.5 voltage from the battery.

There are a few different things to look at:
what voltage was your SCC set to charge to?
What is the high voltage bms cutoff?
Is your SCC dead now - or does it seem to be operating fine?
One other option that could be causing issues…
Your cells in your battery may be out of balance, and the bms initially cutoff at a high cell voltage- not at a high battery voltage. If you had Bluetooth you could answer this question pretty quickly (which is why I only recommend batteries that have some kind of communication). Keep that in mind if you have any other issues. You can fix the cell balance blindly if needed.

Good Luck

 

[Lt.Dan]

What Brand/Model of all the equipment you have? SCC, Battery, Inverter etc.

I'm guessing the SCC failed also, allowing full PV voltage through. The battery hit HVD and isolated the battery from the higher voltage, and the inverter set off an alarm to signal the same.

 

[SpongeboB Sinewave]

Does the battery display battery voltage or errors or warnings ? It should

boB

 

[JBertok]

If your PV is bringing 19.1 Volts to the charge controller, it sounds like it's a PWM type unit. If that's the case, it's eligible for replacement with a Maximum Power Point Tracker type SCC; which would make more efficient use of your panels and allow you to wire them in series for less transmission loss between them and the SCC.
Back to your present situation, there isn't a valid circumstance where it should allow that much voltage to pass to the DC bus side of it. In fact, the max possible ever should be 16V for the specific function of equalizing a floating lead acid battery, if it even supports doing that. If we had the brand and model we can verify what type it is, what battery chemistries it supports and how to verify it's configured for lithium, and someone might even be able to speak to the known reliability of them.
The BMS in the batteries will cut charging if the cells are full and one or more of them reaches cutoff Voltage. As soon as the BMS(s) cut out, the DC bus will get pushed to whatever the SCC is putting out. Unfortunately the inverter will see that too. Even without any specific information, the SCC sounds failed (shorted internally) and the BMS's cut out.
The safest option is to stop using the SCC right now, because those high bus voltages can smoke other stuff. If you have a critical need to bring PV into your battery before the SCC can be verified/replaced, and you have the ability to sit and monitor it closely, you can cut the SCC when the batteries reach 95%. Basically, as long as the less-than-full batteries are on the DC bus with the BMS in good status, the DC bus voltage will not rise to PV voltage because the batteries will hold the voltage and suck up the power. Just don't allow the DC bus to reach overvolt from the shorted SCC - and that will not happen with just 2 PV panels as long as the SCC is shut down before the batteries can approach a full charge. I'd leave a 5% margin; so cut the SCC when they reach 95%.

 

[WorldwideDave]

There’s always a fine balance between providing too much information on your forum, post or providing too little. If I provide too many details, people will ignore the post. Put too little they ask a lot of the same questions.

Let me start by saying that the solar charge controller, the monitor that is connected to the shunt on the PV input side, and the monitor connected to the shunt on the battery side all displayed 19V all at once when I saw it.

Battery mentioned above is lifepo4 chins no Bluetooth. Single 12v. No more no less.

No battery buss bar as just one battery. Own a blue sea buss bar but waiting until I make a change to put it into this system.

SCC seems fine now though everything is off.

I looked at spec sheet on my battery a while back. I noticed that the alarm for the low voltage on the inverter was .3 volts higher than my battery. So the alarm would sound for 15-30 minutes on the inverter before the bms would ever kill the battery. My assumption is that the high voltage alert on the inverter is likely similar. A few volts less than the actual cutoff. Alarm was going off but by the time I noticed it - could have been hours - the monitors and scc read 19v.

The SCC is mppt labeled ACOPower which is call a renogy knock off. Says 20 amps but I doubt it. Maybe because the sun was so bright and clear today that the watts coming in from PV were close to 300 which would exceed 20 amps and perhaps cause the SCC to freak out and send all 19V through to the battery?

Maybe that’s what happened. Otherwise maybe the alarm was going off on the inverter because battery had actually shut off. If battery shut off to protect itself what would the meter and SCC display?

The SCC does not have any adjustable settings other than battery chemistry. It is set to LFP.

Maybe the SCC allows 14.5 but battery doesn’t like 14.4. Let me check:


Charge voltage: 14.2V~14.4V

Max Depth of Discharge (DoD): 100%

Max continuous charge current: 50A

Max continuous discharge current: 100A

Peak discharge current: 300A (Duration: less than 5 seconds)

Standard charge current: 40A, Charging time approximately 6 hours

Think I found it…says over voltage disconnect at 14.6. That’s .1 over what my SCC says is ‘full’. Maybe that’s the issue. Not enough breathing room. Just shut itself off. Thoughts?

 

[JBertok]

A few points:
- When we talk about "DC bus" it refers to the common power terminals that your battery, inverters, and charge controller all share connections to, not a physical bar. The "DC bus" voltage is equal to the battery voltage always, unless the battery is faulted and/or disconnected.
- If the inverter ever sees over voltage, it 100% of the time means the battery is disconnected and/or faulted.
- Using a battery that has a BMS with no monitoring or communications capability makes troubleshooting impossible and renders the entire system unreliable. You need to be able to see individual cell voltage to monitor the state of balance, and fault conditions, cause, and optionally history as a bonus. Would be best to omit and replace that with a battery that can be properly monitored.
- No 12V solar charge controller, whether PWM or MPPT, should ever pass 19 volts through to its battery (DC bus) side. Never, no exceptions. It is failing to do its only job. If this is normal behavior for this brand, then it is valueless.

Your reply says "the inverter is mppt labeled ACCpower .." I think from context you are referring to the SCC. This unclear. This is why we ask for brands and exact model numbers. And then talking about too much sun and the SCC freaking out.... Again: there is absolutely no circumstance whatsoever in which it can be expected or accepted for a 12V SCC to pass 19V through to the battery side. When you say it's a knockoff of Renogy that is cringe-level scary. Renogy is decent at marketing, only. What you have sounds somehow 'worse', if that's even possible. Having no setpoint adjustability is another stratospheric red flag.
The ball's in your court, good luck.

 

[WorldwideDave]

Correct. SCC not inverter. I was sleepy.

So if the battery shuts off, the SCC goes nuts because the SCC has no power source except the PV side. And because the dc bus is still connected to the inverter, the inverter sees the overvoltage from the scc, and causes it to alarm. Am I understanding correctly?

Yes I know a battery with no Bluetooth was a bad purchase on my part. Bought before knew about forums.

ACO Power is brand of SCC. This is old photo so ignore wiring please. Away from home. Still shot from video. 12 / 24 20 AMP is features/model I believe. I don’t think they make this model any longer. Can’t find at their Amazon store.

I should add that the positive battery cable goes straight to inverter, negative goes straight to shunt then inverter, and the positive connection from scc goes to battery positive and the negative from scc goes to battery shunt on the same side the inverter is connected on. So no funny business.

As mentioned before the positive from the scc to battery has a fuse and kill switch inline. There is also a dc breaker between the pv and scc.

 

[Brett V]

You mentioned the SCC is working normally now but I wouldn’t trust it. Speaking to the title of your post, no you weren’t in danger of a fire or explosion. The BMS disconnected when you hit the high voltage threshold.

 

[WorldwideDave]

But how do we know for fact the bms cut it off without Bluetooth? How can I test this theory? I could remove the positive battery cable from the battery and turn off the kill switch and turn the panels back on, thus leaving the battery out of the equation. I know this is bad for scc to have pv go to it and no battery connected but essentially that’s what happens when bms shuts off battery correct?

Why I’m so curious is because I had something similar happen 6 months ago but with a lead acid battery I was charging with a cheap MPPT. I went out to view the SCC and it also said 19V on the battery side. I would think the lead acid would have exploded or melted or whatever they do. I had no kill switch or fuse at that time. Battery was in my truck. Anyway, it seems to be a pattern with the scc I have used twice. That system has been removed and scc thrown away.

Today I am draining my lifepo4 battery running load.

 

[Brett V]

But how do we know for fact the bms cut it off without Bluetooth?

Because at that voltage, the cells would have been destroyed if actually connected.

Why I’m so curious is because I had something similar happen 6 months ago but with a lead acid battery

You can’t compare LiPo4 and Lead in this situation. They’re going to act completely different. Even FLA and AGM wouldn’t react the same.

 

[Rocketman]

Toss that SCC and get a Victron mppt
100/20 or 100/30.

You will find it won’t ever give you 19v to the battery and you will like the history and the data if there ever is a problem in the future.

The 100/20 will be right at maxed out. (That’s not an issue at all unless you want to add more panels). I believe it’s max is 290watts.

The 100/30 can handle about 400w (I forgot the exact number). So if you want to add a third panel- go with that one.

Yes they will be slightly more expensive than than the ones you have been getting- but they come with a real warranty and much better quality.

Good Luck

 

[robbob2112]

But how do we know for fact the bms cut it off without Bluetooth? How can I test this theory? I could remove the positive battery cable from the battery and turn off the kill switch and turn the panels back on, thus leaving the battery out of the equation. I know this is bad for scc to have pv go to it and no battery connected but essentially that’s what happens when bms shuts off battery correct?

Why I’m so curious is because I had something similar happen 6 months ago but with a lead acid battery I was charging with a cheap MPPT. I went out to view the SCC and it also said 19V on the battery side. I would think the lead acid would have exploded or melted or whatever they do. I had no kill switch or fuse at that time. Battery was in my truck. Anyway, it seems to be a pattern with the scc I have used twice. That system has been removed and scc thrown away.

Today I am draining my lifepo4 battery running load.

The constant them seems to be 'cheap' stuff, which is in fact expensive because you have replace it and whatever else it damaged.

Buy quality in all things, or keep replacing it.

 

[SpongeboB Sinewave]

Any lithium battery with BMS should have an error or warning indicator LED to show that it turned of...

Bluetooth not needed for that information

boB

 

[robbob2112]

Any lithium battery with BMS should have an error or warning indicator LED to show that it turned of...

Bluetooth not needed for that information

boB

They don't. Typically you can look on the vendor website to see what they do about protected mode. If it came with a manual it should as well.

Usually protected mode will be an artificial voltage at the terminal. If you try to charge it there will be zero current. If you try to discharge it again, zero current.

Some batteries will wake themselves back up after a few minutes. Others require a DC power supply to force a current through it at a specific voltage. Depends on the vendor and battery model.

 

[mikefitz]

have a kill switch between the SCC and the battery

This is not a good idea. Isolating many solar controllers from the battery can cause the controller to behave in a strange way, often with dual voltage , 12/24 types defaulting to the 24 volt setting, or supplying panel volts to the system. Since a battery BMS protection event that opens the charge path may be similar to a battery disconnect, the correct performance of the controller cannot be assumed. Even the better designed solar controllers, like the Victron range cannot immedially respond to a battery disconnect and may 'spike ' the volts momentary. What a Victron controller will not do, is to change system volts. Once initially connected to a battery a Vitron controller fixes system voltage and will happily operate delivering power to a system bus even with the battery disconnected.

 

[WorldwideDave]

This is not a good idea. Isolating many solar controllers from the battery can cause the controller to behave in a strange way, often with dual voltage , 12/24 types defaulting to the 24 volt setting, or supplying panel volts to the system. Since a battery BMS protection event that opens the charge path may be similar to a battery disconnect, the correct performance of the controller cannot be assumed. Even the better designed solar controllers, like the Victron range cannot immedially respond to a battery disconnect and may 'spike ' the volts momentary. What a Victron controller will not do, is to change system volts. Once initially connected to a battery a Vitron controller fixes system voltage and will happily operate delivering power to a system bus even with the battery disconnected.

Thank you - I learned that in a useful lesson. Because I was seeing bad voltage of 19V from the SCC going to my 12V LiFePO4 battery recently, I did use the kill switch to disconnect the battery, which did fry the SCC. I only paid 20 for the SCC. I think what we determined here, though, was that the battery BMS had killed it beforehand, and there was the 19V being sent to the other load I had (DC pump to circulate water for pool) that got all the voltage. It wasn't damaged.

I have since made some major upgrades and changes. battery connected now to victron smart shunt 500A. After that it goes to a fuse, and then on to a bus bar. Bought a victron Smart MPPT to replace the bad MPPT I had, and the victron MPPT is now connected to the bus bar as well with a 50 amp fuse (hope it never needs to blow). Finally I have a victron batteryprotect device between the bus bar and a blue sea fuse panel. I have the DC pump I'm using connected via a fuse to that fuse panel (vs directly to the battery & shunt before). The net result is that if battery voltage is too high or too low, the battery protect will kill power to the DC load(s). If the MPPT goes out of control and sends high amps to the bus bar, the fuse should blow first. If there is too much amps going to or from the battery, the inline fuse should blow protecting the other equipment. There is no kill switch right now between the 12v battery and the shunt or bus bar. I could add one but would need a larger one I would think. I also have quick disconnects on the DC load so I can unplug that from the fuse panel for maintenance or to move my solar 'station' somewhere else. Right now it is next to the pool equipment but I can move it just about anywhere on wheels. I should note that I still have an inverter connected to the battery & shunt post. The conductor between the battery shunt and the bus bar is not a huge wire - 8 AWG I believe. For a 5 amp load on the DC side and a 20 AMP max from the MPPT, I should be fine. The ground for the battery are also 8 gauge, but no bus bar as it just goes between the battery and the ground stud on the fuse panel, and I have the MPPT also going to that same stud with 8 AWG as well. So using the ground on the panel as a bus bar right now.

 

[WorldwideDave]

Any lithium battery with BMS should have an error or warning indicator LED to show that it turned of...

Bluetooth not needed for that information

boB

To your points, I wish the battery had a light or a bluetooth BMS. It does not. Looking to ditch 12V and go 48V with more options. Right now I can get a 2nd 12V non-bluetooth BMS battery, 200 Ah just like the one I have, for $250 cash. That's very affordable, but same issue. So I'd have 2 batteries in parallel at 12V for 400 Ah, but still have no way to see what it is doing. I'm this far into my solar investments - about 1600 spent so far on panels, battery, and all the gear - should have saved up more and paid cash for everything I wanted all at once vs. going slow and learning.

This is said over and over on the forums and Will's YouTube videos. I've learned. At least I can repurpose this gear for other homes.

 

[HRTKD]

Any lithium battery with BMS should have an error or warning indicator LED to show that it turned of...

Never underestimate how cheap some battery vendors are.

 

[WorldwideDave]

Toss that SCC and get a Victron mppt
100/20 or 100/30.

You will find it won’t ever give you 19v to the battery and you will like the history and the data if there ever is a problem in the future.

The 100/20 will be right at maxed out. (That’s not an issue at all unless you want to add more panels). I believe it’s max is 290watts.

The 100/30 can handle about 400w (I forgot the exact number). So if you want to add a third panel- go with that one.

Yes they will be slightly more expensive than than the ones you have been getting- but they come with a real warranty and much better quality.

Good Luck

Done - victron 100/20.

 

[WorldwideDave]

The constant them seems to be 'cheap' stuff, which is in fact expensive because you have replace it and whatever else it damaged.

Buy quality in all things, or keep replacing it.

glad battery had bms to kill overvoltage. However, the inverter was still getting the 19V, which caused its alarm to sound. Used it twice so far - seems to be okay.

 

[WorldwideDave]

Toss that SCC and get a Victron mppt
100/20 or 100/30.

You will find it won’t ever give you 19v to the battery and you will like the history and the data if there ever is a problem in the future.

The 100/20 will be right at maxed out. (That’s not an issue at all unless you want to add more panels). I believe it’s max is 290watts.

The 100/30 can handle about 400w (I forgot the exact number). So if you want to add a third panel- go with that one.

Yes they will be slightly more expensive than than the ones you have been getting- but they come with a real warranty and much better quality.

Good Luck

That’s what I did.