Trying to destory my SCC's: I can't do it!

[SolarMuppet]

I have done this many times accidentally and now do it fairly routinely. I do have several controllers paralleled together so to an extent they keep each other happy. Electronically there is really no reason why they should die. they see full solar voltage in normal use when batteries are full after all. That said some controllers do give a problem in that if The sun sets and comes up again or there is a solar disconnect and reconnect before battery voltage is re-applied, they can set themselves up for the wrong voltage battery bank and when you do reconnect it may think it is a 24v bank and not all are clever enough to realise they have got it wrong and will overcharge. For this reason I always advise those on my group to stick to the recommendation just in case.

 

[Dzl]

I read in the manuals that you must NEVER connect an SCC to an array without connecting it to a battery first, because the potential that it can fry.

I've been browsing through the Victron Smartsolar 75/15 manual, I can't find any explicit statement prohibiting or even cautioning against leaving the SCC connected to the PV array but disconnected from the battery/loads.

I do see that in there install instructions, they advise connecting loads (switched off), then batteries, then PV, but they don't emphasize the point, or imply there is a risk of damage if the advice is not followed. And beyond installation there is no mention of danger/damage from leaving SCC connected to PV but disconnected from batteries (for example using a breaker or switch between batteries and SCC).

This is the only reference I can find in the manual:

Section 3.4 Cable connection sequence

• First:connect the cables to the load, but ensure that all loads are switched off.
• Second: connect the battery (this will allow the controller to recognize system voltage).
• Third: connect the solar array (when connected with reverse polarity, the controller will heat up but will not charge the the battery).

The system is now ready for use.

Can anyone (@Justin Laureltec maybe) clarify whether Victron specifically cautions or prohibits placing breakers or switches between the battery & SCC?

 

[Justin Laureltec]

Can confirm that they don't actually care, and in fact require a fuse or breaker between the SCC and the battery. Technically the wording is in there because of a conceptual problem on paper that they wanted to make sure would never happen, but this was written before the days of LFP and BMS systems and all that. Their own systems now will shut off the battery when necessary, which would obviously create the very problem that they're trying to -theoretically- avoid.

I too have tried really hard to make a Victron SCC fail in this way, under various conditions including the full-bore-charging sudden disconnection event that the wording was theoretically written to avoid, and I have never managed to cause a problem by doing this.

The official word from Matthijs on this is that no one has ever heard of this condition actually causing a problem, it's just that an engineer back when his dad was originally developing these decided to include the language to cover for a theoretical problem that has never, in anyone's experience, actually occurred. With that in mind, they've been going through and slowly updating manuals accordingly... there definitely used to be some stronger language in the manuals that's now being removed (can't guarantee it's out of all the manuals yet) with only the language about connecting the battery first being left in - and that's just so the units can recognize and set the system voltage.

 

[sharpey]

Sorry if I'm dragging up an old thread here... but I have something to add/ask...

I have a Tracer 3120AN which is going to charge a 24V battery bank.... I want to use the "load side" to connect to a 12V battery charger... Soooo
1) I'm guessing I'll need a 24-12 DC DC converter to do this right? Or can these tracer units do 24V to battery and 12V to load?
2), assuming main battery bank had a BMS disconnect event, surely the Tracer would still be putting current out to "load" terminals still... thus maybe that would prevent damage to the Tracer SCC, as current still has somewhere to go?

Cheers. Loving this forum (and Will's videos... so much positivity is infectious (forgive word choice in these trying times)...

 

[Capt Bill]

So I took every EPEver/Victron/PWM/Renogy solar charge controller, and tried to fry it by connecting it only to solar panels, and not to a battery... guess which one survived?

EVERY SINGLE ONE! I couldn't destroy any of them, and I left them connected to a high voltage array (80 volts) for 4+ hours each.

I connected each one to a lifepo4 bank after the test, and they functioned perfectly. Tested output with a watt meter before and after as well, no change.

I read in the manuals that you must NEVER connect an SCC to an array without connecting it to a battery first, because the potential that it can fry. I know that having improper gauge wires on an SCC can cause overheating around the terminals (dedicated voltage sensing leads would probably fix this problem, but many SCC use the charging lines as voltage sensing, which makes it wise to over gauge them most times. The voltage drop of a long run of hot wire can be horrible). But to actually connect an array to an SCC, and not to a battery, in my experiments, no issue.

I am thinking that the feedback signal in the converter circuit needs a reference voltage at the output to work. Then it can track the power point between the panels resistance and internal resistance of the battery, then push current to the max. If you only have the input powered up but no current is flowing, what would it stress? The panel would be in an open circuit voltage, and possibly use some power to charge up caps on that side of the circuit, but thats about it. Should be fine to leave connected.

Am I wrong? I know some MPPT's circuit designs are pretty complex, but they are still a simple converter circuit with inductor and capacitor and basic logic system to modulate it. I know some current limited converters can handle amp sources at input/output, and others can't. but because the solar panel is open circuit in this instance, and the output is also voltage sensing of the battery, I don't think any damage can occur.

What do you guys think? How can I destroy one?

How about doubling the max solar panel watts Input to MPPT. Even though solar panels rarely put out rated watts, I wonder what the limits of oversizing solar input beyond ratings will do, and what is are the limits.

 

[Craig]

How about doubling the max solar panel watts Input to MPPT. Even though solar panels rarely put out rated watts, I wonder what the limits of oversizing solar input beyond ratings will do, and what is are the limits.

I do not think it is a problem. Think of this if your batteries are full and your SCC is in float mode it is holding back 90% if the PV power and the SCC does not even get warm in float mode. So I'm thinking you could throw 10x the rated capacity with no I'll effect. Not that I would try 10x but 3x seems reasonable

 

[Capt Bill]

I do not think it is a problem. Think of this if your batteries are full and your SCC is in float mode it is holding back 90% if the PV power and the SCC does not even get warm in float mode. So I'm thinking you could throw 10x the rated capacity with no I'll effect. Not that I would try 10x but 3x seems reasonable

my post got inserted here on page three, but flipping through threads; I was respond to beginning of thread and Will's:
Trying to destory my SCC's: I can't do it! ... How can I destroy one?
(letter got big from copy n paste/ not my intension)

 

[Cal]

I've been using a Blue Sky 2512i charge controller for 14 years. If battery is disconnected the controller will still output voltage. I know this when I disconnected the battery to work on electrical, and then sparks started to fly when shorting + to ground. I don't know what voltage the charge controller outputs when no battery connection, but if it's panel Voc then electronics connected to the system could fry.

Better check charge controller output voltage when battery is disconnected.

 

[Craig]

my post got inserted here on page three, but flipping through threads; I was respond to beginning of thread and Will's:
Trying to destory my SCC's: I can't do it! ... How can I destroy one?
(letter got big from copy n paste/ not my intension)

Right

 

[Dzl]

How about doubling the max solar panel watts Input to MPPT. Even though solar panels rarely put out rated watts, I wonder what the limits of oversizing solar input beyond ratings will do, and what is are the limits.

I have spent way too much time looking into this . Short answer, you can do this, but it depends on the controller. Victron very clearly states (scroll down to the section on oversizing your pv array) its okay to do so long as you keep the Voc and Isc (max voltage and max current) of the array below the max input voltage and max input current of the controller--which for Victron controllers means that you can substantially 'over-panel' without risking damage to the controller or system, excess power is just not harvested. An extreme example is the Victron 100/50, at 12v it can output about ~650W, but based on the input specs 100V 60A the array could be upto 6000W.

Epever controllers (and the Renogy controllers made by whoever makes Epever controllers) have the same stipulations about keeping Voc and Isc below max scc input voltage and current, but also state that max input power (Watts) can't exceed max output power (Watts) by more than 3x. Not sure about other brands

You may be interested in this post on the topic

 

[Lisa]

So I took every EPEver/Victron/PWM/Renogy solar charge controller, and tried to fry it by connecting it only to solar panels, and not to a battery... guess which one survived?

EVERY SINGLE ONE! I couldn't destroy any of them, and I left them connected to a high voltage array (80 volts) for 4+ hours each.

I connected each one to a lifepo4 bank after the test, and they functioned perfectly. Tested output with a watt meter before and after as well, no change.

I read in the manuals that you must NEVER connect an SCC to an array without connecting it to a battery first, because the potential that it can fry. I know that having improper gauge wires on an SCC can cause overheating around the terminals (dedicated voltage sensing leads would probably fix this problem, but many SCC use the charging lines as voltage sensing, which makes it wise to over gauge them most times. The voltage drop of a long run of hot wire can be horrible). But to actually connect an array to an SCC, and not to a battery, in my experiments, no issue.

I am thinking that the feedback signal in the converter circuit needs a reference voltage at the output to work. Then it can track the power point between the panels resistance and internal resistance of the battery, then push current to the max. If you only have the input powered up but no current is flowing, what would it stress? The panel would be in an open circuit voltage, and possibly use some power to charge up caps on that side of the circuit, but thats about it. Should be fine to leave connected.

Am I wrong? I know some MPPT's circuit designs are pretty complex, but they are still a simple converter circuit with inductor and capacitor and basic logic system to modulate it. I know some current limited converters can handle amp sources at input/output, and others can't. but because the solar panel is open circuit in this instance, and the output is also voltage sensing of the battery, I don't think any damage can occur.

What do you guys think? How can I destroy one?

 

[Lisa]

So I took every EPEver/Victron/PWM/Renogy solar charge controller, and tried to fry it by connecting it only to solar panels, and not to a battery... guess which one survived?

EVERY SINGLE ONE! I couldn't destroy any of them, and I left them connected to a high voltage array (80 volts) for 4+ hours each.

I connected each one to a lifepo4 bank after the test, and they functioned perfectly. Tested output with a watt meter before and after as well, no change.

I read in the manuals that you must NEVER connect an SCC to an array without connecting it to a battery first, because the potential that it can fry. I know that having improper gauge wires on an SCC can cause overheating around the terminals (dedicated voltage sensing leads would probably fix this problem, but many SCC use the charging lines as voltage sensing, which makes it wise to over gauge them most times. The voltage drop of a long run of hot wire can be horrible). But to actually connect an array to an SCC, and not to a battery, in my experiments, no issue.

I am thinking that the feedback signal in the converter circuit needs a reference voltage at the output to work. Then it can track the power point between the panels resistance and internal resistance of the battery, then push current to the max. If you only have the input powered up but no current is flowing, what would it stress? The panel would be in an open circuit voltage, and possibly use some power to charge up caps on that side of the circuit, but thats about it. Should be fine to leave connected.

Am I wrong? I know some MPPT's circuit designs are pretty complex, but they are still a simple converter circuit with inductor and capacitor and basic logic system to modulate it. I know some current limited converters can handle amp sources at input/output, and others can't. but because the solar panel is open circuit in this instance, and the output is also voltage sensing of the battery, I don't think any damage can occur.

What do you guys think? How can I destroy one?

Wow, impressive. Question: I need a 2400 watt hour battery bank with 3000 watt inverter. Can I build it cheaper/better myself than just buying a Titan unit? I want to be able to transfer it to different venues as well as try to use for my house AC, so I wouldn’t be permanently mounting anything, but rather mount on transfer boards for easy portability. (I live in the high desert and would like to rework my house unit to off-grid my roof mounted AC/Heater.

If answer is to build it myself great......of course I would need you to direct me. I have your book and figured from page 21, I’d just go with that. I just received the 4-pack of Rich Solar poly panels. But would need to know your best performance and cost effectiveness for all the other components. I know you’ve done videos, but fishing through all of them for each recommended component takes time and I’m a beginner. I saw your panel test video that’s why I was confident buying Rich Solar 4-pack.

 

[Capt Bill]

Wow. That is interesting? Re: Your Testing to Destroy a SCC Mission: What happens when you Short out the DC output with a Short Thick Oversized Wire for the DC outs / like shorting out + to - and/or Gound. I wonder if any SCC might protect from that ? I do not really encourage ya along that line, but since you are asking for destroy ideas ... Did ya try that one yet? YES, That is really interesting you can get em to work without a battery. I wonder what the shortcomings might be to trying that idea on as a long term plan for using using electricity just when enough sun was shinning .... (while accepting: no sun on panels = no DC to Inverter for AC output ??? Batteries cost a bit; so some folks might bite on that idea, and maybe do batteries later.

 

[HaldorEE]

I have had my solar array (~180V open circuit) connected to my Victron charge controller (SmartSolar MPPT 250/100) as well without a battery - no problems. Then again, for the cost of that one I wouldn't expect it any other way.

Did the SCC battery output turn off without the battery? I plan on pulling the battery out of my van during the summer (so it doesn't get cooked by the heat) and I would like it if the solar panel could continue to power the ventilation fan. I am considering putting in a small, essentially disposable battery pack for use around town so the lights/ventilation fan would still work. Obviously the Inverter wouldn't work, but I don't need that unless I am boon-docking in which case I will have the big battery pack installed.

 

[upnorthandpersonal]

Did the SCC battery output turn off without the battery?

Sorry, don't know (or don't remember) and can't easily find out...

 

[Fred S]

Last fall my Epever 4215BN was subjected to multiple bms trips (so, battery disconnects) during high charge rates. It shut off its PV input relay (presumably), which caused a small voltage spike (35v) for each trip (24v system). But each time after reconnecting, it resumed normal operation, and it continues happily to this day.

 

[gnubie]

Did the SCC battery output turn off without the battery?

It will continue to supply regulated voltage, within the abilities of the panels to hold it up of course, once it sees that the load has dropped and it enters float mode. It doesn't go into voltage regulated mode straight away, from memory it does a bit of probing to see what the heck just happened. There's no need to manually set the battery voltage as the controller learns that the first time (any firmware on a smart model out of the box should behave this way) it is connected to a battery and stores that for future use. A factory reset will return it to the initial autodetection state again.

I'm not sure how much overshoot there is with a 100/20 smart model, but I have a supply of them so I can hook up the scope and take a look.

 

[HaldorEE]

It will continue to supply regulated voltage, within the abilities of the panels to hold it up of course, once it sees that the load has dropped and it enters float mode. It doesn't go into voltage regulated mode straight away, from memory it does a bit of probing to see what the heck just happened. There's no need to manually set the battery voltage as the controller learns that the first time (any firmware on a smart model out of the box should behave this way) it is connected to a battery and stores that for future use. A factory reset will return it to the initial autodetection state again.

I'm not sure how much overshoot there is with a 100/20 smart model, but I have a supply of them so I can hook up the scope and take a look.

Cool. I created a separate thread about why I care.

 

[gnubie]

Tested the 100/20 with a lab power supply on the PV input for convenience of control. A single 12V 18AH AGM battery with a lightly loaded 1000 watt inverter (approx 40 watts) was used to drag the battery down. The battery was connected to the device to allow it to detect and store the voltage before tests were started.

With no battery connected to the controller at 'sun up', and a meter on the load output terminals and PV input being slowly raised to simulate normal conditions the load output stayed low until PV exceeded the +5v requirement for the Victron to start outputting current and then it went to regulated float, regulated 13.8

With a battery connected, and PV at a low level the battery was disconnected with almost no current flowing to the battery and the voltage rose up to 17.9 before dropping back down as capacitors discharged to 13.8. This only happened once, I could not repeat the result, even with various voltage and current limits from the lab power supply to the Victron. Even going to 5 amps into the battery and disconnecting it, the output resolutely stayed within limits, never exceeding absorption stage voltage. It may have been the cheapie lab power supply having its own issues and briefly yanking the PV input quite high, with the Victron doing its best to contain it.

 

[HaldorEE]

Tested the 100/20 with a lab power supply on the PV input for convenience of control. A single 12V 18AH AGM battery with a lightly loaded 1000 watt inverter (approx 40 watts) was used to drag the battery down. The battery was connected to the device to allow it to detect and store the voltage before tests were started.

With no battery connected to the controller at 'sun up', and a meter on the load output terminals and PV input being slowly raised to simulate normal conditions the load output stayed low until PV exceeded the +5v requirement for the Victron to start outputting current and then it went to regulated float, regulated 13.8

With a battery connected, and PV at a low level the battery was disconnected with almost no current flowing to the battery and the voltage rose up to 17.9 before dropping back down as capacitors discharged to 13.8. This only happened once, I could not repeat the result, even with various voltage and current limits from the lab power supply to the Victron. Even going to 5 amps into the battery and disconnecting it, the output resolutely stayed within limits, never exceeding absorption stage voltage. It may have been the cheapie lab power supply having its own issues and briefly yanking the PV input quite high, with the Victron doing its best to contain it.

Thanks for testing this.

So I think what this means is I wiil be able remove the house battery and still be able to run a fan off solar power.

That is wonderful. I live in Phoenix and don't want to leave the house battery installed in the vehicle during the summer. Much better than what I was thinking I would have to do (install a sacrificial, smaller and cheaper battery just for the summer months).

Are you a Victron dealer or just a very interested hobbiest? I still haven't purchased the rest of my system yet. All I have so far is the Multiplus.