Just a quick comment about flipping breakers randomly. This also applies to AC-coupled systems. There should be zero risk of flipping breakers in random order. These devices are there to prevent overcurrent and disconnect circuits safely under load. If there is a specific order in which breakers must be turned on for the system to function properly, I consider that poor system design. And the issue is pervasive in the industry. If there is a safety hazard with flipping breakers in random order, these components should never pass testing IMO.
On Thu, Feb 2, 2023 at 6:53 PM Kienan Maxfield via RE-wrenches < re-wrenches@lists.re-wrenches.org> wrote: > Hello all, > > I have been an off-grid specialist for 12 years now, and I have never seen > or heard of a charge controller blowing itself up when it was disconnected > from the battery while it was in steady state. What I mean is that if it's > in bulk mode, or absorb mode, or float mode, and the battery disconnect is > suddenly opened, nothing has ever happened. And this actually has happened > a lot of times in my career. Most of my clients have a DIY attitude, so if > they think something is wrong, they'll start flipping breakers off randomly > until they have shut everything down in order to "reset" the system, and > then they turn it all back on, and if the problem persists, they feel like > they've tried something, so then they call. I've had helpers who just can't > remember which breaker to shut off first. Since I've never seen or heard of > an actual case where this happened, I don't worry about it to much. > > I have seen something similar blow up an Outback FM80 once. The charge > controller was 7 years old at the time. I was watching the whole time. The > system was shut down when we arrived, then the PV breaker was turned on, > then the battery breaker was turned on momentarily, then the battery > breaker was shut back off. The charge controller went into the startup > procedure, and it went to sweep the IV curve, and as it did, it was pumping > all that power into it's capacitors and it had nowhere to go. I watched the > voltage on the screen skyrocket and then it suddenly burned out with a > small pop. The charge controller was stuck in the startup, and it wasn't > able to stop producing current. If the battery breaker had been left on > while it stabilized, then it was shut off, it would have been fine. So if > you turn on the system, don't suddenly trip the disconnect until it has > been on for a minute. > > Also, inverters have capacitors that are much, much, much larger than the > capacitors in the charge controller, so when a main battery disconnect is > thrown and the charge controller is connected to an inverter > > Now, I completely avoid cheap charge controllers (Amazon charge > controllers, etc.). I don't touch them with a 10 foot pole. I have seen so > many DIYers reject my advice, install a cheap one, and have it burn up > within a couple of years or less. I wouldn't be surprised if suddenly > disconnecting the battery would be a likely cause of failure in these cases. > > Also, with any quality brand, if this somehow did happen, they'll still > honor it under their warranty, and this will be a rare occurrence. > > William said that SolArk can't handle having the breaker thrown while it's > charging the battery, so there are definitely exceptions. I've never used > SolArk, but with everything else I've heard about them, I'm really not too > surprised. I'm not faulting SolArk, and I'm not a SolArk hater, I just know > that their hands are somewhat bound by the real manufacturer who is in > China. SolArk only has limited control of their product. But as boB from > MidNite pointed out, it all equipment can and should be designed with this > in mind. Fuses will blow, breakers will get tripped, and any quality > manufacturer is going to take that into consideration. They can take the > low road and simply plan on replacing some under warranty, or the can > engineer the product to withstand it. > > One last note about codes, there are some codes that I hate and try to > avoid, but I also personally know 2 or 3 of the people on the code panels. > There are some people on the code panels who are not kind to our industry, > but there are a couple of people on those panels who really are our > advocates. If someone is on the code panel, they are actually limited in > how they can suggest new changes to the codes, they can only promote public > inputs that are submitted by people like us, so even if it feels like a > waist of time, it really is important that we all submit our ideas and > thoughts through the official pathways so that our advocates who really > want to promote our best interests have something they can leverage for us. > To those here who do help with the codes and help to advocate for us, THANK > YOU SO MUCH!!! > > Thanks, > Kienan > > > *Green-Go Solar Distribution LLC Maxfield Solar LLC (installation and > consulting company) * > *maxfieldso...@hotmail.com* > *(801) 631-5584(Cell)* > ------------------------------ > *From:* RE-wrenches <re-wrenches-boun...@lists.re-wrenches.org> on behalf > of bob--- via RE-wrenches <re-wrenches@lists.re-wrenches.org> > *Sent:* Wednesday, February 1, 2023 8:06 PM > *To:* RE-wrenches <re-wrenches@lists.re-wrenches.org> > *Cc:* b...@midnitesolar.com <b...@midnitesolar.com> > *Subject:* Re: [RE-wrenches] Remote battery disconnects > > > SPDs or (MOVs) on the PV input side of a charge controller are not wired > to snub excessive PV voltage. > > They are wired from PV+ to GND and the other from PV- to GND and only the > two in series, at double the > MOV clamp voltage would have any effect on clamping the PV+/PV- voltage. > SPDs are wired to keep the charge controller's insulation system to below > the Hi-Pot voltage the unit is > tested with. i.e. They are wired for common-mode and not differential. > That voltage is much higher > than maximum controller or inverter input voltage. > > What *IS* in place that might help limit PV voltage is the PV array > itself. Any PV voltage that would try go > go above the array's Voc would be clamped across the array. This would > be during the day or at night and > of course that Voc is determined mainly by PV cell temperature. Solar > panels are just a bunch of diodes > in series so will be forward-biased when Voc is exceeded by an inverter or > charge controller. > PV modules make great space heaters and can even melt snow, ya know. 😁 > > As for charge controllers blowing up when charging hard and then > disconnecting, I am very anal in > designing in safe guards to keep this from happening on the MidNite > Classic at least. That was done > several years ago now. > > But even then, electronics, especially power electronics, break once in a > while and it is sometimes very > hard to know why it happened. > > With our new HV MPPT controllers, their E-Panels also include > remote-trip PV breakers, triggered by the controller's > hardware in order to reduce battery side over-voltage in case something > goes wrong. > > So, I understand that we have a remote battery disconnect device basically > done but have held off due to > not knowing how important it would actually be. 300 amps from an external > switch closure or open. > Our older BD module basically went away with the bird house and bird next > shut down system. > > There are NEC requirements that are not enforced and some installers > don't worry about including, > but from this discussion, it sounds like this battery disconnect better be > finished sooner than later. > > Now we know. Thanks ! > > 🌜boB🌛 MidNite Solar > > > > > On 2/1/2023 2:49 PM, Brian Mehalic via RE-wrenches wrote: > > Most firefighters are not electrical engineers; nor are most insurance > agents. However both of those groups are stakeholders with influence over > codes and standards. Some may say too much influence, but the fact of the > matter is that code making is a group/consensus process, and very often > none of the groups get exactly what they want (in fact sometimes a group > accepts exactly what it doesn't want to leverage that for something they > do; yes it often smacks of politics). I would appeal to y'all to submit a > proposal for the 2026 NEC® - they are due by September of this year. Better > yet would be to circulate language that this, or some other, group can work > on, agree on, write a solid technical justification for, and sign their > names to and submit - the more stakeholders that support a proposal the > more weight it has. > > It seems that the PV Industry Forum, or another similar body, may again > begin work to develop PV and storage industry stakeholder-consensus PIs to > submit; in the past this was a very successful endeavor. I'll post on this > list if and when that happens so that anyone that is interested can get > involved, but don't let that possibility keep you from submitting any PIs > on your own. > > Maybe in the meantime, a control system that shuts off the PV, and then > the batteries, would be worth designing. > > Brian Mehalic > > > > > On Wed, Feb 1, 2023 at 2:10 PM James Jefferson Jarvis via RE-wrenches < > re-wrenches@lists.re-wrenches.org> wrote: > > > > On 2/1/2023 2:58 PM, Starlight via RE-wrenches wrote: > > Have you (or any) installed surge suppression on the PV input side to > > clamp the open circuit voltage surge? > > That's not where the issue is and isn't really a solution. As I > explained in my previous e-mail, the issue is the open circuit on the > output leaves no where for the energy in the MPPT controllers inductor > to go and the only option is for the voltage to rise until it finds > somewhere to go. > > Surge suppressors, such as sold by Midnite Solar, are nothing more than > Metal Oxide Varistors. Or in the case of Delta, they are pieces of wire > in sand. They require large rise in voltage before they conduct. > > MOVs are sometimes found on the battery side of inverters and charge > controllers, but their clamp time and voltage before clamping requires > additional circuitry that works faster to protect fragile semiconductors. > > > If you are proposing using a surge supressor to regulate the voltage of > an island between a charge controller and an inverter when the battery > is disconnected, that's also a no go. Once the MOV clamps, it stays > clamped until voltage goes essentially to zero or until it blows up. > It's not a regulator. > > - > > To further stir the pot, it is definitely possible to design electronics > that can deal with load dumps and survive most anything. Aerospace > electronics come pretty close. But all that costs money and takes space > to do. Are we comfortable with requiring $16,000 charge controllers so > they can handle load dumps reliably from a poorly thought out NEC > requirement? I think the fossil fuel industry would be very happy with > the cost of renewable energy electronics being an order of magnitude > more expensive. > > > > > > > > Larry Crutcher > > Starlight Solar Power Systems > > > > > > > > On Feb 1, 2023, at 1:23 PM, William Bryce via RE-wrenches > > <re-wrenches@lists.re-wrenches.org > > <mailto:re-wrenches@lists.re-wrenches.org>> wrote: > > > > I can also backup what Jim has said, and have seen the same gear > > destroyed by removing the battery abruptly when the controller is under > > heavy load. They can die, and sometimes die spectacularly. > > > > Have seen SolArk inverters integrated MPPT controllers blow up when > > lithium battery BMS disconnects. Not a field fixable issue. > > > > Just flip off the breaker when the solar is working hard and and the > > SolArk will give up the smoke. > > > > Like I originally said, it’s the non talked about issue that is a big > > issue depending on what gear your using. > > > > On Wed, Feb 1, 2023 at 2:49 PM James Jefferson Jarvis via RE-wrenches > > <re-wrenches@lists.re-wrenches.org > > <mailto:re-wrenches@lists.re-wrenches.org>> wrote: > > > > > > > > On 2/1/2023 12:25 PM, Alex MeVay via RE-wrenches wrote: > > > Although our controllers are probably smaller than what you would > be > > > considering in this discussion, surviving a load dump (suddenly > > > disconnected battery) is an engineering requirement for us, and > > likely > > > would be for other responsible MFG's on this list (boB?). The > charge > > > controller can either handle full input voltage on the output, or > > > there is a comparator that will shut the controller down instantly > > > when the output voltage gets too high. > > > > So that's part of the picture. > > > > The other part of the picture is the rest of the system. The > discussion > > and what NEC is mandating is that the battery be disconnected. As > > far as > > I can tell, there isn't an explicit requirement in all cases that > > all of > > the power inputs into the system are all going to go away at exactly > > the > > same time .... or ever. This leaves things like charge controllers > > getting input power potentially from PV or wind or grid or generator > or > > something else. And nothing in the NEC, as far as I can tell, is > > mandating that all of the DC loads be disconnected. So the loads are > > online. Now the regulation circuit (switching power supply in the > case > > of a MPPT controller) is regulating variable loads and nothing is > > providing substantial resistance to change. Normally the battery is > > acting like a very very very big capacitor. But without the battery, > > there isn't enough damping in the control loops and voltage stability > > will suffer. This is where you get 250 volts on your normally 48 volt > > battery bus. Or 3 volts. Or -80 volts. Or all of those in a fraction > of > > second. This sort of thing is hard on electronics and will cause > > failures. > > > > > > Alex's comment about Genasun's controllers handling full input > voltage > > on the output is probably unique to their niche product. Looking at > > their biggest controller, it appears to support VOC of 34 volts. At > 34 > > volts, he can use 50V or 100V rated components on his output. For a > > 150V > > input controller, you probably can. But you wouldn't because it > > would be > > too expensive. But on a 600V or 1000V controller, there's just no way > > that you do that because 1000V rated components are big and expensive > > and their spacing requirements are huge compared 100V level sort of > > stuff. So the way bigger MPPT controllers deal with load dump is with > > transient voltage supression or other diodes to handle the voltage > > spike > > caused by the inductor when the load goes away. When operated in > > parameters, these parts don't wear out. But it can be interesting to > > size them adequately to account for inductance elsewhere in the > system > > adding to voltage and energy that has to be absorbed. > > > > > > There is a very simple experiment that anybody can perform to see how > > equipment handles a load dump: Simply wait for a sunny day and turn > off > > the battery breaker. If no magic smoke was released, turn back on > > battery breaker. If still no magic smoke was released, then great, > your > > system survived a load dump. > > > > If you are at all uncomfortable doing this and/or your system gets > > destroyed in the process, think back to my earlier security comments > > about having a self destruct switch on the outside of your building > > allowing anyone walking by to do this experiment for you. > > > > I have personally destroyed Outback, Midnite, and Morningstar > > controllers inadvertently or intentionally doing load dumps by > shutting > > off their output breaker. Typically the TVS diodes short out and > > secondary over current protection (circuit breaker) trips before > things > > catch on fire. Usuaully the UL94V0 rating on the circuit board and > the > > box the circuit board is in prevents fire from spreading when things > do > > get wild. > > > > But I've also seen all of those brands survive a load dump. > > > > I have multiple customer who have fielded lithium battery systems to > > cold locations and have had battery BMS disconnect the battery from > the > > rest of the system. Ten's of thousands of dollars of equipment has > been > > destroyed in these islanding events. > > > > > > Some thoughts, for what they are worth. > > > > -James Jarvis > > APRS World, LLC > > > > > > _______________________________________________ > > List sponsored by Redwood Alliance > > > > Pay optional member dues here: http://re-wrenches.org > > > > List Address: RE-wrenches@lists.re-wrenches.org > > > > Change listserver email address & settings: > > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > > > There are two list archives for searching. 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