[RE-wrenches] Remote battery disconnects
Jason Szumlanski
jason at floridasolardesigngroup.com
Fri Feb 3 06:39:28 PST 2023
The visible load break disconnect thing really needs to die. We no longer
have problems with AHJs, but both of our local utilities still require them
for PV systems over 10kWac (after a short stint where they were not
required). It's a bizarre requirement and actually creates a potential
safety problem because the utility disconnect switch may not be the rapid
shutdown switch in some situations and could be misconstrued as such. In
many cases, the utility disconnect switch doesn't shut down the PV in an
ESS system, and a separate RSD switch is required, but not necessarily
colocated.
Jason Szumlanski
Principal Solar Designer | Florida Solar Design Group
NABCEP Certified Solar Professional (PVIP)
Florida State Certified Solar Contractor CVC56956
On Fri, Feb 3, 2023 at 9:29 AM August Goers <august at luminalt.com> wrote:
> It’s been fun watching this (at times) rather lively discussion. It’s been
> making me think about the differences between NEC 480 Storage Batteries vs
> 706 Energy Storage Systems.
>
> If I can boil it down, it seems like the offgridders are frequently
> working with systems that are custom assembled including separate DC
> batteries. This is because the more mainstream energy storage systems on
> the market are primarily focused on the on-grid market with both grid-tied
> features and battery backup. But these ESS systems frequently don’t include
> all the features, especially generator control, to run in full off-grid
> mode 365 days a year.
>
> It seems increasingly difficult to meet the NEC with these legacy battery
> systems - tons of disconnects, bespoke design, assembly, programming, rapid
> shutdown, etc. I feel for those of you that need to put together really
> robust off grid systems and meet all of these codes.
>
> On there flip side, we’ve fully embraced energy storage systems for our
> urban market in the Bay Area. It’s been super challenging in many ways, but
> I can’t say that the NEC is particularly causing us the majority of pain.
> The fire code is causing a lot of pain, but that is a whole different
> story. We’ve recently started selling Tesla’s Powerwall+ systems which
> includes a solar inverter, battery, and battery inverter in one ESS. One
> nice part of this system is that we can meet NEC 706.15 ESS Disconnecting
> Means and 690.12 Rapid Shutdown of PV Systems all with one switch. That’s
> pretty nice. Some AHJ’s may still be insisting on visible blade lockable
> disconnects, so we always in a process of educating them, but most are
> accepting this one switch to do it all.
>
> Good luck out there everyone - it seems like one thing is for certain -
> batteries and energy storage (in all their forms) are here to stay!
>
> August
>
> On Fri, Feb 3, 2023 at 5:27 AM Jason Szumlanski via RE-wrenches <
> re-wrenches at lists.re-wrenches.org> wrote:
>
>> 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 at 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) *
>>> *maxfieldsolar at hotmail.com*
>>> *(801) 631-5584(Cell)*
>>> ------------------------------
>>> *From:* RE-wrenches <re-wrenches-bounces at lists.re-wrenches.org> on
>>> behalf of bob--- via RE-wrenches <re-wrenches at lists.re-wrenches.org>
>>> *Sent:* Wednesday, February 1, 2023 8:06 PM
>>> *To:* RE-wrenches <re-wrenches at lists.re-wrenches.org>
>>> *Cc:* bob at midnitesolar.com <bob at 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 at 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 at lists.re-wrenches.org
>>> > <mailto:re-wrenches at 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 at lists.re-wrenches.org
>>> > <mailto:re-wrenches at 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 at 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. When one doesn't work, try
>>> the other:
>>> > https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/
>>> > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>>> >
>>> > List rules & etiquette:
>>> > http://www.re-wrenches.org/etiquette.htm
>>> >
>>> > Check out or update participant bios:
>>> > http://www.members.re-wrenches.org
>>> >
>>> _______________________________________________
>>> List sponsored by Redwood Alliance
>>>
>>> Pay optional member dues here: http://re-wrenches.org
>>>
>>> List Address: RE-wrenches at 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. When one doesn't work, try
>>> the other:
>>> https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/
>>> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>>>
>>> List rules & etiquette:
>>> http://www.re-wrenches.org/etiquette.htm
>>>
>>> Check out or update participant bios:
>>> http://www.members.re-wrenches.org
>>>
>>>
>>> _______________________________________________
>>> List sponsored by Redwood Alliance
>>>
>>> Pay optional member dues here: http://re-wrenches.org
>>>
>>> List Address: RE-wrenches at 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. When one doesn't work, try the other:https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>>>
>>> List rules & etiquette:http://www.re-wrenches.org/etiquette.htm
>>>
>>> Check out or update participant bios:http://www.members.re-wrenches.org
>>>
>>>
>>> _______________________________________________
>>> List sponsored by Redwood Alliance
>>>
>>> Pay optional member dues here: http://re-wrenches.org
>>>
>>> List Address: RE-wrenches at 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. When one doesn't work, try
>>> the other:
>>> https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/
>>> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>>>
>>> List rules & etiquette:
>>> http://www.re-wrenches.org/etiquette.htm
>>>
>>> Check out or update participant bios:
>>> http://www.members.re-wrenches.org
>>>
>>> _______________________________________________
>> List sponsored by Redwood Alliance
>>
>> Pay optional member dues here: http://re-wrenches.org
>>
>> List Address: RE-wrenches at 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. When one doesn't work, try the
>> other:
>> https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/
>> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>>
>> List rules & etiquette:
>> http://www.re-wrenches.org/etiquette.htm
>>
>> Check out or update participant bios:
>> http://www.members.re-wrenches.org
>>
>> --
> August Goers
> Luminalt
> o: 415.792.6666
> m: 415.559.1525
> august at luminalt.com
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20230203/6684aeb0/attachment-0001.htm>
More information about the RE-wrenches
mailing list