[RE-wrenches] ~5,000 amps @ 48 volts

david quattro david at quattrosolar.com
Mon Dec 22 12:32:19 PST 2025 

The service is 240v single phase.  The customer does prefer to interconnect
to utility, but Load-history is very low to justify this amount of solar.
   As electricians, We know that we can take two hot legs of 480v 3φ and
transform it down to 240v split. It’ll still be 60Hz. But getting PGE to
agree to interconnect that architecture.. seems like such a long shot that
they would agree, I don’t even want to try.  That’s one reason I’m leaning
toward SolArk 18K as the inverter choice.
   Another facet of the same issue - let’s say I magically did get the
green light from all entities to interconnect a higher voltage 3φ inverter
into standard residential single phase. That would mean that Phases A and B
would essentially always be carrying significant load, and C phase would
only see action during Emergency outages. That degree of phase imbalance
could set us up for a “no warranty” argument from manufacturers.
    Another detail: if we’re interconnected, part of the goal is to offset
real-time load of 5 disparate utility meters. When I anticipate receiving
input from 5 sets CT’s (over significant distance), feeding it into an MDI,
correcting for voltage, verifying L1 versus L2 five times, etc etc.   it’ll
be hard enough to do it with 240 split phase native gear.   I think it will
be a nightmare getting all that to grok correctly with a 480/240
transformer in the mix while saying yes to a permanent phase imbalance.
   The customer wants a generator. So then that generator would have to
push 480v onto ‘critical loads.’  It’s also really weird to see 480 in a
residential setting, and could be dangerous for any other electrician
besides me and my foreman. Especially, say 5, 10+ years from now if I’m not
available.
   Avoiding all that ,,  these are the reasons I think it makes most sense
to keep everything the same phase and voltage.



On Fri, Dec 19, 2025 at 8:26 PM Jerry Shafer <jerrysgarage01 at gmail.com>
wrote:

> Interesting exercise here,
> 5000 amps at 48 vdc, this would be 20+ Fortress evault max 48 vdc cabinets
> and l dont think you can put that many on the BMS.
> What service does he have, a 3 phase 120/208, 277/480, a 120 208 3 phase
> it would be around 600 + meter main, single phase close to a 1000, amps.
> You may want to consider a commercial solark inverter as l recall they are
> high voltage DC, It would be more efficient, smaller and less copper wire
> even with a transformer to step it down. Get more info on this existing
> service, voltage, phases, gets us all out of our boxes and thinking.
> Fun times
>
>
> On Fri, Dec 19, 2025, 2:49 PM Kirk Herander via RE-wrenches <
> re-wrenches at lists.re-wrenches.org> wrote:
>
>> I do think the Electrician tried to balance the loads in the three 240 V
>> panels, but how close he really came especially with add-ons down the road
>> I don’t know. It does work fine, and the system is 5+ years old now without
>> any issues.
>>
>>
>> *Kirk Herander / **kirkh at vermont.solar <kirkh at vermont.solar>*
>>
>> *Owner|Principal, VT Solar, LLC*
>>
>> *Celebrating our 34st Anniversary 1991-2025!!*
>>
>> dba Vermont Solar Engineering
>>
>> 802.559.1225
>>
>>
>> On Fri, Dec 19, 2025 at 5:46 PM david quattro <david at quattrosolar.com>
>> wrote:
>>
>>> Kirk,    it sounds like phase imbalance is not a problem
>>>
>>> On Fri, Dec 19, 2025 at 2:42 PM Kirk Herander <kirkh at vermont.solar>
>>> wrote:
>>>
>>>> Hi,
>>>> I’ve done one large off grid system with 480 -3 - phase inverters and 1
>>>> mwh, 850 vdc LFP storage.
>>>>
>>>> We created 240vac  by stepping each 480v L-L phase down to 240 through
>>>> its own transformer of proper size.
>>>> So we have three 240/120 VAC panels for typical household loads.
>>>>
>>>>
>>>> *Kirk Herander / **kirkh at vermont.solar <kirkh at vermont.solar>*
>>>>
>>>> *Owner|Principal, VT Solar, LLC*
>>>>
>>>> *Celebrating our 34st Anniversary 1991-2025!!*
>>>>
>>>> dba Vermont Solar Engineering
>>>>
>>>> 802.559.1225
>>>>
>>>>
>>>> On Fri, Dec 19, 2025 at 5:25 PM david quattro via RE-wrenches <
>>>> re-wrenches at lists.re-wrenches.org> wrote:
>>>>
>>>>> I’ve thought about HV and 60K model, but my loads are 240 Single
>>>>> phase, across 5 separate contiguous parcels.  all these homes already have
>>>>> their own utility meters.  There is one owner.  The plan is to have an ATS
>>>>> at each meter.
>>>>>    Regarding 3 phase offgrid, I’ve been concerned about phase
>>>>> imbalance. Maybe I don’t need to worry about that.
>>>>>
>>>>>
>>>>>
>>>>> On Fri, Dec 19, 2025 at 1:51 PM Michael Morningstar via RE-wrenches <
>>>>> re-wrenches at lists.re-wrenches.org> wrote:
>>>>>
>>>>>> A couple or three Discover HVs and Sol-Ark 60ks. Done quickly
>>>>>>
>>>>>> On Fri, Dec 19, 2025 at 1:00 PM Kirk Herander via RE-wrenches <
>>>>>> re-wrenches at lists.re-wrenches.org> wrote:
>>>>>>
>>>>>>> Why 48v, why not commercial DC, like 850? What are you looking at
>>>>>>> for kwh storage? A1000vdc buss, homemade or otherwise, would drop the buss
>>>>>>> rating down to about 300 A. Commercial grade  inverters, such as 3-phase
>>>>>>> Delta PCS inverters are spec'ed for these situations.
>>>>>>>
>>>>>>> On Fri, Dec 19, 2025 at 1:13 PM david quattro via RE-wrenches <
>>>>>>> re-wrenches at lists.re-wrenches.org> wrote:
>>>>>>>
>>>>>>>> Hi everyone,
>>>>>>>>    I am still helping an uber wealthy owner determine if he really
>>>>>>>> wants this much power. If he does, do any of you have experience sourcing a
>>>>>>>> 48v battery-combiner on the order of 4500 to 5000 amps?
>>>>>>>>   I also want to get clear on how to best wire from batteries to
>>>>>>>> combiner, and from combiner to inverters. I read here on the Wrenches list
>>>>>>>> about some electricians who strategically sized conductor AWG so that
>>>>>>>> resistance matches, which seems straightforward once we get our components
>>>>>>>> mounted and accurate distances can be determined. Can anyone on list
>>>>>>>> provide feedback about that, I really appreciate it!
>>>>>>>> Thank you
>>>>>>>> _______________________________________________
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>>>>>>>
>>>>>>> --
>>>>>>>
>>>>>>>
>>>>>>> *Kirk Herander / **kirkh at vermont.solar <kirkh at vermont.solar>*
>>>>>>>
>>>>>>> *Owner|Principal, VT Solar, LLC*
>>>>>>>
>>>>>>> *Celebrating our 34st Anniversary 1991-2025!!*
>>>>>>>
>>>>>>> dba Vermont Solar Engineering
>>>>>>>
>>>>>>> 802.559.1225
>>>>>>> _______________________________________________
>>>>>>> List sponsored by Redwood Alliance
>>>>>>>
>>>>>>> Pay optional member dues here: http://re-wrenches.org
>>>>>>>
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>>>>>>
>>>>>> --
>>>>>>
>>>>>> Michael Morningstar
>>>>>>
>>>>>>
>>>>>> Morningstar Electric Inc
>>>>>>
>>>>>> PO Box 1494
>>>>>>
>>>>>> Mount Shasta, CA 96067
>>>>>>
>>>>>> 530-921-0560
>>>>>>
>>>>>> CSLB 1116835
>>>>>>
>>>>>> mjmorningstar at gmail.com
>>>>>>
>>>>>>
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