[RE-wrenches] 120 Vac and 12Vdc mixed distribution system

Fri May 3 15:13:31 PDT 2024

For this application I was originally thinking about a 48V inverter with
120V output, but there are not many options in the size range I was
considering. It hit me that I could potentially get a 120/240V split-phase
inverter and run the DC converter from one leg and the 120V loads from the
other leg. The Sol-Ark 8K would probably be the right size for this
application. Despite there being no 240V loads, they "could" add them in
the future if needed. I know about imbalance issues with the 12k, but have
not heard this same feedback about the 8k, so please let me know if you
know otherwise.

I really doubt there will be enough imbalance here to cause issues. The
biggest load on the DC side is a tiny 12V DC pump and the largest load on
the AC side will be the new refrigerator, or maybe a big ceiling fan
starting up. The inductive loads are almost negligible. Really the only
reason I want an inverter this large is for the charger capacity. The owner
wants a 9.6kWh LiPo battery minimum, so I want a sizable charger.

BUT, the client would need to replace their 120V portable generator with a
split-phase unit. That could be a sticking point taking me back to a 120V
inverter.

I was hoping for an all-in-one for this particular job, but the only one I
can find that is 48Vdc and 120Vac is the EG4 6500EX-48. At the price point
they offer it, I guess it can't hurt to try! I can even have a spare on the
shelf for less in total than the cost of a Victron inverter charger and
separate charge controller, and still have money to spare. I have been
dabbling into the EG4 brand, mostly with clients that went ahead and bought
EG4 batteries before they ever met me, and I haven't had any real issues
other than battery to inverter closed loop comms. It's too early to say I'm
impressed, but the prices are in the too-good-to-be-true category. I don't
want to get off topic here with batteries and manufacturer reliability, but
I wanted to mention the EG4 6500EX-48, which seems like perfect specs for
this job.

And... I know... someone is probably thinking that we're up to a 9.6kWh
battery with a small 120V generator, and that's probably not a good match.
I get that, but the client expects the PV to handle all of their needs with
the generator only serving as an emergency backup. I have alerted them to
the potential mismatch. I still want a sizeable charger in case they
upgrade their generator for faster battery recharges.

Jason Szumlanski
Principal Solar Designer | Florida Solar Design Group
NABCEP Certified Solar Professional (PVIP)
Florida State Certified Solar Contractor CVC56956
Florida Certified Electrical Contractor EC13013208

On Wed, Apr 24, 2024 at 1:52 PM John Blittersdorf via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

> Jason,
>   Just using the converter works fine. They are considered a battery
> charger or a regulated power supply. I am currently running that way now
> with the battery cables going nowhere.  I was thinking of putting the
> battery back in the system just for triple redundancy when my inverter hits
> low battery cutoff voltage on a cold winter night and no fuel for the
> generator (or it won't start).
> My Iota DLS puts out a regulated 13.4 volts up to 30 amps.
>
> John
>
> On Wed, Apr 24, 2024 at 8:25 AM Jason Szumlanski via RE-wrenches <
> re-wrenches at lists.re-wrenches.org> wrote:
>
>> Ah ha! I didn't consider using a small 12V battery with a charger. I was
>> thinking of just using a 120V -> 12V converter to handle the DC loads. Is
>> the 12V battery really necessary, or can I just power the DC loads directly
>> with a converter? If I just have lights and fans on the DC system, the load
>> should be pretty minimal.
>>
>> I could use a separate 12V battery, but I would like to eliminate that
>> cost and complexity if possible.
>>
>>
>> And yeah, I am not considering this a money making opportunity. It's
>> really just a challenge to ward off boredom from the daily grind.
>>
>> Jason Szumlanski
>> Principal Solar Designer | Florida Solar Design Group
>> NABCEP Certified Solar Professional (PVIP)
>> Florida State Certified Solar Contractor CVC56956
>> Florida Certified Electrical Contractor EC13013208
>>
>>
>> On Wed, Apr 24, 2024 at 8:01 AM John Blittersdorf via RE-wrenches <
>> re-wrenches at lists.re-wrenches.org> wrote:
>>
>>> Jason,
>>>   I have a customer with the same situation except he already has a 12 V
>>> VFX inverter,  He has a sunfrost fridge and other small loads with a very
>>> fancy custom control board
>>> originally set up to handle AC and DC systems.  We are adding a lot more
>>> solar and I was considering a dual battery system but the owner didn't like
>>> that idea.  We are going with and Iota 12v power supply (i use one at my
>>> house for my sunfrost) to power up all his DC loads and will be adding a
>>> large 48 V battery bank and over 4Kw of solar using a VFXR3648 directly in
>>> place of the 12V inverter.  He complained that the existing inverter would
>>> not handle all his current AC loads very well.  My own house is fully wired
>>> for 12VDC as well as AC (lots of #10 copper not being used) and I have been
>>> considering getting a small LFP 12V battery to put back on by DC System.
>>> Then use the Iota as a secondary charging method with some of my large
>>> stash of older modules hooked up for 12V direct with C40 charge controller
>>> to recreate my original system just for kicks. I'm only using DC for my
>>> Sunfrost and one "emergency light" in the livingroom right now.  For your
>>> customer, a small LFP 12v battery (approximately $500 or less) to replace
>>> his old battery bankm and more larger ones for the new AC side with 48V
>>> inverter fed by his generator or through an Iota 48 V charger ifusing a
>>> smaller non charging inverter. Unlike Dave, I like these challenges. Maybe
>>> thats why I never seem to make money.!!
>>>
>>> John Blittersdorf
>>> offgridvermont.com
>>>
>>>
>>> On Wed, Apr 24, 2024 at 7:22 AM Jason Szumlanski via RE-wrenches <
>>> re-wrenches at lists.re-wrenches.org> wrote:
>>>
>>>> Fortunately, the owner is pretty handy and is willing to live with any
>>>> negative consequences. That said, I want to offer him something as simple
>>>> and bulletproof as possible. I am walking into this with eyes wide open,
>>>> for sure.
>>>>
>>>> Jason Szumlanski
>>>> Principal Solar Designer | Florida Solar Design Group
>>>> NABCEP Certified Solar Professional (PVIP)
>>>> Florida State Certified Solar Contractor CVC56956
>>>> Florida Certified Electrical Contractor EC13013208
>>>>
>>>>
>>>> On Tue, Apr 23, 2024 at 5:47 PM Dave Angelini Offgrid Solar via
>>>> RE-wrenches <re-wrenches at lists.re-wrenches.org> wrote:
>>>>
>>>>> Not being helpful but I  walk away from these.  It will come back to you.
>>>>>
>>>>> *Dave Angelini Offgrid Solar
>>>>> "we go where powerlines don't"
>>>>>    <http://members.sti.net/offgridsolar/>https://offgridsolar1.com/ <https://offgridsolar1.com/>  <http://members.sti.net/offgridsolar/>
>>>>> e-mail  offgridsolar at sti.net <offgridsolar at sti.net>
>>>>> text 209 813 0060*
>>>>>
>>>>>
>>>>> On 2024-04-23 2:40 pm, Jason Szumlanski via RE-wrenches wrote:
>>>>>
>>>>> I have an off-grid client who is working on replacing old equipment at
>>>>> a cabin. He has a lot of 12 volt distribution in the house for lighting,
>>>>> fans, and a 12 volt refrigerator. He also has 120 volt AC loads that run
>>>>> through a separate distribution panel where the only source is a 2000 Watt
>>>>> Honda generator. There is no inverter present. The batteries are charged
>>>>> through a Trace C40.
>>>>>
>>>>> He currently has a few ancient solar panels and a struggling Bank of
>>>>> AGM batteries. It's time for an upgrade. I can easily supply enough PV
>>>>> power for what he needs. He currently has a 9 kilowatt hour battery
>>>>> capacity that he was happy with when the batteries operated optimally.
>>>>> Nonetheless, I would probably future-proof him with a 10 to 15 kilowatt
>>>>> hour LiPo to double or triple his usable capacity.
>>>>>
>>>>> For convenience, obviously it would be nice to have an inverter to
>>>>> eliminate or reduce the generator requirement. But he seems committed to
>>>>> keeping his 12 volt distribution because it would be costly to replace
>>>>> fixtures. I think he would consider replacing the 12 volt refrigerator if
>>>>> he has an inverter.
>>>>>
>>>>> He definitely wants LiPo batteries.
>>>>>
>>>>> I don't like the idea of 12 volt direct from a battery plus connecting
>>>>> an inverter to that same battery. It is going to be hard to measure and
>>>>> monitor things.
>>>>>
>>>>> I am thinking about using a 48 volt battery with a single phase 120
>>>>> volt inverter, getting him to change to a 120 volt refrigerator, and using
>>>>> a DC converter to give him somewhere in the range of 100 amps at 12 volts
>>>>> for his existing DC lighting and fan loads. Is this a bad idea? Should I
>>>>> stick with a 12 volt battery system? He does have a tiny 12 volt pressure
>>>>> pump which might be an issue for the converter. I'm not sure. I am a bit
>>>>> worried about the efficiency loss and capacity of DC converters and not
>>>>> sure how to size it.
>>>>>
>>>>> Jason Szumlanski
>>>>> Florida Solar Design Group
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
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