Interesting, but I'm not sure I completely follow.
Batteries, particularly Li ion, don't have linear voltage. They stay
pretty much near their nominal voltage until nearly discharged and
vice
versa. I don't know the voltage curve for solar panels but I'll make
an
assumption it is more or less linear with the amount of light. Given
that, doesn't that mean that the panels will charge the battery only
part of the time, when there is strong light ? Is that an adequate
percent of the time ? Also, you have to monitor by hand, right ? Once
the battery is up to max voltage, you need to disconnect or you will
destroy the cells.
Peri
------ Original Message ------
From: "Robert Bruninga via EV" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Cc: "Robert Bruninga" <[email protected]>
Sent: 02-Sep-19 7:20:27 AM
Subject: Re: [EVDL] V2G for my grid tied solar? (constant current
charging)
>One final point about grid down charging (under a must have armagedon
>scenario): (And only for those fully experienced in HVDC)
>
> Remember that Solar panels are current limited power sources. This
means
>It will provide its rated current at ANY voltage from 0 (short
circuit) up
>to its nominal operating voltage.
>
>This means I can just clip the 450 volts DC straight from any one of
my 3
>kW solar panel arrays and run it straight to a 12, 24, 48, or 72 volt
>battery (or 240v prius) directly for a temoporary 7 to 9 amp charge.
WHICH
>ONE MUST MONITOR to know when to disconnect. AND one must have
arc-flash
>eye protection because you will draw a lightening bright arc flash
when you
>disconnect (and or while connecting if the connection is not made
>cleanly). But you will get a 7 amp charge (in my case of older
panels).
>New 300W panels can give 9 amps.
>
>(You MUST disconnect from your GT inverter of course,. You do not
want any
>capacitor holding the 450v or it is no longer a perfect current
limited
>source).
>
>And with 6 such separate panel arrays, I can combine the currents at
the
>battery to give me up to 42 amps at 12, 24, 48, 72... (or 240) volts
if
>needed. But again MUST human monitor in real time. It is not easy
to
>throw together a charge regulating circuit to open a relay when the
charge
>is complete as agaiin, you must use very expensive HVDC contactors
and or
>snubbers. And by th time you do all that , you could have build a
more
>direct DC/DC converter.
>
>So again, this is just an emergency data point. For example, while
drawing
>1 kW (80 amps) from my prius 12v battery to power the house, all I
need at
>240v DC is 4 amps from the solar array. And in my 14 year old
Priuses I
>know exactly where the HV battery posts are and can connect there and
am
>happy to take the risk. Not sure I wouild take the risk for the 350v
>battry in the newer Volt (which could give me 2 kW from its DC/DC
>converter)..
>
>Anyway. just thought I would mention it. Oh, and the open circuit
voltage
>of the solar arrays on the brightest and coldest day can approach 600
>volts, not the 450 nominal load point... But again, just short that
600
>volts with an ampmeter and you will still see only the 7, 8 or 9 amp
>current from your arry even at zero volts. Just protect your eyes
from the
>arc flash when you disconnect (oh, it will also vaporize pieces off
your
>clip leads too each time), and it can just melt the tip off the
copper wire
>to molten copper and catch fire to the insulation and anything else
within
>a few inches if you let the arc continue...)..
>
>NOT SOMETHING TO PLAY AROUND WITH!
>
>But you can charge any battery... ;-)
>
>Bob
>
>
>On Sun, Sep 1, 2019 at 2:17 PM Robert Bruninga <[email protected]>
wrote:
>
>> Again, if you find a 72v UPS (6 12v batteries) then you can tap
your
>> arrays in groups of three and use that to provide the current to
the UPS to
>> dirive your car charger. Just 9 panels in 3 parallel strings of
90v will
>> give maybe 20 amps (or the minimum needed to charge L1) But 12
panels (or
>> about one string array) will give you plenty of current over more
hours of
>> the day. That's why I like string inverters beccause I have
access to all
>> the DC inputs and ground mount so I can get to them any time I
want.
>>
>> Bob
>>
>> On Sun, Sep 1, 2019 at 1:20 PM Robert Bruninga <[email protected]>
wrote:
>>
>>> You already have what you need for continuous operation at night
in the 1
>>> kW class (refrigerator, well pump and lights, etc)
>>> See http://aprs.org/powerwheels.html
>>>
>>> But it assumes you have the Sunny Boy GT inverter with "secure"
power
>>> when the grid goes down to charge your EV. $1500
>>> Or if you are lucky to find a UPS of at least 1800W capacity to
charge
>>> the car, and then you can drive that from batteries that you
charge from
>>> voltage taps on y our DC array that match the input voltage of
the UPS.
>>> But ONLY if you seriouisly know what you are doing and do not
overcharge
>>> the intermediate battery., etc.
>>>
>>> Bob
>>>
>>> On Sun, Sep 1, 2019 at 12:28 PM Damon Henry via EV
<[email protected]>
>>> wrote:
>>>
>>>> I know there has been a lot of churn the last few years over
Vehicle to
>>>> Grid technology. I'm not sure how many people really want the
utilities to
>>>> take over their vehicle state of charge, so I'm not sure how
viable the
>>>> whole concept is.
>>>>
>>>> With my grid tied solar system my solar stops producing if the
grid goes
>>>> down. One way to prevent this is to have a battery backup
system in
>>>> place. That's usually an investment of at least several
thousand dollars.
>>>>
>>>> I have two factory OEM PHEVs sitting in my driveway with
significant
>>>> battery packs. I also have a Juicebox 40 for charging which has
some
>>>> charging intelligence already built into it for their Juicenet
program, but
>>>> not really V2G. I feel like I am tantalizingly close to a great
solution.
>>>>
>>>> So here is the question that I have. How far am I from being
able to
>>>> utilize my car batteries through the OEM port and an EVSE
charger, to feed
>>>> an inverter and keep my house alive and my solar producing
during a power
>>>> outage? Is this tech currently being developed, or is it still
just a
>>>> dream that my come true some day?
>>>>
>>>> BTW - I have lived in my house for 20+ years and rarely lose
power, but
>>>> "being prepared" is always on my agenda. I suspect that if I
really want a
>>>> solution within the next couple of years I will need to buy a
separate
>>>> battery for my solar system, or a generator...
>>>>
>>>> thanks
>>>> Damon
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