used ev battery use

ws9876
ws9876 Solar Expert Posts: 450 ✭✭✭
in Advanced Solar Electric Technical Forum #1
In the near future used ev batteries will be a common sale item even at 70-80 % capacity.
To use them conveniently in homes we will need charge controllers that can charge at those higher voltages.Rather than dissecting the modules in the pack to make a 48volt pack.
 How would you handle the charging and how would you run say 200 vdc into a common all in one inverter like the 6000 xp so you can use its 48 volt inverter...??
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  • ws9876
    ws9876 Solar Expert Posts: 450 ✭✭✭
    #2
    solar charging
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,623 admin
    #3
    The voltage miss-match is a "big issue" with solar vs used EV Batteries and such...

    The NEC treats voltages under 60 Volts as (more or less) less than instantly lethal and "OK" for "home owner" use.

    Anything over 60 volts needs to be behind a "locked door", panels that require tools to access (screwdriver, wrench, etc.).

    Realistically, 120/240 VAC is really more dangerous vs 120/240 VAC (in terms of electrocution):

    https://www.electricaltechnology.org/2019/08/ac-dc-which-is-more-dangerous.html

    Add the high current available from large battery banks (arcs, fusing of wiring, etc.) is also a big issue. In the USA, normal "residential utility transformers" are limited to 10,000 Amperes max--Still lots of current (and energy), but that means that mains circuit breakers, fuses, and such have a "known" maximum current.

    Add that it is pretty cheap an easy to use transformers for higher voltage AC to drop to lower voltage AC/DC (power supplies) voltages, AC switches are smaller/cheaper vs same rated DC switches (circuit breakers, fuses, etc.), and that you can get cheap AC Ground Fault Interrupters/Circuit Breakers (to trip shocks to 0.010 Amps or so max)--Not easily available for DC powered wiring.... Add that typical battereis are something like 2-4 VDC per cell--Placing enough cells in series for 120/240/Whatever VDC is a major design issue (per cell voltage monitoring, cell temperature monitoring, etc.)--Looking at those large/high voltage EV battery packs (with their own BMS/Battery Managvement System--And how to "comunicate" between your "home grown" solar side, vs the used battery bank integrated BMS... More issues.

    So far, the only >60 VDC input inverters I have seen (not that I am big into industrial systems), have been larger inverter systems for Data Centers and such.

    A quick check of the Tesla Power Wall specifications:

    https://energylibrary.tesla.com/docs/Public/EnergyStorage/Powerwall/3/Datasheet/en-us/Powerwall-3-Datasheet.pdf

    Battery buses (as far as I can tell) are rated 52-92 VDC, and Vmp-array rating is 62-480 VDC (550 VDC max not to exceed).

    It appears, at this time, that any "high voltage" battery banks are going to be limited to industrial and "factory" designed and constructed systems.

    I would be very leary of an "average certified electrician" ability to properly design and install an "overall safe/well protected" mixed high voltage AC/DC power system...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,906 ✭✭✭✭✭✭
    #4
    LG Resu 16 is 400v marketed in US with a Growatt 400v inverter/ Charger. Schneider Home is also 400vdc with its own electronics.

    You definately can not go to Costco and build a temporary batttery today if you have a battery failure.
    😉
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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