The Tesla Powerwall battery packs is wired for a 350-400 volt range, and come bare bones except for some equalization circuitry, (no charger nor inverter). Any modifications to the battery pack itself would likely void the warranty. How ever adding a low voltage circuit does have it merits, but the Powerwall will not be a factor.
I have considered running a solar/battery backed up 32-35 volt DC supply into the house, and use a number of 5-pack LM2596S stepdown inverters. The adjustable nature of these DC buck converters can power DC fans, Security system, DVRs, Antenna amps, Sat boxes, night lights, laptops, LCD monitor, door bell, automation system, charging stations, etc. The higher distribution voltage keeps losses to a minimum while providing uninterrupted power.
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