Potentially an incredible energy storage opportunity for me? Free Lion's

[inetdog]

And some data centers have experimented with running their power distribution at high (300-400V) DC voltages instead of running AC to the racks. The touted efficiency increases do not seem to have materialized yet though.

[Sunking]

I was thinking 120v AC (possibly being able to use an inverter to convert 120 DC to AC) would be essentially wall power. I'm just trying to brainstorm. I understand the dangers of HV I bus up and de bus these batteries to and from 640 volts regularly.

Voltage the Inverter operates at if designed properly depends on the Invert's Wattage. Higher wattage requires higher voltages to keep current manageable, cost effective, and safe.

12 volts up to 1000 watts.
24 volts up to 2000 watts
48 volts up to 4000 watts.

What does this all have in common? Answer is 100 amps or less.

Note pushing those limits does not mean a good practice. At 4000 watts I would prefer 330 volts. But you consumers and DIY's cannot do anything over 48 volts.

[Sunking]

Even large datacenters with huge amounts of batteries stick with 48V for what they do.

No that is not entirely accurate. Telecom is -48 volt, and some of the equipment you find in a Data Center operates directly from - 48 volt battery plants. However that is prety much for Transport, not processing. In a Data Center most of the processing equipment runs on 240/208/120 volts AC power supplied by a UPS. A Large Data Center can have up to a 2 Mw UPS and battery voltages on those can be as high as 590 volts the maximum voltage NEC will allow without significantly stricter requirements over 600 volts.

One very common Voltage you see for small UPS and Industrial Inverter is 144 volts. There are tons of 144 volt Inverters on the Telecom and Electric Utility Salvage markets. Any electrical sub-station you see will likely have a 144 volt battery bank and a 2 to 5 Kwh Inverter used to power SCADA and Protective Relay Switching Control Circuits.

From a code perspective there are 2 lines drawn in the sand. One at 50 volts and another at 600 volts. When you cross those lines, rules change significantly.

[aaronllewellyn]

120V DC wouldn't be standard.
12, 24, 48 - those are standard (or at least common) DC voltages.
IIRC at 60V or higher there are more requirements for properly handling/wiring DC.

Even large datacenters with huge amounts of batteries stick with 48V for what they do.

I was thinking 120v AC (possibly being able to use an inverter to convert 120 DC to AC) would be essentially wall power. I'm just trying to brainstorm. I understand the dangers of HV I bus up and de bus these batteries to and from 640 volts regularly. You're very right, I have first hand experience dealing with handling HV, as far as safety goes. right now I'm just trying to come up with a way to potentially use these modules as storage at the cost of free, if only as an experiment.

[foo1bar]

, would it be possible to wire three 40v modules in series and reach 120v DC? that seems like a far more standardized voltage.

120V DC wouldn't be standard.
12, 24, 48 - those are standard (or at least common) DC voltages.
IIRC at 60V or higher there are more requirements for properly handling/wiring DC.

Even large datacenters with huge amounts of batteries stick with 48V for what they do.

[Sunking]

Old Lithium cells are dangerous, especially ones that have deteriorated as much as you indicated. Personally I would not risk having many around. Old cells are prone to thermal runaway, and once it starts you cannot stop it or put the fire out. All you can do is get back and let it burn itself out. Fire department wil not even try, just keep it contained to your house. So if you are OK with that, have at it.

What kind of Lithium Cells are you talking about? If they have any Cobalt or Manganese I would not touch them. Perhaps if they are LiFeP04 or Titanate but in small quantities. Another huge issue is how are you going to integrate them into a Solar System designed to operate at voltages of 12. 24, or 48 volts? You would have to tear them apart to get down to individual cells and reconfigure. Otherwise you would have to design and build the equipment to work with Queer non-standard operating voltages the batteries are configured for.

Lots of challenges and risk.

[aaronllewellyn]

Close thread. I'm going to do more research before asking any more questions.