Technology inside Tesla Powerwall - Page 1
Forum section: electronics / general

author: station240
author_rank: Unknown
timestamp: January 11, 2016, 01:23:58 am
content: I've been interested in what is actually inside the Tesla Powerwall, but we are yet to see anyone pull one down to look inside.So I did a lot of poking around and found some information.Firstly we have the install manualhttps://www.teslamotors.com/sites/default/files/pdfs/powerwall/Powerwall%20Installation%20and%20User%27s%20Manual-online-B.pdfIt has a single DC input/output (bi-directional) .capacity: 6.4kWhpower in/out: 3.3kW 350-450V 9.5Acells: nickel-manganese-cobalt (5000 hours)comms: CAN/modbus (hardware switchable)The basic concept is to use a DC-DC converter to convert the voltage from the battery to ~400VDC which is fed directly into the inverter's main DC rail. Power can flow both ways, so during the day the batteries are charged from the same rail that feeds the H bridge in the inverter.Now the DC-DC converter is a ?uk converter, Dr Slobodan ?uk works for Tesla, and they have access to his various patents. It's a simplified combined buck/boost converter easily converted to bi-directional operation.I don't believe the CAN/modbus protocols are publicly available, which is a problem as they are needed to switch the Powerwall between charge and discharge mode,According to this articlehttp://www.catalyticengineering.com/top-ten-facts-about-teslas-350kwh-powerwall-battery/the battery pack likely uses two modules the same design as the Model S. Each module has 6 groups, and 74 cells in parallel per group. This makes a total of almost 900 cells, with an operating voltage of about 48 VDC. I've not seen any confirmed information on the pack voltage.The pack is packed in a coolant, as in the Model S, Tesla stated this somewhere.Anyone else found useful information on the Powerwall ?It's difficult to get beyond the news stories in the search results.

author: miguelvp
author_rank: Super Contributor
timestamp: January 11, 2016, 01:44:53 am
content: According to this case study:http://www.nrel.gov/docs/fy16osti/64987.pdfOn page 10:Code:Table 3: Tesla Powerwall Specifications Property ValuePrice $3000Capacity 7 kWhPower 2.0 kW continuous, 3.3 kW peakEfficiency 92%Voltage 350 – 450 VCurrent 5.8 A nominal, 8.6 A peakWeight 100 kgDimensions 1300 mm x 860 mm x 180 mmIt also states the following:Quote

author: orion242
author_rank: Unknown
timestamp: January 11, 2016, 02:18:13 am
content: http://www.modbus.org/Full spec is there.

author: station240
author_rank: Unknown
timestamp: January 11, 2016, 03:18:23 am
content: Quote from: orion242 on January 11, 2016, 02:18:13 amRubbish, look at it in detail, modbus is simply a way to set memory address X with value Y.You still need documentation for each device to know what you are changing !There is a SunSpec Alliance, which adds solar specific concepts, but is a work in progress and hasn't gotten to batteries yet.

author: orion242
author_rank: Unknown
timestamp: January 12, 2016, 12:19:28 am
content: Didn't say it wasn't rubbish. Welcome to the wonderful world of modbus.

author: reagle
author_rank: Unknown
timestamp: February 03, 2016, 01:52:23 am
content: Hmm, how would one use it with a grid tied system using ACPV panels? Looks like I'd have to take its output, feed it into a dedicated inverter then somehow feed that into combiner box that connects to my array? Sounds like it'd break all kinds of anti-islanding rules

author: station240
author_rank: Unknown
timestamp: February 03, 2016, 08:48:53 am
content: Quote from: reagle on February 03, 2016, 01:52:23 amAh we call those tiny inverters on the back of panel Micro Inverters, real problem for use with batteries.Easy solution would be to connect a battery charger to the mains, set to only run when there is excess solar power. Then run another inverter off the battery to power the house. You can get all in one units with the charger and inverter in one box.Aternative option is to replace the micro inverters with a set Solar Edge Power Optomizers, and their related big inverter.http://www.solaredge.com/groups/powerbox-power-optimizerI recall their system is one of the few that work with the Powerwall, not cheap however.

author: AndyC_772
author_rank: Super Contributor
timestamp: February 03, 2016, 09:15:13 am
content: Modbus? Really? Out of choice, in a world where at least one protocol that'snotModbus exists?(For those unfamiliar with it, Modbus is a multi-master serial interface, a bit like RS485. The end of a message is indicated by a time gap 3.5 characters long - no more, no less - and replies from slave devices contain no information about what they're actually replying to... justtheir owndevice ID, length, data and CRC).

author: mtdoc
author_rank: Super Contributor
timestamp: February 03, 2016, 09:29:40 am
content: Quote from: AndyC_772 on February 03, 2016, 09:15:13 amFor better or worse, I believe it's the standard communications protocol used in the RE industry.

author: mtdoc
author_rank: Super Contributor
timestamp: February 03, 2016, 09:36:13 am
content: Quote from: station240 on February 03, 2016, 08:48:53 amThe common way to do it is to create what is called in the solar PV industry anAC coupled system.The big obstacle for incorporating the Tesla Powerwall into a standard battery back up (or off grid) system is that the voltage is too high for the currently available battery based inverters.