My New Favorite Battery.

[donald]

In the presentation Musk says "it has....the dc to dc converter". Then he says it is designed to work with existing solar systems.

I suppose he could be talking about the charge controller taking a range of voltages. But he used the term "converter".

Coming out with 400v dc would make it easy to parallel the system. But then they have to build many sizes of inverters to work with 2000 to 18000 watts. I have a hard time seeing Musk or solar city wanting to be in the inverter business.

I get using a 400v bus on the utility side of these products. It seems non-standard to expose that in the residential business.

[DanKegel]

Trojan warranty has teeth

Yeah, for their new line that Sunking likes (e.g. the IND9-6V), it's free replacement to 3 years, then prorated to 8 ( http://www.trojanbattery.com/pdf/TRJ...edWarranty.pdf ).
And according to http://www.trojanbattery.com/wp-cont...n_Overview.pdf they
are unlike most FLA's, and don't mind it if you don't charge them fully.

They're not for people who can't do this:

http://www.trojanbattery.com/pdf/BatteryMaintenanceLog.pdf

but they are real. I'm looking forward to seeing some whole-system writeups
showing examples of where they pay off in real life.

[Sunking]

Concerning the 14 wire, he could have been talking about the interconnects between multiple units. They also said the powerwall works with some existing solar city installed inverters.

Guess who sits on the Board of Directors at Solar City and majority stock holder? Can you say Elon Musk? Solar City has exclusive rights to the Battery. You cannot touch one for less than $7000 just for the battery. Want equipment to work with it? That is extra and Solar City has to sell it to you and install it.

[donald]

Concerning the 14 wire, he could have been talking about the interconnects between multiple units. They also said the powerwall works with some existing solar city installed inverters.

[Sunking]

I believe I heard that in the presentation. I hate to listen to the whole thing again. I just don't see them exposing 400v dc in a residential application.

You heard what you wanted to hear. From Chief Technology Officer JB Straubel said that the Powerwall is a 400 volt battery that "doesn’t use heavy gauge wire, so that makes the installation easier and faster"

He is absolutely correct operating at 400 volts pumping 2000 watts only takes 14 AWG wire with 5 amps ran in conduit.All you need is $7000 and you can have one too.Now all you need is the Tesla Hybrid Inverter to make it work.

[donald]

Real cost for the battery is in excess of $7000 installed by exclusive installer Solar City.

Maybe for now. I doubt there will be high volume of Powerwalls manufactured before 2017. There should be one or two quality competitors by then, probably using different lithium formulations. It's not a good PR move for him to have people complaining about their Solar City quotes. Prognosticators had the powerwall costing $13,000 too.

[Sunking]

80% is 1500 cycles. Probably less off grid. What will the life be in real world solar where the batteries seldom get through absorb?

Wrong, current testing is above 2500 cycles started in 2009. But regardless Trojan warranty has teeth my friend, not promises. Tesla has no testing or stats. And for $7000 installed is pure Bait and Switch. Musk own both Solar City and Tesla. He has a lock.

[donald]

Not even close. The Trojan lineup can be operated to 80% DOD same as Tesla to over 2500 cycles with a real 8 year capacity warranty. No need for any BMS, Liquid cooling or inverters not on the market. The charger for Tesla is a plain ole 240 VAC line voltage. No way to input solar other than GTI. You got all your facts wrong.

80% is 1500 cycles. Probably less off grid. What will the life be in real world solar where the batteries seldom get through absorb?

[donald]

Not to my knowledge or anyone else. Just 350 to 450 DC output.

I believe I heard that in the presentation. I hate to listen to the whole thing again. I just don't see them exposing 400v dc in a residential application.

[Sunking]

So add $500-$700 for a 48v 2000w inverter. Or less if the output can be reduced below 48v.

All in all a good deal. Sunkings nice Trojan batteries used at 50% DOD are about the same cost per watt hour.

Not even close. The Trojan lineup can be operated to 80% DOD same as Tesla to over 2500 cycles with a real 8 year capacity warranty. No need for any BMS, Liquid cooling or inverters not on the market yet. The charger for Tesla is a plain ole 240 VAC line voltage. No way to input solar other than GTI.

Real cost for the battery is in excess of $7000 installed by exclusive installer Solar City.

[Sunking]

The Powerwall converts the DC out to 48v.

Not to my knowledge or anyone else. Just 350 to 450 DC output.

[donald]

The Powerwall converts the DC out to 48v.
The 400v figure is internal. I suppose Tesla is proud off that number because that is apparently how their supercharger works on their cars.
The input/charger side of the powerwall is apparently AC and DC. They build a similiar charge controller into their cars.

So add $500-$700 for a 48v 2000w inverter. Or less if the output can be reduced below 48v.

All in all a good deal. Sunkings nice Trojan batteries used at 50% DOD are about the same cost per watt hour. But no charge control, no BMS, no fancy software interface that hasn't been shown yet.

After listening to Musk's presentation, I now think these will allow off grid in the warranty.

There's not going to be anything highly unusual for a residential install of this device, like wiring for 400v DC. I'll even bet that it's designed to be installed by a single person. Too many Apple employees at Tesla for this to be a half baked product.

[DanKegel]

What difference does it make if the batteries are 48V or 350V?

Maybe this is part of what he's talking about: http://en.wikipedia.org/wiki/Low_voltage mentions "the United States 2005 National Electrical Code (NEC) defines low (distribution system) voltage as 0 - 49 volts. Low distribution system voltage is covered by 250.20(A) of this code."

[foo1bar]

One of the magic 50V limits comes from the National Electrical Code, which adds a lot more restrictions on what you can do once you go above 50 volts.

What difference does it make if the batteries are 48V or 350V? Either way it's tying into house voltage at 110/220 AC. So it seems to me that it's just whether you're dealing with half the system being over 50V or all of it.

My guess is it'll probably be even easier than a typical 48V system. My guess is the battery banks and the inverter will come pre-wired so all that has to be done is plug them together and hook them up on the AC side. (where typical 48V system you have to deal with all the wiring from one battery to the next, and big cables from the batteries to inverter.) Even if they aren't setup to just be plugged together, it's probably going to just put some conduit between them, pull 6-10 AWG wire through the conduit, and hook up with simple connectors (screw or spring clamp) instead of crimping on big connectors onto big cables.

[inetdog]

Tesla said they're partnering with SolarEdge, which has been making noises about coming out with a battery inverter ("StorEdge") since June 2013, but evidently that's a 48v system (from http://www.aurora-energy.com/solar-e...ckup-solution/ ).

Where does the "magic 50 volt limit" come from? Is that from limitations in power semiconductors?

BTW I agree that the cost for a system using Tesla batteries is probably higher than the $3500 battery-only figure quoted. http://www.bloomberg.com/news/articl...rting-at-5-000 mentions an installed system price of $7140.

One of the magic 50V limits comes from the National Electrical Code, which adds a lot more restrictions on what you can do once you go above 50 volts.