Tesla roof with power wall for off gird?

[electrofelon]

I know off grid knowledge and experience is rather sparse on this forum, but are these systems suitable for off grid use? If so, does anyone have any thoughts on it vs a conventional off grid system?

 

[jaggedben]

They are not designed to be commissioned without the grid. So jumping through that hoop would be difficult. But if sized correctly they could be disconnected from a grid source semi permanently and run indefinitely. Same goes for Enphase. I believe Sonnen can be commissioned without the grid, but I'm not 100% sure. Warranties might be voided.

The Tesla solar roof is kind of a red herring. Most Powerwalls are coupled with conventional panels.

What do you consider a 'conventional' off grid system?

 

[electrofelon]

They are not designed to be commissioned without the grid. So jumping through that hoop would be difficult. But if sized correctly they could be disconnected from a grid source semi permanently and run indefinitely. Same goes for Enphase. I believe Sonnen can be commissioned without the grid, but I'm not 100% sure. Warranties might be voided.

The Tesla solar roof is kind of a red herring. Most Powerwalls are coupled with conventional panels.

What do you consider a 'conventional' off grid system?

Thanks. I have a cousin and cousin in law who are considering buying some property and building a house, and they may not be able to get utility power there. I am trying to talk them out of the fairy tale of living off grid. He mentioned the solar roof with power walls and I wasnt sure if it was suitable for off grid use.

I guess by "conventional " I mean a system with (probably) lead acid batteries, a (probably) 48 volt inverter/charger, maybe one of the 600V string capable charge controllers (schneider or morningstar)......Ive been ongrid for 6 years, and dont think about off grid stuff anymore so Im probably a bit behind the times.

 

[JoeNorm]

There are great 48v lithium options now. Blue Planet for example.

Those combined with Schneider, SolArk, or Outback equipment would make an awesome fully off-grid system. Tesla stuff was designed with the grid in mind.

 

[curt swartz]

We just completed a project where Tesla Powerpacks were used for off grid. It was the first single family dwelling installation of Powerpacks. I have no idea if Powerwalls will eventually be able to be configured the same.

 

[electrofelon]

There are great 48v lithium options now. Blue Planet for example.

Those combined with Schneider, SolArk, or Outback equipment would make an awesome fully off-grid system. Tesla stuff was designed with the grid in mind.

Yeah that was the main thing I wasn't sure of, FLA vs LI for battery banks. 6-7 years ago FLA was still king. Seemed like there were a few people dabbling in LI but it wasn't mainstream.

 

[JoeNorm]

Li is certainly mainstream now and of course still quite expensive compared to FLA. But the "no maintenance" is worth the cost for people with the money all day long. and you can essentially drain them to zero without damage. A far cry from FLA.

Inverter manufactures are now writing software to to work specifically with various Li battery BMS's.

As far as retrofitting an older system with new Li battery, be ready to work out quite a few bugs. If you don't want a few headaches I would not do it.

 

[JoeNorm]

For your smaller "cabin" style systems, FLA is still a good option IMO

 

[electrofelon]

Seems like the issue with LI is lifespan. Based on what I have seen for lifespan in my tools, phone and laptop batteries, I am not impressed. What kind of life are people seeing in their Teslas?

 

[jaggedben]

Comparing LI to FLA you gotta compare apples to apples. The usable capacity of LFP is near 100% as compared to less than 50% for FLA if you want them to last. So that's one thing. As far as longevity of lithium at home energy storage scale, most manufacturers are warranting 70% after 10 years. I don't think small electronics are comparable.

 

[electrofelon]

Comparing LI to FLA you gotta compare apples to apples. The usable capacity of LFP is near 100% as compared to less than 50% for FLA if you want them to last. So that's one thing. As far as longevity of lithium at home energy storage scale, most manufacturers are warranting 70% after 10 years. I don't think small electronics are comparable.

Yes certainly agree with the regular capacity limit of FLA of about 50% and near 100% with LI. That would definitely be figured in when sizing a battery bank. If they can do 70% after 10 years than that is great. Any idea why it is so much different for electronics and tool batteries?

 

[jaggedben]

...Any idea why it is so much different for electronics and tool batteries?

Probably because those tools and electronics aren't expected to last that long, or they are even intended to crap out on you so that you have to spend money to replace them (designed obsolesence). Those manufacturers have no incentive to invest in a good BMS if the consumer doesn't see the value proposition. Also with tools I think there's no real control over the discharge. With electronics I imagine that they could do a better job if they wanted to. With the dollar amounts spent on home energy storage scale items you need the extra assurance of a good BMS, and it's a lower marginal cost. Finally, most of those smaller portable batteries are NMC which just isn't as stable. The home energy storage mfrs who are pushing the warranty envelope (e.g. Sonnen) are using LFP. I suspect/hope that in the coming years we'll see LFP batteries go to 12.5 or 15 year warranties to put competitive pressure on Powerwall. I think that would allow them to price at a somewhat higher $/capacity and still be considered a better deal.

 

[electrofelon]

Probably because those tools and electronics aren't expected to last that long, or they are even intended to crap out on you so that you have to spend money to replace them (designed obsolesence). Those manufacturers have no incentive to invest in a good BMS if the consumer doesn't see the value proposition. Also with tools I think there's no real control over the discharge. With electronics I imagine that they could do a better job if they wanted to. With the dollar amounts spent on home energy storage scale items you need the extra assurance of a good BMS, and it's a lower marginal cost. Finally, most of those smaller portable batteries are NMC which just isn't as stable. The home energy storage mfrs who are pushing the warranty envelope (e.g. Sonnen) are using LFP. I suspect/hope that in the coming years we'll see LFP batteries go to 12.5 or 15 year warranties to put competitive pressure on Powerwall. I think that would allow them to price at a somewhat higher $/capacity and still be considered a better deal.

Ok. I kinda assumed pretty much all LI were essentially the same technology and size was the only thing that changes. Seems that may not be the case.

 

[GoldDigger]

Ok. I kinda assumed pretty much all LI were essentially the same technology and size was the only thing that changes. Seems that may not be the case.

Different chemistry means different volumetric and mass energy density, different pickiness of charging, different fire risks, different service and charg cycle life. Physical electrode and envelope design means a lot. Form factor affects cooling, vibration resistance, maintainability, etc.