PowerWall alternative

apacheguy · May 3, 2015

So the Powerwall's got me thinking. I have an existing grid-tied solar system. I do not want to go off-grid, however, I would like to have a limited backup in case of emergencies or black outs. I don't need 7-10 kWh of storage or anything near that. All I need is to be able to power my fridge and maybe a couple appliances during the day and I don't care about losing power at night for emergency purposes.

Question is am I best off paying for 7 kWh of storage that I don't really need or is there an alternative, maybe 1 kWh system that wouldn't power me into the night but at least it would let me power limited appliances during the day while I have solar production? Anyone else have experience in this area? Not DIY solutions like wk057, please.

GSP · May 3, 2015

Call a local solar installer and ask for a quote. They have been installing PV with battery backup for critical circuits since the beginning. Ask for a Li-Ion battery with a BMS to keep the maintence minimal. Then see how much less expensive the powerwall is, and how much better the powerwall warranty is. It will be worth waiting for, I think.

GSP

PS. Don't go with lead-acid. The maintence is a PIA, and life is much shorter. Espically if you forget to do maintence on time as so many people do.

dalalsid · May 3, 2015

apacheguy said:
So the Powerwall's got me thinking. I have an existing grid-tied solar system. I do not want to go off-grid, however, I would like to have a limited backup in case of emergencies or black outs. I don't need 7-10 kWh of storage or anything near that. All I need is to be able to power my fridge and maybe a couple appliances during the day and I don't care about losing power at night for emergency purposes.

Question is am I best off paying for 7 kWh of storage that I don't really need or is there an alternative, maybe 1 kWh system that wouldn't power me into the night but at least it would let me power limited appliances during the day while I have solar production? Anyone else have experience in this area? Not DIY solutions like wk057, please.

I have a UPS connected to one of these - Amazon.com : Reliance Controls 15114A Transfer Switch 15 Amp 120V Transfer Switch : Generator Transfer Switches : Patio, Lawn Garden - it doesn't power from solar or anything but can run a few lights for a few hours. I had it put in along with my solar system because during outages my fireplace and gas shut off and I need to power them. If you find a bigger UPS you can power more stuff.

jerry33 · May 3, 2015

I have a 6KVA PowerWare UPS to run the electronic devices. If I needed to run the refrigerator for an extended period, I could hook up an inverter to the Prius. When the UPS is no longer functions, a Powerwall would be the logical replacement.

apacheguy · May 3, 2015

Yeah, I probably should ask around for estimates from local solar dealers.

As far as the UPS suggestions, not really what I'm looking for. I want something that is tied into solar so that I can operate for weeks on end if necessary. Same would go for generators and is why I'm not interested in them.

Saghost · May 3, 2015

The one I'm waiting to see details/pricing on is Enphase's "AC Battery" solution, which is supposed to be coming later this year.

(It is of course impossible to create a battery cell with chemistry that produces alternating current; the name is a marketing description for a collection of small modular battery packs in which each battery module (1.2 kWh) includes a microinverter/charger within the box and couples via 240V split phase rather than the battery's DC Voltage.)
Walter

apacheguy · May 3, 2015

Awesome. That Enphase system looks exactly like what I'm looking for. I will also be awaiting the details.

GreenPenguin · May 3, 2015

This company tried to talk to me after I installed my solar. Too startup working in a garage for me to take a serious look, though.

Egen - Powering the World for Future Generations

miimura · May 3, 2015

I agree that the Enphase AC Battery looks interesting. My solar uses Enphase inverters and they imply that the battery system integrates with their monitoring system. The thing they don't say is who manages the charge/discharge, except that it "Helps stabilize and manage the grid". They also don't say if they will have a way for their system to operate when the grid is down.

Saghost · May 4, 2015

miimura said:
I agree that the Enphase AC Battery looks interesting. My solar uses Enphase inverters and they imply that the battery system integrates with their monitoring system. The thing they don't say is who manages the charge/discharge, except that it "helps stabilize and manage the grid". They also don't say if they will have a way for their system to operate when the grid is down.

Agree that there are a lot of important details they haven't spelled out yet. However, I'm pretty sure that the answers to both your big questions lie in the 'Enphase Energy Management Unit' that the diagrams show installed between the meter and the rest of the house. I would expect that to contain the transfer switch you need to enable grid free operation, and also to determine when power is used.

Newb · May 4, 2015

another thread that would perfectly fit into a dedicated Tesla Energy Forum. Just want to keep track of those discussions, and to date there's half a dozen threads about this important topic spread around TM Forum, News, General Forum and so on...

chris75sf · May 11, 2015

Exactly, it looks like Enphase is betting on the AC side, and Tesla Energy, on the DC side
Back in November 2014 when Enphase announced their AC Battery I dove into the details I could find and wrote a post on it, hoping it could help understand the technical details behind it; The heart of it is their new bi-directional S275 inverter (S for Storage I guess, and 275 is the next step after M215, M250, etc)
http://www.myelifenow.com/2014/11/enphase-ac-battery-technical-details.html

wycolo · May 13, 2015

I keep 2 truck batteries in the mud room. They are too long to fit in the pickup trucks so they are here by default providing emergency power. When a lightning strike takes out the village grid a few times a year, I clip a 400 watt inverter to one of the batteries and run the extension cord over to a workstation UPS and a 60 watt equivalent LED lightbulb. That is my media for the duration of the outage, which is usually no more than a few hours. Our electric coop has been much more reliable this past year so no incentive to go the next step to propane convert the Honda inverter generator.
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