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# 177085 21-Jul-2015 17:50
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I really want to get solar power panels installed on our roof but not until they can store electricity to use during the night.

Any idea when this will be available? Obviously it's possible now but expensive and none of the solar companies i've looked into offer it.

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  # 1349460 21-Jul-2015 17:56
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wrong forum :)

there are already systmes that have them, vector do one, but i wouldnt call them financially viable yet.

few threads already on this on here:
http://www.geekzone.co.nz/forums.asp?forumid=141&topicid=133819
http://www.geekzone.co.nz/forums.asp?forumid=141&topicid=130771

better to ask in one of those than duplicate a thread

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  # 1349514 21-Jul-2015 20:51
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Id wait for elon musk's magical powerwall...
http://www.scientificamerican.com/article/tesla-s-elon-musk-unveils-solar-batteries-for-homes-and-small-businesses/




 
 
 
 


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  # 1349524 21-Jul-2015 21:08
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Powerwall is a bust, it can't support much current draw. Get ten of them you'll be fine.

You can easy get storage systems for solar power, they're just expensive - from a chat with a friend who has panels at least $10K for anything worth having - could be wrong though. So he has panels and uses it to heat his water in winter (2 tanks plus spa), and a few other things. I got the same savings by switching to Flick, but in summer he should come out ahead.

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  # 1349531 21-Jul-2015 21:25
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timmmay: Powerwall is a bust, it can't support much current draw. Get ten of them you'll be fine.

You can easy get storage systems for solar power, they're just expensive - from a chat with a friend who has panels at least $10K for anything worth having - could be wrong though. So he has panels and uses it to heat his water in winter (2 tanks plus spa), and a few other things. I got the same savings by switching to Flick, but in summer he should come out ahead.


Well thats s***....had my hopes up there for a while.
dam u elon musk!

Interesting....always wondered the feasibility and how many years it would pay off..10+ im guessing...?




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  # 1350087 22-Jul-2015 21:51
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Battery technology is changing but I dont see the price coming down any time soon.

I build a large number of small scale solar systems for hilltop radio transmitters - so not exactly a house sized system, but i watch the pricing anyway.

Right now we have a choice between lithium and sealed lead acid (SLA)

Side by side, if you took a 200ah SLA vs a Lithium
Lithium will last longer

Lithium is capable of around double the number of discharge cycles compared to SLA, before the battery will reach 60% of its original 200ah storage capacity.

Lithium is 40% the weight of SLA
For a 200ah battery its 23kg vs 61kg

I havent fully read elon's power wall specs but I believe it will be lithium based technology and I believe he is entering that market so he can increase battery production for the tesla cars.

Now Cost
A 200ah Lithium is approx $2500 vs $700 for an SLA

People ask me why I dont use lithium batteries at my radio and the reason is simply that
If a lithium battery lasts almost exactly twice as many discharge cycles as an SLA, then it makes no sense until a lithium drops in price to almost exactly double the price of an SLA

Also the lead in the SLA's from our radio site replacements and the alarm batteries that we also replace go to the metal recyclers and it pays for the family holiday away at christmas.
I am not sure if the metal recycler can extract usable material out of the lithium batteries.




Ray Taylor
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  # 1350139 23-Jul-2015 00:31
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It is far cheaper to simply reduce your power consumption. (buy more efficient appliances, better insulation ect) And to use other energy sources (things like gas for cooking, woodfire for heating and hot water)Than it is to combine solar with storage. And when you have finished making all of the efficiency improvements and alternative energy sources. Your power bill would probably be less than $100 per month.

So spending $10K+ just to save $100 per month. And then you have to pay for maintenance / replacement yourself instead of the power company. Yeah nah.





JWR

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  # 1350142 23-Jul-2015 01:27

raytaylor: Battery technology is changing but I dont see the price coming down any time soon.

I build a large number of small scale solar systems for hilltop radio transmitters - so not exactly a house sized system, but i watch the pricing anyway.

Right now we have a choice between lithium and sealed lead acid (SLA)

Side by side, if you took a 200ah SLA vs a Lithium
Lithium will last longer

Lithium is capable of around double the number of discharge cycles compared to SLA, before the battery will reach 60% of its original 200ah storage capacity.

Lithium is 40% the weight of SLA
For a 200ah battery its 23kg vs 61kg

I havent fully read elon's power wall specs but I believe it will be lithium based technology and I believe he is entering that market so he can increase battery production for the tesla cars.

Now Cost
A 200ah Lithium is approx $2500 vs $700 for an SLA

People ask me why I dont use lithium batteries at my radio and the reason is simply that
If a lithium battery lasts almost exactly twice as many discharge cycles as an SLA, then it makes no sense until a lithium drops in price to almost exactly double the price of an SLA

Also the lead in the SLA's from our radio site replacements and the alarm batteries that we also replace go to the metal recyclers and it pays for the family holiday away at christmas.
I am not sure if the metal recycler can extract usable material out of the lithium batteries.


Does the storage efficiency of lead acid drop off at a a similar ratio to the capacity?

Also, does the capacity drop off at a reasonably linear rate?

I was wondering what an array of second hand forklift batteries would be like.

Relatively low cost to buy and still has value as recycle material when their life is over.

 
 
 
 


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  # 1350152 23-Jul-2015 06:33
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timmmay: Powerwall is a bust, it can't support much current draw. Get ten of them you'll be fine.

You can easy get storage systems for solar power, they're just expensive - from a chat with a friend who has panels at least $10K for anything worth having - could be wrong though. So he has panels and uses it to heat his water in winter (2 tanks plus spa), and a few other things. I got the same savings by switching to Flick, but in summer he should come out ahead.


My electrickery skills are vague, but I remember something from school about how if you decrease the voltage the amperage must go up, so if the Powerwall puts out 350-450volts at 5.8 to 8.9amps to give 2 to 3.3Kw of power, what would the current be if you dropped the voltage to the 220-250volt range ?

Or am I thinking along the wrong lines of thought ? :-)

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  # 1350155 23-Jul-2015 07:02
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Mark:
timmmay: Powerwall is a bust, it can't support much current draw. Get ten of them you'll be fine.

You can easy get storage systems for solar power, they're just expensive - from a chat with a friend who has panels at least $10K for anything worth having - could be wrong though. So he has panels and uses it to heat his water in winter (2 tanks plus spa), and a few other things. I got the same savings by switching to Flick, but in summer he should come out ahead.


My electrickery skills are vague, but I remember something from school about how if you decrease the voltage the amperage must go up, so if the Powerwall puts out 350-450volts at 5.8 to 8.9amps to give 2 to 3.3Kw of power, what would the current be if you dropped the voltage to the 220-250volt range ?

Or am I thinking along the wrong lines of thought ? :-)

You're right and wrong at the same time.
Yes, if voltage decreases current increases, BUT Power (W / kW) stays the same.
P=VxI (W=VxA).




Location: Dunedin

 


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  # 1350745 23-Jul-2015 20:23
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andrewNZ:
Mark:
timmmay: Powerwall is a bust, it can't support much current draw. Get ten of them you'll be fine.

You can easy get storage systems for solar power, they're just expensive - from a chat with a friend who has panels at least $10K for anything worth having - could be wrong though. So he has panels and uses it to heat his water in winter (2 tanks plus spa), and a few other things. I got the same savings by switching to Flick, but in summer he should come out ahead.


My electrickery skills are vague, but I remember something from school about how if you decrease the voltage the amperage must go up, so if the Powerwall puts out 350-450volts at 5.8 to 8.9amps to give 2 to 3.3Kw of power, what would the current be if you dropped the voltage to the 220-250volt range ?

Or am I thinking along the wrong lines of thought ? :-)

You're right and wrong at the same time.
Yes, if voltage decreases current increases, BUT Power (W / kW) stays the same.
P=VxI (W=VxA).


Ahh .. power is not the same as current though is it ?  Which is what Timmmay was saying was not that high on the Powerwall.  

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  # 1350798 23-Jul-2015 20:57
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Mark:
andrewNZ:
Mark:
timmmay: Powerwall is a bust, it can't support much current draw. Get ten of them you'll be fine.

You can easy get storage systems for solar power, they're just expensive - from a chat with a friend who has panels at least $10K for anything worth having - could be wrong though. So he has panels and uses it to heat his water in winter (2 tanks plus spa), and a few other things. I got the same savings by switching to Flick, but in summer he should come out ahead.


My electrickery skills are vague, but I remember something from school about how if you decrease the voltage the amperage must go up, so if the Powerwall puts out 350-450volts at 5.8 to 8.9amps to give 2 to 3.3Kw of power, what would the current be if you dropped the voltage to the 220-250volt range ?

Or am I thinking along the wrong lines of thought ? :-)

You're right and wrong at the same time.
Yes, if voltage decreases current increases, BUT Power (W / kW) stays the same.
P=VxI (W=VxA).


Ahh .. power is not the same as current though is it ?  Which is what Timmmay was saying was not that high on the Powerwall.  

Powerwall specs say 2kW continuous, 3.3kW peak. You couldn't cook dinner with that unless it was microwave food or a single pot meal.

Pretty much any heating application will max out one of these. Two heating applications at once...
Heating applications include: jug, toaster, oven, hob (one element may overload it), microwave, washing machine, dishwasher, dryer, etc.




Location: Dunedin

 


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  # 1351600 25-Jul-2015 14:19
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Mark: Ahh .. power is not the same as current though is it ?  Which is what Timmmay was saying was not that high on the Powerwall.  


But kW is kW, regardless of voltage and current.

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