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Battery / Energy Backup for Solar Power Systems

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  • Sat, Feb 22, 2020 - 10:48am



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    Battery / Energy Backup for Solar Power Systems

I didn’t see any posts, at least nothing recent, about backup systems for solar energy systems. Would love to hear about what folks have done in this space, experiences, what worked well, what didn’t, etc.

I’m researching a solar system for home right now and given that I live in California and PG&E is our utility, I want to not only be able to leverage solar as a renewable and independent power source, but I also want to make sure my plan is resilient and my energy production doesn’t stop because of planned or unplanned outages.

I’m considering the latest AGM battery systems but I’m also curious about the Tesla Powerwall. Would love to hear all experiences and thoughts on this topic.

  • Sat, Feb 22, 2020 - 03:46pm

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    Reply To: Battery / Energy Backup for Solar Power Systems


We have a LG/ Enphase grid tied system and really like it. Enphase is suppose to come out with a system called ensemble this year that will allow for ac batteries charged with the solar panels. May be a little less expensive than powerwall.  Overall the solar is great. We live in Canada so winters do not produce much power summer spring and fall rock. LG also has a battery system


  • Sat, Feb 22, 2020 - 04:02pm



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    I have one

I have had a grid-connected, battery back up solar system here in California for 21 years.  I have what people now consider to be a “small” system, but it has always been sufficient for our needs here.

I have an all electric house, but I never use the electric heat, I only use the wood stove, and I have a very modern, low particulate air tight wood stove.  I had to replace last year, and now have a Lopi Endeaver.  I also put in a closed loop solar hot water system, as I have electric hot water heater.  I could bring in gas, propane, and run a hot water heater and cooking stove off of propane, which is how everyone else around me gets thru our seasonal power outages ( I live in an area that gets multi day outages due to bad weather,  the wind storm the other week left us without elecricity, internet or phone line for 3 days. ) so I have had practice before PG and E started the planned outages.  So, when the electric grid is down, I cannot use my electric stove or hot water heater.  Since it is only for a few days,  I just heat food and water on the wood stove, in general.  I also make use of many small appliances to cook, since I do have battery back up, like the electric kettle for hot water for beverages,  the toaster, bread machine, etc… I have a stand alone portable single induction burner I could plug in to cook on, but I have never bothered.  Maybe now that we have PG and E planned outages when it is hot, I might.  Last one I just used the solar oven outside.  I do run the water pump off of the back up batteries ( I am on a well and have a water tank with a pressure pump) .


So, my original system had 24 110Watt ( label rating) panels on the roof, for a “real” 2kWatt after the inverter, system.  I added another couple panels on the unused half the inverter 7 years ago, so now have around a net of 2.5kWatt.  My inverter is a Trace SW4048, from back when they were built in California and it has been working for the 21 years also, as well as charge controller.  The same SW4048 architecture is still available for sale from a different company name, as buy outs happened over the years ( I think it is currently Schneider ? ) .

So, my system is a 48V DC system.  I used to have Trojan lead acid solar batteries, 4 of them.  maybe the whatever 16’s.  I killed my batteries thru neglect when I became ill, otherwise I highly recommend the tried and true trojan lead acid batteries, or the Iron Edison.  The Iron Edison ( nickel/Iron) can last forever ( with some kind of electrolyte replacement or something every decade ?  Look it up.  I am not healthy enough to be able to do this, so I dont have them, but I think they are likely the best ) The batteries I got last time were Aquion, which is a salt water electrolyte, carbon/maganese.  I have 3 48V S-stacks, but 4 would have been better, each are 2.2kWh.    You cannot buy them in the USA right now as they were bought by a company that took it to China.  I have been happy with them, they work well, and it is true that you can discharge all the way to nothing and not harm them,e tc…

I do not like the power walls or other lithium ion for home use.  For many reasons.  The advantage of these batteries for mobile applications like car and electronics are irrelevent to home use where weight and size are not considerations,  certainly not enough of a consideration to make up for how expensive they are.  The other thing I did not like about them is how dangerous they would be in a fire.  And, also, how they need a tighter temperature range, so they would be unhappy in my location, in my garage where it would be too hot for them, and I would need to use power to cool and heat during parts of the year.  It turns out that the cars do use power from the batteries for temperature control, too.

You could use the AGM batteries, especially if you have a non-vented area or might forget about maintenance,  otherwise a flooded lead acid is less expensive

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