AGM for home storage?

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memecode
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AGM for home storage?

Post by memecode » Tue, 22 Oct 2019, 09:06

So I've been looking around for home storage solutions for a while now. For instance the powerwall 2 would be a nice amount of battery but I balked at the 12k cost. I doubt I'd ever see a return on that. For reference I have a 3.35kw solar array that most of the time feeds back into the grid at 12c/kWh. We might see 20kWh of generation on a sunny day in summer and maybe 10kWh in winter. If there was a solution for well under $10k where I could store around 10kWh I'd be pretty keen.

Today I was just googling around and bumped into this AGM battery bank. And it's a lot under the price of a powerwall. But obviously it doesn't come with any BMS or inverter. And yes I'm aware that I'd need to keep the discharge to 50% for any real cycle life. A lot of the year our house uses just 10kWh on average.

I'd like to know what sort of round trip efficiency these AGM's could have? Is there a reason that a lot of home storage is lithium based chem?

What would I need to turn it into a functional system, ie BMS and solar/mains/house/battery connectivity? Obviously I already have an inverter, but I doubt it's ready to plumb in a battery as well.

Maybe there are companies that can just do that all for me? (Im in Sydney). I don't mind a bit of DIY but there are limits.

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jonescg
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Re: AGM for home storage?

Post by jonescg » Tue, 22 Oct 2019, 10:24

Lead batteries have been the mainstay for off-grid and stationary energy for a long long time - as long as the solar charge controller is set up to charge lead properly they are a solid choice.
Not exactly cheaper though - particularly since you aren't able to access a fair bit of the energy stored as the sag is pretty bad.
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T1 Terry
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Re: AGM for home storage?

Post by T1 Terry » Tue, 22 Oct 2019, 11:36

I received an "invitation" to attend a Powerwall 2 sales pitch event and was interested to see the comparison between $/Wh between the Powerwall 2 and inverter v our lithium system using Winston cells and inverters. the set up came out to 72.4c per Wh for the Powerwall 2 and 26.5c per Wh for our set up with a 5kW inverter that also included an 80 amp MPPT solar controller and a 60 amp mains charger.
As far as lead acid v lithium for off grid power or back up power, $ per useable Wh and expected cycle life, lead acid is not even close to competing. A system we installed about 3 yrs ago at the local marina had all the neh sayers telling him they'd catch fire, they hadn't proved themselves, they were far too expensive etc. The same people are now paying for their second set of batteries because they pushed them too far in an attempt to prove they could do the same with their lead acid batteries as he could do with his lithium batteries. Now they reckon he must be cheating and has a hidden power cord plugged into the mains supply that he isn't telling them about :roll:
If anyone tells you they are getting more than 3 yrs out of their lead acid batteries it is because they aren't using the available 50% capacity they have installed. If they only use 25% the battery needs to be 75% stuffed before they realise they have a problem.

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paulvk
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Re: AGM for home storage?

Post by paulvk » Tue, 22 Oct 2019, 15:09

Lead acid the rule is use 20% to get long life
Lead acid sealed no more than 1/10 of Ah as current so 100Ah 10 amps max , 500Ah 50 amps max
Flooded lead acid can cope with greater discharge currents because you can add water
Giant power batteries "STAY AWAY" too many having problems!
Best lead battery for the money is the T105 series flooded (about $4500 with central watering 450Ah two banks 16 batteries) as so many are manufactured used in golf carts and lots of industrial machines.
When I finally get my Nickel Iron ones installed I will let every body know how they perform

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4Springs
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Re: AGM for home storage?

Post by 4Springs » Tue, 22 Oct 2019, 17:02

memecode wrote:
Tue, 22 Oct 2019, 09:06
Today I was just googling around and bumped into this AGM battery bank. And it's a lot under the price of a powerwall. But obviously it doesn't come with any BMS or inverter. And yes I'm aware that I'd need to keep the discharge to 50% for any real cycle life. A lot of the year our house uses just 10kWh on average.
For $5000 you'd get roughly 15kWh of Francisco's NCM lithium cells: viewtopic.php?f=17&t=5909&start=25
Not that I'm suggesting they would be the best chemistry for a home storage battery, just pointing out how cheap lithium is getting.

Lead acid is much simpler to use, electricians know how to hook them up, and you don't need a BMS.

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