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PurePower

DIY Powerwall with 18650 batteries

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Hi Gents, 

How feasible is this??? I've seen plenty of youtube videos and forum posts saying that its all possible. But in real terms... is it sustainable and safe for long term use?

Check out the below links for more info...

https://www.youtube.com/channel/UC0pBauLp63yzf6sVdEOIUbA

https://hackaday.com/2016/09/29/homebrew-powerwall-sitting-at-20kwh/

https://motherboard.vice.com/en_us/article/kzz7zm/diy-powerwall-builders-are-using-recycled-laptop-batteries-to-power-their-homes

https://greentransportation.info/ev-batteries/diy/18650-powerwall-clone.html

 

There is an entire forum dedicated to this: http://www.diypowerwalls.com/index.php

 

Has anyone in SA attempted this? Is anyone willing?

This seems to be an interesting topic , comments will be appreciated.

 

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I was considering it. It is as safe as the BMS you use. There are instructions on a DIY BMS on the AEVA forum. Since @Coulomb was involved I willing to say it is top notch.

The Karoo is a long way from a source of secondhand  18650 cells. I think the reason I eventually canned the idea was that you would tinker with it forever replacing cells as they age.Plus you going to spend a fair amount of Tom on all the fiddly bits. You will build it cheaply but need to factor in your time. With the rumbles of thunder I think I am about to get busy so instead I am now getting ready to raid the piggy bank for some Pylontechs. 

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I'm struggling to understand what the battery make up convention like 80p14s; does that mean 80 cells in parallel and then 14 strings? Totaling to 1120 cells? 

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1 hour ago, PurePower said:

I'm struggling to understand what the battery make up convention like 80p14s; does that mean 80 cells in parallel and then 14 strings? Totaling to 1120 cells? 

Looks about right. I know Pete from HBPowerwall had 80 cells in parallel and 7 packs in series for a 24V system. Charging to 4.2 V that would give you 58.8V. I would be inclined to charge to 4.1V or 57.4V. Yes you would have less capacity but just build a bigger bank.

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It's doable , very time consuming breakung up packs , charging , discharging, testing , waiting and then test again. It took me about about 4 months to put together a 182p14s182p 14s 17Kwh battery pack.

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29 minutes ago, seant said:

182p14p 17Kwh battery pack.

I am guessing 182s14p 182p14s...

I would love to give that a go - where did you find 2548 cells, what did it cost, are you using a BMS, are you happy with the resulting performance?

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On 2017/09/22 at 10:57 PM, Mazs said:

There is a real risk of starting a fire. I would not dare try this in my house.

But your cell phone and laptop etc all with diffrent lithium battery chemistries and no fire as of yet I take it. Talking about things that go bang  what about the off gassing from the lead acid batteris in a small room . There is a potential for a lot of things to catch fire and worse. If it goes wrong Li-ion cause a nasty fire and there isn't too much you can do to stop it .  Use a bit of common sense , like you said don't put it in your house , don't use dodgy batteries and keep an eye on the battery packs and all should be fine

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It took quite some searching but I ended up getting a pile of the same cells from someonewho was scrapping some electronics. I haven't got a BMS yet but that's on my list. Fortunately as they are all of similar capacity the keep themselves quite well in balance within about 0.08v of each pack. As for the capacity and performance , I had a 48v set of batteries from a forklift and the Li-ion battery works extremely well compared.

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1 hour ago, seant said:

But your cell phone and laptop etc all with diffrent lithium battery chemistries and no fire as of yet I take it.

This is not quite true.

Each chemistry has its own thermal runaway 

The earliest Lithium chemistry was Lithium cobalt and  has a thermal runaway temp of 150°C . This low thermal runaway temperature, poor cycle life and the high cost of cobalt has resulted in this chemistry being replace by blending  manganese with other active materials for the cathode  

Lithium manganese oxide was one of the first replacements of lithium cobalt with a thermal runaway of  250°C. Like lithium cobalt rapid charging can lower this figure. It also  suffers from a shorter cycle life.

Lithium Ferrous Phosphate with a thermal runaway of 270°C can safely be stored fully charged. It has excellent cycle life and is one of the safest chemistries. With a max charging voltage of 3.65V it does not have the same energy density of other lithium chemistries   but that is not a major factor in the solar industry.

Lithium Nickel cobalt aluminium oxide  shares many characteristics of lithium cobalt  but is cheaper and has a longer cycle life Thermal runaway is also about 150°C 

Lithium nickel manganese cobalt oxide (NMC) is one of the newer cobalt blends results in lowering of costs and  better safety (thermal runaway of 210°C ) making it a favoured chemistry of the electric car industry.

Lithium Titanate  no thermal runaway problems and has a high cycle life but cost are high and is largely limited to the electric car industry.

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2 hours ago, Chris Hobson said:

Lithium Nickel cobalt aluminium oxide

Some car manufacturers are looking at this one because of the lower cost. It does however sport lower energy density as well, so NMC is still preferred. For house applications, the top contenders remain NMC (I believe the Daimler and Tesla batteries are NMC) and LFP, although again a case can be made for NCA, because NCA is cheaper than NMC but has better energy density than LFP. Or at least... that's how I understand it.

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2 hours ago, Chris Hobson said:

This is not quite true.

Each chemistry has its own thermal runaway 

One of my friends brother was fiddling with a small PV system with old laptop batteries... don't have technical details so can't comment on what happened but in short... his house (the whole thing) burnt down in November! ... the wife just managed to get out in time.  They lost everything!

So rather more careful than not... if you watch the HBPW and the other Auzzy guys they all have a battery shed apart from the main house - for good reason.

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5 hours ago, seant said:

But your cell phone and laptop etc all with diffrent lithium battery chemistries and no fire as of yet I take it.

O nooo. 

After a 2 sec Google, for I remember the drama about cellphone batteries and fires and explosions recently. 

https://www.cbsnews.com/news/lithium-battery-fire-risk-samsung-galaxy-note-7/

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8 minutes ago, The Terrible Triplett said:

After a 2 sec Google, for I remember the drama about cellphone batteries and fires and explosions recently. 

The Bee had a really really good satirical article on it. Can't remember the last time I laughed so hard. I figure I can post that here seeing as we do occasionally venture over to that side... and I love humour of all kinds. If you can't joke about yourself... why bother?

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I've seen a cellphone battery explode while being charged, the phone ended up up on one side of the room and the battery casing embedded in ceiling. And people still charge them next to their beds when going to sleep. Still there is tons of info out there on how to build your own powerwall and make it relatively safe. Recycle and reuse a stack of batteries that would otherwise have ended up in a land fill and have a relatively cheap Li ion battery pack, that suits me quite well.

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So far very well. Six months down the line the packs all stay well balanced and it hasn't burst into flames . It delivers the power I need and I couldn't ask for more

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6 minutes ago, seant said:

So far very well. Six months down the line the packs all stay well balanced and it hasn't burst into flames . It delivers the power I need and I couldn't ask for more

please send me some more details about your battery pack?

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8 minutes ago, SilverNodashi said:

please send me some more details about your battery pack?

Sure, I built a roughly 17Kwh 48v battery pack from 18650 batteries which I recovered from used battery packs , there are 14 packs in series and each pack is made up of 182 batteries in parallel. Each 18650 cell has a capacity of approximately 1800mAh.  Each cell is soldered to a buss bar with a fuseable link . As soon as the budget allows I'll add a BMS but in the mean time I keep a close eye on the battery pack voltages.

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Maybe you can post some photos for full pack and close ups ?

Are you using inverter for charging ? Axpert ? Can you share settings ?

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