Who wants to build their own storage bank?

rayra

Expedition Leader
Lots of interesting battery battery tech here, some at pretty good prices. 'Some assembly required'

 

Martinjmpr

Wiffleball Batter
On one of the electric bicycle facebook groups I'm in there are a lot of people who build their own power cells for e-bikes by combining lots of little AA-sized Lithium batteries together into a single unit. It's an interesting hobby but I'm not sure all the work is worth it.

In the example above, the 120AH is at 3.6v. So assuming you wanted a ~12v system that would actually work out to more on the order of 30AH right?
 

plh

Explorer
3.6V/4.2V as shown in the Battery Hookup link isn't great for a 12.6V to 14.2V bank. 4 in series works out to 14.4V/16.8V
 
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rayra

Expedition Leader
'stackable' and you could tailor storage to higher voltages, higher solar and inverter inputs. A larger dedicated storage bank in a smaller form factor / higher energy density.

A lot of the tech in this sector is built around the '18650' style battery, which is sort of a fat AA size, a good bit longer and thicker. Lots of YouTube channels with guys making their own versions of Tesla Power Walls. Pretty much an 'adult erector set' sort of thing. There's also a lot of 're-purposing' of old gear and recycling. As well as the whole 'build it yourself' thing.
 
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trae

Adventurer
3.6V/4.2V as shown in the Battery Hookup link isn't great for a 12.6V to 14.2V bank. 4 in parallel works out to 14.4V/16.8V
You could put a buck converter online, couldn’t you? That’s a great price to build 1700Wh system for around $200+.


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plh

Explorer
You could put a buck converter online, couldn’t you? That’s a great price to build 1700Wh system for around $200+.


Sent from my iPhone using Tapatalk
guess it would work, depending on the Amps draw planned load is to convert. I have not seen many bucks over 20 amps though.
 

Rando

Explorer
Those appear to be lithium polymer pouch cells. They are very high energy density (per volume or per weight) but you REALLY need to know what you are doing to DIY a house battery out of these. These are a much less forgiving chemistry and form factor than prismatic or cylindrical LiFePO4 cells that are typically used for mobile house batteries, such as Battleborn or Victron. I had the misfortune of putting a screw through a much smaller pouch cell like these, and it resulted in an almost instant tower of flame and toxic smoke. There is also the issue of the voltages not really being aligned with traditional automotive 12 - 14V range.

I built my own lithium house battery, but out of surplus LiFePO4 cylindrical cells. There is a lot of money to be saved here by DIY (I built 150Ah at 13.2V for < $300 which has been working well for the past 3 years) but you have to enjoy an arts and crafts type project wiring it all up and have some knowledge of electronics.
 
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hour

Observer
For those with the funds, these seem to be the best bang for buck with plenty of capacity tests. And if you can wait for the slow boat.

 

iggi

Ian
Stackable cases seemed neat and safer than unpackaged lithium pouch cells.
Was hard to resist as even with shipping North of the border the four cells were less than a lower powered AGM battery sourced locally plus a lot smaller/lighter.

I ordered four and they arrived a couple days ago.
All cells balanced at 3.58V

Looking at the specs of my devices, voltage range seems reasonable. Looking at a depth of discharge chart most of the useful range of the pack is in the 3.6-3.7 range. So roughly 14.8V.
My inverter is rated for a maximum input of 15.5V and my solar is customizable in it's charge voltage. Lithium batteries have a longer life if the maximum charge voltage is limited.
So, using my inverter max input as the max charge will limit the max AH of the pack to (I think) about ~85% capacity but in exchange for a lot more charge cycles.

Of course, I could be wrong as I'm kind of a hack when it comes to this stuff so feel free to wait a month and see what I blow up before considering any of this to be good advice.
 
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