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My (so far) under £600 Build
New Shed for everything to sit in all built from recycled materials cost zero,zip,zilch (free)

60 Cells in each pack first 4 packs I made using 2300mah+ 5 pack using 2000mah+ then as I run out of cells the last 2 are 1700mah+ these will be replaced if I can acquire some better cells but to be fair they are holding up quite well.

Old netbook monitoring The mppsolar 2424msx and my 20amp epsolar
Solar panel input switches are 2 3 phase 400v mains switches that were given to me and for now car spade fuses they seem to be working well.

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So as you make packs that contain lower capacity cells, are their more cells in those packs to equal the amount of energy to the 2300mAh packs ?
If not, I assume you know, your going to get top and bottom end balance issues. Balances is a combination of SOC and capacity of the packs.

Big Meat Pete (HBPowerwall) noticed this when he made some lower cap packs using the same amount of cells,
when he hit the bottom end the lower cap packs went screaming down to unacceptably low voltages.

If you keep up above 3.3v per cell and well below the 4.2v you shouldn't really notice this.

Mikes DIY powerwall in NZ showcases this well, hes made sure that each pack contains the same capacity overall, so all his packs have different amounts of cells to get the packs having the same mAh value, therefore balance stays the same over the SOC range due to the same amount of energy = same OCV at different SOC values.

Clear as mud? good! <grins>

kind regards.
3nergE Wrote:Clear as mud? good! <grins>

Crystal Clear - you have just influenced my design with that post - Thank you!
Happy to help mate, I get a lot of criticism from some ppl, but in the end i really try hard to share what i know and learn so other ppl dont have to break shite.

kind regards
Hi 3nergE yes I know about the lower cells I keep between 3.2 and 4.1v the only reason for the lower cells is I have a health condition that stops me from being able to work although ive tried no one will touch me with barge poll I was called an insurance liability by a supermarket :!: so because of that I have little money to spend, Now that wasnt a massive problem when you could get old laptop batteries for free from local computer shops but now im seeing 50 selling for £150 on ebay far too out of my budget I know theres a lot of people who wont use anything under 2000mah but im having no probs with cells at 1600+ as long as I keep within the voltages ive set.

Anyone in the uk have any cells that are 1600 - 2000mah they wont be using I would greatly appreciate them Big Grin

And a GREAT BIG thanx to Pete I was using old lead acid car batteries then one of his videos popped up in suggested vids I even watch the recorded live feeds just in case theres a snippet of info that helps. Wink
Check this other discussion mate : <!-- l --><a class="postlink-local" href="">viewtopic.php?f=10&t=168&p=1194#p1192</a><!-- l -->

In that post I basically say that you can get new laptop batteries (cheap ones) and get the cells out.
They are usually 1800-2000mAh no brand cells, but cap test out at up to 2200mAh.

Cell cost ends up being around $2 per cell. Not too bad.

kind regards
(12-07-2016, 12:03 AM)3nergE Wrote: Check this other discussion mate :

In that post I basically say that you can get new laptop batteries (cheap ones) and get the cells out.
They are usually 1800-2000mAh no brand cells, but cap test out at up to 2200mAh.

Cell cost ends up being around $2 per cell.  Not too bad.

kind regards

Using the website from chris bird which is is great to make sure the packs are balanced and lessen the top/bottom balancing issues, i setup a 24p7s setup and it worked really well.  Are you in the UK?

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