Chuck's 18650 14S120P+1 UK Powerwall.

chuckp

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Jul 29, 2018
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345
Hi guys

After many months of following the threads, and asking a ton of stupid questions (sorry many more to come), I'm now processing cells for my homebrew powerwall.

Found a couple of slow sources for old laptop batteries and I've started to process them, latest count is approx 550 between 2000 mAh and 3000 mAh (averaging out at around 2200)for the packs. Approx 200 between 1500 mAh and2000 mAh that willget put in if I can't source enough cells above 2000 mAh. About another 100 or so that are less than 1500 mAh sat in a box waiting for smaller projects and approx 390 scrap cells that areless than a few hundred mAh, won't charge or can't be recovered.


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I've also built a DIY MOT spot welder. I will put up some details on the spot welder forum.


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Only problem I now have, just had spinal surgery and I'm not allowed to do anything for a minimum of 6 weeks.
So project has now came to a holt for the time being, still plenty of time on my hands to read many more posts.

I will update as things progress.
 

Korishan

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Hope you heal quickly and get plenty of rest.
 

chuckp

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Korishan said:
Hope you heal quickly and get plenty of rest.

Yeah I'm behaving every time I even look at a cell the Mrs is on my case lol
 

Kenbat

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Jul 26, 2018
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Take it easy, man. Exciting project! I've just had to have a break from my powerwall project too, but I'm back in the game with 50 laptop batteries to process!
 

chuckp

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Kenbat said:
Take it easy, man. Exciting project! I've just had to have a break from my powerwall project too, but I'm back in the game with 50 laptop batteries to process!

I think that I may need to sign up to a LA (lithium anonymous)group meeting.

Since I'm not allowed to do anything for the next six weeks i find I'm thinking of ways to try andprocess my cells that won't stress my back while it heals.

The Mrs is on my case every 5 mins or so because I keep looking at them just sat there begging me to get on with it, God knows what she'd be like it i actually picked one of them up.
 

chuckp

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Jul 29, 2018
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Managed to get a few more cells processed up to 850 now.

So do i build a 14s60p and start storing and then build another 14s60p to add to it or wait until i have enough to build a 14s120p?
 

hermitdave

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Aug 12, 2018
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I am barely getting to 200 processed cell mark. I was thinking of doing 100A pack though I might give it 6 months and see how far I get.

You can always attach additional packs to existing ones to make them larger.
 

Korishan

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chuckp said:
Managed to get a few more cells processed up to 850 now.

So do i build a 14s60p and start storing and then build another 14s60p to add to it or wait until i have enough to build a 14s120p?

As long as each string has its packs close in capacity, it doesn't really matter either way. Because once they get connected, they are electrically the same.
It just depends on what you want to move around. Based on your health you mentioned earlier, the lighter packs would be easier on you. The larger the pack, not just the weight goes up, but the awkwardness of carrying it. So you have to keep that all in mind when building the packs.

hermitdave said:
You can always attach additional packs to existing ones to make them larger.

So as long as they are all connected at the same session. You don't want to connect a few packs, then wait awhile to build some more and then connect those. The whole string needs to be connected in one session so you don't have balancing issues that'll have to fight later on.

Unless, of course, the string isn't in operation during the upgrade phase.
 

chuckp

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345
Korishan said:
chuckp said:
Managed to get a few more cells processed up to 850 now.

So do i build a 14s60p and start storing and then build another 14s60p to add to it or wait until i have enough to build a 14s120p?

As long as each string has its packs close in capacity, it doesn't really matter either way. Because once they get connected, they are electrically the same.
It just depends on what you want to move around. Based on your health you mentioned earlier, the lighter packs would be easier on you. The larger the pack, not just the weight goes up, but the awkwardness of carrying it. So you have to keep that all in mind when building the packs.

hermitdave said:
You can always attach additional packs to existing ones to make them larger.

So as long as they are all connected at the same session. You don't want to connect a few packs, then wait awhile to build some more and then connect those. The whole string needs to be connected in one session so you don't have balancing issues that'll have to fight later on.

Unless, of course, the string isn't in operation during the upgrade phase.

Korishan, yes that was my thinking too about pack size and wieght, while the recovery period from my operation is only 6 weeks, I am only allowed to return to work after that if on light duties for the next 6 months to a year.

Hermitdave, yes I would connecta full 14s60p string and then build another full 14s60p to connect as a separate string, I'm going with the Batrium bms so the additional longmons won't be an issue.

Also it will help with the location of a rouge cell when one goesdown. Less of a pack rebuild.
 

jdeadman

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I like the smaller pack Idea where at camp I have a wall of 7s56p cells but those 56 cells are broken into 8p packs (I scored 8 cell holders a long time ago off ebay for stupid cheap) and I put those 7 sets of 8 on bus bars for each cell. Now if I have an issue with a pack or a cell I can just pull that set of 8 out and the rest of the wall remains intact and running.

For my home wall I am going bigger number of cells in Parallel so I purchased some of the 4x5 holders from Keith (Da Man) and am going to make 20p packs for an eventual 7s 400p Wall as I will be looking to run 120V inverter and the ones I have my eyes on are 24V only (MPP LV series)
 

chuckp

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jdeadman said:
I like the smaller pack Idea where at camp I have a wall of 7s56p cells but those 56 cells are broken into 8p packs (I scored 8 cell holders a long time ago off ebay for stupid cheap) and I put those 7 sets of 8 on bus bars for each cell. Now if I have an issue with a pack or a cell I can just pull that set of 8 out and the rest of the wall remains intact and running.

For my home wall I am going bigger number of cells in Parallel so I purchased some of the 4x5 holders from Keith (Da Man) and am going to make 20p packs for an eventual 7s 400p Wall as I will be looking to run 120V inverter and the ones I have my eyes on are 24V only (MPP LV series)

Yeah I like the idea of the smaller packstoo. Only thing I'm thinking is that once I've set up a string of 14 packs,trying to match up another 14 packs to exactly the same capacitiesmay be difficult and cause balancing issues. I'm assuming that multiple batteries in parallel works the same as cells in parallel. So a slight variation in total battery capacity won't cause to much of an issue. Or does it not work that way with batteries.

If not I'm probably better of waiting until I've processed enough for the 120p packs but build them as 28 x 60p and then either link them up in a sort of 14s with 2 x60p in parallel still using only 14 longmons.


chuckp said:
jdeadman said:
I like the smaller pack Idea where at camp I have a wall of 7s56p cells but those 56 cells are broken into 8p packs (I scored 8 cell holders a long time ago off ebay for stupid cheap) and I put those 7 sets of 8 on bus bars for each cell. Now if I have an issue with a pack or a cell I can just pull that set of 8 out and the rest of the wall remains intact and running.

For my home wall I am going bigger number of cells in Parallel so I purchased some of the 4x5 holders from Keith (Da Man) and am going to make 20p packs for an eventual 7s 400p Wall as I will be looking to run 120V inverter and the ones I have my eyes on are 24V only (MPP LV series)

Yeah I like the idea of the smaller packstoo. Only thing I'm thinking is that once I've set up a string of 14 packs,trying to match up another 14 packs to exactly the same capacitiesmay be difficult and cause balancing issues. I'm assuming that multiple batteries in parallel works the same as cells in parallel. So a slight variation in total battery capacity won't cause to much of an issue. Or does it not work that way with batteries.

If not I'm probably better of waiting until I've processed enough for the 120p packs but build them as 28 x 60p and then either link them up in a sort of 14s with 2 x60p in parallel still using only 14 longmons.

Sorry I'm being a total twat.

Even if the additional14 pack capacities are different it won't matter as long as they are balanced between them.

It would be no different from putting cells of different capacitiesin a single pack onceconnected in parallel.
 

jdeadman

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I use an excel spreadsheet to load my cells data into and build a string of 7 (or 14 in yourcase.) And generally make sure to have about 1/3 more cells than needed to make the pack balanced in capacity. Now what I have found that testeing the cells alone and then making a pack then testing that pack there are some differences in capacity when testing at a lower rate of discharge so the combined tested mah does not add up to what I get out of the built packs.

So combat this I have put together a 20p Testing board and hooked it up to one of my RC chargers and after I test each cell and put them through repackr and organize them into packs I take the cells of that packs and put them together in the 20P testboard and test the capacity. My RC can discharge at 10A and charge at 15A so I cycle the battery pack twice and average the numbers. I generally get about an extra 5% out of the cells but it varries with the cells that go into the pack.

I then take that data from the set of 7 packs and if there is one out of spec with the rest I will swap out a cell or 2 and test again. and get it close as a pack
 

chuckp

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jdeadman said:
I use an excel spreadsheet to load my cells data into and build a string of 7 (or 14 in yourcase.) And generally make sure to have about 1/3 more cells than needed to make the pack balanced in capacity. Now what I have found that testeing the cells alone and then making a pack then testing that pack there are some differences in capacity when testing at a lower rate of discharge so the combined tested mah does not add up to what I get out of the built packs.

So combat this I have put together a 20p Testing board and hooked it up to one of my RC chargers and after I test each cell and put them through repackr and organize them into packs I take the cells of that packs and put them together in the 20P testboard and test the capacity. My RC can discharge at 10A and charge at 15A so I cycle the battery pack twice and average the numbers. I generally get about an extra 5% out of the cells but it varries with the cells that go into the pack.

I then take that data from the set of 7 packs and if there is one out of spec with the rest I will swap out a cell or 2 and test again. and get it close as a pack

That sounds like a great way of doing it.

At the moment I have only added all the tested capacities for a14s60p tothe rePackr, the packs all come out at a -1 mAh to 2 mAh divergence,between 159 mAh to 273 mAh deviation and a capacity of131 Amps.
 

chuckp

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Jul 29, 2018
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Another night unable to sleep. So thought I'd have a quick test run of my homebuild spot welder.


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First attempt at welding fuses to cells went well.


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Practice spot weld fuses to cells and solder to busbar.


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Soldering to busbar needsa little more practice but its getting there.
 

chuckp

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Complete U turn on my project. I have now decided I'm going to go with 40P packs.

Start off with a 14S40P to get it upand running.
Than build another2 sets of 40P and add the packs in parallel with the first set, once I have another full set.
I will go with 3 sets of 40P and make them up to a 14S120P for the first string. Once up and runningas a 14S120Pthen I'll start on a second string. Once thats running then I'll start to build some higher capacity packs and swap out the lowest capacity 40P packs.

Started on the first of my many packs this evening.


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I have used resistor wires for the -ve side and glass axial fuses on the +ve. Spot weldedthe fuses and links to cells will solder to busbars.

Ran out of solder before I could finish all the joints so I've ordered more in for tomorrow.

Going to use some 10 AWG Silicon coated flexible wire and Anderson plugs for the connections.
 

chuckp

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Jul 29, 2018
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Solder arrived. So full steam ahead with my pack builds.

Pack 1 completed,


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Now on to the next.
 

chuckp

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4 down 10 more to go for my fist string.


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I really like these Anderson connectors,
 

chuckp

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Daveyboy said:
Seriously neat job with the fuses there! Nicely done :)

Thanks buddy. :) I've 8 done now slowly getting there.
 
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