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Nickel Fuse Build
#1
I have now got to face up on a design on my PW, orginally I was going to go moduler but now I am thinking of just building one full pack.

The pack is going to be 40P14S with the ability of expansion later on.

Currently, if I go with a single large battery rather than separate modules it will be either:
  • 10 cells high, 56 cells wide, with each parallel module being 10 cells high, 4 cells wide.
  • Or 20 cells high, 28 cells wide, with each parallel module being 20 cells high, 2 cells wide.
Both will have a copper or alloy busbar on the + & - (start and finish) modules to spread the load out from the terminal to the nickel.

The second option will give me more amps and I probably wont have to spot weld addional nickel between modules (I got battery hookups older design that has the cutout squares between cells, less current spread, was an accidental buy).

My battery has to handle peaks of 100A so in a lot of aspects the second option is better suited, but I cant scale the more than 2.5x (840 additional cells).

The first option will provide better scalabilty as I will be able to add another 2240 cells before I hit the floor, but will need to get the nickel between modules to get current up.

Whats your guys thoughts on this? moduler, single large pack, 2 cell wide modules or 4, what ya reckon?

Thanks
Dave
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#2
Here are some images to illustrate the 2 different full pack designs I am thinking of.



Also I am looking to run a batrium BMS, Tosing up between a centralised or decentralised BMS, I like the idea of a per cell temp, but thinking 28amp/day is over kill for wll balanced cell packs.

The cells are ex medical and have only been cycled 4-5 times most are still holding the same 2.2a/h that they are spec'd at, so they should be pretty good if i get the modules as aligned.
Jack of all trades, master of none.
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#3
You are designing a 14s40p system, not 40p14s. Voltage series portion first, then parallel. This is the standard for this forum and will help keep things clear in discussions Wink

It doesn't matter which one you build, they both will have the same voltage/amperage output. One will not be higher amps over the other as it's still 40p regardless.

Both designs are fine. What you need to figure out is the storage location of your packs. That can dictate the pack design. Several DIY'ers have server racks they've built their powerwall into, so the long slim pack is more accommodating. However, there are others who use narrow shelving so the more squarish pack is better for them. Just depends on your particular application. It also depends on your workspace. If you have the space to work on a flat surface without needing to keep moving stuff to build the pack, then go that size. You need a flat surface that is free of debris of any sort. One stray wire, solder ball, or other metal object on the surface when you move the pack around could be dangerous or deadly (especially if you've already connected most of the pack together).

The one thing I would question more than the pack design is how many of these packs do you plan to put into service? If each pack is a system voltage, you could run into other problems, like how many bms systems will you need, what happens if you connect a string to the system.

If you go Batrium, you might be able to use one Watchmon for the whole setup, as it can handle lots of longmons. But each pack would essentially need it's own monitoring as it has it's own system voltage. Sure, 1 Watchmon can do all of them, but I'm not sure if you can set it up in software where it splits the packs apart so you can monitor each pack individually. It just looks at each parallel pack as an individual and then displays them all on a bar graph side by side.

Now, if you made individual parallel packs, and then just had 1 string, you could then add more to the parallel packs as you get more cells processed. You just would need to make sure that you had 14 packs ready to install at once, though. You don't want mismatched capacity packs.


Just woke up and hadn't had my breakfast or coffee yet, so I hope I explained clear enough Tongue
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#4
Of you balance your packs in terms of capacity then there is really little need for heavy balancing.  My 15kWh system has not needed to be balanced any more than 1Ah since I installed it more than 6 months ago.   

As for large packs the really only downsides is the weight.    each cell is around 45g and the holders and wire/bus bar are fairly negligible.    but still your looking at 25kg.  Which can be hard to move around.

My system is 7s40p packs and I currently have 6 of those packs.    right now it's moving to it's new home but this is the setup


******Hi My name is Jason and I have SOCD (Solar Obsessive Compulsive Disorder)*******
Current Powerwall - 1400 Cells 7s200p (modular 40p packs) ~ 12kWh of storage     4x 315W Canadian Solar Panels

Working on the next 7s40p packs     ~2.5kWh

Waiting on 2000 Cells of unused Sony vt4 (2000mah 30A) ~ 15kWh      hehehehehe  More Power
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#5
(11-20-2019, 01:14 PM)Korishan Wrote: You are designing a 14s40p system, not 40p14s. Voltage series portion first, then parallel. This is the standard for this forum and will help keep things clear in discussions  Wink

It doesn't matter which one you build, they both will have the same voltage/amperage output. One will not be higher amps over the other as it's still 40p regardless.

Both designs are fine. What you need to figure out is the storage location of your packs. That can dictate the pack design. Several DIY'ers have server racks they've built their powerwall into, so the long slim pack is more accommodating. However, there are others who use narrow shelving so the more squarish pack is better for them. Just depends on your particular application. It also depends on your workspace. If you have the space to work on a flat surface without needing to keep moving stuff to build the pack, then go that size. You need a flat surface that is free of debris of any sort. One stray wire, solder ball, or other metal object on the surface when you move the pack around could be dangerous or deadly (especially if you've already connected most of the pack together).

The one thing I would question more than the pack design is how many of these packs do you plan to put into service? If each pack is a system voltage, you could run into other problems, like how many bms systems will you need, what happens if you connect a string to the system.

If you go Batrium, you might be able to use one Watchmon for the whole setup, as it can handle lots of longmons. But each pack would essentially need it's own monitoring as it has it's own system voltage. Sure, 1 Watchmon can do all of them, but I'm not sure if you can set it up in software where it splits the packs apart so you can monitor each pack individually. It just looks at each parallel pack as an individual and then displays them all on a bar graph side by side.

Now, if you made individual parallel packs, and then just had 1 string, you could then add more to the parallel packs as you get more cells processed. You just would need to make sure that you had 14 packs ready to install at once, though. You don't want mismatched capacity packs.


Just woke up and hadn't had my breakfast or coffee yet, so I hope I explained clear enough  Tongue
Ah the sleep dep is getting to me, paralleling my series lol I should know better  Big Grin

The only reason I liked the longer pack design was that spreading the load out I wouldnt need to do any addional bridging between each pack as there would be enough nickel to carry 100A. but if I go the individual packs then It doesnt matter much as each pack will have a busbar soldered to the nickel.

Yes, space is not to much of an issue as I have a 6m long wall to play around with. I have been thinking about the weight of the cells and having one large pack is probably the big draw back in that situation, Indiviidual packs can then have their own mounts. As space is not much of an issue the individual pack are starting to make sence to me, especally in the context of a string and a singular BMS module for each string of packs rather then doing something like 40p14s2p.

In the latest teaser video from HB he had a bus ar mounted on what looked like a 80P or 120P pack, might be the way to go.

Have to go searching for some busbars then  Tongue  Thanks for th ideas.

(11-20-2019, 01:19 PM)jdeadman Wrote: Of you balance your packs in terms of capacity then there is really little need for heavy balancing.  My 15kWh system has not needed to be balanced any more than 1Ah since I installed it more than 6 months ago.   

As for large packs the really only downsides is the weight.    each cell is around 45g and the holders and wire/bus bar are fairly negligible.    but still your looking at 25kg.  Which can be hard to move around.

My system is 7s40p packs and I currently have 6 of those packs.    right now it's moving to it's new home but this is the setup



Good point with regards to the weight, I have always wonderd what kind for comprssion load the cells could handle. My wall is steel framed with 12mm ply on it, should make an alright surface, might just need to knock some decent mounts together.
 
Hopefully I can get each pack fairly closely matched, they are all tested to +/-5mA.
Jack of all trades, master of none.
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#6
(11-20-2019, 02:02 PM)davidknowles Wrote: In the latest teaser video from HB he had a bus ar mounted on what looked like a 80P or 120P pack, might be the way to go.

Have to go searching for some busbars then  Tongue  Thanks for th ideas.

Yeah, Pete has 2 different setups. He has an 80p based wall, and he also has a 120p wall. The more cells in parallel, the less each cell will be stressed under load. So if you want to do a continuous 30A, then you should have at least 40p so each cell is drained <1A/cell. If you have 80p, then <500mA/cellm, which is even better. The lower the current per cell, the longer it will last in terms of capacity and life span.You will almost always get more capacity charge/discharge from a 200mA current than you will with 800mA current. So take that all into consideration when building the parallel portion of the packs.

Also check out DIY Tech & Repairs (Daromer) videos as well. He goes into pretty good detail about bms systems. Not only Batrium but a few other cheaper options.
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Proceed with caution. Knowledge is Power! Literally! Cool 
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#7
if you use repackr with testing each cell they come out great in my experience
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******Hi My name is Jason and I have SOCD (Solar Obsessive Compulsive Disorder)*******
Current Powerwall - 1400 Cells 7s200p (modular 40p packs) ~ 12kWh of storage     4x 315W Canadian Solar Panels

Working on the next 7s40p packs     ~2.5kWh

Waiting on 2000 Cells of unused Sony vt4 (2000mah 30A) ~ 15kWh      hehehehehe  More Power
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