How to set up my packs and HELLO to everyone :)


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The-J-Man

Member
Joined
May 2, 2017
Messages
260
Greetings everyone,

Joined here yesterday and super excited to be part of this community.


I have just started my project and I am not quite sure how to set up my packs because I have a somewhat different situation with my cells.

So:

  • I have 1600 cells that are all from hoverboards. It was 80x 36v 4.4aH packs. The cells are Samsung ICR18650-22P, all produced November 2015 and all in working order. Every pack measured between 32-41V, with about 50 being at36V so I lets just say I was real happy when I got these. I am in the process of taking these apart. I am testing only 2 cells from each pack at the moment to see their capacities (is this enough? dont know why they would be very different...?), my BT-C3100 is measuring most at 2250-2400mAh at the moment, subtract roughy 13% from these figures due to the inaccuracy and Im left with cells between 2000 and 2100mAh. Pretty perfect if you ask me.
  • Secondly I have about 1400 cells from laptop batteries. I am testing these but as you all know this process takes a lot longer.
I have a pretty constant stream of laptop batteries coming in and I should be able to get another 40 hoverboard packs identical to what I have this month.

So here is my actual question,
Should I just start building with the hoverboard cells, create packs with identical cells? Im thinking 14 packs of like 115cells (14s115p) - 170cells in parallel (170 if im getting another 40 of the hoverboard packs)? That would still total a pack capacity of 12kWh (correct me if im wrong). As these cells are essentially close to identical in terms of capacity, cycles and specs Im thinking I might be able to not bother with a bms, but let me know what you think please :DThese packs should last virtually forever, compared to laptop cells atleast.
Then as I get more and more good laptop cells I can expand and build packs that only consist of laptop cells and create another 14 packs that I can hook up in parallel again under the hoverboard packs. How should I setup these packs? mix and match high and low capacities like some are recommending or do what HBpowerwall is doing and build packs that consist of only certain capacity cells?

OR

Should I build packs with a combination of laptop cells and the hoverboard cells, mixing and matching the packs as I go, create larger packs of lets say 160p-200p. Kind of would make sense im thinking but then again im mixing relatively new cells with old ones where I dont know the lifespan of. I might create tons of extra work if I have to start exchanging old cells in the packs.

Thanks for the help everyone, any suggestions would be welcome.

J

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jdeadman

Member
Joined
Mar 28, 2017
Messages
967
Nice pile of batteries. Personally I'd test them all as there are always variances. match them in size and build your bank accordingly. Looks like you are off to a great start
 

daromer

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Oct 8, 2016
Messages
5,662
I wouldn't mix them unless you are sure they are of the same type of cells.

Ie high current vs low current. I would build the strings per type basis. Ie laptop 1 string and hover board 1 string. Since you seem to have enough cells to do that.


I also recommend to do n+1. So you always have spare. Do not fill the first string with ALL cells of that type you have. Save so you can swap out cells or even whole pack in that string to a new one if something happens!
 

hbpowerwall

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Oct 7, 2016
Messages
2,080
  • Test every cell
  • Nice pile
  • Test every cell
  • welcome
  • Te.... never mind
 

The-J-Man

Member
Joined
May 2, 2017
Messages
260


daromer said:
I wouldn't mix them unless you are sure they are of the same type of cells.

Ie high current vs low current. I would build the strings per type basis. Ie laptop 1 string and hover board 1 string. Since you seem to have enough cells to do that.


I also recommend to do n+1. So you always have spare. Do not fill the first string with ALL cells of that type you have. Save so you can swap out cells or even whole pack in that string to a new one if something happens!
Not going to mix :p just not worth it when I have this many cells that are most definitely good. The hoverboard cells are powercells I believe, rated for like 20A i think I read.. I will keep them totally separate.

Interesting, not sure what you mean by string, im working on my battery vocabulary so bear with me :DNevermind of course I know what you mean by string :p m a bit tired...

Definitely keeping a spare pack now that you say it. Just from the 1600 hoverboard cells i can do 105p and have a spare 15th pack.

thanks for your help
hbpowerwall said:
  • Test every cell
  • Nice pile
  • Test every cell
  • welcome
  • Te.... never mind

hahahha thanks, ill take your advice :D


jdeadman said:
Nice pile of batteries. Personally I'd test them all as there are always variances. match them in size and build your bank accordingly. Looks like you are off to a great start

Thats a lot of work but probably worth it in the end. Got 2 more charger coming tomorrow!
thanks mate
 

daromer

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14s is one string :)
 

The-J-Man

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Joined
May 2, 2017
Messages
260
daromer said:
14s is one string :)

Right yeah ok so 14 packs of hoverboard cells as one string and then 14 more packs of laptop cells (in the future) as a separate string.
 

VicRC

New member
Joined
Apr 26, 2017
Messages
6
How my cycles do you need to apply to each cell for testing? Is the process of fully charge and discharge to get mah of each cell enough test?

I am building banks of lifepo4s 32650 cells. I have searched and see no information on a powerbank using lifepo4 cells.
 

Wattsup

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Joined
Feb 19, 2017
Messages
512
I would imagine the hover board cells could be higher drain than laptop cells.
Hava a look at the data sheet for what you have, if you haven't already.
Nice haul and welcome
 

jdeadman

Member
Joined
Mar 28, 2017
Messages
967
I'm working with 1 12s7p Bank so It's only 84 batteries (small potatoes) but I do the charge\discharge fully twice then average the capacity
 

daromer

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Oct 8, 2016
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5,662
I run 1 single test only. Would not work to do 2 for me. Next couple of 100 tests will be in the big pack ;)

When I started i tested 1-5 tests but there was no difference based on actually charge/discharge. The diff was merely between chargers and/or contacts in my case.
 

The-J-Man

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May 2, 2017
Messages
260
VicRC said:
How my cycles do you need to apply to each cell for testing? Is the process of fully charge and discharge to get mah of each cell enough test?

I am building banks of lifepo4s 32650 cells. I have searched and see no information on a powerbank using lifepo4 cells.
I do one test only.
Wattsup said:
I would imagine the hover board cells could be higher drain than laptop cells.
Hava a look at the data sheet for what you have, if you haven't already.
Nice haul and welcome
They are indeed. 10A continuous max discharge current.
I was quite pleased when I got those, and best of all I have to this date paid nothing for all of my cells :blush:
daromer said:
I run 1 single test only. Would not work to do 2 for me. Next couple of 100 tests will be in the big pack ;)

When I started i tested 1-5 tests but there was no difference based on actually charge/discharge. The diff was merely between chargers and/or contacts in my case.
I do one test and after the discharge I leave them "empty", the bounce to 3.3v-3.6v afterwards but I dont charge them again. Is this ok, or should I charge them again to like 70%?
 

daromer

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You should charge them if you ask me. But i have no evidence that it actually do help.
Neither less you should charge them up and leave them for a week or 2 or 3 to meassure how much it self discharges over time. That is important because i have had cells go down to 3V within 1 week! They can destroy a functioning pack fast.
 

jdeadman

Member
Joined
Mar 28, 2017
Messages
967
With leaving them discharged, It's not bad to leave them at 3.6. but like @Daromer mentioned it's a good plan to leave them fully charged (4.1ish) to check for self bleeders. I have left mine after 2 capacity tests for 2 weeks before assembling my packs.

And then I check the voltages and sort the batteries by capacity then once in groups of 100mah (ie all 2500 - 2600 together) I then organize it by voltage to make my packs. If the voltage gets below 4V I put them aside for other uses
 

The-J-Man

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May 2, 2017
Messages
260
Ill charge them to about 4.1 and leave them lying here until I assemble my packs then. So far all these hoverboard cells have been in mint condition. I had 4 of these packs below 2.5v per cell (20cells /pack) 2 of them at 0.9v. I revived them and tested these. The c3100 is displaying 2300-2450 mAh. So absolutely perfect, no loss in capacity what so ever despite being way discharged.

Ive noticed some of my laptop cells drop down to 4.12v within a few days...
 

The-J-Man

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May 2, 2017
Messages
260
Still planning and testing here.
I have a question about the current I can draw from my cells / packs and therefore what I need for Busbars and Fuses.
All my cells are rated for a 10A continuous discharge.
Now I dont want to use the cells at 10A but Im thinking I should build my packs to at least support more then 1A per cellit so that I can have a high output when necessary.

Currently Im thinking 120p packs to simplify the build. (shying away from that more and more considering the amps flowing through the busbars here, starting to understand why people are building 80p packs)
So if I have 120p and I want to utilise the full potential of the cells how thick would I need to make my busbars?
2.5mm^2 cable handles 16Amps so 6of them together for 90A, seems to be what people are using for their 80p packs with 1A discharge per cell. Judging by that I would need like 75of those wires together for the full 10A per cell. Definitly not possible to do :D
Ok so lets say I want to draw up to 3A per cell, then thats 360A, so I would need 23 of 2.5mm^2 cables together, also not possible...

Any suggestions on how I can build my busbars and maybe how I should build my packs to support more then 1A per cell discharge?

And then of course for how much should the fuses be rated that I use?


PS: My plan with this system is to store solar power from a 6kW system during the day so that I can then replenish the electricity used in my electric carfrom my 100km daily drives from work, at night. I will NOT be running my house of this DIY battery pack.Im thinking it would be convenient if I could set up the system to support up to 11kW charging capability, only when I really need it, other times I would charge at the standard household plug 3kW as I have plenty of time at night.

thank you :) :heart:
 

daromer

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You should setup the packs based on your actual equipment if you ask me. If your stuff max will do 150A dont go above that with busbars and such. Thing is that 6*2.5mm2 can do way more than 90A. It can easily do 200A as well. yes it will cause voltage drop and some heat generated but how often do you stress it that high? Perhaps if you go and charge your car but i doubt you need to push it that hard. If so its better with more packs.

This if of course my opinion in the matter. If you do 8*2.5mm2 the 200A would not be such a big deal and not that huge voltage drop either.

single 2.5mm2 can easily carry 25-30A on that short distance without big voltage drop. Dont forget that the fuse wire will give you some drop too :)
 

The-J-Man

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Joined
May 2, 2017
Messages
260
daromer said:
You should setup the packs based on your actual equipment if you ask me. If your stuff max will do 150A dont go above that with busbars and such. Thing is that 6*2.5mm2 can do way more than 90A. It can easily do 200A as well. yes it will cause voltage drop and some heat generated but how often do you stress it that high? Perhaps if you go and charge your car but i doubt you need to push it that hard. If so its better with more packs.

This if of course my opinion in the matter. If you do 8*2.5mm2 the 200A would not be such a big deal and not that huge voltage drop either.

single 2.5mm2 can easily carry 25-30A on that short distance without big voltage drop. Dont forget that the fuse wire will give you some drop too :)

Thanks for your reply mate, again ;)

I really need to start planning what equipment I am getting/ need to get!!

I might end up doing 7or 9*2.5mm2. That would support 240A (2A per cell) if I do stress it every now and then. And the bit of heat generated and voltage drop I just wont care about. I will have cooling anyway.
No idea how thick that wire would be then, about 6mm im guessing. Should be ok :D
Feel like taping7 together and placing them on top of the pack and taking a picture?Need to know if there is enough space for my fuses. :heart:
Im ordering wire tomorrow!


Should I get a fuse wire that trips at about 5A then?

thanks
 
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