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First pack build - BMS issue
#21
(05-06-2019, 11:33 AM)DCkiwi Wrote:
(05-06-2019, 08:44 AM)sunkmail Wrote: I was planning on doing a breakout of some kind to see the current for the exact reason you mention - 3A just seems like overkill.  I may add a large Cap on the output to act as a reservoir for occasional spikes, just in case.

I still have to find a suitable barrel jack though - as mentioned, I don't actually own the hardware, so I can't just snip it off the existing power supply.   
          It's a fairly small one, probably about 1/2 the size of the really common size used on Arduinos and the like -  but I haven't actually measured it yet.

ok, I respect your decision not to cut into 'their' power supply/lead, BUT ... where are you based?
(it might be wholly your property when contract is paid out, but I won't go on, or press you on this point).

your profile location reveals nothing (*hint hint*) ... BUT ... regardless of where you are / local supply situation... check out your hardware stash ... you got one, right?  if not, time to start one ... this includes chopping off barrel connectors when a PSU fails (start grabbing those around you) ... which happens amazingly often ... eventually, you will end up with every connector you need.  Keep/maintain a good collection.

right now, all you need is something that can plug in.  check out your local recycler ... your local IT shop ... do the dumpster diving there ... you CAN find a lead that matches.  keep looking!

and .. they all have 'standard' names/measures, but for now, I recommend just grabbing them all and learning as you go.  no point focussing on these details for now ... you need a stash of connectors, as this kind of problem is annoying at best ... beat it! ; )

NB for this project to work you will absolutely need a PSU plug that fits.  Non-negotiable (according to your plan/words) so I think this should be a massive priority, right?

Quote:(Parallel, Series, 2 cells of each, whatever)

as for that ... you are talking 2p.  important to get your p's and s's right, and to speak clearly ... (*hugs*)


hoping this helps.  don't stop ... building OR sharing your progress/questions.  you are in the right place.  : )


Thanks for your suggestions.  Smile

I'm in Vancouver, BC, Canada.    The hardware remains property of the service provider (At least with the two major ones).  It works out well in that if it breaks they have to replace it at their cost, and occasionally they provide no-charge upgrades when the equipment starts getting older.  The only real downside is having to return it if you change providers.

I do have a hardware stash!   And where I work is constantly throwing away old/dead equipment.  (It's where I got my Cells - all 592 of them!)
      I should be able to get over to the recycling area tomorrow to scrounge. Smile
I need to go through everything at home, and finding free time at home has been a challenge.  I'm actually typing this at work - I have more free time here than at home. Tongue
I have a little time off work coming up, so I'm hoping this is one of the projects I can cross off my list soon.


I think I may not have been clear on my comment you quoted ...

The holder I thought I had ordered had wires coming out for each cell, so on a single 4-cell holder I could make:
4P
4S
2P2S

Use another, of the expected holders, (2x 4-cells) and you open up to even more possibilities - especially if you don't mind having an empty position or two. Smile

8P
8S
4P4S
3P2S
3S2P

Add another one ....    You get the idea. Smile

The 'Whatever' part was suggesting someone could make whatever combo they wanted, depending on how they wire the holders and how many they use.


The project in this post is a 4S1P, Don't worry. Smile



I'm hoping to put together a 14S ?P powerwall type system 
         - mostly just to see if I can, and have some (albeit limited) power during an outage. 
         - Partly to make some sort of practical use of the cells so my wife doesn't throw them away, and partly in hopes that we will be able to get a detached home someday and I can actually hook up some solar.
     The 14S size is so I can easily use the powerwall to charge my 13S Bike Battery, if needed.  (I have an appropriate adjustable DC-DC converter for those voltages)
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#22
I took some pictures of the current state of the project:
            (Cells removed for clarity)

Top View:
 

Bottom View:



Inside Views:
 

Outside View:


The Red and Black wires going out of shot are the Charger/Load connection.

I know it's hard to see exactly what I did. I just couldn't get a picture that shows it clearly...

         (With all cells removed)

         I made a small opening (with my iron) in the sides of the case where there is a natural 'slot' in the outside case. 
                    (The slot is where the plastic Cell dividers in the holder start/end.)

         I then made a small hook on the end of some tinned 24 AWG wire (maybe 22 AWG) through this new opening and around the connecting wire between the cells.

         A dab of solder and done - Easy Balance lead in a 4S off-the-shelf holder.

         While I was at it I also beefed up the B+ & B- leads, they seemed a little too thin for my liking.


For any future builds using these holders I want to try soldering to the rivet portion of the connecting wire to see if that works without damaging anything.

          If that fails, I will use a small drill bit in a Pin Vise.  

Either way, the end result should look a lot cleaner than my example here.  
            (plus I'll make sure I don't short myself on wire length and have to kludge on a stubby little extension wire Rolleyes )



Cheers
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#23
Something to take note of. Some of those BMS are fussy about what order you connect the batteries in. Some will even burn if you put batteries in that are too far out of balance.
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#24
(05-09-2019, 01:49 AM)Geek Wrote: Something to take note of. Some of those BMS are fussy about what order you connect the batteries in. Some will even burn if you put batteries in that are too far out of balance.

I have seen that a few places during my initial research.  It's usually badly translated, but I think the rule of thumb is to start at Cell 1 and work your way up in order.

Has anyone seen something different?
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