The care and feeding of a123-based packs...

[pwbset]

Gary is there any way you could tell me what those battery spring numbers are from Mouser, I'm looking for some also.

+1

Also looking for good springs.

 

[GGoodrum]

They are made by Keystone and come in two sizes: 534-211 and 534-211D. I've used both in the past, but the larger ones are a bit too big, I think, especially trying to use them on the negative "button" end of an a123 cell. For this application, I'm using the smaller version, which are also available from Digikey.

-- Gary

 

[Jay64]

just clarifying here, the 534-211 is the smaller of the two, correct?

 

[GGoodrum]

just clarifying here, the 534-211 is the smaller of the two, correct?

Yes.

 

[reagle]

Could also use a few of Infineon BTS555 automotive solid state switches (basically a smart FET) for cutting off the load at LVC. Those things parallel easily and have integrated protection. I've never been able to kill them despite doing some really stupid things.It's good for lower voltage (sub 34V) packs, but is build like a tank
http://www.infineon.com/dgdl/Datash...4671e&fileId=db3a304412b407950112b436f516671f

This was designed by Randomly. I have not tested it, but see no reason why it won't work.
The number/size of the FETs depends on your maximum current requirement and heat sink size.

 

[manfred59]

Would it be possible to unite the great BMS with an active cutoff?
It would be fine for my 4 cell BMS which has no controller with break connector.
I could do a layout if anybody could publish a circiut of this solution.

 

[GGoodrum]

Would it be possible to unite the great BMS with an active cutoff?
It would be fine for my 4 cell BMS which has no controller with break connector.
I could do a layout if anybody could publish a circiut of this solution.

Here is the schematic for my LVC-only board that includes Randomly's active cutoff circuit. You don't need the 12V regulator portion if it is combined with the full BMS circuit, so the 12V zener can go, but I'm not sure about what else.

Originally, I was going to do a standalone 12V/4s BMS, for an SLA replacement pack setup, but never got around to it. I did work on a 24V/8s full BMS board, with active cutoff, but I don't think I finished it. I'll look around for this version.

-- Gary

 

[CGameProgrammer]

Guys, I have dead cells! It's been about a year since I last rode my e-bike, and when I tried charging it, one of my 10s6p packs wouldn't charge; the charger returned an error. I'm using the stock DeWalt charger, using the stock BMS only for charging.

I checked the voltages, and one 6p string is 0.1V! The others are all 3.2V or 3.3V.

Is that string definitely dead or might there be some sort of hope for reviving it? That pack was made by effectively just putting six DeWalt packs in parallel so that would be a difficult thing to repair...

 

[MitchJi]

Hi,

Guys, I have dead cells! It's been about a year since I last rode my e-bike, and when I tried charging it, one of my 10s6p packs wouldn't charge; the charger returned an error. I'm using the stock DeWalt charger, using the stock BMS only for charging.

I checked the voltages, and one 6p string is 0.1V! The others are all 3.2V or 3.3V.

Is that string definitely dead or might there be some sort of hope for reviving it? That pack was made by effectively just putting six DeWalt packs in parallel so that would be a difficult thing to repair...

http://endless-sphere.com/forums/viewtopic.php?f=14&t=8469&p=128540&hilit=+easyly+declare#p128540

Guys,,, you know all that i have great experience with these dewalt packs 8)

There is something i discovered that impressed me alot about these low cells that we easyly declare: dead ....

I had many of them that i kept for me instead of selling them that i tested again.

I was surprized to see that many cells clos eto zero V was still good with capacity and RI !!

I mean... these famous 1 or 2 "bad"... or even low cells that had 0.9V or 0.2V still gaved me 2150mAh and 10 mohm !! ..

and same results with 5 cycles after that!!

I also had a pack that i kept for me that measured 0.8V with every cells between 0.1 and 0.2V that i successfully charged using individual charger/cell and that gaved me 2100mAh ! with Ri between 10 and 13mohm /cell !!
since the last full charge of that pack i let ist to sit for 2 month on my desk and it still measure 34.75V of SOC !

That's why i say these cells are like buletproof and so incredible!
i'm not saying that everybody should keep these to match with their ebike batt project.. but for something like boostpack they are excellent!

If you try to recharge these lower cells, you will see quickly if they survived or not... the really BAD/DEAD cells will just heat up and will not keep their voltage when you remove the current

The best solution to ravive low cells is to begin the charging process at 500mA and when they reach 3.0V you can increase the current.

The DEAD cells will never reach more than 1.5V durin g the 500mA charge process.. the rest should succed.

SO DONT PUT THE LOW "DEAD" CELLS IN THE TRASCAN IMMEDIATLY !

Doc

 

[manfred59]

Originally, I was going to do a standalone 12V/4s BMS, for an SLA replacement pack setup, but never got around to it. I did work on a 24V/8s full BMS board, with active cutoff, but I don't think I finished it. I'll look around for this version.-- Gary

What I did is a layout for a 4cell LVC, but I need help!
I tested this LVC with a 4 cell pack of bad cells of the high power cells from voltphreaks. The voltages I have read you can see on the photo (no motor or 12V light bulb connected).
There are some questions:
Are the wires correct connected as shown in the photo?
When I connected the LVC with this setup the shutdown did not work right. One cell was below 2V but the load (a 12V light bulb) stay lit.
I also tried to short pin 8 and 7 like I did with the BMS, but this was no good idea , because the transistor Q1 (2N7051) exploded!
It's also possible that there is a fault in the layout, I don't know?

 

[GGoodrum]

Manfred --

I see one problem, one that got me initially as well. Q1, which is a 2N7051 NPN Darlington has the E-C-B pinout, instead of the more common E-B-C configuration. You need to swap the base and collector leads for Q1 on your layout.

I'll post something if I find anything else.

-- Gary

 

[manfred59]

Thanks @ Gary!
That was really the goal! I have swapped the base and the collector -- and it works!

 

[GGoodrum]

I finally got around to finishing off my 16s5p a123 pack, which I made using a combination of the existing DeWalt end covers from the 10-cell tool packs, some copper "hanger tape" from Lowes and some nickel-plated battery springs from Mouser. This pack also has a 16-channel LVC board, with Randomly's active cutoff circuit, that mounts on the front of the pack. I posted some early progress pics, a few pages back, but I'll repeat them here:

Each 8s5p sub-pack consists of four 10-cell blocks that are held together via two 6-32 threaded rods.

The two 8s5p sub-packs stack one on top of the other and then the 16-cell LVC board bolts to the front of the completed pack.

Finally, the completed assembly gets an outer shrink-wrap layer.

The completed pack, as shown, is 4-1/2" x 5-1/2" by 14", and weighs 14 lbs 13 oz, or about 6.7kg. The reason I went with an LVC board, instead of a full BMS, is mainly one of fit. Without resorting to surface mount parts, I just couldn't fit 16 full BMS channels on the size the board needed to be to be mounted on the front of this pack. The other issue is that this configuration is pretty well sealed, and while not waterproof, it's pretty water-resistant (I have a plug/cover that goes over the 18-pin connector on the board...). With a full BMS, I'd need to expose the LEDs and probably at least the power resistors, so that there'd be some way to let the heat out. The main use for this style pack is on my folding bikes, where the pack will attach to a rear rack, so it is exposed. Anyway, making it "splash" resistant is desirable.

My plan is to do a "CMS" box, which is basically just the full BMS minus the LVC portion, similar to the one shown below:

This can go between the charger/supply and the pack. In the meantime, until I have time to finish this, I will bulk charge this pack most of the time, and occasionally use my 16 2A VoltPhreaks chargers to make sure each block of cells get a full charge and the pack stays relatively well balanced. I also have coming a bunch of the 48V-3.7V/20A DC-DC supplies Bill has been selling, that I plan to use in my work area, with a 0-60V 0-15A HP supply I got off eBay. I mainly plan to use these to quick-charge blocks of cells as I build packs, but this setup could also easily be used to balance this pack occasionally.

Eventually, I plan on reconfiguring several other 16s a123 packs to use this construction method/scheme, but this first one will go on my 16" Dahon Mariner (the one in my avatar...), which currently has a Cyclone 1000W setup.

-- Gary

 

[Doctorbass]

wow.. that's a really clean and nice job you did Gary!!

I wonder have you thsted the max current one single spring can gandle before to heat too much?

I ask because i had the occasion to test the max current of the spring on the original dewalt side cover.. dor balancing.

I measured 1A max before it heat too much and could melt plastic.. and i would recommand max 0.5A..

I know the one you are using are bigger so have you tested a max current?

Doc

 

[slayer]

Only 1 amp doc are you sure ?

or is it 1 c meaning 2.3 amps ?

still it would not be enough to use them in the way Gary used them i was tempted to try them but i was afraid it would not handled the about 3 c i am going to use on them ?

would you say 3 c is too much current for them?


Also did you try just the current going thru the thin wire and not using it while it is being compressed it would make a world of difference i think?

 

[GGoodrum]

wow.. that's a really clean and nice job you did Gary!!

I wonder have you thsted the max current one single spring can gandle before to heat too much?

I ask because i had the occasion to test the max current of the spring on the original dewalt side cover.. dor balancing.

I measured 1A max before it heat too much and could melt plastic.. and i would recommand max 0.5A..

I know the one you are using are bigger so have you tested a max current?

Doc

Hi Doc --

The springs i'm using are much thicker and are much stiffer than the ones in the DeWalt packs, and are nickel plated. I've used these before, in my 4p packs, and routinely hit 80A peaks, which would be 20A each. In normal use, I've never had them even get hot. Tightly compressed, they make very good contact with the cells. When I was building this pack, I had problem where a two cells in series were dead shorted for about 5 seconds, before I could get the end cap back off. The springs got red hot, but they didn't melt.. I replaced the springs, but the ones that got hot seemed fine afterwards, but were discolored. Anyway, these seem to work just fine.

-- Gary

 

[oatnet]

Wow Gary, that is a really elegant solution, I like it. I saw your hanger-spring picture earlier, but didn't get that you were using that between the dewalt cell holders. I might just emulate your design when I get back to ebikes!

-JD

 

[GGoodrum]

Hi JD, and thanks. I'm really looking forward to following your progress with the VW bus conversion.

Although the spring/hanger tape method works pretty well here, it is still way too labor intensive. I will continue my "holy grail" quest for the "perfect" a123 pack construction method.

-- Gary

 

[Doctorbass]

Gary,

After examinating every details and advantages and (uhhh.. no dissadvantage ! 8) of your pack construction.. many times since you posted it.. I can conclude that you fins the best A123 pack construction method ever build :wink:

Your method is:

-Perfect for people that feel unsure about their welsing performance and wans a valuable solution
-Perfect for replacing a cell that could have problem.. Fast, simple and safe
-easy to build.. every extra parts can be accessible and found at any home depot or surplus store
-Give a strong pack with every cells protected from shorting together(they still sit in their black dewalt cover)
- That will make it easy for any new battery builder!
-The only thing that is missing is to fins that little powder that you just need to add water and that in 2 days you get a beautifull bonzai with A123 cells growing from it!!!

Well.. Perfect Gary!

Congrat! 8)

Oh and some award for this historic even! :wink: (wich one do you prefer ?? )

Doc

 

[GGoodrum]

Ha! that's great, Doc. All are very clever, but gotta go with the legs!

 

[silicium]

Merci doc pour ce site, les effets sont excellent

Et bravo pour l'dée de l'intégration des éléments A123 !

 

[GGoodrum]

OMG, in addition to your excellent engineering talents, you both have mad Photoshop skills! These are amazing!

 

[CGameProgrammer]

This has probably been answered but I can't find it -- If I have two 10s subpacks connected in series (as one 20s pack), can I safely use two DeWalt chargers (and BMS) to charge each 10s subpack simultaneously without disconnecting them from each other (so they're still connected in series)? Or do they have to be disconnected or a diode used? If the latter, I would prefer the diode approach, but have no idea what I'd need to use.

 

[mn_aerorider1]

This has probably been answered but I can't find it -- If I have two 10s subpacks connected in series (as one 20s pack), can I safely use two DeWalt chargers (and BMS) to charge each 10s subpack simultaneously without disconnecting them from each other (so they're still connected in series)? Or do they have to be disconnected or a diode used? If the latter, I would prefer the diode approach, but have no idea what I'd need to use.

I tested this approach once and it worked fine. The Dewalt Chargers appear to have sufficient isolation from main power.

Brian

 

[Doctorbass]

I tested this approach once and it worked fine. The Dewalt Chargers appear to have sufficient isolation from main power.

I approave!

That was my second battery setup.. I had 20s2p +4s4p boost pack.

The first 20s was charged using two dewalt pack.. both 10s pack was connected in serie while conected on the charger that was on AC.... no prob!