Group Buy? Dr.Bass Steveo found 7s3p Module! Awesome Price!!

[zEEz]

Just finished the CBA test at 1A on a 7S3P module and, 59.729 Ah \o/ and IR is 3.7 mohms

I will recharge and retest again.

Ah number is fine but Ri is not a very conforting number ... being a parallel of 3 cells with average Ri=2 mohm.
I hope something is not good in your setup for testing, otherwise this would point out to a 10mohm per cell
that is like to say those cells are quite used and old and would heat up very quickly under strong current load.

hope for the best

[oatnet]

Just finished the CBA test at 1A on a 7S3P module and, 59.729 Ah \o/ and IR is 3.7 mohms

I will recharge and retest again.

Ah number is fine but Ri is not a very conforting number ... being a parallel of 3 cells with average Ri=2 mohm.
I hope something is not good in your setup for testing, otherwise this would point out to a 10mohm per cell
that is like to say those cells are quite used and old and would heat up very quickly under strong current load.

hope for the best

I think (hope) that is the IR for the 7s pack, not a single set of cells, which would mean .52mohm per 3p-supercell. When I IR tested the cell_man a123 prisimatics a few years back, they were between 1.00 mohm and 1.16 mohm, mostly around 1.06mohm.

Sutho, thanks for the capacity test, that is reassuring. When I saw your picture, I first thought you had gotten a totally different BMS, nice clean install of your new one. I have been thinking about cutting the connectors off too, but I might just put andersons on the balance wires instead.

Were your original BMS dated 2009 or 2010?
What color was the thermal paste/sidecovers/BMS date on the units you got marked for the fisker?

-JD

[SlyCayer]

I think (hope) that is the IR for the 7s pack, not a single set of cells, which would be .52mohm per 3p-supercell. When I IR tested the cell_man a123 prisimatics a few years back, they were between 1.00 mohm and 1.16 mohm, mostly around 1.06mohm.

This is the whole pack IR, not just 1 pack of 3P, it's the IR from + TERMINAL to - TERMINAL of the whole 7S3P pack, I think it's pretty good.

[zEEz]

This is the whole pack IR, not just 1 pack of 3P, it's the IR from + TERMINAL to - TERMINAL of the whole 7S3P pack, I think it's pretty good.

Ah, cool! this is great news! This is very good indeed
This bring you perfectly in the ballpark numbers given for the Ri of an average
new A123 cell ... so it seems that -at least for you- this Victorpower order
was a good bargain!

have fun!

[ga2500ev]

Can we get an update on the total cost + shipping for received modules?

Even though it seems like a crap shoot, it still may be worth getting a couple if the end to end cost
isn't too outrageous.

ga2500ev

[oatnet]

Can we get an update on the total cost + shipping for received modules?

Even though it seems like a crap shoot, it still may be worth getting a couple if the end to end cost
isn't too outrageous.

ga2500ev

A number of people posted their pricing/shipping costs in the beginning of this thread.

-JD

[John in CR]

A123 recommends float charging their cells a 3.4V (actually they say charge them to 3.6V then float them at 3.4V). My testing shows about zero capacity difference between 3.4 and 3.6V, you just get to the fully charged state a lot quicker a 3.6V

That's enough variance that a direct connection to a DIY solar panel made up of .5V cells might just work. I didn't test many, but each of the cells I did test in varying amounts of sun put out .5V , and the current output is what varied. 7 solar cells in series + 1 low voltage drop diode repeated for each series cell in my pack and I've got a solar powered balance charger made up of single cell solar chargers.

I must be missing something, because it sounds too good to be true.

[texaspyro]

I would highly recommend a voltage regulator in there... Solar cells voltage varies widely depending upon the load. A fully charged pack represents a rather light load.

[davec]

"Just finished the CBA test at 1A on a 7S3P module and, 59.729 Ah \o/ and IR is 3.7 mohms"

the ir seems ok
but 1amp discharge on this pack is like 0.01C ? at such a low c it better deliver the full 60ah
any battery will do good at 0.01c question is what can it do under a real load
1c 60a draw would be more useful
or even a 0.5c

edit: and a graph as well

[999zip999]

Good news is good news.

[kevo]

Sutho, sorry to hear of your warranted disappointment.
Oatnet glad you fared better it seems.
Regardless, both are important data points for this approach.

[oatnet]

"Just finished the CBA test at 1A on a 7S3P module and, 59.729 Ah \o/ and IR is 3.7 mohms"

the ir seems ok
but 1amp discharge on this pack is like 0.01C ? at such a low c it better deliver the full 60ah
any battery will do good at 0.01c question is what can it do under a real load
1c 60a draw would be more useful
or even a 0.5c

edit: and a graph as well

I can't believe this a123-hating Troll is still posting in this thread, like he has any experience with the subject or something relevant to add. Obviously, a standard CBA can't handle the 1500 watt load from a 1c discharge on a 7s 60a pack. Obviously, the pack is going to deliver really similar WH at 0.1c and 1c, and probably up to 10c. Skippy, go throw your poo at something else.

-JD

[miro13car]

especially after he accused me and Lithuanian people of lies about faulty A123 cells.
He seems does not see what other can see on my pictures, or he pretends.

[oatnet]

After leaving the packs sit for a few days, most of the cells in the 28s and (3) 7s packs are around 3.57v-3.58v, one was 3.55v.

I accidentally let the bulk-charge run too long on one of the 7s packs, and I ended up with some cells at 3.68v and some at 3.5v. I used a light bulb to discharge the highest cell down to 3.4v, and then used the balance chargers to bring them all up to 3.65v, and left them on all night - and all of those cells are still sitting around 3.63v. I thought I saw something similar when building the Headway pack on my Vectrix, it seemed that after a charge/burn off part of the fluff charge/re-charge, or maybe it was sitting on the balance charger for an extended time, the cells held voltage much much longer. Because charging to peak voltage is hard on the cells, and as texaspyro demonstrated it does not yield significant WH, I would NOT want to do on a regular basis. Further, I'm not entirely sure I am not whacky and mis-correlating events... but if I am not, I wonder if holding voltage means that this opens pathways in the cells, or helps with top balance.

Anyhow, I built some cables to connect the batteries, using 4ga wire and lugs with 1/4" hole, crimped, soldered, with thick adhesive shrink-wrap for strain relief. Since there are two holes on each terminal, I ran two of the cables for each connection. Per the '3-up' rule, the two 4ga are equivilant to a 1/0 cable. I am running 4/0 cable through the rest of my VW bus, but the runs between the modules are so short it shouldn't matter. I also like the redundancy - if one of the cables comes loose at 175v, instead of a plasma-ball-generating arc, the other cable should still be connected.

It is really impressive to see a 9kw pack take up so little room, shown against a 17" car rim for scale. Next, I'll make power cables for either end of the pack, slap it in my VW Bus, and see what it can do.

-JD

Why did I make 8 cables when I only needed 6?

a_IMG_3621.JPG (81.21 KiB) Viewed 587 times

9kw 175v pack, ready for a car.

b_IMG_3627.JPG (98.68 KiB) Viewed 587 times

[rolf_w]

I have tried to identify the major chips on the A123 BMS (from a 7s3p battery) in order to understand the principle functions of it. Some ICs I couldn't identify - probably some here in this thread would be better qualified?

IC1 (Quadruple 2-input NOR gate)
NXP HEF 4001BT (e.g. http://www.alldatasheet.com/datasheet-p ... 001BT.html)

IC5 (Quad 2-Input NAND Schmitt Trigger)
VHCT 132A PPJG (e.g. http://www.alldatasheet.com/datasheet-p ... 132AD.html)

IC9 (???)
CEP
JX2

IC10 (Freescale Semiconductor: Microcontroller)
S9S08DZ32 (e.g. http://www.alldatasheet.com/datasheet-p ... F2CLF.html)
CLH 1M 74K
CTDR 1020Q

IC12 (Analog Devices:???)
C
4S

IC17 (Intersil Corporation: Precision, Low Noise FGA™ Voltage Reference)
21009BF (e.g. http://www.alldatasheet.com/datasheet-p ... B812Z.html)
Z41

IC19 (Analog Devices: Triple-Channel Digital Isolator)
UM1301W (e.g. http://www.alldatasheet.com/datasheet-p ... 01ARW.html)
SRWZ5SS

IC23 (NXP Semiconductors: High-speed CAN transceiver)
TJA1051 (e.g. http://www.alldatasheet.com/datasheet-p ... 1051T.html)
TC AB

I haven't shown the backside of the pcb , it contains amongst others the bleeding resistors ...
r

[oatnet]

Dragged my super-accurate (but heavy) scale downstairs, leveled it, and tared the piece of wood the 28s would sit on. When I sild the battery on the scale, it came up exactly 107lb - minus maybe 1.3lbs for the two BMS and a handful of screws I've stripped off. That is 1.27lb per cell, packaged for installation.

IMG_3666.jpg (130.58 KiB) Viewed 560 times

I made the main power leads today - 1/4" for the M6 bolt end, and 1/2" for the connection to the 4/0 cable going back to the controller.

IMG_3638.jpg (161.12 KiB) Viewed 560 times

I test-mounted a pair of M6 x 10 stainless hex bolts today using the new '+' power leads. One of my packs came with a few nice star-head bolts, over nylon nuts, locktite-red, which I wanted to emulate. I tried a nylon washer under an M6 washer it on the left bolt, I can only figure that the nylon is intended to prevent overtorquing. On the right, I used M6 washers and spring washers, and felt that one held the cable more securely, so that is what I will use, along with locktite blue.

IMG_3652.jpg (159.06 KiB) Viewed 560 times

The complete wiring harness, removed so I can move the modules to the VW Bus!

IMG_3653.jpg (144.54 KiB) Viewed 560 times

[peterperkins]

Does the A123 BMS appear to function in a standalone mode?

I.E. when connected to the pack are the bleed resistors becoming active when a cell gets above voltage x?
Or is it waiting for some master controller over the can bus to operate it?

If you could establish which bleed resistors = which chanel you could fake one channel voltage to BMS so it thinks cell is high and see if resistors start bleeding?

It might allow us to use it in some limited fashion?

On a seperate note can all those who return packs as faulty mark them in some subtle / covert manner with UV pen or similiar so we can check any new arrivals.
Under the BMS cover possibly?

[Sutho]

On a seperate note can all those who return packs as faulty mark them in some subtle / covert manner with UV pen or similiar so we can check any new arrivals.
Under the BMS cover possibly?

Good idea.....but then you'll know.....and then you'll want to do something about it.....and then you'll be in a similar position as me.

[cwah]

Anyone from UK interested in a group buy? This seems to be a good deal if we can receive good cells

[deVries]

Anyone from UK interested in a group buy? This seems to be a good deal if we can receive good cells

Read the recent posts starting with "page" 24 to understand the odds of getting a good module. Also, if you just need 1-2 modules, then waiting for a group buy won't save you much money. If they sell the modules for $155, then it would be a very good deal. IMO.

[cwah]

Yeah, but I suppose the group buy would be in US. For me in europe it's not that interesting. So probably have to go for cells only.

Had a quote for 29.75$/cell... damn.. I better go lipo lol

[drdmdmd]

xin wang <victpowersales@victpower.cn> wrote:

Dear:"........

Thx for ur mail

Im sorry , we dont any guarantees for those modules

And no after sell service

Buy or not , it;s up to you .....

Best Regards

[oatnet]

Yeah, but I suppose the group buy would be in US. For me in europe it's not that interesting. So probably have to go for cells only.

Had a quote for 29.75$/cell... damn.. I better go lipo lol

Victpower's new single-cells are great, and $25/cell delivered - and are rated for 3000 cycles.

[totinen]

xin wang <victpowersales@victpower.cn> wrote:

Dear:"........

Thx for ur mail

Im sorry , we dont any guarantees for those modules

And no after sell service

Buy or not , it;s up to you .....

Best Regards

So, she is honest.

[totinen]

Anyone from UK interested in a group buy? This seems to be a good deal if we can receive good cells

Read the recent posts starting with "page" 24 to understand the odds of getting a good module. Also, if you just need 1-2 modules, then waiting for a group buy won't save you much money. If they sell the modules for $155, then it would be a very good deal. IMO.

Or then there should be someone checking modules prior shipment.