Dr.Bass Steveo found 7s3p Module! Awesome Price!!

[kevo]

Nice reference links Sutho, subscribed

 

[MitchJi]

Hi,

SO WITH SHIPPING WERE LOOKING AT $20.60 A CELL, 42 cells!

Dan

A saving of about $4.40 per cell. Seems like a bad deal to me if you can't use them as packs.

Anyway, I think replacing a bad module for free IS much better than no warranty at all. I think you have snagged an awesome deal, *IMO*.

Paying $7 per cell in shipping isn't exactly free.

 

[deVries]

Hi,

SO WITH SHIPPING WERE LOOKING AT $20.60 A CELL, 42 cells!

Dan

A saving of about $4.40 per cell. Seems like a bad deal to me if you can't use them as packs.

Anyway, I think replacing a bad module for free IS much better than no warranty at all. I think you have snagged an awesome deal, *IMO*.

Paying $7 per cell in shipping isn't exactly free.

That's for shipping 2 modules, so a group buy or volume purchase may *possibly* be cheaper. Anyway, no one in China ships anything free to the USA, whether it's new or a replacement. At least the defective module is replaced free of charge, which is a savings of $283. Free shipping does not really exist... shipping is factored in the cost whether it's "free" (not itemized) or not. But coming from China? Get real. Be realistic. :wink:

Hopefully, the price will come down further, because there will be too much supply rather than demand. Hopefully, most modules will not be defective, so there will be few returns to deal with anyway. Hopefully!

***EDIT: I changed this to now read: One very positive aspect about these 7s3p modules is it appears these are made in 21 cell rows, so it looks like it might *POSSIBLY* be a simple process to separate these cells using a dremel blade with vacuum. Pure speculation on my part.

 

[bigmoose]

Note on this picture of the buss bars, that it looks like there are two dissimilar metals, perhaps ultrasonically welded together between the anode triplet and the cathode triplet. Now if you can slice either metal between cells and solder to both, WIN... a big "if" ...

Notice that the cell tap leads are always attached to the buss bar that connects copper tabs.

I also notice what looks like a piece of high density foam between the last cells and the end caps. What I learned from this is that structural loads into the cells (vib, gravity, etc.) is carried through the endplates against the cell faces. They do not carry any loads from the edges or the tabs. Clearly we should clamp these cells into the cases we (who have bare cells) make for them.

 

[mistercrash]

I don't know much about welding but it looks to me like the difference in color is the cell tabs showing, one is copper and the other aluminum? It's a bit hard to say from the pic but those balance wires look like they are soldered to the bus bars so they might be Nickel. If that's the case then it would be easy to solder to, or together.

Sorry for this question but there seems to be an awful lot of balance wires going to that balance plug, shouldn't there be only 8 balance wires for a 7S pack? Or is there other stuff that I don't know about like temp sensors? Those little blue wires kinda look like exactly that. Or could it be that every single cell is monitored?

 

[Teh Stork]

One very positive aspect about these 7s3p modules is it appears these are made in three separate 7s strings, so it looks to be very simple to separate these into 7s1p modules by just cutting the parallel connections or wiring connecting the three 7s strings together as 7s3p.

No, judging by the picture - you could not split a 3p module intp 1p module easily. You could certainly easily split them - but saying the result would be a module would be wrong.

I'm seriously concidering buying some modules just to keep for a future project. 3kWh gokart would be fun, the fact that they are already assembled is a plus in my book.

Sea freight from China to USA, or Europe - anyone have experiences?

Ref balance connectors: I think there are two thermal sensors, each connected by the blue wires.

What can we deduce from the picture and thread about the individual cells? I would make a guess around; Width: 7,5mm (cell width)*21 =158mm. Height: ~250mm (Cell with tab are about 250mm). Lenght: 165mm. So we're looking at about 158x250x165 [mm]. Add some padding to make the numbers abit more realistic.

 

[etard]

Subscribed

 

[darkone040]

One very positive aspect about these 7s3p modules is it appears these are made in three separate 7s strings, so it looks to be very simple to separate these into 7s1p modules by just cutting the parallel connections or wiring connecting the three 7s strings together as 7s3p.

it looks the opposite to me, it looks like 7 separate 3p strings
so if i wanted a 21s1p battery which would be more ideal for an ebike i would have to flip every middle cell in each group of three then somehow figure out how to connect the nickel plate together.. not as bad of a mess as i thought it would of been..

but if i were to build a motorcycle these packs would be ideal, 60ah would give you a nice range and come in a robust module.. now im rethinking about building an emotorcycle.. hmm

it seems like the extra wires are temp sensors, but that first from the left black wire seems to split in 2 after the heatshrink..

edit: teh stork beat me to it

 

[Icewrench]

Ooops

 

[mistercrash]

A guestimate on dimensions of the pack? I could fit three in my scooter. hmm...

 

[Teh Stork]

So, I've tried to fully understand why these modules are scrapped for car use? Are there simply some welds that could fatigue and fail - or is this problem with the clamping of the cells? Could someone sum this up shortly?

 

[pgt400]

So, I've tried to fully understand why these modules are scrapped for car use? Are there simply some welds that could fatigue and fail - or is this problem with the clamping of the cells? Could someone sum this up shortly?

No one knows for sure....the cells that have been bought are definately new and meet the same spec as that posted by Mavzin...offical A123 supplier. As for the packs, they are worth the gamble because they can't be BOUGHT anywhere else for ANY price. They are being sold as surplus and very cheap. $280 for a 7S3P pack that A123 probably sells for $3-4K.

 

[MitchJi]

Hi,

So, I've tried to fully understand why these modules are scrapped for car use? Are there simply some welds that could fatigue and fail - or is this problem with the clamping of the cells? Could someone sum this up shortly?

One of four automated tab welding machines in the prismatic cell manufacturing process at our Livonia, Michigan facility was incorrectly calibrated, causing a misalignment of a certain component in some prismatic cells. This defect was undetected by our standard visual and electrical inspection.

When the defective prismatic cells were subsequently compressed as part of the module assembly process, a mechanical interference was created between the misplaced component and the foil pouch which contains the cell. In certain cases, this interference breaches the foil pouch electrical insulation causing an electrical short which can cause premature failure of the battery module or pack, leading to decrease in performance and reduced battery life.

Anyway, I think replacing a bad module for free IS much better than no warranty at all. I think you have snagged an awesome deal, *IMO*.

Paying $7 per cell in shipping isn't exactly free.

Anyway, no one in China ships anything free to the USA, whether it's new or a replacement. At least the defective module is replaced free of charge, which is a savings of $283. Free shipping does not really exist... shipping is factored in the cost whether it's "free" (not itemized) or not. But coming from China? Get real. Be realistic. :wink:

Someone posted that his shipping cost is going to be about $140 per module, and that he will have to pay shipping on warranty replacements. It will cost him about $140 in shipping costs to get his "free" replacement. If they require him to return the bad module it would cost him about $280.

Your response was "replacing a bad module for free". I never said anything about free shipping. You ignored the shipping cost component of the warranty and I pointed that out.

 

[deVries]

One very positive aspect about these 7s3p modules is it appears these are made in three separate 7s strings, so it looks to be very simple to separate these into 7s1p modules by just cutting the parallel connections or wiring connecting the three 7s strings together as 7s3p.

No, judging by the picture - you could not split a 3p module intp 1p module easily. You could certainly easily split them - but saying the result would be a module would be wrong.

My Bad. Caused by early morning sleep deprivation.

I changed it to read:

***EDIT: I changed this to now read: One very positive aspect about these 7s3p modules is it appears these are made in 21 cell rows, so it looks like it might *POSSIBLY* be a simple process to separate these cells using a dremel blade with vacuum. Pure speculation on my part.

 

[lukehutch]

A guestimate on dimensions of the pack? I could fit three in my scooter. hmm...

Trying to get an idea of how many modules I'd need for different sized vehicles...

These are 20Ah per cell at 3.3V, right? So in 7s3p configuration, you'd get 3.3V * 7 = 23.1V for 20Ah * 3 = 60Ah per module? So with three modules connected in parallel you'd get 23.1V, 180Ah or for three modules in series you'd get 69.3V, 60Ah? What is typical voltage and current for a motor sufficient to drive a scooter? (Want to make sure I'm doing the math right...)

 

[deVries]

These are 20Ah per cell at 3.3V, right? So in 7s3p configuration, you'd get 3.3V * 7 = 23.1V for 20Ah * 3 = 60Ah per module? So with three modules connected in parallel you'd get 23.1V, 180Ah or for three modules in series you'd get 69.3V, 60Ah?

We do not know how the wiring or connections specifically work for these modules, so it is pure speculation how to configure these modules for a specific application such as your project. I think you mentioned you are new to electric bikes, so this is a very complicated issue for a newbie to take-on, imo. You'll need to wait until others get these modules AND post the details about these modules. In the meantime keep reading other topics & threads, so you can find answers to the questions you have below. You will have to invest the time to read & learn, since there are already answers to the questions you have below that are ready to be found now on the forum.

Also, most people will charge these cells to 3.6v to get a top-off or surface charge, so you need to take that into consideration to match the proper controller you might use. BUT, this is Off-Topic for this thread, so you'll need to post elsewhere about this.

What is typical voltage and current for a motor sufficient to drive a scooter? (Want to make sure I'm doing the math right...)

Sorry, Off-Topic... Please post this elsewhere. :wink: There is a Scooter/Motorcycle section of ES you might want to check-out.

 

[lukehutch]

What is typical voltage and current for a motor sufficient to drive a scooter? (Want to make sure I'm doing the math right...)

Sorry, Off-Topic... Please post this elsewhere. :wink: There is a Scooter/Motorcycle section of ES you might want to check-out.

I don't understand how somebody making a statement about mounting three of these on a scooter is not flagged as off-topic, but me asking a question about how whether that many of these cells would actually work for that purpose is flagged as off-topic, but fair enough.

Thank you for the advice to wait until somebody actually gets the cells before drawing any conclusions.

 

[deVries]

I don't understand how somebody making a statement about mounting three of these on a scooter is not flagged as off-topic, but me asking a question about how whether that many of these cells would actually work for that purpose is flagged as off-topic, but fair enough.

That post provided useful "estimate" information to this thread: Estimate of Module Dimensions 8)

Check your ES Inbox for a PM. More explanation about what to do next... *IMO*

The topic of the thread you are posting in now is to learn specific information about these modules (construction, specs, cells, pricing, shipping, etc.), and whether we can do a group buy to save money.

(That really has nothing to do with your personal project application speculations or possible unknown or vague scooter build/parts questions... at this point you only have about 5 posts on ES & are just starting out by joining *only* yesterday. lukehutch 10 µW Posts: 5 Joined: Fri Apr 20, 2012 3:59 pm)

Please invest in more reading & learning on ES & post questions in the On-Topic threads or start a new one of your own.

If anyone wants to help lukehutch (click link below), then here is his thread he started yesterday!

Electric conversion of Sachs MadAss

 

[MitchJi]

Hi,

2. What is the cause?
One of four automated tab welding machines in the prismatic cell manufacturing process at our Livonia, Michigan facility was incorrectly calibrated, causing a misalignment of a certain component in some prismatic cells. This defect was undetected by our standard visual and electrical inspection. When the defective prismatic cells were subsequently compressed as part of the module assembly process, a mechanical interference was created between the misplaced component and the foil pouch which contains the cell. In certain cases, this interference breaches the foil pouch electrical insulation causing an electrical short which can cause premature failure of the battery module or pack, leading to decrease in performance and reduced battery life.

NOTE: "certain component" and "undetected by our standard visual...inspection" sound like something inside the pouches rather than the tabs.

I also notice what looks like a piece of high density foam between the last cells and the end caps. What I learned from this is that structural loads into the cells (vib, gravity, etc.) is carried through the endplates against the cell faces. They do not carry any loads from the edges or the tabs. Clearly we should clamp these cells into the cases we (who have bare cells) make for them.

Very clever to spot the potential problem but clamping these particular cells could be a big mistake. Definitely need to figure out a way so that in terms of vibration the pouches, tabs and wires/bus bars are rigidly connected.

 

[Teh Stork]

Yeah, well - that just adds to my confusion at this point. If it was the clamping and misaligning that was the problem - why are we seeing 'new' cells being sold by themselves, not having been assembled or being dissassembled from packs, on the market?

The price is redicolously low. You could buy an extra pack 'just in case' one fails for car building. The balance connector are beefy and everything seems to be high quality.

 

[Sutho]

Yeah, well - that just adds to my confusion at this point. If it was the clamping and misaligning that was the problem - why are we seeing 'new' cells being sold by themselves, not having been assembled or being dissassembled from packs, on the market?

Because the misalignment fault in the cell only becomes apparent when the cells are compressed into a module.....which they need to be to retain their shape and capacity when operating.

 

[deVries]

Yeah, well - that just adds to my confusion at this point. If it was the clamping and misaligning that was the problem - why are we seeing 'new' cells being sold by themselves, not having been assembled or being dissassembled from packs, on the market?

My *guess* is that the batch of cells that passed through the misaligned torch did *not* all get made into modules. The potentially defective cells were caught in time before going into the modules, so there is a limited supply of cells too.

Very clever to spot the potential problem but clamping these particular cells could be a big mistake. Definitely need to figure out a way so that in terms of vibration the pouches, tabs and wires/bus bars are rigidly connected.

Agreed. As I posted a couple of times before, my theory is it may be possible to save the *potentially* defective cells by relieving the tensioned bands or the compression pressure that is on the cell stack now inside the modules. Reducing that compression force may actually *prevent* the defective cells from being damaged. IMO. :wink: (Of course, doing that may cause other issues that are problematic too.)

I've seen that video of the (heavy-set older) man casting these same stacked cells in a urethane casting. That could be one method to prevent compression loading, yet keep the cell tab areas protected from vibration damage too. Using a lightweight urethane foam or other lightweight resin casting foam of some kind with a mold should work too. Or, perhaps use some lightweight shipping/packing dense foam to encase the cells. Of course, I realize this is not making any good use of the modules if the cells have to be removed or repacked in some way.

It may be possible, though, to relieve the stack compression, and then spray on a foaming agent around the edges of the cells that hardens & maintains the stack integrity. Or, use silicone rubber (or similar) material to make caulking lines/rings for a flexible banding, or use lower tensioned flexible bands like the idea of a bungee cord to keep a lower compression level on the cells.

 

[Sutho]

A guestimate on dimensions of the pack? I could fit three in my scooter. hmm...

A slightly more accurate guesstimate on the dimensions would be:

The width and height are dimensions I found in a document. The length is approximated from some known dimensions...

 

[bigmoose]

Hi,

2. What is the cause?
One of four automated tab welding machines in the prismatic cell manufacturing process at our Livonia, Michigan facility was incorrectly calibrated, causing a misalignment of a certain component in some prismatic cells. This defect was undetected by our standard visual and electrical inspection. When the defective prismatic cells were subsequently compressed as part of the module assembly process, a mechanical interference was created between the misplaced component and the foil pouch which contains the cell. In certain cases, this interference breaches the foil pouch electrical insulation causing an electrical short which can cause premature failure of the battery module or pack, leading to decrease in performance and reduced battery life.

NOTE: "certain component" and "undetected by our standard visual...inspection" sound like something inside the pouches rather than the tabs.

I also notice what looks like a piece of high density foam between the last cells and the end caps. What I learned from this is that structural loads into the cells (vib, gravity, etc.) is carried through the endplates against the cell faces. They do not carry any loads from the edges or the tabs. Clearly we should clamp these cells into the cases we (who have bare cells) make for them.

Very clever to spot the potential problem but clamping these particular cells could be a big mistake. Definitely need to figure out a way so that in terms of vibration the pouches, tabs and wires/bus bars are rigidly connected.

Mitch you make a good point!

Also putting things together the way you did, makes me opine that a critical piece of additional insulation is missing. As I understand it the foil pouch is perhaps nylon coated. The provides some inherent insulating capability. What if a thin, additional piece of insulation "spacer" insulation is missing/displaced?

Perhaps guys who have crunched cells could very carefully do a destructive physical examination with a scalpel and carefully, perhaps on a discharged cell, taking pictures as they go. Maybe we could piece together what is dislodged, misaligned or missing. It has to be the layer right under the pouch.

 

[mistercrash]

A guestimate on dimensions of the pack? I could fit three in my scooter. hmm...

A slightly more accurate guesstimate on the dimensions would be:

The width and height are dimensions I found in a document. The length is approximated from some known dimensions...

I think you are way off on the 240 mm dimension. Dimensions from DoctorBass showed the cells to be 7.25 mm thick, so that times 21 is 152.25 mm. From the pic it looks to me like the plastic parts at either end of the module are almost the thickness of three cells but not quite. To me it adds up to just under 190 mm. Anyway, you'll have the real dimensions soon. Really looking forward on your feedback from the modules you ordered.