A123 20AHr Pouch Cell Battery Build & Info Thread

Actually just realised your on the 80V limit, for a full pack once you've took the top off.
During charge you'll probably have a good in- line fuse out from the charger anyways that would protect on charge.
If you get a heavy battery fault on the road it should drop the cell terminal voltage down to 70Vish and on blowing and bounce back to about 80V after blowing.
You'd have a lot of in line impedance, if it was a controller fault, should drop it down some. Should be 8)
 
So does this mean I can use the slightly smaller strip fuses or do I still need the larger 80V ANL ones, (The main in line fuse in the original 48v SLA setup was an 80V ANL)

Also the voltage for each module is 18V nominal, which is the level I need protection in this case (there will be a main in line fuse on the pack leads to handle the full pack voltage).
 
I see what your getting at with wanting to protect each module, understandable, but a fault could happen in the assembled pack which could be up to 80V, so 80V rating would still be the go.
You'd obviously have to co-ordinate if you have main and sub fuses, e.g. 100A main and 150A subs or get rid of the main fuse, 1 less insertion loss.
 
I read a couple of posts about the material used in the osn kit and as a first time battery builder I can vouch that after I shorted the pack ,welding the socket and bar across 36 v, that the epoxy does not burn or melt untill the metal bars , bolts and tabs are bright orange and /or evaporating ! They do melt ... But my unfortunate experiment suggests that it happens around the same temperature that welding occurs ... I have a very interesting melted 8 mm socket .... On the bright side one advantage of the osn kit is I could replace the burnt melted pieces easily .... ( I was just doing a final tighten check and I slipped : ( , I now know the advantage of insulated tools ! )
 
Thanks for the heads-up! Got any pictures? :twisted:
 
Here is some pics of some 24S packs we made with "pickle" and my young niece(one of the packs is for her new cro downhill bike). The others are for my folding bamboo bikes :twisted:
It took about 10hrs for all 3 packs to this stage. We wrap the packs with 1 layer of Mylar packing tape and then wet layup 3 layers of epoxy/fiberglass(approx 1mm) and use some smooth boards with Mylar tape on them as a compression mold to make a nice square box shape about 2hrs of work per pack. We will use emissions free BMS's .
I do not know why people clever enough to design and make these PCB then go and bolt the Mosfets down directly to the PCB and bond an aluminum plate heat sink onto the back of the non conductive plastic side of the mosfets. I think the fets can electrically handle the 80Amps or 120amps depends which model, but the board quickly gets over heated lifts traces and blows up! So i would not say they can pass the rated amps at 100% constant duty cycle. :x
Maybe with a some sensible heat sink mods they will prove more reliable?
It seems a shame the cells supply may dry up. These where from Nancy at OSN top customer service.
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Zappy
 
Nice battery porn Zappy.
Did you say you have insulating between cells too?
 
Sorry to trouble you!

The 40pieces A123 20ah short tabs korea cells have been sent today, when I got the tracking number, I will let you know.

There is one thing I think I need to discuss with you.

As you know, for the bankruptcy of A123systems, there are less A123 20ah cells in the market and we now just sell stock.
About the short tabs Korea cells, we have about 2300pieces at hand, after we ran out of the stock, we are NOT sure if we can get the cells or not.
I just got the news from my manager. One of our regular customer who usually bought 500pcs cells once a month from the other sales girl in my company, he got the news that we do not have much stock, so he now is discussing with my manager to buy all our stock of the short tabs Korea cells.
Of course, he will NOT buy all the cells this time, but he ask my manager to allow him to pay 30% deposit for all the cells, then we should keep the all the stock for him.
And he will pick up 500pcs cells once in a month. That's to say, even we have stock of the cells in the future month, but we can not sell them to other customers.

To be honest, that is NOT a good news for me. because my customers also need the cells.
So I just wondering, do you still need the short tabs Korea cells in the future month?
If you do not have enough money to pay at this time, I can ask my manager to allow you pay 30% deposit and we can keep some of stock for you.
How do you think so?

Sincerely hope you can answer me ASAP, because after the regular customer paied the 30% deposit for all the cells, as a sales girl, I can not sell the cells to you any more.
Looking forward to hearing from you soon.
Best regards,
Nancy
Click to expand...
I was going off this email
I hope this helps

Zappy
 
I am trying to find a supplier for these AMP20 cells. I was looking at the lot of 40 pouches from "Shenzhen Victpower Technology" for $780 shipped: http://www.aliexpress.com/item/free-shipping-No-logo-full-tab-A123-20Ah-system-3-2v-lifepo4-battery-cell/708063093.html

I've been reading the okay and bad on this supplier, I will end up needing 30 of these cells for my pack. If 10 pouches were junk, that is about $26 per good cell. This is all speculation, how is the market today for the AMP20s?
 
I would not go for these at the moment. You could use supercapacitor lifepo4 cells. They show good results on discharge up to 15C, are capable of 28C burst. IR <4mOhm, hard case, ~100g heavier than a123, bolt termination.
Dont go with victpower, big trouble. Ods of getting what you pay fore is scarce.
 
I've had great success buying both factory a123 modules and a123 pouches from Victpower - but buying from ANY chinese vendor is a gamble.

-JD
 
did you really get the BMS heatsink so hot that it damaged the BMS or is that just a supposition? your modification has made the BMS more liable to damage because the thermal breaker is now exposed to the air and has no contact with the heat sink as it does when the BMS is manufactured.

i just cannot believe you can carry enuff current on the traces to overheat that BMS. there are 14 of those RuiChip mosfets. they have a Rds of 3.6 mohm each so an equivalent resistance of 2.47e-4 ohm so if you are using 100A continuous, which would exhaust the battery in 5-6 minutes, then the total heat produced by the mosfets that the heat sink has to handle is only 2.6 watts.

i just cannot believe it gets hot enuff to require the heat sink modification and now you have lost the thermal protection by removing the thermal breaker.

you should at least put a switch in the thermal breaker wire to be able to turn the BMS on and off so the battery can be turned off when connecting to the controller.
 
oatnet said:
I've had great success buying both factory a123 modules and a123 pouches from Victpower - but buying from ANY chinese vendor is a gamble.

-JD
Click to expand...

Perhaps. I had same great success victpower including, but remind me when you did bought them???
The better part of the cells are sold and whats left smells bad
 
dnum said
did you really get the BMS heatsink so hot that it damaged the BMS or is that just a supposition?
Click to expand...
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dnum said
thermal breaker is now exposed to the air and has no contact with the heat sink as it does when the BMS is manufactured.
Click to expand...
I am sorry this BMS heat sink is not finished yet. Notice no bolts on the FETs yet. The factory thermal breaker is siliconed onto the aluminium heat sink plate which then has silicone insulation onto the back of the good insulator epoxy side of the FETS(not the copper side like a controller is). The factory thermal breaker has NEVER saved 1 of these units. It seems equivalent to mounting your car engine temp pickup on your bonnet. I have 2 more of these BMS's that have fried exactly the same(like mirror image!) with lifted traces under the FETS.
This is a different brand BMS 70A similarly modded and now runs nice and cool.
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Ping's BMS's can also get hot and start to "smell" a small heat sink can help them too. I really liked doctorbass's FET upgrade and simple really effective heat sink on his Ping BMS. Nice work.
dnum said
i just cannot believe it gets hot enuff to require the heat sink
Click to expand...
dnum said
i just cannot believe you can carry enuff current on the traces to overheat that BMS
Click to expand...

Ok please continue screaming the world is flat.

Zappy
 
steelmesh said:
I am trying to find a supplier for these AMP20 cells. I was looking at the lot of 40 pouches from "Shenzhen Victpower Technology" for $780 shipped: http://www.aliexpress.com/item/free-shipping-No-logo-full-tab-A123-20Ah-system-3-2v-lifepo4-battery-cell/708063093.html

I've been reading the okay and bad on this supplier, I will end up needing 30 of these cells for my pack. If 10 pouches were junk, that is about $26 per good cell. This is all speculation, how is the market today for the AMP20s?
Click to expand...

I'm currently in an Aliexpress dispute with them right now over an order of 32 cells that are nothing like the previous samples they supplied. While they were fully helpful discussing the deal by email, they have turned decidedly cold with their latest response despite my suggestions of paying for return shipping so it's not like they are even losing out financially. The official dispute process takes 3 days so I don't want to say any more here until I have a definite ruling from Aliexpress. If I lose out then I'll be chalking it up as as one of my harder lessons in life and will probably put them up for sale here for half price or something (full details/disclosure of course - I HATE SCAMMERS!).

If this is not the right thread, please let me know. It was initially about pack construction but seems to have morphed somewhat recently into AMP20 suppliers. I've enjoyed reading it, regardless, and am planning a 180s1p Drutledge-style high power pack split into 3 or 4 sections (with my own tweaks/improvements of course - after all, I am an engineer!).

Edward
 
Got my pack finished and installed :D

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Each of the four modules weighs 19KG .

Each case is 5mm chequer plate apart from the end one which is 2mm stainless so it can fit under the seat.

I used clear silicone sealant on the connector plates to insulate and keep moisture out.

The brown covers are 1mm phenolic sheet, the end plates are 6mm phenolic.

The cases are strapped with 1000 x 12mm stainless steel cable ties, tensioned with a Band-it strapping tool, this provides good compression on the cells.

All connector bolts are stainless steel and threadlocked on.

25mm welding cable for main power leads.

The difficult part was getting it in the bike without damaging the thin BMS wires which are all wired into the same plug, I had to make them extra long for this reason.
 
I finally got my pack all setup and running. I used a agniusm kit for the connections as I really likes his compact design. 16s. It was quite a lot of nerve racking work together but I think it will really hold up well!

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I didn't isolate between cells and still need to figure out how much pressure to put on the cells. So far I have barely put any torque on bolts. I ran a capacity test and got 18.49ah @ ~15 amps / 950wh according to the meter. The first night I accidentally left the pack on the charger before doing my true balance charge so some cells were sitting at 3.8 or 3.9v for almost a full 15 hours :oops: Lame BMS doesn't shut the pack down till 3.8 or 3.9 not sure which. Weighs in at around 22lbs with case and everything
 
That's a nice case, did you make it?
What BMS are you using?
 
flexy said:
That's a nice case, did you make it?
What BMS are you using?
Click to expand...

Yah case is my own, I'm using a greenbikekit 16s BMS. I am only using the BMS for charging and cell monitoring during discharge. I will setup a thottle shut off if the BMS shuts down during a ride. http://www.greenbikekit.com/index.php/bms-pcm/16s-48v-lifepo4-bms.html
 
Very nice build of the battery pack. Factory quality.
Where you guys get those 3D printers? i guess you feed them with ABS? looks like good quality 3D print, would that be one of those expensive commercial printers?
 
No 3d printer here, I'm using a cnc milling machine. You can see it cutting:

[youtube]2R2PD73RkzQ[/youtube]

Everything I have seen come out of 3d printers is weak, unfinished, and not very accurate. Unless of course it is a fancy powder base one that cost 30k and is 1k for every liter of volume :roll:
 
Nice build like the great compression end blocks. Is it compression or just not letting them expaned ? They will always find a way if the reaction starts in the cell. I just have mine rapped in tape. The compression question ??? Question's
Where did you get the cells ?
16s is a good ebike size and 17ah is fine. As my 24s is heavy. But how can I go back to a lower voltage know ?
 
My design only compresses the cell along the large flat surface. I pretty sure it is not required to compress the sides and ends. If those areas are unfolding or bubbling though the sides you have some really series issues about to occur.
 
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