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

deVries said:
Texaspyro posted a huge fireworks "rocket" explosion in the desert at night with him running very fast hopefully in the opposite direction! :twisted:
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Actually was not an explosion, that's just the way that motor works. It has titanium granules in the fuel matrix for doing the sparks. And I wasn't running. Just standing there taking my daily pyro shower. I was closer to the pad than normal (but still outside the Minimum Lethal Distance because the rocket had a tracking beacon in it that was on a frequency that was close to the wireless launch controller and was jamming the control link.

I used to shoot some large Fourth of July type shows, but after 9/11 the gooberment goobered everything up and the paperwork became really opressive... hard to get volunteer slave laborers to go through FBI background checks, alien anal probes, etc. Now, I am reduced to trying to get unsuspecting schmucks to connect the big red wire to the big black wire :twisted: One can only hope...
 
so I'm looking at how the packs are wired with 1 balance wire for each string of 3 parallel cells, with the corresponding circuity on the BMS boards. It makes me wonder how a pack can be considered "balanced" when the cells are only monitored in strings rather than individually. Did A123 measure and group the cells so precisely off the production line that they were confident that string-to-string balancing would be sufficient?

sourcing a 24v 7s BMS+charger for this pack seems to be easy enough but a 72v 21s one looks to be a custom and expensive endeavor.
 
TheWizard said:
so I'm looking at how the packs are wired with 1 balance wire for each string of 3 parallel cells, with the corresponding circuity on the BMS boards. It makes me wonder how a pack can be considered "balanced" when the cells are only monitored in strings rather than individually.
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Battery Basics: It is not possible to monitor or charge parallel cells separately - once they are in parallel, they function as a single unit.

For example, if you parallel two cells, one at 3.55v, and one at 3.65v, the 3.65v will charge up the 3.55 until they are the same voltage. If one cell fails to 0v, the other will discharge itself into the failed cell until it also reaches 100% DOD.

So they could run (3) balance wires to the tabs, but they would all have the same voltage.

-JD
 
Ah, durr durr. Thanks oatnet. I knew parallel cells self-balance, but I thought measuring across a single battery's leads would get an isolated reading (path of least resistance?).
 
TheWizard said:
sourcing a 24v 7s BMS+charger for this pack seems to be easy enough but a 72v 21s one looks to be a custom and expensive endeavor.
Click to expand...

Doctorbass & Jeremy Harris have done some interesting charging with DC to DC convertors. You might be able to bypass a BMS all together if you won't deplete your pack too far down & monitor the LVC differently.

I wonder if anyone has tried two Hyperion chargers to do up to 28s ??? :idea:

Here's an exotic bulk charge method using DC to DC...

Cheaper Lightweight Charge to 100v :shock:

Here's a very cool idea from, none other, than who else, but Doctorbass. :twisted:

Convert your 48V charger into 100V for 24s for CHEAP !

Doctorbass said:
I am tired of parallel charging 2 x 12s .. that make alot of aditional connections and contact resistance.

A great cheap and easy solution i was thinking about for long time and finally decided to test is teh use of a 1:1 ratio DC-DC converter.

Teh idea is to connect the output of a 48V dc-dc in serie with his input to double the voltage. Tmost of the dc-dc have an isolated output vs input.. SO YOU CAN connect the output with the input!

Few dc-dc that take 48V input have variety of output from 3.3V to 48V. by connecting a dc-dc with a 48V in and 48V out you can get 96V out.. and play with teh trim pot to rise the total output to teh desired voltage around 100.8V is you need for 24s lipo... 8)

For sure the total power output will decrease a bit and you might loose aroud 7-8% total power due to the efficiency of the dc-dc that is around 90%.. but it's just for half the voltage ( the 50% that represent 48V out of 96 of the dc-dc output)..

Let say you bought a 48V 10A ( 500W) meanwell psu. by connecting the 48-48v dc dc with it you will get around 100V at 4.5 to 5A out... for around 450W..

but.. you will be able to keep your pack connected in 24s!.. no more need additional serie parallel connection for 2 x 12s !!

I will test that and comeback with review once i'll get the dc-dc arrived from ebay.

DC-DC are great cause you can accehive the dedired voltage from any lower psu by connecting their output in serie to the input! :mrgreen:


I already did that to convert my 1500W meanwell 48V to a 66Vout for my friend bruno for chargin his battery with two BXB150 48vin 5v out in serie to acheive +10V to the output. ( the 48V meanwell can do up to 56V out.. so 56+10=66V

If you search on ebay you wil lfind CHEAP dc-dc.. not the one you see at 75-100$ but most around 25-30$ each.

That is a good solution for compact size charger. and for those who dont want to have to buy another psu connected in serie with the first!

I found some that output 250W out for 20$ !

Doc
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For starters: I am only an egg :)

That said, I've been working on the A123 cells for about a month now; what interests me about these packs is *not* the cells per se, but the wrapping around the cells. The aluminum sheets, the end places, the plastic routing bars, and whatnot are far more impressive than the cells.

So far I have built an 8 cell module for my Robomower with drilled aluminum interconnects and plastic spacers. I'm boosting it now to 36 volts for an Elec-trak, and based on that thing's responses (it can pull 60a mowing, up to 250a tilling) I should have enough info as to what would be needed for a 300 volt electric truck (which needs batteries oddly enough).

The hardware that A123 makes is what's hard to get/source/build myself. So if anyone wants to cut up these packs and send me the ends/tops/little Aluminum things I would be *MORE* than happy to discuss.

But reading all 30+ pages of this discussion has been fascinating.

Chris
 
Monster battery made with 12 modules of 7s3p...

EV Battery Pack using A123 7s3p Modules

EV Battery Pack using A123 7s3p Modules
Sutho » Thu May 24, 2012 5:31 am

Have finally finished the assembly of the rear pack for our EV project. This pack consists of 12 x A123 7s3p connected in series for around 280Vnom. This will be connected in series to another 6 module pack in the front of the vehicle to give about 415Vnom.
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I got my next 28s3p last night - all cells appear good and are balanced to 3.27v, picture below. The box was more solid, and did not bend at all, so the case is STRAIGHT, it is MUCH cleaner, and the BMS' don't have that bad smell. :lol: I wonder if the first ones pulled off the container were the worst ones, or if they sold off their worst stock first... But so far Peter Perkins got a bunch of good modules, and all of the modules on both of my orders have been good.

I just placed my order for the next 28s3p module - as long as I keep getting good ones, I'll keep buying more, and reporting back here so you know what kind of quality I am getting!

Has anyone ordered more 7s modules lately, and did they arrive in good shape? I probably should stock up on a few of those too, so maybe on my next order I'll get some 7s before ordering more 28s.

-JD

IMG_4012.JPG
 
oatnet said:
I got my next 28s3p last night - all cells appear good and are balanced to 3.27v, picture below. The box was more solid, and did not bend at all, so the case is STRAIGHT, it is MUCH cleaner, and the BMS' don't have that bad smell. :lol: I wonder if the first ones pulled off the container were the worst ones, or if they sold off their worst stock first... But so far Peter Perkins got a bunch of good modules, and all of the modules on both of my orders have been good.

I just placed my order for the next 28s3p module - as long as I keep getting good ones, I'll keep buying more, and reporting back here so you know what kind of quality I am getting!

Has anyone ordered more 7s modules lately, and did they arrive in good shape? I probably should stock up on a few of those too, so maybe on my next order I'll get some 7s before ordering more 28s.

-JD

Click to expand...

Last time I emailed them about the 28s module, they said they don't sell it anymore...??? Are they lying to me.... When was you last order for a 28s pack?

Edit: never mind, I checked the email again, and it said they don't sell the 6s13p or the 42s3p anymore.
 
oatnet said:
I got my next 28s3p last night - all cells appear good and are balanced to 3.27v, picture below. The box was more solid, and did not bend at all, so the case is STRAIGHT, it is MUCH cleaner, and the BMS' don't have that bad smell. :lol: I wonder if the first ones pulled off the container were the worst ones, or if they sold off their worst stock first... But so far Peter Perkins got a bunch of good modules, and all of the modules on both of my orders have been good.

I just placed my order for the next 28s3p module - as long as I keep getting good ones, I'll keep buying more, and reporting back here so you know what kind of quality I am getting!

Has anyone ordered more 7s modules lately, and did they arrive in good shape? I probably should stock up on a few of those too, so maybe on my next order I'll get some 7s before ordering more 28s.

-JD

Click to expand...
What was your total shipping cost on this shipment?
 
Anybody can give some statistics about the percentage of 7s3p modules that
came in good conditions to the buyers?
Since I'm still thinking if to buy a few of them for a full size motorbike electric
conversion and what I wonder about is:
If those modules were in full working order why they are decommissioning them
and selling them as crap???

have fun!
 
i'm not sure if its been mentioned but on taobao you can find the empty a123 battery boxes ( 48v or 60v) dirt cheap,
they probably dont have any welding tabs but the boxes maybe very handy.
Untitled 2.jpg
Untitled 3.jpg
 
whatever said:
i'm not sure if its been mentioned but on taobao you can find the empty a123 battery boxes ( 48v or 60v) dirt cheap,
they probably dont have any welding tabs but the boxes maybe very handy.
Click to expand...

Are you sure they are empty boxes? They look like complete modules to me. Got the compression straps, busbars, etc. :?
 
Sutho said:
whatever said:
i'm not sure if its been mentioned but on taobao you can find the empty a123 battery boxes ( 48v or 60v) dirt cheap,
they probably dont have any welding tabs but the boxes maybe very handy.
Click to expand...

Are you sure they are empty boxes? They look like complete modules to me. Got the compression straps, busbars, etc. :?
Click to expand...


At about 5 bucks each yep they are empty. Note I never really trust the photos on that site.
 
SplinterOz said:
Sutho said:
whatever said:
i'm not sure if its been mentioned but on taobao you can find the empty a123 battery boxes ( 48v or 60v) dirt cheap,
they probably dont have any welding tabs but the boxes maybe very handy.
Click to expand...

Are you sure they are empty boxes? They look like complete modules to me. Got the compression straps, busbars, etc. :?
Click to expand...

At about 5 bucks each yep they are empty. Note I never really trust the photos on that site.
Click to expand...

Why is all the text on the taobaoenglish.com site in Chinese.....and unable to be translated? :(
 
JRP3 said:
whatever said:
i'm not sure if its been mentioned but on taobao you can find the empty a123 battery boxes ( 48v or 60v) dirt cheap,
they probably dont have any welding tabs but the boxes maybe very handy.
Click to expand...
Can't find them, do you have a link?
Click to expand...

Here:
http://item.taobao.com/item.htm?id=17683140670

They are whole batteries(?), but on hire. I translated with Google Translate.
 
Totinen that's a great find. I would like 2-36v's and would hope they come with the tray under the buss bar for tap seperation ? Hope we can crack the chiniesse codes.
 
yes that was the link, I just assumed they were empty boxes, there was another one but probably same advertiser
my mistake
 
Interesting stuff at that Taobao site.

Looks like they are trying to add tabs back on to cut-tab cells. Looks a little corroded, won't pass current too well with corrosion.
http://www.englishtaobao.com/Product/15404307617/New+%3Cspan+class%3DH%3EA+%3C+span%3E+%3Cspan+class%3DH%3E123+%3C+span%3E+%3Cspan+class%3DH%3E+iron+phosphate+%3C+span%3E+%3Cspan+class%3DH%3E+lithium+%3C+span%3E+battery+%3Cspan+class%3DH%3E+%3C+span%3E+3.3V+20%3Cspan+class%3DH%3EA+%3C+span%3E+h+%22hardware%22+car+battery+%3CSpan+class%3DH%3E+battery+%3C+span%3E+model+%3Cspan+class%3DH%3E+battery+%3C+span%3E/#tab-pdt

Looking at this link: http://www.englishtaobao.com/Product/15867816844/%3Cspan+class%3DH%3EA%3C+span%3E+%3CSpan+class%3DH%3E123+%3C+span%3E+20%3Cspan+class%3DH%3EA+%3C+span%3E+h+new+to+100%2C000+%22hardware%22+long+electrode+%3Cspan+class%3DH%3E+iron+phosphate+%3C+span%3E+lithium+%3Cspan+class%3DH%3E+%3C+span%3E+%3Cspan+class%3DH%3E+battery+%3C+span%3E+electric+%3Cspan+class%3DH%3E+battery+%3C+span%3E/
Does it look like that is what we'd be left with if we removed the cells out of these 7s3p or 28s3p modules?

Edit: What I like about this Taobao site is that they actually have a feedback section. Something we don't have with Alibaba, I think it's a nice additional element as it could mean that we could get a better idea of whether or not we are getting something good, and if not we can post that we didn't.
 
Well the least they could have done is made both tabs copper so they could be soldered - bastards.
 
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