# LiFePo cells, aluminum shells vs plastic



## Jb24601 (Aug 29, 2019)

i thought all the single cell Calb-style batteries had shells (cases) made of plastic. Now I see some with aluminum shells. Anyone have experience with these for EV use?


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## john61ct (Feb 25, 2017)

No, but the big questions for each make you inquire about

1 is the shell **very** well isolated electrically from the anode **and** cathode ?

2 does their case design mean that compression plate / strapping is no longer needed against swelling?

3 can cells be laid on their side? only on edge or also stacked?

4 are spacers available to allow for cooling gaps between cells?


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## brian_ (Feb 7, 2017)

That would be CALB's CAM Series. It would be nice if the manual covered case isolation, but I didn't see anything.

CALB sells complete battery packs, but I haven't seen any components from them for building up a pack, other than the cells themselves. The aluminum cases are supposed to provide a cooling advantage, but they don't seem to provide any guidance regarding cooling provisions.


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## Jb24601 (Aug 29, 2019)

Thanks Brian_ for the education and the lead! CAMs? Who knew? A quick search led me to CALB’s website so I emailed the manufacturer john61ct’s questions and received this:

In terms of clamping the aluminum shell and plastic shell cells are treated about the same but are different from cell to cell due to different geometry etc. The following is the clamping recommendation for CAM72
Qty Squeezing force/KN
1 200
2-5 n x 100
>5 500
(The table didn’t post, so this is my by-hand copy)

Aluminum does offer some thermal advantage in terms of thermal exchange with the shell however overall thermal performance largely depends on external thermal design of the system. LFP cells have good thermal stability and can operate at 55C maximum cell temperature. For low stress home build EV usually air cool is enough to provide reliable operation however it is up to end user to determine the required cooling based on duty cycle and cell temperature reading. CAM aluminum shell cells comes with holders that help facilitate assembling the cells into pack. The holders help create a gap between cells to improve airflow and have four 6mm holes to be used for mounting and compression. The length of standard bus bars for CAM72 is also designed to include the thickness of the holders.

We recommend cells be placed with the terminals facing upward for best performance and cycle life. Placing the cell with terminals facing horizontal orientations have been used for special applications with success but we generally no not recommend it specifically for vehicle applications.

No, aluminum shell cells are almost identical to plastic shell cells in terms of actual use.

Form my understanding the cathode side is connected to the shell and the anode is isolated front the shell by plastic isolation inserts. The shell is wrapped with insulation film. I’ll have to confirm this with factory engineers.
Thanks,

Toby Zhang

Sales Director
ACCU-Power Corporation
www.accupowerus.com

********************

The “Squeezing force/KN” I guess is referring to kilonewtons (kN)?
(One kilonewton, 1 kN, is equivalent to 102.0 kgf, or about 100 kg of load under Earth gravity, source: Wikipedia). Does that sound ok? And how does that translate to a build?

I’ve also got pictures of the batteries. They look like metal shell batteries fitted inside a plastic “sleeve”. No apparent support but it covers the terminals and provides spacing from its neighbor along with a base that has mounting holes. 
If someone would like to tell me how to post the pictures, could you pm me?


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## john61ct (Feb 25, 2017)

Great work there. These are the CALBs right?

I like IMGUR for pics, free pic hosting site, no need to resize

helper apps for whatever your platform make it easy to

upload a batch of full-size pics to a "gallery", then either just post one link back here to that collection

or (a bit more work) get a URL for each, and an appropriately sized thumbnail shows here, with click-through for zooming.


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## john61ct (Feb 25, 2017)

Jb24601 said:


> A quick search led me to CALB’s website so I emailed the manufacturer john61ct’s questions and received this
> 
> …
> 
> ...


What contact info did you use to contact CALB itself directly? Did you get any response from them?

How did you get onto this distributor ACCU-Power and "Toby"? No such website, not a good sign. . .


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## Eddie49 (Dec 6, 2018)

john61ct said:


> What contact info did you use to contact CALB itself directly? Did you get any response from them?
> 
> How did you get onto this distributor ACCU-Power and "Toby"? No such website, not a good sign. . .


Accu-Power USA looks legitimate to me.

The company was registered in City of Industry, CA 91748 just over a year ago, the President is Yaotian Zhang:
https://www.corporationwiki.com/p/33575z/accu-power-corporation

On 26. December last year they imported a 20 foot container of CALB CA100:

https://www.seair.co.in/us-import/shipments-of-98971137.aspx


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## Jb24601 (Aug 29, 2019)

I just looked up CAM battery and up popped calbusainc.com, to whom I addressed the questions. They were forwarded to Toby, who quickly responded twice to my questions. Neither Accupower nor Calbusa sell direct, instead directing me to their distributors who include EVWest and others.

I saw these metal shells for sale on the site electriccarpartscompany.com. What caught my eye, and started this thread, was a 176ah weighing in at 8.8Lbs, (not made by Calb). Compare that to a plastic case 180ah at 12.3. Near 30%, +/-. Worth asking questions.


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## john61ct (Feb 25, 2017)

Given the same chemistry, heavier will always mean better longevity IMO.

The "fortune" cells are I believe made by Jiangsu Frey

maybe JIANGSU FREY NEW ENERGY CO.,LTD

or Jiangsu Frey Battery Technology Co., Ltd.

Personally so far I'd recommend sticking with CALB, and plastic casing.


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## swoozle (Nov 13, 2011)

The CAM versions are newer than the original blue plastic CALB cells. I bought the original version 8 years ago and they weren't new then. Technology marches on and weight does not equal longevity.

They can keep the cathode and anode "isolated" and in close contact. Keeping them both isolated from the case is trivial in comparison.


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## john61ct (Feb 25, 2017)

With the aluminum CALBs, the isolation falls to the system designer and installer, as their authorized distributor just stated anyway.

No thanks, knowing only the terminals are live is the way to go for me. The plastic wrap is certainly too fragile to rely on as a barrier, unless maybe stationary in my basement.

Lightest weight may be important for some but not me, if it was might go to NCA or NMC or even LiPo, all twice as dense as LFP these days.

And technological development of new chemistries does march on, but does not change basic physics of how LFP itself works, lighter cells **of the same chemistry** generally do mean inferior quality, less longevity.

Of course if the no-name cells are half the price delivered might be worth buying over tried and true players proven over decades

but not to just save 20-30% IMO.


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## evric (Oct 26, 2008)

Jb24601 said:


> i thought all the single cell Calb-style batteries had shells (cases) made of plastic. Now I see some with aluminum shells. Anyone have experience with these for EV use?


Be careful with these blue metal cased cells. They have the inherent problem of having a part potential on the case relative to the top terminals.This means that they have to be insulated from each other and from the frame or box in which they are placed.


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## evric (Oct 26, 2008)

Recently I replaced my 10 year old Thundersky 90Ah cells with Westart NCM 75Ah modules. I used 2 in parallel to give me 150Ah in each position. This pack fitted into same place as the Thunderskys but with nearly twice the capacity and 144Volts instead of 132Volts.
They have stainless steel cases (and terminal studs) and the cases are completely electrically isolated from the terminals and cells inside. One 75Ah module contains 3 off 25Ah pouch cells.
The new pack is only 8Kg heavier that the old one.


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## john61ct (Feb 25, 2017)

Interesting. But I'm confused about the layout and total cell count.

3x 25Ah cells if 3P1S means yes 75Ah but still at 3.6V

40 of those in series gets you to 144V nominal

total 120 cells, still at 75Ah

240 cells for 150Ah

480 cells to get to 300Ah if "2 in parallel to give me 150Ah in each position" is accurate

90Wh per cell would be 43.2kWh

big bank, lotsa range there

Please correct the above if I got it wrong.

Do you have a build thread? Particularly interested in your Thermal Management System, and hopefully redundant overtemp shutdowns, especially when charging

given how susceptible to thermal runaway NMC is compared to LFP (boom bad!)


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## evric (Oct 26, 2008)

Hi John,

2 of 75Ah NMC modules physically take up less space than the single 90Ah cell.
(Each 75Ah module is made up of three 25Ah pouch cells in parallel)
Before I had 40 off 90Ah Thundersky LFPs for 132Volts.(each cell 3.2V nominal with charge voltage of 3.65V). Approximately 11KWhs
Now I have 78 NMC modules 2P 39S configuration to give me 144Volts.
NMC cells 3.7Volts nominal per cell with a max charge voltage of 4.2Volts.
Approximately 21.6KWhrs. 
All this in the same physical space... actually less space, I had to space them out (3.5mm) so that my hold down mechanism would still work.
The height of the Westart NMC modules was exactly the same as the height of the original Thunderskys!
Images show the comparison of the LFP and NMC size, wiring the NMC BMS (showing the nickel plated copper straps) and the hold down bars in operation, looking through the clear poly-carbonate cover, also showing the space between each cell.


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## evric (Oct 26, 2008)

Hi John,
Re. your question about the BMS.
I am using a brand new system from ev-power.com.au called BATMON.
This has one temperature sensor for each cell board - one cell board for up to 12 cells, in my case there are 4 distributed around the whole pack. Also the maximum charge voltage and the maximum temperature is fully programmable via the Configurator. Making this max voltage adjustment sets it for every cell in the pack. When the first cell reaches the maximum set, the charger is turned off. When a maximum temperature is reached this also turns the charger off. A minimum for low voltage per cell can also be set - which when it occurs gives an audible alarm. Balancing can be turned on or off and is at a maximum of 100mA per cell. Balancing is not easy to arrange for NMC cells as the charge curve is completely different to LFP cells.
I obtained the NMC modules from EVPower as well.


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## john61ct (Feb 25, 2017)

Beauty, thanks. Be careful!


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## nebster (Aug 15, 2017)

swoozle said:


> The CAM versions are newer than the original blue plastic CALB cells. I bought the original version 8 years ago and they weren't new then. Technology marches on and weight does not equal longevity.


Agreed. John's assertion is clearly questionable.



> They can keep the cathode and anode "isolated" and in close contact. Keeping them both isolated from the case is trivial in comparison.


Disagreed. There are, apparently, issues attaining complete isolation between the case and the battery inside. It's either a very high resistance or a temporal issue, but most of the aluminum shell manufacturers will tell you to space them out or risk slow leakage current over time. 

That's okay, doing that gives you better thermal management anyway.


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