Optimum China Batteries

Post by **woody** » Fri, 17 Apr 2009, 22:31

I have been conversing with maggie at optimum-china.com:

I initially enquired about their square 8085200 cells which are 10Ah.

She said they were 30A Max, and suggested a 38120 cyclindrical cell as an alternative:

maggie wrote: And here is the detail information for 38120 cells:
Const.discharing rate: It could be according to customer requirements. We can meet 10C, even 15C, but different rate with differnt price.
Pluse discharging rate: It is also depended on customer's requirments. Our cells could be 20C.
Const.charger rate: 0.2-0.5C
Pluse Charge rate: 1C
Depth of discharge for highest number of cycles:70% DoD for 2000 cycles, 80% DoD for 1500 cycles, 50% for 3000 cycles
Discharng protection votlage: 2.0V
Charger protecting voltage: 3.65V.

I asked for 15C and qty 230...

maggie wrote: Thank you so much for your reply.

Do you confirm that you need the battery with 15C discharging. for High rate discharing, the capacity for 38120 would be 8Ah.

And the price for 38120 8Ah with 15C discharging, the price would be USD16.5/RMB112 FOB SHENZHEN.

Here attached the picture for 38120 cells. It is cylindrical 38mm diameter X120mm length.

Now I have asked for weight and internal resistance (oops):

maggie wrote: The weight would be 340g for per cell.

I made a mistake, the internal resistance would be 6 mohm.

15C / 6 mOhm 3.2V I work out to be 67kW with 224 cells.

These should suit a short range high voltage (600V) EV, 208 cells for 28km @ 150Wh/km, ~US$3400 FOB.

Post by **acmotor** » Fri, 17 Apr 2009, 23:26

~100kg to ship US$1,000 so US$4400 =AUD$6100
+ AUD$610 GST
~AUD$6710 landed for 8Ah 759V 6kWh
+ BMS $15?/cell (AUD$3450)

total AUD$10,160 ? still not cheap !

That would go nicely in red suzi (drops off 230kg but with similar range)

Woody, were the cells with spot welded tags ?

Post by **Hemonster** » Wed, 22 Apr 2009, 20:03

Hey Woody,

Have you progressed with this? I too will be interested if they do their own spot welding to make up the tabs ... the good thing with EVPST cells is that they have screw terminals and are prismatic. However the pricing here is cheaper than EVPST.

Greensaver quoted to me USD$85 + USD$14 insurance to ship 360kgs worth of batteries and chargers via sea, so I don't think it will be that much more for these cells.

Post by **woody** » Wed, 22 Apr 2009, 20:53

I haven't taken it further. They are a bit cheaper than EVPST, but not as good on paper.

Anything else to ask other than if the cells come with tabs on ?

Facebook · Post by **Speedily** » Fri, 24 Apr 2009, 23:52

I have been chatting to a suppler in china that's got A123 3.3V 2300mah Nano Phosphate for $5.40 USD per cell #
Nominal capacity: 2.3Ah Core cell weight: 70 grams
Internal impedance: (1kHz AC) 8 mΩ typical
Typical fast charge current: 10A to 3.6V CCCV
70A continuous discharge
120A, 10 sec pulse discharge
Cycle life at 10C discharge, 100% DOD: over 1,000 cycles

I have to buy 1000 to get that price

Post by **Johny** » Sat, 25 Apr 2009, 00:00

Hmm. 1000 would make a 70Kg pack with 11.5Ah at 200 cells (660 VDC) for US$5400.
Are these tag batteries? What is the cell format?

Facebook · Post by **Speedily** » Sat, 25 Apr 2009, 00:26

i asked for no tags but ill ask

or 678 should get me moveing @ 320v

Post by **evric** » Sat, 25 Apr 2009, 00:29

How would you wire them up without tags?

Facebook · Post by **Speedily** » Sat, 25 Apr 2009, 01:08

i was thinking of making a spotweld (http://www.philpem.me.uk/elec/welder/)or something along that line

I think from what ive read sofar it makes the hole thing much simpler to build

Post by **Hemonster** » Sat, 25 Apr 2009, 01:27

Are you sure these are A123 nano phosphate cells? not just some company trying to pass off their cells as A123 and cream the premium? Not trying to be cynical, just that I know there are a fair number of rip offs around - and batteries (like memory cards) are prime for the rip off market because its difficult to tell whats "really" in them.

edit: spelling

Facebook · Post by **Speedily** » Sat, 25 Apr 2009, 01:40

No not yet but i will before i spend with them.. the last thing i want is battery coming out the

that wont run a 2watt light

I like the idea of batt and caps for racing

Post by **acmotor** » Sat, 25 Apr 2009, 05:59

Speedily, have you asked for 10 @US$5.40 as a sample to test them out ?
(With solderable tags.)
If they are any good, you could get interest from other EVers and make a bulk order. I'd be interested in some.

edit: dis#elxia

Post by **antiscab** » Sat, 25 Apr 2009, 06:59

Speedily wrote: i was thinking of making a spotweld (http://www.philpem.me.uk/elec/welder/)or something along that line

I think from what ive read sofar it makes the hole thing much simpler to build

a note with using capacitive welders on A123 cells.
the required weld pulse (from memory) is 4000A for 10ms.
any less current and it doesnt weld properly.
any more time, and too much heat conducts into the cell itself and damages it.

this means you need to use an IGBT, rather than an SCR for weld pulse control.
the control circuitry also has to be a little more complicated, to keep the pulse length to 10ms.
you also need to use a larger capacitor, to keep the RMS current of the pulse around 4000A.

not that its not doable, but it is a bit trickier than the setup in the link you posted.

Matt

Facebook · Post by **Speedily** » Sat, 25 Apr 2009, 15:06

ive asked for ten so who's going to test them....

Post by **acmotor** » Sat, 25 Apr 2009, 17:42

I'll test, if there are no other takers. On these terms...

I'd be looking at ESR, charge discharge curves at various C, temperature rise when cycled (usual things, just confirming they perform to spec) then putting them to task in my EV as an end of 600V string add on and see how they perform real life. (within their 2.3Ah)
This would be as a single 10x 3.3V arrangement (33V) taking them to 80A peak and also applying regen of peak 12A. (average less than 10A)
I am not likey to test number of cycles. There may be someone patient enough to do that ! IMHO cycle tests need to be done over 5 years or so with lithium batteries.

I would want the solder tagged version (with supplier spec that solder tag is good for 70A cont rated current).

I would use O/V and U/V monitor and shunt eq. on each cell.
I am not interested in abuse testing. No overcharges or 6 inch nails. That is for someone else !

I will return the cells to you with still 900+ cycles to go. (If they are up to spec)
You have to buy them and do all the leg work to get them to me.
(or I might want to keep them, so sent me the bill !)

Post by **miquain57** » Wed, 06 May 2009, 19:11

I have been looking into these cells for RC planes

Going to make a 4 cell and 6 cell pack.

Will be using them in large planes with 2meter wingspan.

These batteries have taken off in the US, people are smashing apart Dewalt battery 36v packs to get these batteries.

on the http://www.a123systems.com they have a link for bulk orders??

I would be keen to do testing on these packs. i can measure mah in and out. but the max amps i would be pulling is about 45.

Let me know if you want me to go in if you want to buy 20 packs

Michael
miquain57@hotmail.com

Post by **woody** » Wed, 06 May 2009, 19:33

Hi & Welcome Miquain,

the a123 batteries are different from optimum. The optimums I am talking about are larger. The a123s in Dewalt are about 2.3Ah, the optimums are 8.

a123 has developed a larger battery or 2, (10Ah) but I don't think they are manufacturing in bulk yet.

The a123s should manage 50 Amps, the optimums around 160 amps, but they are much heavier/larger.

cheers,
Woody

Post by **Hemonster** » Thu, 07 May 2009, 02:46

Hey Woody,

Are you still interested in EVPST cells as well? I thought of getting a few samples, but wondered if you had already got them and done some testing?

Post by **lithbattboss** » Thu, 07 May 2009, 02:56

If they are genuine, new A123 cells at 5.40USD then that is a brilliant buy.
There are many A123 cells being supplied from China and Hong Kong at the moment and most of these cells are either-
1) secondhand (about 12 months use from them) or
2) cells removed from old stock Dewalt power tool batteries remaining in China when the A123 manufacturing contracts in China were cancelled.

Two questions to ask the supplier so you ensure you get the real thing-
1) Ask for a close up photo showing the ends of the cells. The photo on this post shows the side of the cell only (ends aren't visible). If you see 4 spots on the ends these are the remnants of spot welds from batteries which were removed from Dewalt packs and are probably not new.
2) Ask the supplier how it is that at 5.40USD per cell (even on the quantity quoted) they can supply the cells at this very cheap price from China even though they are far more expensive in the USA where they are manufactured?

There are copies of A123 cells which are now made in China and which look identical to genuine A123 cells. I was sent photos/information of these cells from a battery manufacturer in China who asked me if I wanted to sell them in Australia. The manufacturer told me that they were a copy but the specifications were the same as A123 cells.

As I said before if they are the "real deal" and have tabs fitted or you have a proper battery tab spot welder (very important so as to prevent battery failures in use)grab them because it is a very good buy indeed.

Post by **woody** » Thu, 07 May 2009, 04:13

Hemonster wrote: Hey Woody,

Are you still interested in EVPST cells as well? I thought of getting a few samples, but wondered if you had already got them and done some testing?

The EVPST still look the best to me, but I haven't got samples or the equipment to test, and I'm not buying them for 6+ months so I haven't got my act together.

The EVPST - 10 and EVPST - 7 are the two that interest me most, the EVPST- 12 would be fine if I wasn't a leadfoot and the Optimum 8 fits in above the 12 on my list. I can't see the point of the EVPST - 8 as it's the same weight as the 10 with less capacity and power, wheras the 7 is smaller and lighter for almost the same capacity.

I see a pack of 224 cells peaking at:
1. EVPST-10: 175kW
2. EVPST-7: 127kW
3. Optimum-8: 80kW
4. EVPST-12: 66kW

Cheers,
Woody

Post by **Johny** » Fri, 08 May 2009, 17:29

This looks like as good a place as any to put these ramblings.

AC Induction Motor with commercial VFD.

Target range of around 40km - HOWEVER, I would like about 10km "grace" for the once-in-a-while occasion - more later...
Assume 200wh/km for the sake of this post.
Need a 600 VDC pack.
Need 90 Amps for 60 seconds (I'm going to regard this as continuous as it is not really "peak") but this may rise to 130 Amps once the car is on the road and I start "playing".

The EVPST 10 delivers the power required but at 80% DOD only gives us 4.8kw/h which translates to 24km range.

So to get close to the target range, 20ah cells are required.
Lithium 20Ah cells are usually low-rate discharge - limited to 3C or 60 Amps. High rate Lithium cells are almost double the low-rate price per Ah. BTW the EVPST 12 is only 4C so 50Amps - not enough.

The only reasonable available 20Ah cells are lead-acid AGMs. There are lots to choose from but then we need to keep DOD to around 50%.

20Ah at 50% gives 6kw/h which translates to 30km range. The "on-occasion" extension is also there so 50km is possible with care and the knowledge that the pack has suffered a bit. BUT, as we know they are H_E_A_V_Y.

I can see why the commercial AC designers keep to less than 320 VDC - the cell availability lends itself better to these voltages.

A boost converter is not beyond the realms of possibility and we have seen a few examples in links posted on the AEVA Forum recently but it's a big project just in itself. The ultracaps topics indicate a boost converter is the ultimate answer there as well. Dream on John...

Anyway, I have a feeling that others are in the same boat as me - hemonster for one.

The 30Ah cells that weber/coulomb are pursuing may be interesting but I haven't seen a price yet.

Ramble mode off.

Post by **Hemonster** » Fri, 08 May 2009, 18:04

Hey Johnny,

Exactly in your boat. Though I've written to EVPST to send me 2 samples of each 10AHr adn 12AHr cells. I plan to test these using a labjack setup such as Ian did on Zeva.

I don't need the sort of lead foot power levels that you're after, so 50A is quite adequate for continous, range is more important to me so I'm happy with the specification of the 12AHr cell - so just need to verify it's discharge curve over its "rated" limits.

Also note that a 20AH AGM is the rating at 2Hr (or 10A, or 6kw at 600V). At the amps that you are talking about this needs to be heavily derated due to peukert. You may look good at the lights, but you may have to stop after <20km if you want to continue behaving that way

I found that BMI is a good alternative but is at least 1.5 times the price (for the same quantity of cells) which is out of my budget range - thought they are very nice looking cells (spec wise). Need to win lotto

... then its A123 all the way.

Post by **woody** » Fri, 08 May 2009, 18:13

Johny wrote:4.8kw/h which translates to 24km range

Simon's Niki is doing 133 Wh/km wall to wheel with DC Lead Acid.
MightBoyEv is doing 88 - 100 Wh/km battery to wheel with DC Lead Acid.

Why do you think 200 Wh/km ?

I would have thought our little old cars would be about half or 2/3rds that, especially in flat old melbourne...

Wall-to-battery isn't all that relevant to range, it's battery-to-wheel, i.e. the amp-hours used.

Also 224 cells x 3.2 x 10 x 80% = 5.7kWh

85 Wh/km -> 67km
100 Wh/km -> 57km
133 Wh/km -> 43km
150 Wh/km -> 38km
200 Wh/km -> 29km

I work out 50 Greensavers @ 50% Dod = 6.6kWh (but extra 233kg)
50 Firststart 18Ah (12.6Ah 2 hour race) @ 80% DoD = 6.6kWh (extra 188kg)

The main hurdle is the price (2-3 times), but the lifetime should be 3-4 times.

Mostly this is me trying to convince myself to hold out for LiFePO4

Post by **Hemonster** » Fri, 08 May 2009, 18:30

woody wrote: I work out 50 Greensavers @ 50% Dod = 6.6kWh (but extra 233kg)
50 Firststart 18Ah (12.6Ah 2 hour race) @ 80% DoD = 6.6kWh (extra 188kg)

Anecdotally I've seen mentioned that cruising 50-60km/hr is about 6-7kw required? However during modest acceleration you should expect say 30kw (conservative) which is 50A. From a GS cell this is could take approx 20 minutes to discharge the cell, hence it becomes a 16AHr cell. 50% DOD of that is 8AHr or 4.8kwhr. So I guess expected capacity out of the battery is somewhere between these numbers when accounting for cruising, acceleration and regen.

woody wrote: The main hurdle is the price (2-3 times), but the lifetime should be 3-4 times.

Mostly this is me trying to convince myself to hold out for LiFePO4

Yea, me too ... it was either that or compressed air

edit: added GS discharge picture.

Post by **Johny** » Fri, 08 May 2009, 18:39

Hemonster wrote:I don't need the sort of lead foot power levels that you're after,...

Splutter, cough - that's what I say to woody!
With 90Amps max. motor current I do 0-100Km/h in just over 20 seconds.
Acceleration from 60 to 100k/h is about 11 seconds. I don't think these are drag-racing times.

I REALLY don't intend to use this performance much at all. My primary goal is to get to and from work without causing other motorists any grief.
I have to travel 4.2km at tollway speed then about there is about 6km at 70-80km/hr with some 7 degree inclines. The remainder of a 15km one-way is at 60km/h.

woody. I purposely look on the pessimistic side of range figures - partly due to the paragraph above.

My overall feeling is still to go lead-acid - even dropping to 45 batteries if needed (for weight) to assess the range and other stuff for a year or two before deciding long-term battery strategy.
I will drive this car every day - 30km plus side trips, so it'll get a lot of work.