# [EVDL] 20ah A123 lithium, first thoughts....



## EVDL List (Jul 27, 2007)

Well, I got my shipment of eight 20ah A123 Prismatics. Sure enough they 
have tabs, and look very interesting. The form factor is just a tad bit 
shorter than the 26ah Hawkers that are in my 1994 Geo, so it would be 
possible to fit them in the Prizm.

However first they go into the Robomower, then four more will make a 
pack for the Elec-trak.

In addition I picked up a BMS board from the cleanpower people. Nice 
little thing with one tiny problem (more on that later).

Inter-connecting these batteries is going to be a *pain*. For starters I 
used some stock aluminum bar and plastic bar to create a nice little 
sandwich effect, with threaded rods holding pressure from the sides. 
This very simple assembly allowed me to create a quick 12 volt test pack 
that did not warm up under a sample 100a load from my load tester. Then 
I put the batteries in parallel and let them charge on my bench charger 
set at a limit of 3.6 volts.

Second step was to get a BMS going. I drilled and tapped the aluminum 
interconnects to take a small screw to attach the BMS wires, then found 
that even though the lights on the BMS were green it's alarm was 
screaming. That's when I realized that the loop design on the cleanpower 
BMS holds for their centralized board as well. Since I ordered my board 
for 10 cells, it was configured for 10.

Cleanpower support is fantastic: They explained how I can change a 
jumper to allow 4 cells to work for testing, and now the BMS works 
perfectly. This is a well-designed board, I will be using it once I go 
to my full car-sized thing here.

Anyway, next step on my side is to get a really nice little drill press, 
since there is no way in heaven that I am going to be drilling more 
holes with a hand drill. One has to go very slow and smoothly. I like to 
consider these little experiments an opportunity to "upgrade my tool boxes".

After that I will re-design my interconnects to go through holes in the 
cell tabs themselves (with 1/4 inch spacers to insulate the threaded 
rods) and figure out a slightly better way to get power off the AL 
interconnects. One can't use copper of course, I'll have to see if Al 
and Nickel work well; if so I can simply nickel-plate some copper lugs 
and go from there. I also want to see how big a pile I can reasonably 
make that will be less than the height of a 26ah Hawker. Since we can 
remove the plastic spacers in the pack, I might even have enough space 
to fabricate a heat-sink system for the cells.

But first step is to run some more tests, then get them into the 
Robomower. The Elec-trak is an interesting test platform; it's cruise 
current while mowing is around the cruise of a Prizm (60 or so amp 
draws) and I can load it up with the tiller to get 200+ amp draws. Right 
now my E-15 is powered by a single string of 30ah BB600's, so a 20ah 
lithium stack should be a good test point.

Chris

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## EVDL List (Jul 27, 2007)

On Mon May 07 18:04:35 PDT 2012 [email protected] said:
>
>Inter-connecting these batteries is going to be a *pain*. For starters I
>used some stock aluminum bar and plastic bar to create a nice little
>sandwich effect, with threaded rods holding pressure from the sides.

I was looking at some of those cells as well.
Actually, the tabless ones, as they are considerably less expensive.
For a series string of them, could you just drill a pair of holes in each tab, then make a stack of batteries, alternating polarity, then just use some short bolts and washers to clamp the tabs together?


--

Worlds only All Electric F-250 truck! http://john.casadelgato.com/Electric-Vehicles/1995-Ford-F-250

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## EVDL List (Jul 27, 2007)

Where are you getting these from?

Sent from my iPhone



> Chris Zach <[email protected]> wrote:
> 
> > Well, I got my shipment of eight 20ah A123 Prismatics. Sure enough they
> > have tabs, and look very interesting. The form factor is just a tad bit
> ...


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## EVDL List (Jul 27, 2007)

On 5/12/2012 6:32 PM, Mike Golub wrote:
> Where are you getting these from?

Ebay. Just bought 4 more so I can make a pack big enough for my Elec-trak.

I also bought a small Craftsman drill press. Took a day to put it 
together, but MAN is it good for drilling holes in Aluminum. Doing it by 
hand is a screaming nightmare, this thing just zips on through at 600 
RPM. Another one of those "Why didn't I get one of these 10 years ago" 
things.

The second batch of 4 are assembled with drilled tabs. Much better 
interconnection than simple side-compression, and the 1/4 hollow tubes 
allow me to run the threaded rod through the top without problems. I put 
them on charge, and sure enough 30 minutes later the miniBMS shut down 
my charger. Turns out I accidentally was charging a full module with 3 
empty ones. Oops, but saved by the BMS. Excellent buy.

It's now charging away and I will leave it on all night. When the first 
cell is full, it will shut down the charger, no fuss or muss. Then if I 
have time tomorrow I'll drill some more interconnects and tabs and try 
to assemble the 24 volt pack.

One slow step at a time.
Chris



>
> Sent from my iPhone
>
>


> Chris Zach<[email protected]> wrote:
> >
> >> Well, I got my shipment of eight 20ah A123 Prismatics. Sure enough they
> >> have tabs, and look very interesting. The form factor is just a tad bit
> ...


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