December 20, 2010

A123

Replacing the 12v SLA battery in a Ski-Doo !

From this :

to this :

( Insert picture of finished pack to come )

Using these :

Why ?

Well, a while ago, i built a Lipo pack to power an HID ( High Intensity Discharge ) light for a Honda CRF-450r dirtbike. But in winter the dirtbike gets parked and the Ski-Doo snowmobile comes out to play !

After a talking about lighting and lithium and all the strange things i do in my spare time , all my spare time, we decided to try and lighten the load and light up the ride with LED..

The 12v 20ah SLA battery weighs aprox 15 lbs

Each M1 cell weights 75 grams ( using 8 cells = 560 grams ) = 1.2 Lbs !

With the materials, wires, connectors, etc, it should all weigh under 2 lbs !

Below, location of the battery.

I originally wanted to use existing batteries i had here to test with.

Put this together :

12v 10ah PSI Lifepo4 !

It was just a little too tall.. and i mean " just " .. but to get that half inch of space we would have to relocate a bunch of stuff, including the starter relay, fuse box.. etc...

so.. a quick email to the good Dr of Bass from the sphere. and one Dealt pack arrived 4 days later !



Got it tonight.. hacked it apart..

Each dewalt 36v pack contains 10 cells in series..

But to make a 12v pack i need 4 cells in series.

8 cells = 4 Series and 2 Parallel

4.6ah , 12v

Below, notice the difference in size from the PSI ( 10ah ) and the A123 ( 2.3ah per cell ),

Four cells would have done the job, but since this will be used in winter and stored cold, i decided to double them up for good measure.

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For extra light, ebikes.ca Lumenators !

Now, a problem i have to deal with is that the Lumenators will work at 13.x volts, but don't light up fully, i need at least 15v to light up the CL's to full brightness ..

So, after some emails, aparently i can wire up a DC-DC in series with the 12v pack and up the voltage for the light..

So.. got this

It takes 12v in, and puts out 3v out, so taking that 3v in series with the pack powering it, i should get 15v !

I am grouping pairs of M1 cells in parallel, then going to wire those in series, no BMS, just straight up to the ski-doo in place of the SLA and away we go..

4 M1 cells x 3.65v = 14.6v , just about the hightest an SLA cell should go, i don't yet know how regulated the voltage is on the sled but we are going to find out !..

The starter was tested with a clamp-on-ammeter and registered 60 amps cold cranking, and settles down to 40 amps with the plug caps removed motor turning over without spark... so 4.5ah at 60 amps should be ok, even with sub freezing temperatures.. another item to test !!!..
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Ok.. soldered the + tabs to pair up the cells.

Had to use a small piece of copper to bridge one of the pairs..

Weird how the M1's are + and - reversed compared to almost all other cells.

And the negative side below :

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Dec 25 2010

Merry Christmas !

Relaxing at home, and working on this project.. awsome !

So i cut some pieces of G10/bakelite/fiberglass sheet stuff ( never sure what to call it ) to layer between the pairs of cells.



cut some squares of copper sheet.. and cleaned up the edges with a grinding disk to prep for solder...

Covered neighboring cells, just in case, I've been working with batteries for a while now and have scared myself enough times to take precautions against accidents, like dropping a copper plate across the wrong section of cells...BRrrrzzzzzzttt... smoke.. sparks... no thanks.

Turned up my hakko soldering station to max... working my way criss cross.. to prevent heating one place too much for too long.. I left the original tabs on the cells from the dewalt pack, just cut between the cells to seperate them, the original spot welds are good enough to carry the amps i need and by keeping the tabs i can easily solder to that and minimize the heat goin directly to the cell itself..

It's important to do the job quickly and you should be done in less than 3 or so seconds with the iron, otherwise let off and allow things to cool before you try again, very important to have the surfaces you want to solder to, clean, and washed with solvent to remove fingerprints etc..


The other side

Also notice the fiberglass pieces seperating the cells, not a must it protects the cells from eachother and helps give rigidity to the pack., plus it won't wear thru like the cardboard could do.. ( if water ever does manage to get in there.. )

Being carefull not to cover or melt the vents..

after some googling.. and checking various sites for Amps vs Wire gauge.

I was considering double 10 gauge leads with a pair of PP45's.. however i re-evaluated this and decided on a single lenght of 10 gauge turnigy silicone wire with PP75's.. it's a short run and will be in cold weather at all times so this will do ..

The A123 cells are strange in that the + and - ends of the cell are reversed compared to any and all other cells i've ever had my hands on.

I was about to seal it up... but decided to install ballancing leads, figured i'd kick myself for not doing this once installed on the machine and questioning the ballance of the cells... I plan to wrap this up pretty tight and will not have access to the cells for diagnostics..

Installed a 7 pin connector, and started from the + end... Doh.... the HobbyKing battery medic and celllog meters want to start from the negative...... grrrrrrr... un-soldered.. and re-soldered them into the right order ..

Done !

I only needed 5 pins from the 7 pin connector, so i just snipped off the extras and secured it all with hot glue.

All i have to do now is box this sucker up and seal it from water

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Dec 26 2010

Today i got busy with cutting up and bending some ABS palstic..

Started with a cardboard template, got a rough idea of how i wanted it.. basically trying to keep it water-tight so less seams the better ...

Getting better at bending this stuff..

Used Tuck Tape and went up the sides of the box, one more layer to keep out any possible moisture.. then backed it up with lots of hot glue...

Left the ballance connector just enough to plug in the CellLog..

With some help from the Endless Sphere, i hooked this sucker up and crossed my fingers..

 

Before adding the DC DC unit, just straight up 13v

 

And Eureka !!!.. it works !! 16v

Now i need to make a fancy box for the DC DC unit !

Endless Sphere discussion thread

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