Replacing Skidoo 12v SLA with LiFePo4

Ypedal

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A while back, i built a lipo pack for a friend with a Honda CRF450 to power an HID headlight, for winter he rides a Ski-Doo and this is another project for more light and at the same time lighter battery !

Ski-Doo - Renegade 800cc 2 stroke
 

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The PSI pack would be 4 lbs instead of the 20 lbs sla.. but 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.. and one Dealt pack arrived 4 days later !

Got it tonight.. hacked it apart..
 

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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 properly.

So, after some emails, and i'm going to need help with this one but aparently i can wire up a DC-DC in series with the 12v pack and up the voltage for the light..

So.. got this :
 

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And that's where i'm at tonight.. I am grouping pairs of M1 cells in parallel, then going to wire those in series, no BMS and no monitoring, 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 meter and registered 60 amps cold cranking, and 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 !!!..

Fun times !.. will update as i go !
 
Cool.
I want to do something like that for a motorcycle battery replacement.
The typical voltage when the engine is running is around 14v. If you divide this by 4 cells, that gives you 3.5v per cell, which is a bit on the low side for LiFePO4, but might be good enough. I don't think you'd have to worry about shortening the life by holding them at that voltage for long periods. If you had some real simple 3.6v or so shunts, no cell should get overvoltage.

If you forgot to turn off the ignition or left a light on, you could run one to the destruct point, so an active cutoff would be the safest thing, but a pain in the butt to implement.
It seems like you can take them down to zero without killing them immediately, but a cell reversal is instant death. Some kind of beefy diode across each cell to prevent reversal in the event of overdischarge might be better than nothing.
 
Ypedal,I can give some info on the subject of Skidoo's,I was the Skidoo mechanic and warranty repair mechanic for all Skidoo's in the Yukon for 5 years,so I know a few things about them...
First,all the battery does in a Skidoo is operate the starter motor,period. Skidoo models without electric start have no battery,and only use a regulator(that limits voltage to about 13-14v by dumping excess volts to ground,voltage keeps climbing with revs without one) in the charging/electrical system,in fact the lights and acc. are running on AC power from the motors charging coils. A model with a battery and electric start has a regulator/rectifier so the battery will be charged with DC current. Start the machine and check voltage at the battery terminals and at the headlight bulb socket to test generator output voltage at various rpms. I don't know if this will be correct for charging a LiFePO4 battery,maybe rig a charger into the system somehow if necessary...
Will Li-FePO4 hold charge for long periods in extreme cold,maybe how cold it gets where you live matters a bit...I think it will be fine,it only has to spin the motor for a couple of seconds to start it. You still have a recoil starter in emergencies anyway.
As for the stock Skidoo headlight bulb,they were a normal quartz bulb,I used to replace them with a higher watt bulb from the auto-parts store,a stock bulb is usually 55H/50L(Watts),a good replacement is a 100H/80L. I used these bulbs in my truck's Bosch headlights too and they really light things up! I wouldn't worry about the extra current draw,the generator is made to handle extra acc. like heated hand grips etc.
A good idea to lighten your sled! :)
 
There is virtually no difference in capacity of a A123 cell charged to 3.4V and 3.65V See the first post in my thread http://endless-sphere.com/forums/viewtopic.php?f=14&t=20698&start=0&hilit=and+other+effects where I tested lots of A123 parameters and behaviors.

Also, A123 recommends a "float" charge voltage of 3.45V From my testing, it can take quite a bit more time to fully charge the cells at the lower voltages. If your alternator is charging the pack at a little to high a voltage, you can use some seriesed diodes to drop the voltage.

Wasn't Gary working on a black box LiFePO replacement for lead-acid batteries? ... a mini-bms that does all the charging/protecting of the cells that can be sealed up in the pack.
 
cut some squares of copper sheet.. and cleaned up the edges with a grinding disk to prep for solder...

edit to add : after grinding down to shiny copper, i cleaned it with solvent before soldering, even dirty fingers can give you grief when trying to get a quick clean solder, always wipe down with solvent and try not to touch the spot you plan to solder !
 
after some googling.. and checking various sites like :

http://www.offroaders.com/tech/12-volt-wire-gauge-amps.htm

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.
 

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I was about to seal it up... then 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...

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