Currie iZIP - conversion to LiFePo4

S

steveclv

10 µW
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Mar 8, 2013
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I have just purchased a cheap Currie iZip with the standard SLA battery pack

I also bought a pair of 8400mAh 4S LiFePo4 packs intended for RC use (I fly model electric planes for a hobby and have the required charger) which I intend wiring in series to give me 8 * 3.3V = 26.4V - the packs have a maximum safe current delivery of 160Amps (20C)

As the motor on the iZip is rated at 450W, at 24V that equates to approx 20amps

Can anyone forsee any issues with simply replacing the SLAs with a pair of LiFePo4s and keeping everything else stock?
 
It sounds likely to be solid, excluding the potential mismatch in plugs. Typically, the voltage of a lifepo4 cell will be 3.65-3.7, that comes out to be 29.6 volts. I would assume that the controller will be able to handle that for a bit, it'll drop to 3.3 pretty quickly, but otherwise you should be fine.
 
Thanks

Changing plugs to some genuine deans will fix the problem I believe and give me the chance to put my inline watt meter into the circuit to check for max amp draw. Won't be as pretty as a bar mounted cycle computer but at $20 it's the cheaper solution :)
 
Let us know how the conversion goes. We would love to see some videos too!
 
Oughta work well. Just try not to discharge them too deep. Any kind of primitive battery level lights on the bike intended for lead won't work well with lifepo4, so a wattmeter would be good. Controller should have ability to handle up to 30v, but if you should run into any kind of overvolt cutoff, it won't take much to discharge 8s lifepo4 to 28v.
 
Did i miss read what you wrote? What lifepo4 do you have that can deliver 20c "safely"? Beside that the motor is rated at 450w but your controller is actually 35a. Of course the lead can't deliver 35a but the lifepo4 should. So you should feel a bit more power under throttle. Be sure you protect the individual cells from low voltage and don't count on that cheap throttle meter that is only looking at mass voltage. And don't expect the controller to cut out on LVC ether.

All Currie controllers made after 2007 have a voltage limiter set at aprox. 29.6v. An 8 cell lifepo4 pack fresh off the charger is 29.2v (3.65v per cell). I've been running lifepo4 pack on Currie setups for 4 years and not had a problem. I also run the motors on 16 cell packs (48v) using a 48v 50a controller. Started doing this last year and have logged about 300 miles at 48v and so far so good.

Bob
 
Thanks for the offer of the Deans but I avoid the copies - they typically melt when soldering whereas genuine Deans have a more resiliant plastic. They are great connectors if you use a good soldering iron.

The cells I'm using are the Zippy Flightmax 8400 4SP2 which are rated at 30C - that's great if you want to cook and egg on them afterwards but 20C is more realistic. I'm also using a good quality silicon wire. Will post photos and video when done :)

What does everyone suggest for an LVC cutoff - preferably one that is fully automatic and adjustable?
 
The cut all claimed c rates in half rule for what works well in the field still applies.

So call em 15c cells, and you still have no problem with discharging them at about 3c on the Izip.

Best thing for an LVC could be a signlab bms, from pingbattery. You could still bypass it for charging on your RC chargers, but it would give you cell level lvc set for lifepo4.

Lifepo4 is trickier for just watching a voltmeter for a manual human bms lvc because of the flat discharge curve.

If you chose lipo though, just watching a pack level voltmeter can work fine, provided you have no weak cells in the packs.
 
OK, I'll check them out.

I do have some low voltage buzzers for up to 6 LiPos but they are for LiPo and not for LiFePo4 and so probably the wrong voltage thresholds.
 
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