# LiFePo4 Charger



## dimitri (May 16, 2008)

As long as the charger does not put out more than 40 volts, it should be safe for 10 cell pack.

Check the max voltage of those chargers you found ( post links here if you can ).


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## gte718p (Jul 30, 2009)

several people sell this one but I can't find any info on it.

http://www.bmsbattery.com/product_info.php?products_id=38&osCsid=6ff818bdcb75b74ee41a75d18ebc38b9

http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=2150


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## dimitri (May 16, 2008)

Unfortunately they seem to be designed for packs that have multiples of 4 cells.

For example this charger from ELite Power is for 12 cells and has 43.8V output, which would fry 10 cell pack.

Next model down is for 8 cells, so not enough voltage for 10 cells.

http://elitepowersolutions.com/products/product_info.php?cPath=9&products_id=50

You probably be better off to get 2 more cells, get better range and speed while at it.


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## jorhyne (Aug 20, 2008)

I'm curious as to what led you to buy 10 batteries for a motorcycle conversion? 32 volts nominal isn't much for that kind of project.


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## gte718p (Jul 30, 2009)

jorhyne said:


> I'm curious as to what led you to buy 10 batteries for a motorcycle conversion? 32 volts nominal isn't much for that kind of project.


The main reason was space considerations. 10 Fit perfectly. Will its low voltage I figured it would do what I want it to do. 3C discharge of 100 ah cells should be enough to get up a hill, and its mainly an intown commuter.


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## frodus (Apr 12, 2008)

what motor? I doubt you'll be able to get to any decent speeds with 32V, especially with voltage sag.

Why did you think you'd need 300A of battery current?


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## gte718p (Jul 30, 2009)

Mainly b/c I am running a low voltage system. I may be incorrect. It turns out I measured incorrectly I made a NASA error converting metric to english units. I have room for more cells so I'm in the process of ordering two more cells. Helps with the charger, and will help with top speed.


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## frodus (Apr 12, 2008)

why are you "required" to go lower voltage?

Can you answer the previous Q's?
what motor? 
Why did you think you'd need 300A of battery current?


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## gte718p (Jul 30, 2009)

Sorry I missed the motor question. Its the ETEK-R and ALTRAX 4834 controller. 

I had good luck using the origional ETEK 10 almost years ago with 3 AGM batteries on a go cart. With the LiFePO3 batteries I'm going to be about the same weight. I also wanted to hide everything inside the frame so it limited how many batteries I could carry. This is also an introduction to the LiFe chemistry before I mode on to my car. I'm trying to do this on a budget so that's a limiting constraint.

I don't expect to pull 300 amps regularly. However pulling 300 amps at 32 volts is almost 10kw. I thought that would meet my performance goals.


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## frodus (Apr 12, 2008)

300A PEAK is motor side and isn't equal to the draw on the batteries.... 

My motorcycle (signature) had 150A peak lead batteries. I could do 400A on the motor side. Power in is power out.... but current in doesn't always equal current out.

My point is that even with the current capability of the batteries, you likely won't see over 150-200A on the batteries with that setup (300A controller). BUT you'll have all the torque you want for that motor/controller setup and you won't stress the cells. So its doubtful you'd ever be giving full pack voltage to the motor at the same time you give it full current. It'l be less than 10,000W. I'd think it'd be more like 5-6000W, just a guess.

As far as speed, 36V is going to be slower than you might want, but it should be good for zipping around.


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## gte718p (Jul 30, 2009)

frodus said:


> 300A PEAK is motor side and isn't equal to the draw on the batteries....
> 
> My motorcycle (signature) had 150A peak lead batteries. I could do 400A on the motor side. Power in is power out.... but current in doesn't always equal current out.
> 
> ...


I realize that. There are also efficiency issues, and I pay price in losses for running around at high amps. 
My plan is to gear it for a top speed of around 40mph. Speed limit in town is 35 and strictly enforced and I'll never take it on the highway. I have several cars and a trailer for long distance so its not really a concern. I'm hoping all the available torque will give me something that fun to run around town on.

I'm building on a 94 yahama xj600 frame. I really want a newer looking bike, so if this doesn't work out I may do a complete redesign with more batteries on a new frame


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## frodus (Apr 12, 2008)

35-40 should be doable.... definately have to gear it low though, the RPM/volt on the etek wouldn't make it spin very fast at 32/36VDC.

You'll be sacrificing efficiency and likely going to peak out the controller/motor at lower RPM due to the gearing. Just make sure its cooled sufficiently.


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## gte718p (Jul 30, 2009)

I'll look into the cooling. Thanks


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## gte718p (Jul 30, 2009)

Well the bikes done, with the exception of paint. It's a ton of fun. I need to drop the gear ratio on the front. A 13 tooth drive was the only thing I could source locally, however I really want to have a 10 tooth. Should be easy enough to order. Right now it will not get out of it's own way on a hill, but once it's moving it will fly.

I'm still struggling with the charger. I bought the elite power charger. However it is only charging the pack to 41 volts. That seems low for a 12 cell pack. I believe, please correct me if I'm wrong, a full charge should be more in the 46 to 48 volt range. The spec one the elite say final voltage should be 43.8 but I'm not seeing it.


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## frodus (Apr 12, 2008)

I would heavily recommend against a 10 tooth on front.... its too tight of a radius for such a high RPM. I honestly wouldn't go below a 11, and thats cutting it close. There have been many others on ES and ELmoto that have seen the same thing. Its noisy, and it wears the chain more (due to the tighter bend).

Charging voltages for most lifepo4 cells is in the 41-44.8 level (3.65V a cell). The nominal voltage is 3.2V a cell. Look at some charge profiles, the chargers don't HAVE to go to the 4V range. Since all lifepo4 is not created equal, most chargers are made for the lowst upper voltage of the cells it will charge, which is right around 3.65V. At 41V, you're getting 3.4V a cell.... which is ok. Does the BMS kick on?


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