LiPo for Bike lights?

[unterhausen]

Chris, I hadn't even thought about usng the drivers with low voltage cutoff. Great idea.

Just when I realize how useful it is, taskled goes missing. I think it's the only way, otherwise you're duplicating much of the driver in the low voltage protection. This thread was useful, from now on I'm using liIon when I buy batteries. The only reason I'm using lipos is that I had them, and they were throw-away cheap.

 

[chris_m]

Not managed to get near the scales, but realised I had done so previously and posted the results on a different forum.

My 2 cell (7.4V) 2230mAh (got my maths wrong before - they come from a 4460mAh laptop battery) pack weighs 101g including (short) power cable, balance cable and fuse. On that basis a similar 11.1V 2230mAh pack would weigh only ~152g. Beat that with a LiPo!

I'm sure TaskLED will be back shortly - according to Ifor he's just away for a month. Since I was already using low voltage cutoff with NiMH cells and my custom LVR when I went to LiIon, I've never felt the need for a separate protection circuit, and hence always happily used bare LiIon cells from ebay laptop batteries. Was one of the principle reasons I developed custom bFlex/Maxflex firmware, since at the time there was no low voltage cutoff in the stock firmware.

 

[LukeA]

On that basis a similar 11.1V 2230mAh pack would weigh only ~152g. Beat that with a LiPo!

I have a 11.1V 2400mAh Lipo pack that weighs 156g.

If you do the proportion to reduce the weight of the lipo pack pack to 152g, its capacity is 2335mAh, which is 105mAh more than the li-ion pack.

 

[worldedit]

U can use transmitter pack. They are cheaper and lighter than normal packs. The have less discharge rate, but you wouldnt want a bike light that has 5min runtime anyway.

 

[chris_m]

Well for the sake of Lithium one-upmanship, http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=1199 is a 99g 7.4V 2400mAh pack. The only reason mine are a bit lower capacity is they're not quite state of the art (been using those cells for 4 or 5 years).

Though the point wasn't really which are a fraction lighter - I was just pointing out that the idea LiPo were lighter (to any noticeable extent) was a fallacy.

 

[Jamesdh266]

Ok well weight wise I guess they are about the same but what about $ per mAh?

I know the top of the line LiPos that have large C ratings are very pricey but what about the middle or bottom of the range?

Zippy (good middle of the range brand) LiPo 2200mAh $13
http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=6540

Batteryspace pack (Chinese cells) LiIon 2200mAh $22
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=5061

 

[herulach]

To add another question, what charger's do you use for LiPos? Are the cheap dX/Ebay ones ok?

An advantage of 18650s is the cheap chargers

 

[LukeA]

To add another question, what charger's do you use for LiPos? Are the cheap dX/Ebay ones ok?

An advantage of 18650s is the cheap chargers

I use the DX one.

 

[Jamesdh266]

I use the IMAX B6 which is a cheap imitation of the really expensive Bantam ones. They are only inacurate though because to balance the cells they use 1% resistors. There is a guy on rcgroups.com that sells an upgrade kit for a few euros of 0.1% resistors and since then it has charged and balanced to within 0.01V which is pretty good for about $40-$50.

I wouldnt use a really really cheap one but middle of the range is ok if you know what you are doing. I guess they are a bit harder to use than the simply plug and charge LiIon ones.

Do you need to balance LiIon packs?

 

[unterhausen]

I use a pair of FMA Cellpro 4S. They have discontinued this model and put out a m[FONT=Arial, Helvetica, sans-serif]ulti-chemistry version that supports LiPoly, LiIon, LiFePO4, A123, LiMn, NiCd, NiMH, Pb

I want a 10S so I can charge bigger packs or 2 at once, but I can't justify it right now.


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