Anyone here riding with polymer li-ion battery packs?

I've been wondering if it's not too an idiotic idea to use polymer li-ion packs on a XC bike. The idea of having something like that in by backpack or between by legs (in a water bottle on a bike frame) doesn't really attract me much. Are these batteries ok with jumps or some downhill action? I'd need a rigid case for it, right? Anyone done that?


The difference between these and LiFePO4 of the same Wh would be almost twice the weight. Did anyone make a similar choice yet? What did you choose? Or, what would you choose?

Are LiOn packs known for not handling shock well?

Megavvolt said:

I've been wondering if it's not too an idiotic idea to use polymer li-ion packs on a XC bike. The idea of having something like that in by backpack or between by legs (in a water bottle on a bike frame) doesn't really attract me much. Are these batteries ok with jumps or some downhill action? I'd need a rigid case for it, right? Anyone done that?

Click to expand...

If you do it right, it's no more dangerous than having a cell-phone along through similar jolts. (Well, I assume you're going for higher capacity, so more serious consequences if it does blow, but same risk of an incident.) I don't think the shocks would be an issue at all.

The difference between these and LiFePO4 of the same Wh would be almost twice the weight. Did anyone make a similar choice yet? What did you choose? Or, what would you choose?

Click to expand...

What sort of charge and/or discharge rates are you looking at? LiFePO4 are good for insane power density, but unless you need that, you'll get better energy density from LiMn (also safe), narrowing the gap a bit.

I think I'd be OK with the LiPoly; certainly as much as for any street-bike application. But the notion of using off-the-shelf power-tool packs (e.g. Milwaukee V18) with a chopped-off power-tool baseplate mounted on the bike, and a velcro strap for extra security, would tempt me for any bicycle application -- it's so much simpler than rigging your own, and the prices for commercial water-bottle-batteries of any sort looked insane last time I looked. I've been using self-contained lights thus far, though.

The battery is for a HID or a powerful LED light, not for an e-bike.
I don't need crazy discharge rates.

Say you'd have to choose between a water bottle 12.8V 6400mAh LiFePO4 battery and Polymer li-ion 13.2V 5700mAh aluminum box battery:

$110 and 15oz against $160 and 1.5lb

The weight and pricing are from a web store. Do they look realistic?

LiFePO4 has to be heavier, but obviously the AL box adds quite a bit of weight to the polymer battery. Stripping it and heat-shrinking it then doesn't seem like a great idea, but how else can I get the advantage of the higher WH/Pound ratio?

I'm planning on doing this. My plan is to make a hard case that can survive a decent impact, and then surround the battery itself rubber or foam that just barely fits in the case.

I haven't totally figured out if I want to seal it, or vent it, or what...

Ok I'll do it. The moderator will probably remove the links later, but maybe I'll get someone's reply first.

I am looking at two batteries, one is LiFePO4 and another one is li-polymer.

The LiFePO4 one is 12.8V 6400mAh (82 wh), and the weight is 15oz (0.93 pounds).
The Polymer Li-ion is 13.2V 5700mah (84.36 Wh), and the weight is 1.5 pounds.

http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=4834
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=4442


LiFePO4 batteries are supposed to be almost twice less effective in terms of wh/kg when compared to Polymer Li-ion batteries. Why such a 'wrong' difference in weight?

Is this because of the aluminum box of the Polymer battery? Will I be able to use a shrink-wrapped Polymer Li-ion at some downhill? Because if I have to put it into a aluminum box the weight seems to be ever worse than with LiFePO4.

I have a batch of 700mAh lipoly batteries I got on clearance for $1 that were made for toy airplanes. They are in hard plastic shells, but they are very light for their capacity. I've been thinking about using those for lights.

I've been using shrink-wrapped LiPolys for my light. This is used for road riding so I don't see the same amount of shock as you will on XC trails, but they have been perfectly OK so far.

I use a set of 6x2200mA LiPoly cells from an RC place and carry them in a fabric carrier that held onto the frame / handle bar stem with velcro. Capacity is 48Whr, overall weight is about 300g (0.67 lbs).

Looking at the links you posted, the LiPoly one is made of 4 cells which weigh 105g (3.7oz) each. The extra weight from the pack must come from the case and regulator. The LiFePO4 pack is made from 8 cells which weigh 104g each - total is 832g (1.8 lbs). I think the web site has incorrectly calculated the weight of the LiFePO4 pack which is why the energy density is wrong.

Oh, that explains it, thank you BillyNoMates.

you guys do know that basicly all "explosions" from liPo happens during charging use balanced charger to keep the cells on same lvl ect.
second option for explosion is shorting it but i dont see that happening if you make a decent application for it.

atleast i wouldnt be worried using a lipo on an xc bike.