I am building some LED bike lights for use on a 24hour endurance MTB race, they are going to be BRIGHT..

But... I need some fairly chunky Li-Ion batteries, something around 14V with 4Ah would be nice.... I have seen pictures of packs/cells of this spec with built in management (over/under charge etc)...

Anyone know where such things can be purchased at reasonable price?

Tried the usual suspects, Rs, rapid etc, but no luck...

Try brchobbies.co.uk they supply the electric model batteries and have many to choose from.

Couple of somethinng like this maybe

Ebay Laptop Battery For Asus Eee PC 2G Surf 4G 8G NetBook on eBay (end time 01-Jun-11 08:42:07 BST)
ELAS002W

noticed a black & decker drill also used them...

Cheers

Rich

Had considered laptop batteries, but not sure how I would charge them.... Would be a cheap solution though if I could charge them

brc do the chargers too

Might be worth a look here.

I bought a new battery for my aged laptop from them - sound piece of kit. They sell all sorts of battery packs, individual cells, and so on.

hobby king is amazing

http://www.hobbyking.com/hobbyking/store/index.rc

I'd be tempted to use a 4S 5000mAh lipo in a hard case. You can get simple chargers for it. You'ld need some kind of cell monitor but BRC sell a little thingy that plugs into the balancing plug and squeeks like crazy when done.

i've got about 30/40 laptop batteries that i was going to make a power pack from for an electric bike but never got around to it, yours for the postage if you want them.

Perhaps you might be thinking of these?

http://www.electricwingman.com/13v-lead-acid-replacement-battery-4,6ah-clear.aspx

A123 cells have the advantage that you can seriously discharge them without problems. With a LiPo you'll puff them and perhaps even get them to burn. Which if it's between your legs might not be a good thing.

Hmm.. thats prettty big, heavy and expensive! I can get a 14.8v 3ah battery from hongkong for about £50... Still a fair whack mind... Laptop batteries might well the a good call, IF I can understand how to charge them

LI-PO RC flight packs are cheapish now

I have buought from here a few times

These are 2 cell pack but 2 packs for < £25 is still cheapish.

LINKY

No cell management so.
I built low voltage cutouts warnings into my LED drive PCB.

Blinked the LED lights when they started getting low and off when low.

Martin

[Edited on 3/5/11 by rf900rush]

Hows about buying yourself a 14.4V li-ion cordless drill. Then you get your batteries, a charger, and something useful to use after this crazy 24 hours of cycling

I have made my own LED lights and run them off 11.1 V Li-on battery.

I use a Mystery blancer charger and all the stuff has survived 2 winters. The LEDs are 5 W emitters and from memory, the battery should power them for 4 hours - never had them run out as I charged after every run or 2 runs (1.5 hour round trip)

Battery (HOBBYMIX 11.1V 35C 3000mAh LIPO Li-po Akku battery rc ; seller Member ID bulk-verkauf ) and charger (seller cwtco) was sourced on ebay.

Agh nice one, there are some quite good value ones from abroad, will put the lights together and then see what size batteries I need to get the light output I need :-)