Electronics, Lighting, & Gadgets - need a battery!

I need a cost-effective high capacity battery for a biking project. Need 12 volts, about 20 AH or more. How powerful are some of the bigger bat-light batteries already in the bike world? Where do you get good battery packs cheap?

I'm not new to bikes or electronics, but am new to electronics on bikes, and what's commonly used.

Clearly, SLAs would be the least expensive, but heaviest and have the least number of recycling charges. What's it needed for, lights or lights and horn? If it's lights, you'd be able to go with something much less substantial with LED lights. LEDs draw little power. Off the top of my head, three good online sources for batteries at reasonable prices include www.batteryspace.com (http://www.batteryspace.com), www.all-battery.com (http://www.all-battery.com) and www.batteryjunction.com (http://www.batteryjunction.com). I'm sure there are others out there, too. You'll probably be getting some other recommendations in other replies.

Clearly, SLAs would be the least expensive, but heaviest and have the least number of recycling charges. What's it needed for, lights or lights and horn? If it's lights, you'd be able to go with something much less substantial with LED lights. LEDs draw little power. Off the top of my head, three good online sources for batteries at reasonable prices include www.batteryspace.com (http://www.batteryspace.com), www.all-battery.com (http://www.all-battery.com) and www.batteryjunction.com (http://www.batteryjunction.com). I'm sure there are others out there, too. You'll probably be getting some other recommendations in other replies.

It's nothing usual - a custom public address system to be on a bike. So far I think I want 25 watts of amp output and a speaker about the size of a Berthoud front bag. If I really need a 20 ah I'll probably try to do it with a pair of water bottle bats.

look for ebike batteries.
http://www.batteryspace.com/e-bikeskitandbatteries.aspx
the good stuff is Lithium Iron Phosphate, but you're talking $300 for 12v/20ah. But you're around $300 even for NiMH. The only way to get 12v@20ah for cheap is lead acid, where you can pick that up for $50.

The most I've seen i a bottle battery is about 5AH, so you'd need 4 of them to hit 20AH. LiFePO4 bottle batteries hit nearly 7AH, but then you're up to > $100 a pack.

Ok, then it's kind of as i was thinking, my requirements are too stringent, because that $$ for a bat is way too much.