Electric Bikes - Beginner need help

Hello, I just registered here as i recently wanted to revive an e-bike i got back in 2004. Below is the a pic of the bike.
http://www.fetgrek.com/elbike.jpg

The problem I'm having is its terribly weak, it can hardly assist my younger sister who weigh very little. The bike itself and the battery weigh around 44kg which i think is quite heavy. But it should still be able to push more.

The Battery is a -> 12Ah 36V I think. It also says "12AH,12v/3pcs"
Brushmotor 250W 2800r/min 36V 1.oNM

It says its suppose to go, 25km/h(15.5mph) but that never happens. I actually tried to bypass the small black box on it, I think its the "controller", and wired the battery directly to the motor but and it sounded like it spun faster, but the second time i tried it with the wheel on the ground, the battery fuse burned/broke. So now i need to replace the fuse :\ Does anyone know how i can make it stronger without breaking the fuse? and hopefully use the controller as i want to be able to throttle the speed.

Thanks for any help!

I think I have good news for you.

Everything seems fine with your bike except the battery (easily replaced), and the fuse that you busted.

If you leave a lead acid battery sitting for a few years, you can expect it to lose most of its capacity. Lead acid batteries are intended to be stored with a full charge, BUT they generally will lose a significant amount of their charge in the first 6 months (possibly even the first month) that they are left sitting. As far as I know the remedy is to store them plugged in to a "trickle charger". At this point, your batteries are probably beyond being usable and it makes sense to replace them.

The label on your bike tells us what kind of batteries it had. I assume they're in a plastic case, and it's probably easy enough to remove the plastic case, replace the batteries inside, and your bike will be almost like new.

So the batteries you want are ones the same size and shape as the originals, and intended for "deep discharge" use. There are three, and each is a 12 volt 12 amp hour battery. If you happened to find (for example) 12 volt 15 amp hour batteries or 12 volt 10 amp hour batteries, they'll be fine as long as they fit well in the space you want to put them in. You will have to wire the batteries in series (http://en.wikipedia.org/wiki/Series_and_parallel_circuits) to total up to 36 volts; don't go with any other voltage unless you are aware of the risk of damage to your bike. Any number of amp hours is fine but changing the number of amp hours will change the range you get. Batteries other than Lead-acid batteries are fine but require a different charger.

It sounds like your batteries are dead, which isn't unusual if they've been allowed to sit completely discharged for 5 years. If you don't want to buy a new charger, try to determine what type of batteries they are and stick with that type. Otherwise, you might consider buying a LIFEPO4 battery pack, but you'll need to get a charger, too. Good luck.

By the way, I wouldn't ever recommend bypassing the controller except unless you know how to custom design an e-bike that is intended to be used without a controller.

Thanks guys, I actually used it for like 2 years so i would say it's been in the garage from 2006, i also left it with the charger plugged in, either way it does make total sense this problem is caused by a dying battery. I'll look into purchasing a new one, i fear its going to be tough, in my town(Umea/Sweden) there's not that many shops selling this kind of stuff.

I will make sure i wire it back through the controller once i replaced that busted fuse. Don't want to break another one.

Thanks

If you have Sealed Lead Acid (SLA) batteries, be careful if you don't have a 3-stage, smart charger. You can kill SLA batteries leaving them plugged in all the time to a 2-stage charger (sulfonation). (FYI, if these are SLAs, check with stores that sell replacement batteries for UPS (uninterrupted power supplies), they may have suitable replacements for you. Good luck.

btw, is it safe for me to get a multimeter and measure the output of the battery? I'm curious as to how much it actually puts out now a days.