help for newbie

Hi and welcome to the site.

I don't know much about the Merida (never seen one in the flesh) but if you're missing the battery case it might be difficult to attach the batteries to the bicycle. Is it totally lacking a place to put the batteries?

An option many people have done is to use a rear bike rack with a bag on the rack, then put the batteries in the bag. I do this with one of my ebikes using a Topeak bag & rack. The charger goes in the back with the battery making it easy to plug in at any convenient outlet.

By putting 'Merida' in the search box at the top of the page I found several prior postings. And learned that the bike is designed for a 24 volt lead acid battery pack.

While it's pretty trivial to find small lead acid batteries -- they're the kind used for battery power backup systems such as emergency lighting systems -- it's also possible to get batteries using the lithium-ion chemistry. Lithium batteries have a higher power density meaning it requires less weight (and size) to store the same quantity of electricity. It will cost more however than the lead acid route.

You will do well to find a case-- e-bay might be a possibility. The case includes a keyed on/off switch as well as terminals to get the battery power to the bike. Placing the batteries in the case is ideal because it lowers the center of gravity compared to batteries on a rack in the rear. There are pictures around of a modified battery case that allows for larger batteries-- I was able to expand the size of my pack by cutting off the front and fastening part of a plastic rectangular ice cube container from Walmart to the case to allow more room. My first batteries were a pair of 12v 12ah sla's from Interstate Batteries($100.00) that worked well and lasted about 80 charge cycles over about 8 months. A month or so ago I ordered a lithium battery from pingbatteries.com ($350.00) that outperforms the sla for power and distance and is estimated to last over 1000 charge cyclces. The power and distance are great, but only time will tell whether the battery lasts as advertised.

Your biggest guide should be what you want to do with the bike: if you have a certain distance and speed (you can change the rear sprocket to pick up some speed for cheap) in mind then you can begin to find the necessary ingredients-- if you want to tinker then keep the purchases to a minimum.

If you want some pictures or sources for a sprocket, let me know.

Tilt, can you share which lithium battery did you buy and how did you install it? How do you charge it?

I bought a 24v 15ah battery from pingbattery.com and two chargers, so I can keep one at work and one at home. The battery has four leads-- two for charging and two for discharge. I wired the charging jack on the battery case to the charge leads, so I can still charge through the pack jack (I had to install a proper size connector on the charger cable to match the battery charge jack-- easy to get from Radio Shack). I wired the discharge leads to the input lines for the bicycle and everything has worked fine.

I posted some pictures of the battery and case at: http://picasaweb.google.com/wetzelb/2009MeridaImages#

Pingbattery.com has a wiring diagram available as a pdf download that shows the connections-- there was nothing fancy involved, just a bit of soldering for the charger to battery jacks.

I can get you more details if needed.