Monday, July 11, 2011

How to Rebuild the Battery for a Merida TEV 500/550

If you are the owner of a Merida Electric assist bicycle, you are probably aware that it's impossible to get factory replacement batteries, because they are no longer shipped to the USA.

I was able to successfully rebuild my Merida battery, and it now works great! Total cost was about $100 with tax. It took me about three hours labor. If you are more mechanically inclined, you can probably do it in less time than I did.

For replacement batteries I used four WKA6-8.2F batteries from Batteries Plus. These are slightly different than the original batteries, but close enough in size and amp hours to work. The original batteries were two 12 volt 9 amp hour batteries (for a total of 24v 9 ah). Replacement batteries were four 6 volt 8.2 amp hour batteries (for a total of 24v 8.2 ah).

To open the case, unscrew the 4 screws at the base of the battery, and the two ones on the side where the power plugs into. You do not need to undo the screws at the top where the metal plate is. That area controls the ignition and can be left alone.

Inside you will find two SLA batteries that are wired together. You will need to wire cut the old batteries out. Cut the red wire and black wire close to the terminal connections (the two at the bottom right and left of pic above). The important thing is to leave enough wiring for when you put everything back together.

Add in the new batteries. You will need to wire them all together to complete the circuit. I was fortunate in that the guy at at the Kennewick Batteries Plus store soldiered all of my connections together and did it for free! Wire in positive and negative connections on the two ends, these will connect back into the electrical system. Notice that the four batteries fit in quite nicely. Sorry about the cluttered work bench. :)
Crimp the ends back into the wiring system. Use yellow 12-10 gauge crimps - available at any hardware store. Make sure the wiring goes in the same direction as when you pulled it out. :)

The fit is kind of snug for putting the cover back on. Make sure to neatly manage the wiring as best you can, so the cover will go.

Be sure to drop a comment if you do a replacement, I'd like to hear how the process went for you

Happy cycling. :)


Anonymous said...

hi there,
i have a merida tev 550, bought it used and the charge runs for about an hour, but on even the smallest hills the battery plummets and i am left riding a very heavy bike up a this likely due to the need for a new battery or is this standard for this bike? the battery takes a full charge but seems to not handle much stress at all. this is a relatively old blog post, i hope you see this. : ) at any rate i may try to make the battery, thank you!!

Kevin Jackson said...

Sorry, just notice this comment. It does sound like your battery is going dead. Steep hills do take more juice, however, I'm typically able to go up quite a few hills without the battery dying right away. Does you charge light register all the way to the top and stay there for a while? If it drops right away, that's evidence your battery is giving out. On a good battery it will stay at the top bar for a good 30 minutes or so of regular riding.