How can i replace the battery to my eco drive bl5140 watch

SOURCE: eco-drive watch battery recharging

well here it is and you are gonna kick yorself! just had the same problem, put it in light and nothing. you need to pull the pin as though you are setting the time and then just wait, not long just a minute or so ......... and hey presto you're sorted. push the pin back in and its working. if not good luck.

SOURCE: Citizen Eco Drive watch

The Citizen Eco Drive watches use special recharchable batteries.
I started collecting a couple of watches and I noticed sometimes a jeweler replaces them with an ordinary battery. The watch will work and at the same time it will try to recharge this one until it explodes! In newer models they made it harder to use the non-rechargable ones by adding a special connector or clip to the rechargable battery types.
Okay, if you say your battery goes bad, did you store your watch in a drawer as many people do? It may have lost the charge over time. First thing to try is to leave it on the window sill so the dial is in the sun. It will start ticking, but please leave it out there for 3 days to a week. The seconds hand will tick irregularly in steps of one and two seconds, to show you it wants you to readjust the time, as it knows it has lost time. Adjust the time and it should run smoothly.
The seconds hand should run in single second steps, if it takes steps regularly, but every 3 seconds or so, it tries to tell you that its power level is going down. It will be able to continue for one or two days, but you should get it into the sun more often.
Charging the battery under a lamp is possible, however this heats up the watch and this may reduce battery life.
If you need to know more about the Eco Drive, look for detail tech manuals for all types here: http://www.citizenwatch.com/downloads/tech/tech.htm
Those are great watches as long as you remember it needs light to charge.

SOURCE: what is the proper battery placement or orientation for eco-drive

The Citizen Eco Drive watches use special recharchable batteries.
I started collecting a couple of watches and I noticed sometimes a jeweler replaces them with an ordinary battery. The watch will work and at the same time it will try to recharge this one until it explodes! In newer models they made it harder to use the non-rechargable ones by adding a special connector or clip to the rechargable battery types. If you look into the place where the battery goes, you will see a shiny spot where the metal clip needs to touch. If not sure, find the link to tech docs below.
Okay, if you say your battery goes bad, did you store your watch in a drawer as many people do? It may have lost the charge over time. First thing to try is to leave it on the window sill so the dial is in the sun. It will start ticking, but please leave it out there for 3 days to a week. The seconds hand will tick irregularly in steps of one and two seconds, to show you it wants you to readjust the time, as it knows it has lost time. Adjust the time and it should run smoothly.
The seconds hand should run in single second steps, if it takes steps regularly, but every 3 seconds or so, it tries to tell you that its power level is going down. It will be able to continue for one or two days, but you should get it into the sun more often.
Charging the battery under a lamp is possible, however this heats up the watch and this may reduce battery life.
If you need to know more about the Eco Drive, look for detail tech manuals for all types here: http://www.citizenwatch.com/downloads/tech/tech.htm
Those are great watches as long as you remember it needs light to charge.

SOURCE: HOW DO I SET MY CITIZENS ECO DRIVE WATCH

You can get a set of instructions from their web site "citizen.com", select "technical support" and the "setting instructions" and then enter the details off the back of your watch.

You will then be able to download instructions.

SOURCE: can an eco drive battery be replce?

You can easily replace the battery.
You can buy it for $19 from Ebay
Check your caliber on the back of the watch and buy the right one