Citizen AS4020: changing the battery

This model of Citizen came to me having problems with the battery, basically that it did not hold the charge and could not perform operations with the watch.

When I decided to acquire the Citizen AS4020 for a great price, I didn't think I'd have to change the battery a few days later.

Although the advertisement explained the problem, I mistakenly thought it would be a typical problem with sundials: you stop using it in a dark drawer, the battery charge is consumed and as it does not receive light, it does not charge. Finally it stops.

In these cases, at least in most, it is enough to give them a good bath of light for days to gradually recover the charge and the watch returns to normal. This would not be the case.

Once I received it, I noticed that the charge level was very low: as soon as you tried to adjust the time, the hands would stay "halfway" and you had to leave it exposed to the light to charge it. I decide to leave it a couple of days next to a window charging... no way, it still has the same problems.

"Turbo" method for charging the watch battery

So we move on to b plan. This is a method that I use in extreme cases: once I am sure that the watch is waterproof, I leave it several days exposed to direct sun in a bowl or transparent glass submerged in water. In this way, we avoid overheating the watch and damaging it by excessive temperature in full sunshine.

Normally this method works very well, I try it and nothing ... it is clear that it is necessary to change the battery because it is damaged.

The first thing is to locate the accumulator model. Although the original is a Panasonic CTL920, this one is modified, including a brass connector, so we must look for a Citizen 295-69, which is the one indicated for the E670 module, which is the one used by this watch.

We start the change of the accumulator

Once you receive your new battery, it's time to get down to business.

The first thing to note is that Citizen AS4020 does not have a screw cap, but has a snap-on cap. We will have to look for a recess in the contour of the back cover where we will be able to make leverage to be able to open the clock:

Once opened, we can check the curious system of holding the battery in the clock module. I had never really seen it, so I had a hard time taking off the plate that prevents it from coming out of the module.

On the back cover, over the piezoelectric speaker, there is a sticker that warns us that only one battery designed for this module is used:

Once the old accumulator is removed, we have to place the new one. An important detail is to make sure that the position is correct before inserting the new battery. Make sure that the brass connector is inserted into the slot of the new battery.

The plate that holds the accumulator inside the clock module must be replaced.

We can take advantage of this to clean all the dirt we see on the case, and do a "reset" by removing the crown from the time position for at least 30 seconds. And we put the back cover back on. We can help us with a press to make sure the watch is properly closed.

As always, if we want to make sure it is completely watertight, I recommend going to a professional watchmaker for a waterproof test so that we can be sure that our watch will not drown.

We already have our AS4020 in top form!

It would be a good idea to leave it in the light next to a window for a couple of days, charging the battery to the maximum.