JBL GO Battery extension

Recentlty, I scavenged a working JBL GO speaker, but with a dead battery. After using it few weeks in “wired mode”, I decided to replace it’s Lion battery.

Table of Contents

A bit of background

The JBL GO 1 was released back in 2016, offering a decent sound quality in a very compact form factor. JBL was advertising up to 5 hours of playtime on a 600mAh Li-ion battery. Right now, the one I got barely last for half an hour, even less with bass intense music.

Thanks to it’s popularity, there is a lot a material online about disassembling and battery replacement. The internal of this speaker is really tight, with very small space allocated to the battery, which is sneaked under the PCB. Once removed, it’s clearly visible that this cell is at the end of its life, it is puffed out.

The battery has a three wire interface : Positive, negative and a center pin for the battery temperature reading. In order to ensure proper compatibility with the JBL GO charging circuit, the replacement battery should have a similar temperature sensor.

Reusing old phone battery

During my research, I found this interesting video, as it propose to use old phone battery as replacement. Having myself few (very) old phone, I decided to give it a try.

Depending on how old is the phone, different battery pinout exists. Some have 3 terminal, others 4. Most of the time, the third pin is the battery internal thermistor. The fourth pin is used to communicate with the battery protection IC.

Because the status and temperature terminal were not clearly labeled on the battery I had, I decided to reuse the tiny BMS of the original battery. In this manner, I’m sure the charging circuit of the speaker will read coherent temperature values.

Size matter

The case of the JBL GO is quite small, so I had to pick the smallest and oldest battery I had, a 960mAh cell from a 2008 Samsung phone.

I first soldered the scavanged BMS of the battery. After a quick test to make sure  everything was working (including the charge), I double taped the old new battery on the bottom of the case. PCB was still perfectly fitting, but as I mounted the speaker back in place, I realized that the big hole in the board was here for a particular reason..  The speaker is quite deep, and almost go down to the bottom of the case. The battery was preventing it to fit in place. I managed to close it anyway, but doesn’t look that great..   And more critical, it’s pretty dangerous as the battery is squezzed againt the case by the speaker. Under a shock, the battery could be crushed, and ignite itself.

Not acceptable, so I removed this battery, and went back to the drawing board.

Thinking outside the box

Since there is no room inside to fit one of the battery I have, let’s put it on the outside. The idea is to design a 3D printed case extension that will hold the battery. As I have way more surface area available with this solution, I designed the case extension around the biggest phone cell I had, a 2400 mah LG cell.

The design follows the rectangular shape of the JBL GO. It’s basically just a prolongation of the case, with the minimum amount of thickness necessary to protect the cell. I printed it in TPU to have a nice shock proof case.

The BMS was directly soldered on the battery pad. Once wrapped on electrical tape, it went nicely on it’s bed. The case extension is fixed on the back on the speaker with 4 screw plus some glue. A fifth hole allow the battery wires to reach the inside of the case.

Warning : battery pad are not supposed to be directly solder on. Excessive heating can lead to a battery overheating and a risk of fire.

It work pretty well, and this hack quadruple the battery life (and charging time !) of the JBL Go speaker. The downside is that it’s adding 9mm to the speaker, bringing the total thickness of the device at 40mm.

Need more power ?

But what if it’s not enough for you ? Well, turn out three 18650 cells can fit in the back of the JBL GO. A quick re-design of the case extension, and voilà, you got a JBL Go with a 6000mah + battery ! However, it add now 21mm to the speaker’s thickness so you’will have to choose between portability and battery life here.

I will personnaly stay with the flat phone cell, as the autonomy is already enough for me.

Conclusion

I really like this kind of small project. Not complicated, but it’s very satisfying to repair things with stuff you already have around you, and it’s a nice way to limit e-waste.

If you want to fix or upgrade your JBL GO speaker, you will find all 3D files on Thingiverse.

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