Chosen Solution

So the battery on my Marshall MID Bluetooth headphones are no longer accepting a charge and it’s 5 weeks after the 1 year warranty. Marshall has no replacement or repair policy…. just a thanks for your money and here is a coupon towards another pair of headphones that probably will die …. Sooo I’m trying to track down a batter with 3 wires thats 3.7 V 680mah 2.52Wh abd ive found a bunch … but with only two wires . Can I mod these replacement batteries at all ? I know there must be a way to create something work just like this apparently proprietary battery . Thanks in advance for any help or direction ! Original Battery (3 wires)

Hi @wlafty , Have you ensured that the replacement batteries will physically fit into the headphones? Does the original battery have a string of numbers (most probably 6) printed on it by any chance? These numbers represent the dimensions of the battery. This is an example only: ‘405070’ printed on battery near voltage and capacity information. These numbers can be deciphered as follows:

  1. 40 = 4.0 mm depth or height
  2. 50 = 50 mm width
  3. 70 = 70 mm length. The convention with batteries is that the first 2 digits are ALWAYS the depth measurement of the battery in mm WITH a decimal point between the digits. (unless obviously it is an extremely large battery). The next sets of digits are always in mm but sometimes rather than in groups of 2 numbers may be 3 in the case of bigger batteries. Obviously a longer string of numbers) Hopefully this makes some sense. The idea being you can search for suitable replacement batteries by specifying the dimension (as printed on the battery) along with the voltage and capacity (either in mAH or Wh) which makes it easier to find the correct physically sized battery as well as the voltage and capacity required. Hopefully this is of some help.

The original battery contains a small PCB; maybe some charge control electronics. I tried to replace it with a battery with three wires and similar capacity from China.  No success yet. I will try now to use this battery with the pcb from the original battery..