Replacement Batteries For The Sony Discman

Some of the first Sony Discmans included rechargeable batteries. These batteries were nickel metal hydride batteries (because of the technology of the time) and are now well past their service life. The new hotness in battery technology is lithium — it offers greater power density, lighter weight, and a multitude of ready-to-go, off the shelf cells. What if someone were to create a new battery pack for an old Sony Discman using lithium cells? That’s exactly what [sjm4306] did for their entry into this year’s Hackaday Prize.

The Discman [sjm] is working with uses a custom, Sony-branded battery based on NiMH technology with a capacity of around 500 mAH. After carefully measuring the dimensions of this battery, it was replicated in plastic with a 3D printer. This enclosure was then stuffed with a small lithium cell scavenged from a USB power bank.

The only tripping points for this build were the battery contacts. The originally battery had two contacts on the end that fit the Discman exactly; these were replicated with a small PCB wired up to the guts of the USB powerbank. The end result is a direct, drop-in replacement for the original Discman battery with a higher capacity, that’s also rechargeable via USB. It’s a fantastic project, with the entire build video available below.

24 thoughts on “Replacement Batteries For The Sony Discman

  1. I have one of the original Discmans (Discmen?) from the 80s, the whole bottom of the unit is a battery pack, and there is a warning in the manual to always recharge the battery after any use, no matter how short. The battery quit holding a charge sometime during the Clinton administration, and disassembly revealed some sort of wet plate battery pack inside, not sure if it’s a lead acid or what, but it would probably be relatively easy to replace with a LiPo and a charge controller.

  2. Interesting video.

    Though I wonder if it would be possible to create a duplicate of that removable battery compartment panel and blend it together with the battery box design to see if that would free up any more space.

    Then again I wonder if there’s much space behind that discmans battery contact pins……I mean if there’s enough space for that charger circuit then you could use a larger battery.

    1. I “borrowed” the protection pcb from another lipo battery so it does indeed have under/over voltage and over current protection (I actually accidentally shorted the pcb contacts during assembly once and it disconnected the battery so I had to hook up a charger to reset it).

  3. I bought the D-9 around ’89 or ’90. Sounded amazing with well-mastered material. Worked for about 1.5 years then just stopped powering on, either from batteries or adaptor. Eventually bought a later-model replacement (still sony, but plastic body by this time) and thought it sounded so-so in comparison. Would be interesting to hear how one of these earlier units would sound properly recapped. I remember using some consumer headphones that sony was promoting along with their discman offerings. Maybe they were specifically matched.

    Always have wondered if it was just nostalgia, novelty, or if those earlier units did posess higher dynamic range or some other measurable advantage in their signal chain.

    1. If they switched from a metal to plastic body, it’s possible they were already cutting costs on audio internals as well for the PCB.

      But, still, would be cool to find one of each, run the same stuff through it, and compare. I was later to this era, and went through plenty of cheap portable CD players in my time. Some of them sounded great, but even with the same headphones and cd some sounded like crud.

  4. Is anyone aware of a circuit that would allow for a drop-in replacement of Li-ion batteries into old NIMH or NiCad devices that would be capable of charging from the original built-in charger?
    I’ve always thought it would be a neat way to revitalize old equipment. But whenever I think about implementing such a thing, problems like charge detection or self discharge tend to get in the way.
    I’ve often felt that having to remove the battery to recharge it would interfere with the user experience or be completely impractical when the battery was not originally accessible externally.

    1. I have an old Makita drill, I’ve thought the same thing about. Replacing all those NiCD/NiMH pack batteries with lithium.
      However, glossing over the charge methods, the only one that could be easily reused is the constant current charge. For a battery back for a drill, that might work fine since it’s removable.

      For something internal, they would probably use a combination with a temperature based method (also to avoid it catching fire.)

  5. I resurrected my Sony D-250 at the weekend (the middle wheel/cog on the linear drive was all gummed up on the pin/axel). I’m the original owner having purchased it back in 1989. I also have the plugin IR remote eye and remote. I was wondering if you had any plans to make and sell your battery replacement? Cash waiting…

  6. Use a 3.7 volt 10440 aaa size Lithium Battery,You can strip original Bp2 Battery By Preening back the bottom of battery and Pushing orignal sealed lead acid battery out by pushing on the terminal portion at the top of the battery, Once out of its housing the original lead acid batt can be removed fron its plastic housing carefully and then re-use the plastic housing for the new batt soldering it in place observing correct polarity. use 3.7volt 1000mah 10440 AAA size lithium ion batt available on Ebay, original charging circuit will charge these cells correctly and battery display on lcd will indicate corectly,Good Luck.

    1. I did something similar but used a tiny 750mAh 1S LiPo pack. The Discman charging circuit WILL try charge this battery to a voltage level that is too high for a LiPo / Li-Ion cell so it is important to use a battery with a protection circuit. I have the D-25 and the battery charges up to 4.125V before the battery over-voltage cutoff kicks in. The Discman considers the battery dead at 3.5V which is fine for the LiPo cell. I get about 2.5 hours on a full charge.

    2. Peter, would you be willing to make one of these if I send you the parts as I have sight problems but would like to resurrect my Sony D-99 ? Beer tokens could be provided!!

  7. Sony offered a battery holder that held 4AAs and replaced the SLA battery. After the SLA in my DT-4 died, I was glad I did. That, and the applicable remote control, were special order from the “high-end” audio store, but they were both well worth it.

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