SONY BP-2EX battery

Created this thread as I wanted to know opinions about new replacements of the BP-2EX battery which was used in a lot of SONY Discmans.
Some time ago I purchased one based on 2 x 10440 lithium cells, which I was quite disappointed of.

However, measurements done when powering a D-250 unit with my bench power supply revealed the fact this device can't operate at a voltage below 3.7-3.8V.
Given the empty voltage of the 10440 cells is 2.75V, I realised a majority of the cells' capacity is actually not used in this battery pack.
As-is, a full charge can provide playback for 1.5-2 CDs, which isn't that good at all.

Recently I saw @Hyperscope was using a different kind of battery (the one in picture attached) and wondered if this one is better than what I have. Hence why I created this thread.

Anyone else having information about similar batteries that the 2 mentioned is invited to the discussion.

 

Yes the e-bay seller is called wickedkraft and is located in Singapore. (They also have a BP-5 battery for the D-35 /D-350 and D-311 which requires a charger since no room for internal USB charge circuits. I was going to get this battery too but never did. I suggest you buy one since there is one up there now! ) I came across the BP-2EX battery and bookmarked the seller. Months later, when I went to buy one, they were all gone. So I had to message them and ask for a BP-2EX, he made one, listed it and I bought it.

I would rate the BP-2EX they make as "fantastic". Very nice label too. It is a 3D printed plastic box with glued on flat lid containing a 2000mah lithium battery pack with a standard USB charging circuit in the end of the box. I opened it right away to check . Have not timed it or measured how long it lasts exactly in the D-555... but would say 3+ hours. I have pictures of the battery used inside if you want.

 

Several years ago I came across this video which was the first time I had seen or heard of new battery possibilities: Sony Discman DIY 3D Printed Replacement Lipo Battery.

I believe all these DIY type BP-2EX will all suffer from the same problem alluded to in the first post, that is, much of the cells capacity will not be utilized before the Discman cuts off due to low voltage. Will require a different charge / drive circuit with voltage regulation in the battery. Or, in the case of the wickedkraft BP-2EX, just enough capacity to make for a "good enough" run time in most Discman players.

Or make a 125mm x 125mm flat square metal box that can sit under the Discman as a battery box filled with ones own battery / driver combination delivering 9v to the external side jack. This way the Discman gets to operate in supposed "optimal performance mode" and has back-lit display illuminated and the remote control working. A thicker BP-200 Discman battery pack re-worked for 9v with a plug in short wire hanging out the back is one intriguing possibility. Or one of the cast aluminum black powder coated "Hammond" enclosure boxes full of 12 Eneloops as 2 parallel groups of 6 in series. I looked through their listings at every box they currently make but none were the ideal size. I ended up making a basic 6AA box of this type which worked quite well for a few hours.

 

I'm familiar with the DIY version in the YouTube video, that is in fact what I wanted to do myself before buying the one I have now.
As you stated, the big issue with all these batteries is not all the capacity is usable as these Discmans cut off at around 3.7-3.8V, voltage at which the cell still has a lot of charge left.
The original battery was lead acid, on which the difference in voltage between charged and discharged states is low.

Only solution I see to this problem is to add a buck-boost converter so the output voltage remains constant at around 4-4.2V during the whole discharge cycle.
Disadvantage will be the battery gauge will no longer work, showing full all the time. But it's a disadvantage I can live with if I can get 8 hours of play instead of just 3-4 hours.
An external battery pack based on AAs is of course another solution that will work, but a bit too bulky in my opinion.

Attached pictures with the battery I have now, which I'm quite disappointed of.
In regard to pictures of the internals of this BP-2EX made by wickedkraft, I do want to see. Curious if there is any space left to modify it.

A SONY D-250 draws 210mA during playback, so a 2000mAh battery should provide around 9.5hours of playback which is pretty far from what we're actually getting.
Even the 2 x 10440 cells (1200mAh) I use now should provide around 5.7hours of playback if all the capacity was to be used.

 

5.7 hours is quite impressive regardless, are you able to share the link of the battery pack in your pictures that achieves this?
Do the batteries need charging separately or just USB-C? If USB-C how long till full charge, and what wattage do you charge at?

 

Sounds like a proper power management board needs to be created to sit inside the new battery, so it can use all the capacity and also charge/discharge correctly. Charging directly in the unit would be amazing.

 

The 5.7hours is with 2 x 10440 cells I shown in post #4 assuming all the capacity would be used. In reality, the unit is unable to use more than 30-40% of the capacity.
With the 2000mAh cell it will be 9.5hours of playback assuming all the capacity would be used.

Both of the batteries shown here charge via USB-C. Don't know how much it takes until full charge, because I never used the full charge.

As for the power manangement board to solve this problem, don't know if it would fit inside the battery, rather inside the Discman itself. Will update the thread later on about this.

As for charging directly in the unit, the 10440 cells exist both with protection circuit and without.
Those without can't be charged directly in the unit as there's no way to stop the charging once a certain voltage is reached.
The flat 2000mAh cell has its own protection circuit, so that will probably work.
Regardless, don't think it's a big deal to take the battery out and charge it via USB-C.

 

Did a battery run time test with the D-555 doing intermittent listening over a 6 day period. Using the above e-bay BP-2EX battery I noted the following:

28 minutes of play until the first battery indicator segment went out.
An additional 31 minutes for the second battery indicator segment to go out.
Then 36 minutes further play time before the third battery indicator segment went out.
Then 179 minutes before the final fourth battery indicator segment went out.
At this point the battery indicator was empty and started flashing.
6 more minutes until stop.
So 280 minutes playtime on the D-555 using this battery. Intermittent use over 6 days to "simulate" realistic use.
4 hours and 40 minutes available. Pack measured 3.56v at failure.

 

Good morning, I stumbled upon this thread and forum after doing a quick search on the internet, looking for a BP2EX battery replacement. I recently came across a Sony D-303 in mint condition and one of these batteries. After going through this thread, and looking at eBay, the e-bay seller called wickedkraft no longer has the batteries for sale; however, doing a search on Aliexpress for the same batteries, the results are encouraging:

https://www.aliexpress.com/w/wholes...o.store_pc_home.auto_suggest.1.486f4d6cXdXTfw

If anyone has any feedback on a specific pack off Aliexpress, please kindly share; otherwise, I will just pull the trigger on one of them and share the results.

Thank you

 

I had to message Wickedkraft and ask for a battery to be made and listed on e-bay. Then I could buy it. Wickedkraft does not seem to keep a stock up for sale. Try asking them first Otherwise, yes, looks like there are other up on Aliexpress too. I can't add any more than this though.

 

I searched and I found this link. https://www.ebay.com/itm/2859130408...sjp7qHRTvG&var=&widget_ver=artemis&media=COPY He's asking you $44 for the d303 battery replacement