I'd been looking to get a nice USB-C rechargeable Li-polymer battery - and eventually bought one off Aliexpress to check out the quality. Here are my findings: Original Aiwa lead-acid batteries: PB-2 (2v 450mAh) fatter - contacts on top only PB-20 (6v 800mAh) for larger recording units PB-25 (6v 950mAh) for larger recording units PB-3 (2v 470mAh) fatter - close contacts - additional contacts on top PB-4 (2v 550mAh) fatter - close contacts PB-4S (2v 600mAh) fatter - close contacts - super long life PB-S5 (2v 280mAh) thin - wider contacts PB-S5 A (2v 300mAh) thin - wider contacts Modern replacements: PB-3 (works for PB-4 as well) (2v 900mAh * lipo inside states 500mAh *) Cost: £13.92 ($15.90) Source: China (search Aliexpress) Dimensions: L68mm x W17.8mm x D8mm I like the way one package can cover both the PB-3 and PB-4 due to the additional terminals on the top Voltage on Li-Polymer battery pack = 3.67v Voltage on external terminals = 2.41v I'm unsure if the battery pack stating its 500mAh, but the print on external shell stating 900mAh is related to voltage drop from 3.7v to 2v? or just misselling The screws are already loose after opening it a couple of times, so will require some glue in the hole to get some grip back on the thread. PCB looks well made, although I'm going to check the soldering when I get my microscope, as I'm nervous of any shorting from sloppy soldering. The rest of the case is clearly 3d printed and looks reasonable, if a little fragile around the connectors. I'd prefer to have seen some gold plating on all of the contacts, top one's seem to have a plating, but the 2 on the end do not. I'd be interested to know how many recharging cycles the Li-Polymer pack will take, I'll soon test how long a single charge takes to discharge on a Aiwa HS-PX547 and report back. I found replacements for the Lipo battery here or here, after searching for '500mAh lipo battery 6mm' on Aliexpress. max size for the battery to fit would be L52mm x W15mm x D6mm After a good browse of all those currently being sold, I can't see any in that dimension achieving over 500mAh, so that seems the limit for now. PB-S5 (2v 800mAh) - slightly thinner Aiwa battery Cost: £13.92 ($15.90) Source: China (search Aliexpress) Dimensions: L68mm x W17.8mm x D6mm Voltage on Li-Polymer battery pack = 3.84v Voltage on external terminals = 2.42v max size for the battery to fit would be L45.5mm x W15.3mm x D3.6mm The PCB itself appears to be identical to the PB-3 version except it's missing the 2 additional battery contacts on the reverse of the pcb. Interestingly unlike the PB-3 version above, the battery wires on this one are actually attached to the appropriate terminals on the pcb. Other alternatives: Someone in Singapore (wickedkraft) is also selling a similar PB3/4 replacement on ebay and they also have an option for PB-S5 here, but it's $38 - so over 2x the price, when I'm feeling flush I might get one of those as well to compare the quality.
Great summary! Aren’t those original batteries around 300mAh? The replacement will surely be better, with a small risk of delivering 3.7V as mentioned by @Valentin in another thread.
Given the cell capacity is 500mAh, it's obvious that the 900mAh reffers to the 2.4V output. So the assembly has 2.16Wh. @Rossoe Please share a picture where the part numbers of the 2 ICs are visible (pic 5), would be curious to find out more about the design.
@Emiel I hadn't spotted that post - is that pertaining to possible failure of drop down voltage components in the battery then letting the full 3.7v through to walkman circuitry? I'm interested why the battery is wired directly onto components, rather than having it's own trace pad to connect to? maybe it keeps it more compact the way they have done it. Would be good to reverse engineer the little pcb and then be able to print our own, as the remaining enclosure looks pretty easy to knock up ready for a 3d printer.
Yes, those 2. Thanks for the picture. As for the wires, they're probably soldered directly to components as there's not really much space in there. Don't see a major problem, however what I would do is cut the end a bit shorter so there's no risk of the bare copper wire touching other components. About the risk I mentioned, the potential risk with such designs is if the switching element (MOSFET) gets shorted. Then the source (lithium cell in this case) is connected directly to the load (output terminals) through the inductor (which has a very small DC resistance). Personally, I would like to see some kind of protection to make sure the output voltage never exceeds a certain value even if there's a fault with the DC-DC converter. ProAudioRevival claim they make a replacement for the PB-20, but I wasn't able to contact them: https://www.proaudio-revival.com/battery-recellrebuild.html Seems the phone number form doesn't accept RO country code for whatever reason and there's no visible e-mail adress you have to use that form to contact them. If you are able to contact them and find out a price for this battery, please share it here.
They look like the same batteries I use in my small RC Helicopters, see attached image. The ones you see in the image are 520mAh and 450mAh The one you show is typical miss selling as the capacity don’t match what they claim, cheap Chinese Lipo’s are famous for this lie.
ah nice, those might work - can you confirm dimensions for me? I updated the original post with max size for the battery to fit - L52mm x W15mm x D6mm do yours exceed that at all?
@Valentin I emailed them via the contact form, I got an automated reply from "jotform.com", hopefully they will pick it up tomorrow. I will update when and if I get a reply.
Hi Rossoe I checked and they are larger, so they are no good to you. Well I guess, if you remove the packaging they may just fit. From AliExpress click link.
@Valentin Finally had a reply from Pro Audio Revival after prompting via an email address I found on their Facebook page. *============= Sorry about that. Unfortunately we are out of stock at the moment. We'll let you know when we'll have the stock available. Best wishes, Sebastian P. Project Engineer ProAudio Revival =============*
