Sony wireless headset charging circuit - Page 1
Forum section: electronics / general

author: TheAmmoniacal
author_rank: Unknown
timestamp: May 31, 2014, 09:44:00 pm
content: I bought a wireless headset some time ago (sony MDR-RF810R), which simply has a pair of AAA rechargeable batteries in it, they look just ordinary, but they were of a rather low capacity of 500 mAh. At some point they would only last about 8 hours, so I bought a new pair of Duracell 1000 mAh batteries, but then I discovered this note in battery compartment: "You cannot charge any rechargeable battery or dry cell other than the supplied battery."And as it says, no other battery will charge through the headset, and I have tried a whole bunch of brands and varying capacities. This didn't really bother me much as I just had a wall charger for the batteries and replaced them each time, but after some time as I've gotten more into electronics I've developed a bit of a curiosity to this..How do the headphones achieve this? Do anyone know? Where or what is the battery identifier? Anyone know if there's a simple hack? (I would suspect this was common in a lot of consumer 'mid-range' stuff?)Thanks.

author: Richard Crowley
author_rank: Super Contributor
timestamp: May 31, 2014, 10:05:17 pm
content: Isn't your Sony battery actually a "battery pack" in a plastic frame like this?:If it doesn't have an extra contact on one end (or the other), then typically there is a little switch in the battery compartment that detects if the official battery pack vs. just a couple of AAA cells.Note that the recharging circuit is set up specifically for that "chemistry" and you can't switch battery types.Remember also that if you put higher-capacity batteries in there the recharging circuit will probably take longer to charge and/or may not even charge them fully.

author: TheAmmoniacal
author_rank: Unknown
timestamp: May 31, 2014, 10:41:20 pm
content: Quote from: Richard Crowley on May 31, 2014, 10:05:17 pmYes, the battery is a pack like you pictured, but they were both labeled 1.2V NiMH and had nothing connected to the terminals. So they had to be just regular batteries. So what you are saying is that the plastic casing itself is pushing a switch or button inside the compartment?

author: Richard Crowley
author_rank: Super Contributor
timestamp: May 31, 2014, 10:56:39 pm
content: Quote from: TheAmmoniacal on May 31, 2014, 10:41:20 pmYes, I have seen several consumer gadgets that use that scheme to automatically detect their own rechargable battery vs. a couple of random cells.

author: amyk
author_rank: Super Contributor
timestamp: June 01, 2014, 12:45:57 am
content: Not that bad of an idea, as trying to charge non-rechargeable batteries is unlikely to be safe. You could put the rechargeables into the same type of pack and see if that works.

author: SeanB
author_rank: Super Contributor
timestamp: June 01, 2014, 06:17:01 am
content: Some Sony batteries have an exposed metal section at the one end that connects to a contact on the side of the holder that is connected to the charge circuit, so that a regular battery will not get a charge. The extra capacity cell will take longer to charge, but the charge circuit should handle it.

author: TheAmmoniacal
author_rank: Unknown
timestamp: June 01, 2014, 09:24:25 am
content: As it turns out, the trick they are using is incredibly simple, it simply uses a small lever switch that is pushed by the plastic casing. Here's a picture of it.