Overcharge prevention facility in NiMh batteries

  jack 12:24 27 Dec 07
Locked

A Christmas present Wireless headphones[ 2 sets his and hers]
The phones are powered with 2 AAA NiMh cells one in each ear shell.
In each case the bottom 5 mm of the plastic casing is cut away to reveal the metal 'can'
In the chambers at the base[spring] end there is an extra contact.
In the hand book an instruction states that should the batteries need replacement with normal rechargeable NiMhs- to cut away a similar section of the plastic cover so that the 'overcharge prevention' device can operate.
So I am wondering -how does that work?

  Diemmess 17:40 27 Dec 07

Have you a web link to the 'phones?

Have you a charger which plugs in to them or are they meant to be removed for charging?

"Overcharge prevention" baffles me as it does you.
Perhaps this is fractured English, conjoured up by someone who was supposed to know how to inform the natives of this sceptered isle.

  jack 08:55 28 Dec 07

The base station has a power brick and the phones at rest sit on the base station with contact in a socket on the base for recharging.
I may well have a look around the web
The brand is 'Weltech' which is of German manufacture sold by Lidl

  Diemmess 09:45 28 Dec 07

In normal use the brick will deliver a fairly hefty charge current.

The manufacturer has stripped a small part of the normal insulating sleeving to allow a third (voltage sensing) device - contact with the negative case of the battery.

When the charger detects that the battery has reached its proper charge the current will drop to a mere trickle and maintainance charge only.

If this isn't all a load of cobblers.....

When the batteries are old and failing and you need to replace them, then you will have to peel the new ones as instructed to allow this safe charging routine.

  €dstowe 09:57 28 Dec 07

I would have thought it reasonable for this brick to have proper charging circuitry where the current automatically drops to a trickle when it detects the cells are optimally charged. This type of circuitry is not complex and would have added only pence to the costs (if anything at all). To have to modify cells to suit the charger seems unreasonable to me.

  jack 12:00 28 Dec 07

I did find the web site- but it is simply a 'marketing' organization listine what they sell and how good they are at it
The usual load of corporate bovine ordure .
For your interest here is the link
click here
Where incidently the Wireless ohnies get no mention

Interesting topic but not very productive so I'll 'tickit'

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