Post by pinneriteOn Thu, 05 Sep 2024 13:13:46 GMT
Post by fredPost by pinneriteOn Thu, 05 Sep 2024 12:28:20 +0100
Post by Peter JohnsonPost by pinneritePanasonic cordless phones all appear to come with their own
mains-charger plug. To reduce clutter I would like to power mine
from a USB charger hub. Has anyone dived into this at some time?
What's the Pansonic voltage? You'll only get 5v max out of USB and
you'll need to check that your hub can give you that.
The base says it delivers 4.8v at 150mA. I reckon that there's a match
there. I need to replace the lead to the power unit with one with a
USB plug at one end and the RJ type plug that plugs into the base unit
on the other. It would help if I could identify which wire went where.
Multimeters are super cheap these days so no excuse for not having one in
the toolkit. You'll suss your connections in no time.
I have two multimeters but without taking my feet off the bottom and
cutting the existing lead, I will not be able to use the meters. I am
not that confident.
That's the spirit.
The cordless phone has four NiMH batteries in it. You didn't state
the model number, so this is just a guess.
The base is a *battery charger*, not a "power supply" as such.
battery chargers should cut off the charging current, when
the battery is full. The charger has to recognize the "endpoint"
of the charging process. Lithium Cobalt chargers are an example
of a very good charging method -- it has to be good, or there
will be a fire.
Other chemistries on the other hand, can work well
*if* the batteries are Fast Charge type and you can ram a lot of
current into them. The enhanced current makes the endpoint visible.
At lower currents, the endpoint is not distinct, and the other
control methods are "crap". This leads to premature battery failure
due to abuse. It's hard to design a smart charger for NiCD or NiMH,
unless the cell type is Fast Charge. And certain aspects of the
chemistries, don't always allow that (you cannot make 8Ah D cell NiCD
as a Fast Charger type, because the number of amperes that would flow
is prohibitive and the materials will not take such treatment).
https://batteryuniversity.com/article/bu-408-charging-nickel-metal-hydride
You're not fooling with a power supply. This is a
case of a "something else" circuit.
And I absolutely *hate* engineers who do this. The God damn
charger should be *inside* the hand unit. Only a voltage source
should drive the phone, such as a 19V wall adapter. If the
charger solution is self-contained, the input voltage can be
wide range, and you can use a number of power sources for
substitution purposes.
Putting the battery terminals on the bottom of the device
and inviting people to connect 5V voltage sources where they
do not belong, is so so *wrong* . They should not do this.
it's as bad as my fucking Black and Decker battery screwdriver,
where the fools idea of a charging circuit was a single resistor.
This uses the observation that NiCD can be successfully abused
by trickle charging it... forever. Well, I have some bad news
for the idiots. When you do that, the electrolyte blows past the
pressure relief value and coats everything in the vicinity with
a chemical which is a strong base. As you buy one replacement
battery pack after another, it ruins them. This means (of course),
I hardly ever got to use my Blackened Decker screwdriver, because
of the shortcut taken on charging. Your Panny product may not be
that much better...
Summary: Do some extra checking with regard to circuit type before
making the wrong kind of substitution. There be dragons...
I can hear hissing, and the smell of napalm fills the air...
Paul