Panasonic cordless phone

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.

I've got a few of them.

One here has a power adaptor PQLV219E that has stated on it, output 6.5V

The voltage is also written on the cradle, which has a warning only to use the specified adaptor.

The adaptors are small, personally I'm not fussed to DIY an alternative. Doubt many would - these things are left on 24/7 charging batteries and may be connected to the phone network (if used for the main station) and have isolation components for such (i guess?)

It doesn't happen to have a data link socket does it? I have a Gigaset SL400 which has a mini USB socket for exchanging contacts or whatever. Turns out it'll charge just fine from USB.

Theo

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.

pinnerite snipped-for-privacy@gmail.com wrote in news: snipped-for-privacy@gmail.com:

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.

If you wrap some fine bits of wire around each of the multimeter probes, you should be able to get at the gold contacts on the RJ plug, even if the probes themselves are too fat to reach them.

Or buy a matching socket and use that to probe it out with the power cable plugged in.

Since it's low voltage / current there's not much damage you can do if you accidentally short it out.

Theo

pinnerite snipped-for-privacy@gmail.com wrote in news: snipped-for-privacy@gmail.com:

You'll need to dismantle bases to to gain access to terminals for USB power connections so should be able to determine at least polarity from there with the multimeter. Dismantling should be straightforward, I have always found them to be screwed rather than glued. Inside the base is the place to do a proper job/connection but expect to make good soldered connections or to await trouble later on. If you don't want to do that then you'll be using a scalpel to disect the base cable and following that you can use a sharp object to pierce the inners to determine polarity, voltage and so on and then make external connections but that will be a bit of a bodge.

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

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 f****ng 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

Often battery charger bricks are as you say, constant-current (during charging) and then constant-voltage (at top of charge) - CC/CV devices.

But this base also talks to the phone network, ie it's not a pure charger it has some other current draw as well. This would mess with the CC part.

Also this is marked 4.8v, which is only middle of charge for 4x NiMH cells. Top of charge is 1.55v per cell - I suppose ToC for 3 cells would be 4.65v which is not a mile off 4.8v.

That said, I have an ebike charger for a 20S NiMH pack marked 24V 2A - this must be a lie because ToC should be 1.55*20 = 31v. I should measure it.

But the point stands that current limiting in the brick may be needed. The answer to that is to put some flat batteries in the handset and see if the output from the brick remains 4.8v or dips based on the cell voltage.

Theo

My Panasonic's base unit has 5.5V 500mA on the bottom, as has the wallwart powering it. The secondary unit also has 5.5V 500mA on its base (I can't get to the wallwart to see what's on it, but I suspect it's the same one as the base unit uses). The phones themselves uses two AAA NiMH batteries.

Agreed. My phone is now over 11 years old and has no problem with a call lasting an hour. IIABDFI...