Wall-wart issues

[Lobster]

So Christmas has come and gone, bringing with it the usual influx of new low-voltage power supplies for assorted gadgets and gizmos. Unbelievable. When are these things going to get at least half-way standardised to avoid having to have so many lying around?

Anyway...

One new incoming gadget was an LG mobile phone. As it happens, we already have an LG charger in the house from another (now stolen) model: they look physically identical and have the same proprietary jackplugs.

The old wallwart says it puts out 4.8V / 0.9A; but the new one is 5.1V /

0.7A (ie higher volts but lower current).

Can we use the old charger on the new phone without worry, or should I bin it urgently to avoid an 'accident'?

Thanks David

[meow2222]

Hard to imagine any possible situation in which that could cause a problem.

NT

[Geo]

My suspicion would be that neither are as accurate as stated - but can you put a meter probes into the connector of the old one (off load) to check if it really is 4.8v? The lower (if it is) voltage should not cause any damage and the current available is slightly more than required but again no damage likely.

If the unloaded output voltages are exactly as stated then it is /just/ possible that battery would not charge fully - but my bet is that there would be no difference. Try a google for the phone model number (and charger) to see what amazon/ebay etc offer as replacement chargers for that model.

Geo

[John]

All so wasteful of resources.

Campaigners get on their hobby-horse about issues like leaving things plugged in but fail to address the production of items that are not needed.

My pet hate is crap batteries. Little use - shipped from China and end up polluting our land.

[Dave Liquorice]

USB (nominal 5v up to 500mA) is slowly creeping in as a defacto standard on many things but frequently without the smarts that really should be there for proper negotiation to get 500mA. How kit behaves when connected to something that doesn't current limit to 100mA without negotiation seems to be a little variable.

[Andy Dingley]

There's a (tiny) chipset for that.

I recently saw heated gloves with USB power connectors. Seems that off- road cyclists are taking to these things as a simple power connector for a few watts of lighting or heating.

[Andrew Gabriel]

I've never yet seen a USB port which actually polices the current draw against what's been negotiated.

However, some phones detect the difference between about 5V and 5.5V in order to detect if they're plugged into a real USB port (5V) in which case they limit their current draw to low levels, or mains adaptor (5.5V) in which case they'll do things like fast charging at much higher current draw.

[Harry Bloomfield]

Andrew Gabriel presented the following explanation :

Certain (maybe all) Nokia phones can be used with a Nokia sourced charger which come in two versions - the standard one and the fast charger. There is no marked difference in the output voltage on the chargers, so I did wonder how the phone might detect which type of charger it was plugged into. I guess the voltages must be different despite the markings.

[Lobster]

Not readily - the LG connector is a weird, flat multi-pin job with recessed connectors very close together!

Well, AFAICS they seem to sell a generic charger for both phones; however I'm not sure whether that means anything or not.

FWIW the phones/chargers are as follows: LG Chocolate: STA-P51US charger, 4.8V / 0.9A LG Viewty: STA-P52UR charger, 5.1V / 0.7A

Thanks David

[Geo]

Well Orange say it is compatible with both phones...

[Pete Verdon]

I've encountered laptops that do, but not recently. I suspect that the abundance of cheap "USB"-powered devices that don't ask nicely for power means that all modern hosts will supply the full 500mA regardless, otherwise they (rather than the out-of-spec device) are perceived as not working properly.

Pete