mobile phone charger

[Fjbj40]

I don't think it's possible to have a battery hold a voltage under load and not have the amps to carry that load. If the battery is bad it won't maintain voltage under load and the measured voltage collapses as I said.


Mark

I guess what I was trying to say was you may have 12 volts but no current. I have seen so many inexperienced people trying to solve electrical problems by measuring voltage only.

The majority of my electrical experience is in aging aircraft, a system does not work and the people working on it keep saying it's got to be the box as I get 12/28 volts and it still does not work. So they change the box, still does not work. Must be a bad box so change that one, or must be the box that is before that one so change that one.

Me being the crew chief finally steps in, so, did you check see if the voltage will carry a load? What do you mean is often the response. As soon as a load is put on that voltage it disappears! Start digging, and voila, there is a corroded connector causing all sorts of resistance but still allows 12/28 volts to pass through.

[posplayr]

I guess what I was trying to say was you may have 12 volts but no current. I have seen so many inexperienced people trying to solve electrical problems by measuring voltage only.

The majority of my electrical experience is in aging aircraft, a system does not work and the people working on it keep saying it's got to be the box as I get 12/28 volts and it still does not work. So they change the box, still does not work. Must be a bad box so change that one, or must be the box that is before that one so change that one.

Me being the crew chief finally steps in, so, did you check see if the voltage will carry a load? What do you mean is often the response. As soon as a load is put on that voltage it disappears! Start digging, and voila, there is a corroded connector causing all sorts of resistance but still allows 12/28 volts to pass through.

I think you are both in agreement but getting a little twisted up on the words. Yes what matters is being able to deliver a load current as a specific voltage. And classically what happens, if a source is generating more current that it can provide, it's output voltage drops. This is for a variety of reasons even including the dirty connections you mentioned.

But you don't have to necessarily measure current; it can also be determined without having to measure current if you have a relatively known load to put across the voltage source and see if it can meet the demand. So voltage at no load and underload provides the required information to deduce the sources capability.

[Fjbj40]

Sounds good to me

cheers!

[1_v8_merc]

Those little milliamp lights can kill your battery, it happened to mine, after I left it on for one week. I had a cigarette adapter straight to the battery, with a kill switch, and just used it for my GPS.