What is the meaning of Amp in terms of electricity

[TheGizmo]

my cell phone came with a charger rated at 5 volts and 850ma... i bought a charger on eBay that was supposedly for my phone but it says 5 volts 600 ma on it. Is this charger going to fully charge my battery or only charge it 2/3 of the way since its 250 milliamps less. or is this just the speed at which my phone is being charged.

if it matters, my battery is 780mah.

Thanks

 

[91TTZ]

MsDawn is going to kick your ass just for the act of *asking* that question!

 

[skyking]

It will work just fine, only a little slower. It will still reach a full charge.

 

[Compnewbie01]

I'd say it would only affect the speed. As far as I remember, I believe amps are coulombs/second so 850ma would be 850 milicoulombs/second of charge flowing into the battery every second and volts is the potential difference between two charges or something like that. Yea..something like that.

 

[Eli]

Realistically, it should only affect the speed.

If your cell phone actually ever draws over 600mA, it may get a little warm, but thats about it.

 

[Triumph]

think of it like water
voltage is like pressure
current (amps) is like volume of flow
high voltage high current is like pushing alot of water through a pipe with a powerful pump
high voltage low current is like pushing water through a small orifice with a powerful pump (sort of)
low voltage, high current is like a big lazy river. think mississippi.
the math for electricity and hydrodynamics is actually very similar. so it's not an incorrect way of relating to it.

 

[91TTZ]

Originally posted by: Triumph
think of it like water
voltage is like pressure
current (amps) is like volume of flow
high voltage high current is like pushing alot of water through a pipe with a powerful pump
high voltage low current is like pushing water through a small orifice with a powerful pump (sort of)
low voltage, high current is like a big lazy river. think mississippi.
the math for electricity and hydrodynamics is actually very similar. so it's not an incorrect way of relating to it.

Yeah, but you can't drink electricity.

 

[RaynorWolfcastle]

Originally posted by: Eli
Realistically, it should only affect the speed.

If your cell phone actually ever draws over 600mA, it may get a little warm, but thats about it.

So I assume all of you that said it would be fine are electrical engineers, right?

While there's a good chance that everything will be fine, you could overheat components that aren't designed for 850 mA. Battery chargers have some complex circuits in them these days and going 30% above a charger's rated current is not a good idea.

 

[Howard]

Originally posted by: RaynorWolfcastle

Originally posted by: Eli
Realistically, it should only affect the speed.

If your cell phone actually ever draws over 600mA, it may get a little warm, but thats about it.

So I assume all of you that said it would be fine are electrical engineers, right?

While there's a good chance that everything will be fine, you could overheat components that aren't designed for 850 mA. Battery chargers have some complex circuits in them these days and going 30% above a charger's rated current is not a good idea.

His phone came with a 850mA charger.

 

[eits]

amps = volts per resistance

 

[RaynorWolfcastle]

Originally posted by: Howard

Originally posted by: RaynorWolfcastle

Originally posted by: Eli
Realistically, it should only affect the speed.

If your cell phone actually ever draws over 600mA, it may get a little warm, but thats about it.

So I assume all of you that said it would be fine are electrical engineers, right?

While there's a good chance that everything will be fine, you could overheat components that aren't designed for 850 mA. Battery chargers have some complex circuits in them these days and going 30% above a charger's rated current is not a good idea.

His phone came with a 850mA charger.

Right, and the charger he bought on eBay is only rated for 650 mA... That's the whole point of my post

 

[Aluvus]

Originally posted by: RaynorWolfcastle
While there's a good chance that everything will be fine, you could overheat components that aren't designed for 850 mA. Battery chargers have some complex circuits in them these days and going 30% above a charger's rated current is not a good idea.

FWIW the complex circuitry will all be in the phone. But yes, it is possible the device will try to draw more from the DC adapter than the adapter can safely deliver, which would be bad. It's also possible that the phone's original adapter was significantly over-rated and/or the new adapter is significantly under-rated.

Originally posted by: eits
amps = volts per resistance

Not especially helpful since the phone's charging hardware will most certainly not be a purely resistive system.

 

[WHAMPOM]

Originally posted by: TheGizmo
my cell phone came with a charger rated at 5 volts and 850ma... i bought a charger on eBay that was supposedly for my phone but it says 5 volts 600 ma on it. Is this charger going to fully charge my battery or only charge it 2/3 of the way since its 250 milliamps less. or is this just the speed at which my phone is being charged.

if it matters, my battery is 780mah.

Thanks

High amps shotgun.
Low amps BB gun.
FYI A 12Volt charger at 1 AMP will fully charge the biggest 12VOLT battery, but slowly.

EDIT My dial up sucks big. It took four trys to get this posted. NO SERVER, NO SERVER,,,etc.:disgust:

 

[Triumph]

Originally posted by: RaynorWolfcastle

Originally posted by: Howard

Originally posted by: RaynorWolfcastle

Originally posted by: Eli
Realistically, it should only affect the speed.

If your cell phone actually ever draws over 600mA, it may get a little warm, but thats about it.

So I assume all of you that said it would be fine are electrical engineers, right?

While there's a good chance that everything will be fine, you could overheat components that aren't designed for 850 mA. Battery chargers have some complex circuits in them these days and going 30% above a charger's rated current is not a good idea.

His phone came with a 850mA charger.

Right, and the charger he bought on eBay is only rated for 650 mA... That's the whole point of my post

Yeah, so he'll be fine. It will just charge slower.

 

[Jeff7]

Originally posted by: Triumph

Originally posted by: RaynorWolfcastle
Right, and the charger he bought on eBay is only rated for 650 mA... That's the whole point of my post

Yeah, so he'll be fine. It will just charge slower.

I think the point being made is that the charger, not the phone, may overheat.

If the phone is rated to consume up to 850mA, a 650mA supply might not be able to meet that demand, and thus the supply would overheat while the phone tries to suck it dry.


Analogy time:
The phone is a 53' trailer. It came with a truck designed to pull it (the original 850mA charger). Now you're going to eBay to buy a 2-door Honda (600mA charger) to try to pull it. The trailer doesn't give a damn about how fast or slow it moves, but that little Honda is going to bust a gasket or two trying. You'd best get something that is definitely capable of getting the job done without being a fire hazard.

 

[txrandom]

Amp = Charges per second. It should just charge slower.

 

[bdude]

Originally posted by: 91TTZ

Originally posted by: Triumph
think of it like water
voltage is like pressure
current (amps) is like volume of flow
high voltage high current is like pushing alot of water through a pipe with a powerful pump
high voltage low current is like pushing water through a small orifice with a powerful pump (sort of)
low voltage, high current is like a big lazy river. think mississippi.
the math for electricity and hydrodynamics is actually very similar. so it's not an incorrect way of relating to it.

Yeah, but you can't drink electricity.

A bottle of stiff whisky will say different.

 

[tatteredpotato]

I don't think hes worried so much about the charger, which seems to be the only concern here.

 

[TheGizmo]

Cool, sounds good.. slower is ok with me since I usually just plug it in when I go to bed and unplug it in the morning which gives it 8 hours on the charger anyway. With the original charger, it reaches full capacity in just under 3 hours. so I'm guessing the new charger will just take 4 hours or something along those lines.

Another question though, is it bad to leave my phone on the charger after it says "Charge Complete" on my phone? I've been doing it for years, but then again I do notice a significant drop in battery life after 6 or 8 months.

I figure that issue is due to either:

a) Leaving the phone on the charger for up to 5 hours after the charge is already complete
b) charing the phone when the battery is not full discharged (ie. memory issue.. though the battery is Lithium Ion so it shouldn't have that problem right?)
c) just the fact that most batteries start to lose some capacity whether you're using it or not, just because of it getting old

Anyway, thanks for all the info

 

[Furyline]

The charger may overheat. If it doesn't, it should charge in the same amount of time, and it should charge it fully. You could call whoever makes the phone and ask them about it.

Or just hook it up already and see if something bad happens

 

[Eli]

Originally posted by: RaynorWolfcastle

Originally posted by: Eli
Realistically, it should only affect the speed.

If your cell phone actually ever draws over 600mA, it may get a little warm, but thats about it.

So I assume all of you that said it would be fine are electrical engineers, right?

While there's a good chance that everything will be fine, you could overheat components that aren't designed for 850 mA. Battery chargers have some complex circuits in them these days and going 30% above a charger's rated current is not a good idea.

LOL. There's probably about 3 components in his charger. A transformer, and maybe a cap or two and a resistor..

If it's a "light" wall-wart, it's probably a switching supply, in which case it will just go into protection mode in the event of an over-current situation...

I'd be more worried about the chargers voltage dropping in the case of a conventional wall-wart than anything.

I'd also be surprised if the cell phone drew anywhere near 850mA. It was probably just the China special at the time they packaged his cell phone.

 

[RaynorWolfcastle]

Originally posted by: BlameCanada
I don't think hes worried so much about the charger, which seems to be the only concern here.

Uhhh he should definitely be worried about the charger, as running it 30% out of spec is potentially a fire hazard.

Originally posted by: Eli

LOL. There's probably about 3 components in his charger. A transformer, and maybe a cap or two and a resistor..

If it's a "light" wall-wart, it's probably a switching supply, in which case it will just go into protection mode in the event of an over-current situation...

I'd be more worried about the chargers voltage dropping in the case of a conventional wall-wart than anything.

I'd also be surprised if the cell phone drew anywhere near 850mA. It was probably just the China special at the time they packaged his cell phone.

Cell phones use lithium ion batteries, which means they use complex chargers that are more than a transformer a cap or two and a resistor. I assume some (all?) of that circuitry is in the phone, but neither you, nor I know what it does when its paired with an insufficient power supply.

 

[Eli]

Originally posted by: RaynorWolfcastle

Originally posted by: BlameCanada
I don't think hes worried so much about the charger, which seems to be the only concern here.

Uhhh he should definitely be worried about the charger, as running it 30% out of spec is potentially a fire hazard.

They wouldn't have bundled the phone with a 850mA charger if the phone drew 850mA. It's a smart idea to leave a ~30% overhead.

I'd say at worst, the charger is being maxed out, which may shorten its life in the worst case scenario.

 

[RaynorWolfcastle]

Originally posted by: Eli

Originally posted by: RaynorWolfcastle

Originally posted by: BlameCanada
I don't think hes worried so much about the charger, which seems to be the only concern here.

Uhhh he should definitely be worried about the charger, as running it 30% out of spec is potentially a fire hazard.

They wouldn't have bundled the phone with a 850mA charger if the phone drew 850mA. It's a smart idea to leave a ~30% overhead.

I'd say at worst, the charger is being maxed out, which may shorten its life in the worst case scenario.

How do you know they have a 30% overhead and not a 10% overhead? Look if you want to take risks with potential fire hazards in your house, I'm certainly not the one to stop you but please refrain from recommending other people do the same. At the very least, you should tell him that he might be running the device out of spec.

 

[chowmein]

ohm's law ... brings back memories.