Charging a 5V source with 4.5V

Hazaro · Mar 9, 2008

This is ok right? I mean it will only charge it till a 4.5V instead of a full 5V charge, but other than hat it is ok right? Also is 5.5V good, or not, because it will go over the rate?

This is for a 5V DC insource to a 3.7V battery for a Zen Vision M by the way.

Thanks.

Xenocide · Mar 9, 2008

Should be fine but watch your current.

You can pull 5v 500ma off your USB ports IIRC

Roofles · Mar 9, 2008

You should be okay but for a different reason than you think. The idea is that you have to provide a voltage source that is greater than the maximum voltage of the battery. In this case lion batteries hit 4.2V max charging voltage. So in your case you should be fine.

Are you using a 3 AA stack to charge your player? Is that what the question is?

Hazaro · Mar 10, 2008

Nope, I got a 4.5V DV power adapter that fit it, but it only charged till 50-60% of the battery, then stopped giving it a charge.
I went over a cousin's house, but the Zen seemingly has to "sync" to charge via USB and their house had 6 macs. And it hates macs

The Zen is rated at ~6 hours USB charge time and ~2.5 hours adapter charge time. I probably should of though of reverse charing, but I had no spare wires since I was on a trip, I would of cut up a spare 5V adapter I had at home, but I wasn't

Now that I'm back though, I'm interested why it didn't continue charging...

What I used: 4.5V 500mA
Zen spec Adapter: 5V 2400mA (1000mA 3rd party model)

the current rating only determines how fast it will charge at peak correct? The device (Zen) only draws as much as it needs right?
My thinking was that the 5V -> 3.7V filled the battery up to something like 3.9V instead of what you said 4.1-4.2V tops.

So please correct me, thanks.

Hazaro · Mar 10, 2008

bumpo

Roofles · Mar 11, 2008

Hazaro said:
Nope, I got a 4.5V DV power adapter that fit it, but it only charged till 50-60% of the battery, then stopped giving it a charge.
I went over a cousin's house, but the Zen seemingly has to "sync" to charge via USB and their house had 6 macs. And it hates macs

The Zen is rated at ~6 hours USB charge time and ~2.5 hours adapter charge time. I probably should of though of reverse charing, but I had no spare wires since I was on a trip, I would of cut up a spare 5V adapter I had at home, but I wasn't
Now that I'm back though, I'm interested why it didn't continue charging...

What I used: 4.5V 500mA
Zen spec Adapter: 5V 2400mA (1000mA 3rd party model)

the current rating only determines how fast it will charge at peak correct? The device (Zen) only draws as much as it needs right?
My thinking was that the 5V -> 3.7V filled the battery up to something like 3.9V instead of what you said 4.1-4.2V tops.

So please correct me, thanks.

Correct, The current rating is just how fast it will fill up. Batteries are typically rated in Amp-Hours (Ah). So say you have a 2 Ah battery and you are drawing 2 amps from it, your run time is 1 hour. If you say draw 200mA your run time is 10 hours. etc etc. So the case works the same going backwards if you charge at 2 amps, your charge time is 1 hour. So in your case with a lower rated charger you just have a longer charge time.

What I imagine is that the internal charger has some other conditions or safety features going on that shut down charging prematurely. I can only speculate on what those are or how they operate though. I would have assumed initially that your 4.5V source would work just fine...

Simply though, it might be that some internal voltage drop causes the battery voltage not to reach its 4.2V fully charged state and in that case some safety circuitry kicks in and stops all current flow.

Charr · Mar 11, 2008

I am wondering, where did you get the 4.2v figure from? I know that there are 3.7v cells and 1.2v cells for Li-Ion, but nothing that is 4.2v.

Hazaro · Mar 11, 2008

Charr said:
I am wondering, where did you get the 4.2v figure from? I know that there are 3.7v cells and 1.2v cells for Li-Ion, but nothing that is 4.2v.

I measure my 3.7v rated batteries and they give me ~4.2V on average

Now I want to know how fast the battery in the Zen can charge... I can get an adapter with better current if I have to, gonna splice up the end connector either way.

kswaid · Mar 12, 2008

Li-Ion and LiPolymer batteries are rated at 3.7 volts, because that is the nominal voltage they maintain under load. A fully charged battery, however, should read 4.2 volts with no load. Same thing with nicad's and such, they charge to ~1.5v but deliver current at ~1.2v.

Charging a 5V source with 4.5V

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