Trying to charge a portable DVD player... Don't want to kill it

[magician13134]

Hi, my mom bought a portable DVD player and is always complaining how bad the battery life is (it only lasts about an hour). I told her I could probably make an external battery pack for it, so here's what I've got. The DC-in jack says it takes "9-12V 1A", I have a 12V 6AH Li-Ion battery and I bought the conversion plugs I need to make it fit, but I don't want to just plug the battery in for fear that it might put more than an Amp into the DVD player, thus frying it. Can anyone tell me if I should be worried about this or if there's a better way to do it? Should I just measure the current with my multimeter (it has a 10 Amp "unfused" setting)

Thank you.

 

[bychon]

Go to the top of this page and click on "home". Read The amp-hour fallacy on the first page.

 

[magician13134]

Right, I understand that Amp-hours doesn't have an effect on that, but when I measure the current with a multimeter it's 2 Amps. So you're saying this won't be a problem because of the internal resistance of the circuit?

 

[bychon]

If the DVD player is eating 2 amps, something is wrong with it.

 

[bychon]

Hang on. I might be wrong. Read the label on the DVD player and see if it says it eats 2 amps.

 

[magician13134]

No, no. I haven't plugged it into the DVD player yet. It says 2 Amps when I measure with my multimeter across the battery terminals. The DVD player says it takes 1 Amp though, but this doesn't mean it will fry the DVD player, right? It just means that the DVD player will only draw 1 Amp from the battery?

 

[bychon]

Did you read the amp-hour fallacy? The amps don't all jump out of the battery at once and force the DVD player to eat them.

 

[magician13134]

Sorry, I had only skimmed it because I thought it was all about Amp-hours. I wasn't sure if the discharge rate of the battery worked like that or not. Thanks for the answer, I will go back and read that more thoroughly and post back if the charger works well.

 

[MikeMl]

No, no. I haven't plugged it into the DVD player yet. It says 2 Amps when I measure with my multimeter across the battery terminals. The DVD player says it takes 1 Amp though, but this doesn't mean it will fry the DVD player, right? It just means that the DVD player will only draw 1 Amp from the battery?

By connecting an Ammeter directly across your battery is the same as measuring the batteries ability to supply current into a Dead Short, which just proves that your battery is junk. A fully-charged 6AH Li-On would produce a short circuit current of ~20A (and likely self-destruct, or blow the fuse inside the ammeter).

You NEVER EVER use an ammeter that way!!!

 

[audioguru]

You short-circuited the battery with your meter. You are lucky that the battery did not catch on fire. You should never short a lithium battery.
You should connect the current meter in series with a load to measure its current.
With the load connected to the battery then you should measure the voltage to see if it drops too low with the load.

 

[bychon]

It is so frustrating to try helping a person who wouldn't read the answer if it was right here, on this site, one click away!

 

[MikeMl]

I have one of those DVD players. It is designed to play when plugged into a cigar lighter in a car, which when running will supply 14V at about 10A. Haven't damaged the DVD player yet...

 

[mneary]

No, no. I haven't plugged it into the DVD player yet. It says 2 Amps when I measure with my multimeter across the battery terminals. The DVD player says it takes 1 Amp though, but this doesn't mean it will fry the DVD player, right? It just means that the DVD player will only draw 1 Amp from the battery?

The answer to your second question is, you are correct - the DVD will only take 1 Amp when it's hooked up properly.

You might be afraid to ask why your battery or meter didn't explode as predicted when you shorted it with your meter on the 10 Amp "unfused" setting. This probably means your battery is very low or dead. Re-check your 12 6Ah "Lithium" battery and make sure it is lithium. It's not common to sell them as stand alone units to play with, without dedicated chargers. In any case if you only got 2A from it, it needs charging.

Before you play with it, tell us more about this battery. If it's actually lithium, precautions would be in order. Maybe some numbers, mfrs name, and if possible a photo? Or a pointer to where you got it?