Please explain simple 'red/green LED' lipo charger to me

Batteries, Chargers, and Battery Management Systems.
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lesdit   100 W

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Please explain simple 'red/green LED' lipo charger to me

Post by lesdit » Dec 31 2012 8:10pm

I am a bit mystified by how to charge a couple of 160wh lipo professional V mount video camera batteries I just received. They are nice batteries with a fancy LCD 'fuel guage' on the isde as well.
They did not come with a charger, but I do see that they sell some 'travel' chargers that work, with a green and red LED on it. The red led lights until the battery is charged, lighting the green LED when done.
Simple 2 wire connection, I assume the battery itself does some management function. Supposed to charge at about 2 amps.

My question is: How do these simple 2 wire red/green chargers actually work ? They rate the chargers at 14.8 volts output. Is it just a simple voltage regulator with a max current circuit ? Are these simple chargers doing something fancy with a voltage profile as well ?
I don't want to spend $200 on a two wall wart looking things if it's something I can cobble up myself!

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Gordo   100 kW

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Re: Please explain simple 'red/green LED' lipo charger to me

Post by Gordo » Dec 31 2012 8:43pm

The fancy chargers usually charge at 14.8V and then float down to 13.25V, come back on and charge to 13.75V, shut off and float again. Some of them will switch to pulsating DC to finish the first charge.
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SamTexas   100 MW

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Re: Please explain simple 'red/green LED' lipo charger to me

Post by SamTexas » Dec 31 2012 9:07pm

lesdit wrote:I am a bit mystified by how to charge a couple of 160wh lipo professional V mount video camera batteries I just received. They are nice batteries with a fancy LCD 'fuel guage' on the isde as well.
They did not come with a charger, but I do see that they sell some 'travel' chargers that work, with a green and red LED on it. The red led lights until the battery is charged, lighting the green LED when done.
Simple 2 wire connection, I assume the battery itself does some management function. Supposed to charge at about 2 amps.

My question is: How do these simple 2 wire red/green chargers actually work ? They rate the chargers at 14.8 volts output. Is it just a simple voltage regulator with a max current circuit ? Are these simple chargers doing something fancy with a voltage profile as well ?
I don't want to spend $200 on a two wall wart looking things if it's something I can cobble up myself!
Hard to guess based on the info you provided.
Since you said "lipo", it's definitely not a lead acid battery charger with a float voltage. 14.8V is the common notation for 4s LiCo/LiPo. 14.8/4 = 3.70V nominal. If that the case, the highest output voltage is not 14.8 but 16.8V (4.20V per cell). Most lithium charger are CC/CV, and charging is terminated when the terminal voltage (16.8V) is reached and the current has dropped to 1/10 of the rated charge current (0.2A in your case). That's when the green LED is turned on.

For actual operation you need to consult the user's manual, if one exists.

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lesdit   100 W

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Re: Please explain simple 'red/green LED' lipo charger to me

Post by lesdit » Dec 31 2012 9:37pm

Thanks for the explanation guys, so I probably need to get a specific charger for this to do the back off to float charge?
Is there some kind of generic charger I can buy?
It doesn't sound like a limited voltage / constant current charger will do it. That would be easy to make with a couple of three terminal regulators.
Thanks!

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Re: Please explain simple 'red/green LED' lipo charger to me

Post by SamTexas » Dec 31 2012 9:46pm

Why don't you post pics and all relevant info you have on your battery? May be someone is familiar with the battery and thus can help you with the charger.

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dogman dan   100 GW

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Re: Please explain simple 'red/green LED' lipo charger to me

Post by dogman dan » Jan 03 2013 10:12am

Two hundred bucks does sound steep to me, but you'd have about 50 each in a 50w, 2 amp, RC charger such as a B6 AC.

I'd be tempted to buy one b6 myself, since it can also charge just about anything you ever have, up to 6 cells.

You'd have to know exactly what chemisty you were charging to use the RC charger though.

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lesdit   100 W

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Re: Please explain simple 'red/green LED' lipo charger to me

Post by lesdit » Jan 03 2013 1:37pm

I found some 'generic' lipo chargers on ebay for $20, so I ordered two. Charges at 2.5 amps.
I'll see what they do when they arrive.

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dogman dan   100 GW

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Re: Please explain simple 'red/green LED' lipo charger to me

Post by dogman dan » Jan 04 2013 7:17am

You might need a power supply for them too, if they are typical RC chargers. 5 amps 12v per charger.

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lesdit   100 W

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Re: Please explain simple 'red/green LED' lipo charger to me

Post by lesdit » Jan 04 2013 10:21pm

No, these are all self contained, 110-240 AC input, for a fixed number of cells. No operator controls, no balance leads, nada.
Kinda like the ones that come with Ping type batteries. I sure hope the batteries have some cell management, but tool batteries are the same way. Probably simple.

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dogman dan   100 GW

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Re: Please explain simple 'red/green LED' lipo charger to me

Post by dogman dan » Jan 05 2013 7:31am

Monitor your cell voltages then when you start to use them. No telling what "generic" voltage they are set for.

I'll never forget looking at my cell phone battery the first time, from the phone that kept ruining it's battery. A lico cell, the charger took it to 5v everyday!!!!!!!! Shit! I can't belive it never caught fire! No wonder my battery kept failing.

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