How long do you charge your DSO?

--DSO203

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joser-cg
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How long do you charge your DSO?

Post by joser-cg » Tue Feb 02, 2016 10:16 am

I just got my new DSO203 with HW2.81, Sys1.64, APP +A1 1.13, DFU 3.45C, a few days ago. I'm a little concerned about the seemingly long charge times. When I first got it, it had about a quarter charge according to battery icon in the upper left corner. I charged it about 2 hours, disconnected(red charging led was on before I disconnected), turned on, battery icon showed fully charged, then I thought I'd check it out a little with the factory firmware before I installed the latest Wildcat 5.0(Wildcat is awesome!). I've used my DSO a few times already over the weekend, never let it get below half charge according to the battery icon in the upper left corner. It is charging, the battery icon shows full, but I have left it charging overnight a couple times and I was surprised to see the red charge led still on in the morning.

Is a long/slow charge time typical for the DSO203? I just wanna make sure I didn't get a defective DSO and there's something wrong with my charging circuit. I did find the community DSO Quad Manual wiki http://www.seeedstudio.com/wiki/DSO_Qua ... ower_Modes that has a good explanation of the LED Indicators and Power Modes that was helpful because the factory manual doesn't say anything about this.

Dirk.Wesenberg
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Re: How long do you charge your DSO?

Post by Dirk.Wesenberg » Tue Feb 02, 2016 7:34 pm

The battery Icon ( I've read this somewhere ) does not talk the full true.
I was also surprise, that the LED does not goes off in total. I've read also the wiki and I have expect that the LED goes off to 100% - but it doesn`t : If the battery is charged the LED is ON to 100% . If the internal charge-circuit stop the charging, my LED ( HW2.81 & Wildcat 5.0) is dimmed to ~10-20%.

joser-cg
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Re: How long do you charge your DSO?

Post by joser-cg » Wed Feb 03, 2016 6:11 am

Thanks Dirk. I didn't notice if the led had dimmed after charging but I will check that out. I was thinking about reinstalling the factory firmware then charging and seeing if the led turned off, just to rule out Wildcat 5.0 being a possible cause and reporting it if necessary, but then I found this post by Wildcat » Sat Apr 11, 2015 9:27 am
The charging system is completely hardware controlled. The system has access to
the charging state from the charging controller, as well as the battery voltage but
does not control charging. The charge indicator is a red light only, which should go
out when the battery is fully charged. The green light is for standby. My
observations are that the charging system tends to charge these batteries a bit too
much, so I disconnect charging well before the red light goes out.
So it appears Wildcat 5.0 couldn't have any effect on the led or charging. Just to be safe I will take Wildcat's advice and not charge my DSO more than a few hours. Interesting to see that Wildcat says the led turn off when charged tho.

borland
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Re: How long do you charge your DSO?

Post by borland » Wed Feb 03, 2016 10:15 am

The DSO203’s Lipo charging integrated circuit (U14) charges at 4.2 volts max. A 2K resistor (R50) programs/sets the max charge current at 560mA.

When the DSO is powered by USB cable and the power switch is ON, the Lipo battery will be charged, however the battery is electronically disconnected (by a MOSFET) from supplying power. Charging takes place until the battery is fully charged, whether the power switch is ON or OFF. The animated battery graphic shows when charging is active.

When DSO is switched ON and powered by USB, I believe the Vbt meter is actually showing the USB supplied power across a voltage divider used by the processor to sense the battery voltage, not the actual Lipo battery voltage. That might lead to the wrong assumption, that the battery is being overcharge. So, the Vbt meter is only correct when the DSO is battery powered.

There’s also a voltage divider for sensing Vusb, so maybe the designer intended to calculate the state of charge knowing charging state (CHRG) and the voltage drop across the U19 diode (Vusb – Vbt).

Best for long life of the Lipo is to store the DSO with a charge state of Vbt at about 3.80 volts. Since it is a pain to discharge it to that level, best not to charge it more than what's needed.

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