Problem Using Power source instead of Li-ion - Page 1
Forum section: electronics / beginners

author: slimdd
author_rank: Newbie
timestamp: September 09, 2015, 03:20:46 pm
content: Hello Guys,First of all sorry for my english...I have a weird situation with my MP3 player. As nearly all MP3 player it uses an Li-ion single cell battery so 3,7V. When I disconnect that Li-ion battery and use a power source with of course the same voltage the MP3 player doesn't want to start.So I am wandering why this behaviour when normally it should work without any problem.For info the single cell battery has only 2 wires so the TEMP wire doesn't exist.If anyone has a guess on it feel freeThanks

author: Delta
author_rank: Super Contributor
timestamp: September 09, 2015, 04:01:22 pm
content: Try bumping the voltage up to 4.2

author: slimdd
author_rank: Newbie
timestamp: September 09, 2015, 04:20:07 pm
content: Just did it. Nothing happened.It's like just when I push the switch on button it drains some power (few mA ~3 or 4) then nothing.

author: Augustus
author_rank: Regular Contributor
timestamp: September 09, 2015, 04:30:50 pm
content: What external power source are you using exactly? Try to connect a ~100nF ceramic capacitor across the battery terminals (as close as possible to the pcb)...

author: slimdd
author_rank: Newbie
timestamp: September 09, 2015, 04:34:22 pm
content: I'm using a RIGOL DP832. I think it's enough well made to have a capacitor integrated.But Ok i'll try your solution right away.

author: slimdd
author_rank: Newbie
timestamp: September 09, 2015, 04:44:52 pm
content: No effet with a capacitor

author: electr_peter
author_rank: Unknown
timestamp: September 09, 2015, 04:59:01 pm
content: Check that there are no safety switches which are enabled only when battery is inserted.Set current limit up, check all connections very carefully.I would also try rechecking with original. Maybe player itself is half broken, maybe connector is broken.

author: slimdd
author_rank: Newbie
timestamp: September 09, 2015, 05:05:42 pm
content: No safety switches present in it.If I let the Li-Ion battery the device start normally without any problem. It's only when I use a power source with the exact same voltage that the device stay quite.For info the MP3 player is a Achos 5 IT.

author: slimdd
author_rank: Newbie
timestamp: September 09, 2015, 06:43:58 pm
content: After checking with my oscillo the voltage behaviour Li-ion vs Power Supply it seems that for a very short amount of time at start, the voltage from the Power Supply drop from 3,8 to 2,7vWhen I do the same with the battery no voltage dropping.Is there any link with the current? (for info I didn't limited it)I put also a capacitor to avoid this but without effect....

author: jitter
author_rank: Frequent Contributor
timestamp: September 09, 2015, 06:52:01 pm
content: Quote from: slimdd on September 09, 2015, 06:43:58 pmNot limiting the current on the DP832, does that mean full current capability is there at on power on, or do you actually have to set it? Some PSUs seem to remember the last settings others just power on in the lowest settings.If you switch on the player, does the power supply go into CC mode for a short time?Edit: if it's not the PSU, then maybe it's voltage drop in the wires. Cut the to the shortest length possible and try again. Alternatively, use thicker wire.

author: max666
author_rank: Frequent Contributor
timestamp: September 09, 2015, 06:58:19 pm
content: Sounds like you either have the current limit to low, or the wires connecting the PSU and MP3 are to thin, or the contact resistance is too high. A capacitor close to the battery terminals would help with that, or make a better connection.

author: timb
author_rank: Super Contributor
timestamp: September 09, 2015, 06:59:13 pm
content: Some equipment used the battery for excess current (like a giant capacitor) even when plugged in. This is why a lot of cell phones won't turn on until the battery reaches a certain charge level.Are you powering this through the external power port or clipping directly to the battery terminals? Try clipping to the battery terminals and see what happens.Or, try putting 470uF or greater cap, in series with say a 5 ohm resistor, on the battery terminals and then power it from the external connector.Sent from my Smartphone

author: Chris C
author_rank: Frequent Contributor
timestamp: September 09, 2015, 09:34:10 pm
content: Quote from: slimdd on September 09, 2015, 06:43:58 pmMinimum safe voltage voltage for plain Li-ion is 2.7V, so shutting when the voltage dips to that is the correct behavior. is right, startup current can be surprisingly high. I had something which never drew more than 100mA, except at startup, when it was tripping a 3A overcurrent limit on my power supply.

author: max666
author_rank: Frequent Contributor
timestamp: September 09, 2015, 09:54:49 pm
content: Quote from: slimdd on September 09, 2015, 04:34:22 pmActually a good lab power supply must not have to much output capacitance, otherwise you may have already fried whatever is connected, before the current limiting even kicks in.

author: slimdd
author_rank: Newbie
timestamp: September 09, 2015, 10:08:09 pm
content: Hello Guys,I wanna thank you first for your quick answers. I will try different options tomorrow (already late here) but I'm heading maybe of what max666 says. Wires that I use are maybe too thin and limit the current...I will let you know of course the results.Thanks

author: GoneTomorrow
author_rank: Regular Contributor
timestamp: September 10, 2015, 05:49:41 am
content: The Archos 5 IT has a fairly large LCD display, some models even have a hard disk drive (not specified if this one does). So this thing is going to want some serious current.