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[104.222.118.43]) by smtp.gmail.com with ESMTPSA id a52sm1286697qtc.22.2020.09.02.22.03.56 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 02 Sep 2020 22:03:56 -0700 (PDT) From: Jim Ruxton To: Microcontroller discussion list - Public. Sender: "piclist-bounces@mit.edu" Date: Wed, 2 Sep 2020 22:03:55 -0700 Subject: [OT] Simple LiPo charging circuit Thread-Topic: [OT] Simple LiPo charging circuit Thread-Index: AdaBsrGIMFoHSlTUT5GX49XmPuLh7w== Message-ID: List-Help: List-Subscribe: , List-Unsubscribe: , Reply-To: Microcontroller discussion list - Public. Accept-Language: en-US Content-Language: en-US X-MS-Exchange-Organization-AuthAs: Anonymous X-MS-Exchange-Organization-AuthSource: TS500.efplus4.local X-MS-Has-Attach: X-Auto-Response-Suppress: All X-MS-Exchange-Organization-SenderIdResult: TempError X-MS-Exchange-Organization-PRD: mit.edu X-MS-TNEF-Correlator: received-spf: Pass (protection.outlook.com: domain of gmail.com designates 209.85.222.174 as permitted sender) receiver=protection.outlook.com; client-ip=209.85.222.174; helo=mail-qk1-f174.google.com; dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=to:from:subject:message-id:date:user-agent:mime-version :content-transfer-encoding:content-language; bh=Rn/7MafmGwZrx0UNbOk8xrZNAnkCfNASzybp6jreQQ4=; b=lOYc9KAlM9kmX7X2xg7GwsAPzejHoPZo4JB6PCxIQV+1MbVVduSEHxbTg0ZB9zIOdM r/F8E5fm1zV2rRLPDiC681pNq9I2UD35/E27ljYnyMvnWIQWaH8I1fiAeJcOM2jDewwg 8WAnW2v+cbNxeQxnJUgDox7bYziJslX4mAFV+eI98hzgxEYwQ83ABBrlmZeLsqM6ljuv g5QDoz8myNuvQPbAAnuPcDEPaQOIi3WXGAQXhXbO47TJqTwYBffaQdCzrl5dbmxpv1qp 5S7s0TXKxYbOlbLzAioID6mm9mbeyknVWl0Uc0wxStzGzezc2m4mCO95qOlQ/CiZHv5P +Yrw== authentication-results: spf=pass (sender IP is 209.85.222.174) smtp.mailfrom=gmail.com; mit.edu; dkim=pass (signature was verified) header.d=gmail.com; mit.edu; dmarc=pass action=none header.from=gmail.com; user-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 errors-to: piclist-bounces@mit.edu list-id: "Microcontroller discussion list - Public." list-post: x-beenthere: piclist@mit.edu x-mailman-version: 2.1.6 x-received: by 2002:a05:620a:20d4:: with SMTP id f20mr1563965qka.222.1599109436802; Wed, 02 Sep 2020 22:03:56 -0700 (PDT) x-topics: [OT] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 I bought a cheap battery powered speaker/amp . It is only 3 watt but=20 works for my purpose. It's powered by a small 180 mAH LiPo battery. It=20 uses the simplest LiPo charging circuit I have seen. Basically it=20 charges from the 5 volts of a USB port through a 1 ohm resistor and=20 diode in series? I guess it stops charging when it gets to 5 volts -=20 forward voltage of the diode. The diode seems to have about .8 volts Vf=20 so charging stops at 4.2 volts which seems ok for LiPo. I guess I'm=20 wondering how the manufacturer gets away with such a simple charging=20 circuit? Is it only because the LiPo is such low capacity? Is this=20 standard for cheap low capacity LiPo charging? I want to change the=20 battery to a higher capacity battery but I am thinking if I do that I=20 should use a proper charging circuit or IC for the job. I can't just=20 stick a higher, say 1000 mAH battery in here can I? Doesn't seem safe.=20 Thanks for your thoughts on this. Jim --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .