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Meddling with phone battery and charger

I've decided to take apart my old android phone, and since I've been in a great shortage of batteries for my high energy requiring protable projects, I was wondering If I colud use my phone batteries, that are quite capable in terms of Ahs.

I know the hazards of li ion batteries, and the difficulty in charging them, and I've attempted a solution by using the phone very charging circuit, or actually the pcb containing the usb port and the battery terminals.

My question is, is this safe? I've connected the load in parallel with the battery and charging circuit, and whereas the battery should be 3.7V it remains a costant 4V, even without the charger; When I connect a motor, the voltage drops down as expected, but when the running speed is reached it's still 4 V.

I somehow managed to get the batteries to 0V, but i suspect it was some protection, but connecting the charger brings the battery to 4V immediately, whereas obviously he phone woult take hours to charge.

Also, do you think there is some cheap IC that could replace the phone pcb? I would also need to use these batteries in series or parallel, but I don't know hot to treat them tho.

Thanks

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2 Answers

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@qiaoshu you are talking about android batteries and I do have to tell you that it is irrelevant where the batteries come from. Windows, iOS or Android does not matter. What matters, is what specs your batteries have. You need to look at voltages and mA as well as other specs. Those batteries should at least be similar with their specs. After that you need to consider how these batteries connect. Do they use flex cables, wires or pin contacts? If you are trying to use different connectors you have to come up with designing a way to create some kind of common connector. Next, remember that those batteries have most likely 4 connections: Positive voltage-Ground (negative)- Fuel gauge and Temp sensor. Keep this in mind for your charger.

In theory if you would use batteries from only one type of phone you could always use that particular phones schematic (if available) and copy the battery charging circuit from that phone onto a PCB. then use that phones charger for your battery. It will help if you tell us what this is "high energy requiring protable projects" and what the power requirements will be.

You have to check a battery with more than just a voltmeter. For example, you say that "When I connect a motor, the voltage drops down as expected" (because you are starting it with out a capacitor), "but when the running speed is reached it's still 4 V." which is correct. The voltage will not change until the battery gets depleted. You need an ammeter to see how much power the motor is pulling.

Minimum we need to know from you is:

  • how many batteries
  • power requirement for your project (V and Amperage)
  • model of batteries
  • type of battery connector

You say you need to connect them parallel and serial but you are not telling us why. again there has to be a reason why you want to increase the voltage and amperage of your circuit.

So, to try to assist you with this project this question needs more information. Can it be done? Yes, but it will require careful planning.

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I am so sorry that I can't help you. But I think the follow website or forum can give you some help.

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