Over Charge Protection
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Over Charge Protection

by puntyourdonkey on Wed Mar 09, 2016 11:14 am


I am building a small hydro-electric generator for an engineer project at my school. We currently have a turbine hooked up to a gear rig and then to a D.C. motor. We have tested the voltage output by the D.C. motor and we are able to achieve voltages above 5V depending on the speed of the river.

We are using the MCP73871 USB/Solar LiPoly/Li-Ion charger to charge a 3.7 lithium ion battery pack. Then we will have a separate MintyBoost to take the 3.7V battery up to the 5V necessary to charge a phone. This all worked great when we could keep a controlled RPM.

We are worried that when we put the turbine into a river it will rotate too quickly and generate too much voltage for the battery and the phone. Our question is, does the MCP73871 have a charge controller within it to protect the battery and the voltage to the MintyBoost? If not, what components should we buy so that we can prevent overcharging?


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Joined: Wed Mar 09, 2016 10:43 am

Re: Over Charge Protection

by adafruit_support_bill on Wed Mar 09, 2016 11:23 am

The MCP73871 regulates the voltage to the battery, so that is not a problem. What can be a problem is if the generator produces more than 7v, which is the absolute maximum rating for the MCP73871 input. That could damage the charger.

You could prevent that by using a Zener diode to clamp the voltage coming from the generator to a safe level.
The recommended max operating voltage for the MCP73871 is 6v, so I'd use a 6V Zener rated for at least as much current as your generator can produce.
http://www.evilmadscientist.com/2012/ba ... er-diodes/

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