The post explains a simple constant current bicycle dynamo battery charger circuit which can be used for charging a Li-Ion or Ni-Cd battery from a bicycle dynamo electricity source. The idea was requested by Mr. Saif Khan.

Technical Specifications

I want to charge a battery through a dynamo fitted to a cycle. Can you please tell me how to design the circuit for it. I don't know electronics. I will be really grateful.I don't know much but i live with electronic engg guys who know about it so if given a complete schematics they can do it. Can i order these online?

I am not sure a dynamo would be able to produce 28/30V. I have read that it can be limited to 4-20 V mostly
(I am using a simple motor..which will rotate and as well charge the battery). I know i am a total n00b :/

Just few points:
1. The input voltage, being connected to a dynamo fitted to a normal cycle will vary a lot but mostly be less than 20V, right?

2. The li ion battery that will be charged needs to power an LED lamp for about 2 hrs. It has to be charged within 1-1.5 hr of cycling. That's pretty much my project.

And can we charge Ni-MH battery with it if i don't find Li-ion battery anywhere

Thank you once again. Apology for my n00bness i am just a chemistry grad.

Sir i have bought all u asked for lm317..please guide me further thank u


The Design

The second circuit shown in the following link can be implemented for the above application:

The dynamo input should be connected across the points referred 30V and ground, VIA a 1N4007 DIODE.

The 10K variable resistor which may be a pot or a preset should be adjusted to get the desired output voltage.

The LM317 should be mounted on a suitable heatsink.

The IC LM317 can work right from 3V to 35V inputs, so input variations won't affect the outcome.

The pictorial presentation of the proposed bicycle dynamo battery charger circuit is provided below.

It must be ensured that the pinouts of the IC are correctly connected as per the shown designations.

How to calculate current limit for this bicycle dynamo battery charger circuit

Rx is the current control resistor which must be selected as per the charging current specifications by using the following formula:

Rx = 0.6/charging current

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