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I designed a circuit for my graduation project in automotive engineering department, that circuit will measure the heat energy from exhaust system and turn it into electrical energy by using thermoelectric generators (TEG). In the final stage I found two voltage values on TEG which is the matched output voltage and open circuit voltage .

  • Is the matched output voltage is the actual voltage after load?
  • And which value I must depend on (open voltage or matched voltage) to design circuit to charge a 12v battery by using these TEGs?
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You must use both values when designing a circuit around such a generator (or solar panels, alternator, etc)

Your circuit needs to safely withstand the open circuit voltage without damage.

But in operation, drawing the rated current from the generator, you can expect the matched voltage. If you're computing charging times, power ratings, efficiency, this is the value to use.

As the battery becomes fully charged, you will draw less than the rated current, then the voltage will rise towards the open circuit voltage as the current decreases.

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  • \$\begingroup\$ Thank you so much,, Then I must wire them in series until I get around 14V matched output voltage in order to charge 12V battery ? \$\endgroup\$ – MADI Oct 24 '15 at 14:46
  • \$\begingroup\$ That's the simplest way, but you must take care not to over-volt the battery when its fully charged, perhaps with abattery charge controller. There are also converters that can step voltages up or down as necessary, if you can't arrange the correct voltage from the TECs. \$\endgroup\$ – Brian Drummond Oct 24 '15 at 16:38

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