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> Lithium Charger
Guruji
Posted: June 17, 2017 12:54 pm
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Hi guys I built this charger but want it to increase voltage to 20v for five cells in series. Is there a way howto?
http://www.instructables.com/id/How-to-make-Lithium-charger/
Thanks
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AwesomeMatt
Posted: June 17, 2017 07:04 pm
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It's a variable power supply, so, R4 there sets the voltage.

This type of supply only lowers the voltage you give it, so, if you want 20v output, you'd need to have over 20vDC input (I forget what the LM317 is rated for, 30-some volts max). I would find a power supply that's 24v or so.

Also, it will get hot charging batteries so, make sure you have a good heatsink on the LM317.

Might not be the best or cheapest battery charger to make, just FYI. You can grab stuff off the shelf that'll do the job safer and maybe cheaper.
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Guruji
Posted: June 17, 2017 09:20 pm
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QUOTE (AwesomeMatt @ June 17, 2017 07:04 pm)
It's a variable power supply, so, R4 there sets the voltage.

This type of supply only lowers the voltage you give it, so, if you want 20v output, you'd need to have over 20vDC input (I forget what the LM317 is rated for, 30-some volts max). I would find a power supply that's 24v or so.

Also, it will get hot charging batteries so, make sure you have a good heatsink on the LM317.

Might not be the best or cheapest battery charger to make, just FYI. You can grab stuff off the shelf that'll do the job safer and maybe cheaper.

Hi Awesomemstt thanks for response. I am using a 50v transformer but still giving me 5v to 11v.
Would like to higher more the voltage. Maybe if I put R4 larger pot would do the job?
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AwesomeMatt
Posted: June 17, 2017 10:02 pm
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I'm too lazy to do the math but yes, something like that.

This is a normal circuit. Look up LM317 circuits or look up the datasheet and it will have a variety of sample circuits.
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