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Variable Voltage battery charger for nicads and nimh? Answered

I would like to build a charger wherein I could specify up to what voltage to charge my nicads and nimh batteries. I'm currently using a la crosse bc-700 smart charger. it usually charges my batteries to 1.44-1.46v. I would like to build a charger that will cut off, say 1.38v. 

Is that possible? 

Thanks.

5 Replies

user
iceng (author)2013-11-06

A comparator op-amp can easily be set to turn the charge off at any exact voltage

or
better yet use two LM317s one as a voltage limit and one as the current limit.

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user
NotaryBlue (author)iceng2013-11-08

You are a Legend that is the simplest schematic I have seen, thank you I am going to use that.

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user
NotaryBlue (author)2013-11-08

I have to agree with Josehf doing so will simply reduce the lifespan of the cell. your current charger is a nice little beast.

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user
mpilchfamily (author)2013-11-06

Are you saying you want to build a charger that will charge the batteries at 1.38V or do you want to cut that 1.38V from it so it's only charging at .06V?

You do realize reducing the charging voltage will prevent the charger from being able to charge the batteries.

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user

I think they want to charge at 1.38 Volts.
Why so precise I don't know why.
Since batteries and other are built to a tolerance.

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