LT3081 floating reg as battery charger?

I was thinking of using LT3081 regs in series to charge a series of batteries connected in series - each LT3081 keeping its equivalent battery in the series at a set voltage?

This has been done with TL431 & ancillary external transistors (see circuit below) to boost the output current but no need for this with the 1.5A output of the LT3081.

the reason I want to do this is that I want to draw different output voltages, possibly multiple voltages from different series connections of the batteries in this series & the current draw may be 1Amp or more. Each LT3081 should keep each battery charged to its set voltage, I believe?

My concept is to tie the ground points in each LT3081 in this diagram to the negative pole of its equivalent battery in the series

Have I got the correct idea? Am I missing something in this?

Do I need clamping diodes plus 400ohm resistor between SET & OUT pins?

I know LT3081 is more robust with reverse voltage & reverse current protection. Is this idea feasible with LT3083 if I want to draw more than 1.5A from any point in the series?

Parents
  • I guess what my question boils down to is - has anyone used LT3081s in this manner i.e in series & what might be the pitfalls/gotchas?

  • OK, guess, I'll go it alone on this - looking into the online problems with these parts, such as LT3080, it might be best for me to steer away from LT308X parts. Pity as they held some promise.

    But before I completely give up on LT308X parts maybe I can try a suggested approach which is to use one LT3083 across all the batteries in series to deliver the full voltage to the series.

    One thing I wanted to try was this configuration as I needed 4.5A & hoped that this was also a better way of using the LT3083 as using it in voltage out mode is proving problematic - it's not regulating correctly

    Two questions:

    - I presume I could use this with an adjustable LT1963 - it doesn't have to be fixed voltage output & there's no special adjustment to make for this

    - the LT3083 is operating as a current boost which is the connection of the SET pin through 42ohm + 20mohm to OUT pin through 100mohm R. But what is the 33K R to ground for & if the LT3083 was operating in voltage out mode this would be 66K, not 33K  

    Maybe this should be a separate thread?

    If the moderators don't mind, I'll start a new thread with this post?

Reply
  • OK, guess, I'll go it alone on this - looking into the online problems with these parts, such as LT3080, it might be best for me to steer away from LT308X parts. Pity as they held some promise.

    But before I completely give up on LT308X parts maybe I can try a suggested approach which is to use one LT3083 across all the batteries in series to deliver the full voltage to the series.

    One thing I wanted to try was this configuration as I needed 4.5A & hoped that this was also a better way of using the LT3083 as using it in voltage out mode is proving problematic - it's not regulating correctly

    Two questions:

    - I presume I could use this with an adjustable LT1963 - it doesn't have to be fixed voltage output & there's no special adjustment to make for this

    - the LT3083 is operating as a current boost which is the connection of the SET pin through 42ohm + 20mohm to OUT pin through 100mohm R. But what is the 33K R to ground for & if the LT3083 was operating in voltage out mode this would be 66K, not 33K  

    Maybe this should be a separate thread?

    If the moderators don't mind, I'll start a new thread with this post?

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