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PV solar to NiMH charger bq24650

steve maietta
Prodigy 20 points
Other Parts Discussed in Thread: BQ24650, SM72295, SM72441, BQ2000

Hello I am designing a circuit to charge a large (4Ah) NiMH battery from a small solar array.   We have three 6v (at best) solar panels each put out around 100ma.  The battery is a 10 cell, 4-5000mAh NiMh pack.  The pack will power a small radio designed to remain outdoors, running very intermittently, I am hoping this solar arrangement can keep a constant trickle charge so the cells will stay at the ready.  MPPT, boost converter, voltage monitor/cutoff, hysteresis, high efficiency!!  One big thing is that no human interaction is possible for long periods (so no on/off switches etc.  This must run on its own out there, day and night) I have a market and if all goes well will be producing these !!

bq24650 looks like a good place to start, anything to note???

I am not an engineer, but I know basic electronics and construction am not afraid of math etc...  I have been building circuits and soldering for years.

If anyone has any ideas or experience with anything like this it would be greatly appreciated!!!!!  Go easy on me!

thanks

~Steve

  • 0
    Prodigy 20 points

    So in reading the data sheet, I realize that I will need a boost converter before a BQ24650, also it seems to need 25ma to VCC, which is a bit high considering we'll be having from 100-300 ma total...   Which leads me to believe that separating out some of the functions may be a better path to take...?

    SM72441 MPPT controller +SM72295 full bridge driver - too complex..  this is for 6v cells, low current, these IC's seem to be designed for larger EV apps...

    BQ2000 charger -seems to be able to charge only one cell at a time. 

    SPV1020 (STI part, sorry) Boost +MPPT - this looks promising so far..   This part could drive (perhaps):

    LM3647 (obsolete) is a simple solution that can support a NiMH batt pack of up to 10 cells (as we have here)  ..

    ~Steve

  • 0 in reply to steve maietta
    Intellectual 265 points
    Steve

    Take a look at the EVM for the BQ24650, since it provides a good reference point to start.

    The PCB layout is where I think you might experience trouble

    Kindly