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BZ Products MPPT250 guts



What’s inside a REAL maximum power point tracking charge controller. The guts are fairly standard for a simple low end MPPT controller. The brains of the unit consist of a PIC16F88 microcontroller. An LMC6484 quad operational amplifier is used for the current sense and temperature sense signal processing. There are also an LMC7660 potential inverting charge pump driver (which I THINK is used as a negative potential supply for the LMC6484) and an IRS2183 integrated driver MOSFET half bridge (which is probably used as a driver for the buck {solar lights}switching MOSFET).
If any of you watching this are BZ Products engineers and want to elaborate on the specific functions of anything, feel free to do so.
And yes, the black box in this one really is a relay.
One of the advantages of something not made in China (this was made in St. Louis, MO).

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{solar lights} & Wind EBooks
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10 Comments on "BZ Products MPPT250 guts"

  1. Any recommendations on where to buy this unit?

  2. @KyleCarrington This one I got on eBay a few years back for about $130. I just got two more for $106 each plus shipping from Solarblvd. They also have the MPPT250HV version for $118 plus shipping. There are other stores that carry these, but many want close to MSRP.

  3. @randacnam7321 Thanks. Do you anticipate the MPPT function working well, or lossy on that HV model? Any hunches there?

  4. @KyleCarrington There is a bit of increased loss in the MPPT250HV when running on a 48V PV array, but that is normal due to the over 50V potential difference between the PV array and the battery bank. These do not have super excellent MPPT algorithms, but for what they are they are good. I may do some experiments over the summer with designing a DIY MPPT controller if I can get a PIC programmer or the means to solder LQFP surface mount chips.

  5. Ok, came here looking for information about this particular MPPT, didn't expect to end up making corrections.

    First: The "little black box" is a relay yes, but has nothing to do with driving the MOSFET. It simply switches between MPPT and direct mode, to squeeze out those last few watts that just operating the buck would consume. It is triggered by current, somewhere around the 500mA mark, with a little hysteresis and some intervention from the PIC.

  6. Second, the black sealed off component at the end of the grey cable is a thermistor for adjusting float voltage according to battery core temperature.

    Third, the yellow wire is the shunt, no there are no hall devices.

    That said, any idea how to hack the gain adjustment for current sensing? The "I CAL" pot only adjusts level.

    Anyone?

  7. John Oquist says:

    I have solar panels with 20v open volts about 18v loaded. I was wondering since the panels are closer matched for a 12v system wouldn't my small but nice $20 30a PWM do a good job compared to MPPT? I can see where you have 40v and you don't want to lose all that extra voltage and mppt will help there but my 3.6v difference between bulk 14.4v and 18v loaded panels at 10 amps would be 36w gained but the mppt's are expensive for 36w more.

  8. MPPT is usually only worth it for big arrays or if you can make your own MPPT controllers for cheap (expect many dozens of hours spent working on it in the case of the latter), so in your case PWM would be the way to go unless yours is a mobile application where space is at a premium.

  9. I have a video on that. MPPT controllers in general do not like low sun conditions as it messes with their algorithm.

  10. John Oquist says:

    The Chinese MPPT with the dot matrix screen (all aluminum box) works great in low light conditions. It has no minimum, it will convert .5a to .85a and has its best performance on overcast days where 18% increase is normal. I know the BZ would not satisfy me; not enough info displayed. I would hate to adjust the small pot on the BZ to set float when the Chinese unit does it all in the menus/ soft keys. Great little device for 100 bucks.

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