question

Joka GIMENEZ avatar image
Joka GIMENEZ asked

Looking for feedback / reviews on multiple synchronised mppt VS one single big mppt

Hi!

I hear everywhere that synchronized multiple mppts are considerably better than a single big mppt in configuration that regularly get partial shading (sailboat for example).

Could anyone give their real life experience and feedback on the improvement it brings?

I am also interested in the theory behind that statement. I understand the idea is a lower voltage on one panel brings the voltage of all other panels in parallel down, but the diodes should bypass the shaded cells and avoid loosing voltage no?

Any advice welcome, thanks!!

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Mike Dorsett avatar image
Mike Dorsett answered ·

If you have partial shading, then multiple MPPT's are the best option. If you have 2 or more strings in parallel and one string is shaded, that does not bring the voltage down (much), but the shaded string stops producing much current - ie 9A down to 0.2A. The dides in the modules are to take care of any reverse voltage that may happen. However, I've seen posts on this forum that suggest that some of the MPPT's operated in parallel go into float mode early - However with careful setting of the float and absorption voltages and timers this should not be a problem. Module Voltage output for maximum power in general seems to rise slightly as illumination decreases. So as soon as you get even the slightest shade on one string, your power will drop 50% if you have 2 strings in parallel. Using 2 mppt's will probably give you about 75% power.

Mike.

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Joka GIMENEZ avatar image Joka GIMENEZ commented ·
Thanks very much, very helpful info!


FYI from what I've read, to avoid the problem of going to float too early when mppts in parallel, the Smartsolar mppts can be synchronized via bluetooth. Unfortunately this doesn't work on the bluesolar, even with the bluetooth dongle.

Some other brands also offer synchronization between mppt, either by cable or by wifi.

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