Electronics > Power/Renewable Energy/EV's

Buck or buck-boost for a MPPT charging of the 12V lead-acid ?

(1/5) > >>

Oleander:
Hello,

I'm going to design a  MPPT charger fed by 30-60W panel that has a 17.5V max voltage power point and a 22V open circuit
voltage. These are typical values for popular solar panels.
The battery will be of a lead acid type : 12V 20-50Ah.

Will the buck solution be enough for this application ?
Or should I use the boost-buck solution in order to better serve the panel's lower voltage range (below 17V in case of weaker sunlight) ?
I'm looking at a ANALOG (former LINEAR) LTC4000-1 & LT3845A pair (buck) or a LTC4000-1 & LTC3789 pair (boost-buck).
Most examples in LTC4000-1's datasheet suggest a buck solution, however.

fourtytwo42:
It looks to me that the LTC4000 has not been designed with solar in mind. A solar panel is essentially a constant voltage variable current device, connecting a constant voltage output regulator to a solar panel will simply overload the available current causing the solar voltage to drop to the output voltage of the load and produce very little power.

You need a regulator with either MPPT or a regulated input voltage feature, if you are lucky you may find such a device combined with a battery charger (I am sure some other people here will make suggestions).

Oleander:
Almost all examples in the LTC4000-1 datasheet are for the typical solar panels ...

fourtytwo42:
Ahh a matter 0f the -1 sorry I missed that, then in answer to your question you only need buck as the 17.5Vmpp is always greater than the 13.5V lead acid float. Do you have output plots for the panels ? If so you could compare them with the MPP regulation curves given in the LTC4000-1 data sheet. It looks to me that this chip regulates it's input voltage to try for a facsimile of Vmpp without actually actively tracking it if you see what I mean.

In any case this chip seems a poor solution as it also seems to require an LT3845 alongside it, I am sure there are more economical single chip solutions out there :)

MagicSmoker:
PV panel efficiency declines as ripple current increases, and both the buck and buck-boost draw current in pulses so require significant input capacitance if used with a PV source. If you need to extract maximum possible power output then use a boost or Cuk converter, instead.

Navigation

[0] Message Index

[#] Next page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod