Author Topic: mppt controller w/o battery  (Read 58 times)

frankoo

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mppt controller w/o battery
« on: September 08, 2018, 04:30:24 PM »
I'm looking for a mppt controller for a 100 or 120 watt solar panel. I have found mppt solar "charge" controllers but I want to avoid having a battery. The output needs to be a nominal 12 volts dc.
I would like to keep the cost under $60.
Has anyone seen anything that meets this description?

ClassicCrazy

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Re: mppt controller w/o battery
« Reply #1 on: September 08, 2018, 09:41:14 PM »
You need to find something that will turn off at night - because no power will be there. Then it has to be able to turn on when the PV comes back on .

What are you trying to power ?

Look up solar powered pumps - I think there are some that pump directly off of PV and not sure how they do that or if they have some kind of battery powered electronics in between.  Or maybe they do have batteries.

You can get $5 buck converters on ebay that work in the range you want - but not sure how they do with unstable current source like PV would be for them. https://www.ebay.com/itm/DC-10A-300W-Step-Down-Buck-Converter-7-32V-To-0-8-28V-Power-Module-LED-Driver-LK/163005271040?epid=2166251780&hash=item25f3df0c00:g:4xoAAOSwne9Ziq5K

Larry

system one
Classic 150 , 5s4p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system two
Classic 150 ,5s 135 watt Kyocero , 16s Calb 100AH LiFePO4 , Outback VFX 3648 inverter
system three
Midnite KID MPPT 24 DC in to  12 volt AGM batterie

boB

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Re: mppt controller w/o battery
« Reply #2 on: September 09, 2018, 12:26:09 AM »
Another question is, what kind of voltage regulation do you need ?

Sometimes the panel all by itself if good enough if at light loads, between 16V to 21V doesn't hurt anything.

boB
K7IQ

frankoo

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Re: mppt controller w/o battery
« Reply #3 on: September 09, 2018, 02:32:32 PM »
I'm powering a chemical reaction, making bleach. The bleach is to disinfect water in developing countries. The device is designed to be powered with a car battery, making a batch in about an hour.
I can make a sufficiently strong batch of bleach in 2 or 3 hours using a 120 watt solar panel and a dc dc converter. I roll out the solar panel, make the bleach and then put the panel away. I don't need to turn it off or back on.
I've successfully tried dc dc buck converters and they work, but inefficiently. I can only get about 65% of the solar panels rated wattage.
I've hooked the device directly to the solar panel and it's less efficient than the dc dc buck converter.
I'm trying to do better than the 65% by using a MPPT.
I've found MPPTs that are for water pumps but they run $300 up.

ClassicCrazy

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Re: mppt controller w/o battery
« Reply #4 on: September 09, 2018, 02:57:09 PM »
I doubt you will get better efficiences using a mppt controller.
The MPPT controller - I think most are probably buck converter designs with micro controllers too. So doubt  you will see better efficiencies with one of those. More electronics in them.
The rated wattage of a PV panel is for it under the most ideal conditions - perfect sunlight and temperature.
In Wisconsin here I only see my PV getting close to the rated wattage on the very coldest days of winter  when the panels do their best  and when the air doesn't have much of any humidity in it either.
Seems like you are doing pretty good with the buck converter you were using - you could experiment with some other designs or builds - there are so many on ebay - maybe some other type will work a little better . They certainly don't cost too much. Also maybe cooling your buck converter with a small fan or adding larger heatsink would help ?
Here is one
https://www.ebay.com/itm/DC-DC-6V-32V-to-0-32V-5A-LCD-Digital-Auto-Adjustable-Buck-Boost-Module-w-Fan/222852080493?epid=23011209687&hash=item33e304e36d%3Ag%3AxzsAAOSwETJaLkc5&LH_BIN=1

Larry


« Last Edit: September 09, 2018, 03:04:59 PM by ClassicCrazy »
system one
Classic 150 , 5s4p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system two
Classic 150 ,5s 135 watt Kyocero , 16s Calb 100AH LiFePO4 , Outback VFX 3648 inverter
system three
Midnite KID MPPT 24 DC in to  12 volt AGM batterie