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# design of a DC-DC solar to battery converter

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#### seneda

##### Junior Member level 3
Hi all,

I am senthilkumar, I am designing a 12v and 2 amps DC-DC converter using buck-boost topology. The output of dc-dc converter is used to charge a battery. The input of my dc-dc converter comes from a solar panel. I need a circuit to charge a battery for dc-dc converter.

What is the use of MPPT circuit? Is this necessary for my design? can i feed the solar input directly to dc-dc converter or should i give via MPPT?

please some one help me out.

suggest me any good book to design a DC-DC converter.

Thank you,

On a sunny day you adjust the output of your converter, so that it pushes maximum current into the battery.

You'll probably find the most efficient charging voltage to be anywhere between 1.5x and 2x the battery voltage.

The MPPT is useful because it does this automatically, on sunny or cloudy days. MPPT is not the easiest circuit to construct. Do you plan to use a microcontroller? If so, then that will be able to operate your DC-DC converter while it performs MPPT.

VI and Watt curves for PV are readily avail. for various panels vs solar input level.

Typically Max Watts starts at 85%Voc at full sun and drops to 65-75% for low level sun.. This is why Brad suggested Voc=1.5 Vbat for PMT .

i would suggest most lead acid batteries match fairly well using 75-80% of Voc for multiples of 12V, but high efficiency PMMT regulators will improve a bit and much more when mismatched.

help for DC-DC conversion

How to increase the output current value as 2A @12v for the battery charger in a DC-DC converter?

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Constant DC voltage for varies input dc

How can we get the constant DC voltage as 12 volts for the varies input voltages (5-20v)?
The input comes from the solar array, so cant predict the value of voltage?
or Am i wrong? can i predict the voltage range?

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Re: constant DC voltage for varies DC input

Hi,

can i predict the voltage range?
Yes, it is 5-20V

***
Look for buck boost DCDC converter (ICs). Or SEPIC.

Keep in mind, that when a solar panel gives out low voltage it also will output very low current.
So check if it really makes sense to use the solar cell when output voltage is less than 12V.

Klaus

Re: Constant DC voltage for varies input dc

hi,
This is an example of the unit you require.
What is the wattage of the solar panel.?

Features:
Size: 52mm x 38mm x 15mm(L x W x H ) (with fixed column)
Input: 3.5-28V
Output: 1.25V-26V
Maximum input current 3A
Maximum output 3A.
Rated input 1A, Output 1A

Note:
Output voltage independent of input voltage (3.5V-28V input, any value output 1.25V-26V)

Re: help for DC-DC conversion

How to increase the output current value as 2A @12v for the battery charger in a DC-DC converter?

For an increase in Amperes, this implies a voltage reduction. Suppose your panel output is 36V at 1A. Therefore you operate in buck converter mode, and convert it (in round terms) to 18V at 2A.

Re: Constant DC voltage for varies input dc

I am gonna use street light solar panel. how much watt(Vin=Iin=?) this can give? I need Iout=2A & Vout = 12V to the battery
for charging. From the battery, supply the voltage to the GSM module for 24 hours. that battery should have 12 hours backup. so i should design an effective dc-dc converter for my battery. please help me out.

First point: Stop starting new threads about the same problem every day! Forum rules are very clear in this regard.

Secondly: Maximum (and also average) power is asking for the solar panel specification. We can't know it.

Your design would start with an energy balance, calculate the average power accumulated during a cloudy/rainy day, design the DC/DC converter so that it can transfer maximum power under this condition.

As previously mentioned, MPP control is the preferred method.

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