Need help with high current step up DC

Thread Starter


Joined May 30, 2023
Need help with high current step up DC

I need to design external battery for my flash.

I have checked it works with 4-6v DC with ~6a current to charge the capacitor in 2-3 second.

I have 18650 battery planning to use in 1S configuration. And i need to boost the voltage from 3.7v to ~5-6v .

MT3608 boost modules can provide only 1-2amp max
XL6009 boost modues work with >3.5v so it wouldn't work.
XL4015 step down modules is also not working .. short circuit protection getting triggered.

Is there any modules which can boost to ~5-6v from those 18650 battery and can provide peak current more than >5A for a short period of time.

Or any way to step down from 2S battery pack to ~5-6V with peak current >5A.

Any suggestions would be helpful.


Joined May 8, 2012
Analyze the problem using MPT Theory , 50% efficiency loss from Charge Energy transfer and independence of ESR which only affects time to charge T=RC and then review your time requirements to see if those make sense. The way to improve efficiency is not Battery to capacitor which are not conjugate impedances required by MPT Theory. Compute the required energy to be transferred and the amount of excess energy stored to transform using reactive (L &C elements) vs transform using magneto turns ratio transformers which do not store much energy (except 1/2 Lm I^2) and consider the efficiency gain using forward conversion methods. Often SMPS stored 5 to 10x as much energy than what the load can use in a short burst. So broaden your thinking.


Joined Feb 24, 2006
The problem with any BOOST scheme is that you pay for the higher voltage with lower output current. The immutable rule is that: power out will always be less than power in. In some cases, it will be much less.


Joined Nov 6, 2012
Do You want to make your own controller ?,
or buy something already built ?

What You want can be easily made when using
2 Li-Po-Cells to charge your Capacitor with a Voltage activated Electronic-Switch with hysteresis.

This setup can also easily provide substantially more than ~6-Amps if desired.
The Current will only be limited by the Internal-Resistance of the 2 Cells, or,
it may be reduced further, if necessary, by adding a series Resistor.

To properly design this Circuit requires knowing the specifications of the Capacitor.

The Capacitor may not be able to reliably withstand continuous, multiple, repetitive,
Charge/Discharge Cycles for long periods.

Each individual Charge/Discharge Cycle will
add HEAT to the Capacitor which may shorten it's life expectancy,
or even destroy it completely.

In other words, the existing Capacitor has definite, and unknown, limitations as to how fast
and how many Charge/Discharge Cycles it can comfortably withstand without damage.

The Quality and Specifications of the Capacitor may have to be up-graded if
your goal is to substantially increase the Duty-Cycle of the Flash-Unit.

What are your goals for this project ?


Joined Jan 23, 2018
The simple solution does not require much electronic design skill. That soution is to use TWO of the cells in series. Then the voltage will be adquate and the current should be adequate and the capability will be much greater.