I’m having a strange problem here:
When I use two AAA batteries to supply a small slave flash, it charges in 10 seconds, with 1.4A instant draw for the first second and smoothly reducing current draw until 10mA, when fully charged, at the tenth second.
I have these three small dc-dc buck voltage regulators, to lower from a bigger voltage Li battery at 8.4V to 3V, to supply my flash at 3V.
The weird thing is that, when I connect the output of any of these regulators to the flash supply contacts, it works, but it draws much less current, at 200-300mA, alhough these dc-dc regulators are rated at 3A max, 1.5A continuous.
So my flash is taking forever to charge, maybe 30 seconds.
For testing reasons, i’m using protoboard wires, don’t know if it makes any difference just to test it.
Is there any reason these different units would perform The same (be able to supply less current than they should)?
These are the ebay links of them: I don’t have a rank to post pictures yet...q
The first one is the smallest and it’s called Mini 360, and it’s based on the MP2307. Input 4.75-23V, 3A peak, 1.8A sustained
The second one is slightly bigger, nas an enable pin, and it’s based on the RT8727. Input 4.75-24V, 2A max
The third one is similar to the previous, with no enable pin, and it’s based on the MP1584EN. Input 4.5-28V 3A peak, 1.5A
Edit: I may have had some bad connections. I rewired all of then I managed to measure the outputs voltages of all three regulators, when charging the flash unit.
All of them performed similar, charging to full in close to 15 seconds. The first and second regulators had some 0.1V, 0.2V voltage drop, from 2.98v to 2.85v more or less but in the end of the charging they got back to they’re normal voltages.
The third one as the charging begins it raises the voltage from 2.99V to 3.05, as to compensate for the load, and at the end of the charging it gets back to nominal voltage. It seems faster to charge, maybe a sec faster.
If I lower the output voltages of all three of them to 2.6V than it takes a much longer time to charge the flash to full..
But still, why when using two rechargeable NI-MH AAA batteries, at 2.6V (1.3V each) the flash still charges faster than all of these regulators at 2.99V?
Edit 2: I have another flash unit that uses 2 AA batteries. In this unit, when using any of the three voltage regulators I have, the voltage drops from 3V to 1V, leaving no time for the flash to charge and the voltage get back to normal. It turns itself off. If I increase the voltage to 3.2v it drops to 2V and the flash manages to keep on until it charges and the regulator gets back to it’s normal voltage. So, in this particular case, how could I prevent this voltage drop in these small units? Adding an electrolytic capacitor in parallel to the output?