I am using the Pololu 6V Step-Up Voltage Regulator U3V50F6 to step up 3V from two D batteries. When there’s no load on the output, there is 6V at the output. When I attach a 6.6 ohm load on the output (it’s a heating element), the input voltage drops to 2.7V and the output voltage drops to 2.8V. I don’t see why it wouldn’t be able to handle the current because 6V/6.6 ohms = 0.909 A. Maybe I’m missing something…
It sounds like the batteries you are using might not be sourcing enough current and dropping their voltage to below the minimum operating voltage of the U3V50F6 regulator. For your batteries to power the 6V heating element at .9A through the regulator, they would be sourcing close to 2A. The 3V you are using as an input to the regulator is also close to the 2.9V minimum operating voltage, so when your battery voltage drops more than 0.1V, the regulator will not output 6V. You might try using fresh batteries and seeing if that makes a difference. You might also try using 3 batteries, so you are not operating so close to the minimum voltage.
I’m having a similar issue. Is there any spec on a battery that would indicate typical voltage drops under load like this? Do batteries in parallel help this out at all?
The capacity and discharge rate specifications of a battery can typically give you a general idea of what it can handle, but the amount of actual voltage drop you will get at particular current loads can vary on a lot of different factors and even get worse as the battery ages.
We do not recommend using batteries in parallel unless you really know what you are doing. You might find our “Understanding battery capacity: Ah is not A” blog post helpful.