I'm working on this little side project at work and something has got me stumped. Thought I would throw it out here, since we have so many very knowledgeable electronics guys.

I'm working on re-purposing a very common electronic device. One of my goals is to power the device using a better, longer life battery pack. Knowing what the required voltage is for this, I have fashioned a new battery pack with an adjustable voltage step down in line, essentially taking it from 7.2V down to the required 3.7V. However, I cannot get the device to power on. When connected to the bench top DC adjustable voltage power supply, it does just fine. It powers up and goes fully functional without issue. With the battery pack, it will only briefly take power, but not completely power up.

So here's my question. I know too much resistance will cause a circuit to not operate properly. Can too little resistance cause a circuit to not initiate correctly too?

Is it possible the new, custom battery pack is pushing too much amperage to the device, causing the fail safes to trip and not allow the device to power on? Old power was derived from a single cell 3.7V/900mAh battery and new power is 7.2V/2400mAh (stepped down to 3.7V).

Using Ohm's Law, I see that 3.7 @ .09A with 41.1111ohms should net me .3330W. Currently the circuit is only showing 17.89ohms. Using those numbers, I'm now pulling .2068A and 0.7651W.

I think I need to add ~ 23ohm worth of resistors to my power circuit. Sound about right?

Ummm, yeah, no... Well maybe....

And if two trains leave chicago at the same time traveling in opposite directions....

.Just kidding, I have, no idea but I am willing to bet you have an answer or two here before bed tonight

Maybe even sooner. I'm stuck here at work for at least another 30 minutes while the block heater brings me up to 70* (stupid injector issues on the Shark). Now I just need to find that bag of resistors.

Likely you are not providing enough current with the stepdown in place. Measure the device current with the old battery and with the new setup.

Are you certain your voltage step down device is allowing proper amperage flow??? If not I would try using resistors in series with your new toy and the batteries at full strength.

Spec sheet on the Anyvolt Micro shows a max current of .5A, so I should be well within that limit.

On the bench it showed .09 during power up and then peaked at .2.

On the batteries, current draw on power goes to .08A and then drops as something decides to stop working.

Problem solved. It was a dissipation issue with the batteries I was using. Turns out they would only allow for a .08A draw, which explains why I was only seeing .08 across the circuit before the device lost power. I stepped up to a larger battery and everything is working fine now.

See, not enough current.