MintyBoost with HTC one X & Diode protected batteries in paralle

[fico86]

Hi there!

I just finished building my first MintyBoost, and everything appears to be working fine, the output voltages are fine, and when I plug into my HTC one X, it indicates changing. But, the percentage charged actually drops rather than increases. I do have the phone on while charging, so i suppose the phone batter is actually being draining faster than it can be charged. Is there any way to mitigate this? Or is the only option to turn off the phone while charging?

My second enquirer is about using AA batteries used in parallel. I know using them in parallel runs the risk of one battery discharging into another. But what if its protected using diodes, to prevent backwards discharge, as its done here: http://www.instructables.com/id/Double- ... n-parallel. Is that advisable?

This might have been brought up earlier in the forums. If it has, I do apologies.

[adafruit_support_bill]

You should turn the phone off while charging. Many phones will disable power management when connected to a charger and consume batteries even faster.

Diodes will prevent one battery from discharging into another, but they won't prevent the cell with the lower internal resistance from doing a larger share of the work. Also keep in mind that there will be a slight voltage drop across the diode and the diodes need to be sized to handle the anticipated current . It should prevent battery damage, but won't quite double your available power.

[fico86]

Thanks for the reply! I am afraid the first problem was my fault, I was using almost depleted batteries.
For the second problem, I did 2 tests. I got new Energizer rechargeable NiMH batteries with indicated capacity of 2450mAh. For the first test, I configured the batteries in parallel with diodes as shown below.


I set it to charge my girlfriend’s old Galaxy S with an empty batteries. The indicated capacity was 1500mAh. It managed to charge it up to about 70% in more than 2 hours. I also noticed that both the circuit and the batteries were getting very hot.

For the next test I put them in series was has been suggested. Again I started charging the Galaxy S (I drain its battery to 0% first). This time to my surprise, the whole battery was charged within an hour! I connected to another phone after that, and there was still some juice left! And also the whole thing was much less hotter. So indeed, your suggestion to put everything in series is a good one.


Above is the schematic of my series configuration. I added a switch to alternate between 3 or 4 cells, giving me the flexibility of using either the 1.2V rechargeable, or the 1.5V non-rechargeable.


And that a picture of my build. OK that all i have to say for now, thanks a lot for an amazing kit! really enjoyed it!

[RoaminGnome47]

I like the idea of the switch! I may have to implement that on my custom Minty build (built it "normal" in the gum tin but I want to customize it to my needs).