Can I briefly pull more than 500mA from minty boost?

Ideas and questions about MintyBoost kits

Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.
Locked
User avatar
creatify
 
Posts: 37
Joined: Wed Feb 10, 2021 8:15 pm

Can I briefly pull more than 500mA from minty boost?

Post by creatify »

I've confused myself trying to find this answer in all the minty docs — will minty boost allow me to pull more than 500mA from brief periods (ms)?

I am using a minty boost (powered by 3 Ni-MH AAs) to power an arduino micro, 1 neopixel ring, PCA9685 servo driver, and 3 MG90 micro servos. The circuit currently, surprisingly, works fine but I wonder if I'm minutes away from frying the minty-boost. I glossed over the fact that minty boost supplies up to 500mA when I hooked all this up. When I start driving the 3 servos, I'm seeing spikes over 1.8A of current used (I'm using the adafruit Mini Power Meter to view the volt/current) and I'm wondering how I can even see that much draw coming from the minty boost?

User avatar
adafruit_support_bill
 
Posts: 89199
Joined: Sat Feb 07, 2009 10:11 am

Re: Can I briefly pull more than 500mA from minty boost?

Post by adafruit_support_bill »

With reasonably fresh batteries, it should handle brief current spikes. 1.8A is pushing things a bit though. A large-ish capacitor between GND and 5v would help smooth those peaks out somewhat. But a PowerBoost 1000 would be a better match for that load.

User avatar
creatify
 
Posts: 37
Joined: Wed Feb 10, 2021 8:15 pm

Re: Can I briefly pull more than 500mA from minty boost?

Post by creatify »

Thank you, again, this is helpful. Ha, I was just looking at that power boost 1000, it does seem like a better fit, but I wonder if I need to rethink 3X AAs powering this all. When this project is turned on, the servos will only move for a few ms every 1-2 minutes maximum, but 36 neopixels will continuously animate. I'm trying to balance those brief, rather large, servo spikes against the majority of time when <200mA are consumed. 8-10 hours of runtime is what I'm aiming for from the batteries. I plan on a secondary DC jack input for a wall wart for long run times, but it will be much more practical to use easily accessible (AA) batteries (in limited chassis space) in this case. Any thoughts are appreciated.

User avatar
adafruit_support_bill
 
Posts: 89199
Joined: Sat Feb 07, 2009 10:11 am

Re: Can I briefly pull more than 500mA from minty boost?

Post by adafruit_support_bill »

NiMH cells typically have a capacity in the 1200-2000mAh range. Let's assume the lower end of things to be safe.

A 3s NiMH pack will give you nominally 3.6v. Boosting that to 5v at 95% efficiency gives you an effective conversion factor of 0.684. So you will need about 300mA @3.6v from the batteries to get 200mA @5v for your circuit.

So, at 200mA continuous draw at your circuit (300mA from the batteries), you will get about 4 hours of run-time (4h x 300mA = 1200mAh). Factoring in brief excursions to 1.8A, you can expect somewhat less.

You could go with a higher capacity NiMH pack to extend the runtime. 5000mAh C cells should get you closer to your goal.

Another option would be a LiPo cell. We have these as large as 10050mAh. That would be a good match for a PowerBoost 1000-C - which has a built-in charger.

User avatar
creatify
 
Posts: 37
Joined: Wed Feb 10, 2021 8:15 pm

Re: Can I briefly pull more than 500mA from minty boost?

Post by creatify »

Awesome advice, and thanks for that math regarding the conversion, I should be able to make one of these options work!

Locked
Please be positive and constructive with your questions and comments.

Return to “MintyBoost”