Battery Selection - Charger module and step up or step down

Hello,

I'm working on my project which is powered by a 5v 6A power adapter (DC Plug), and currently working on making it portable, and changing the main power plug to a Micro USB.

I'm in the process of researching for a Lithium polymer circuit/module and step up module from 3.7 to 5V or step down module from 7.4 to 5V (haven't decided yet any advice ?)

The average consumption is about 400 mAh but it could reach at times up to 5A (extremely rare, and the code limits that as well) most of the spikes goes up to 2A for less than 3 seconds.

The size of the enclosure is 80-90mm x 50-60mm (I'm thinking of placing the batteries on the case bottom part)

I'm aiming for a run time of about 2 - 2.5 hours, so maybe 1300mah (5C) flat lipo battery would be a nice fit

Also I would like to know what is this "3DPT" component they used in this example: https://learn.adafruit.com/multi-cell-lipo-charging/simple-balance-charger Couldn't find info on google, those this module switch automatically or is it manual, how is the actual switching works.

Any Suggestions ? If its better to use 7.4v (2 batteries) and step down module please let me know... What are my options of turning my project portable ?

Cheers

It is more complex to have a balancing charger, as required for two cells, and the charger may not correctly deal with the situation where the circuitry is on while the charger is charging (a concern with all hobby LiPo charging modules).

The "3PDT" (3 pole double throw) manual switch is Adafruit's answer to this problem: you can't use the cells while they are charging.

Given the expensive destruction associated with overcharging and overdischarging Li-based cells, you are much better off with NiMH cells. 3xAA will provide 3.6 V nominal with 2500 mAh capacity, can be trickle charged continuously, and are far more tolerant of abuse.

jremington: It is more complex to have a balancing charger, as required for two cells, and the charger may not correctly deal with the situation where the circuitry is on while the charger is charging (a concern with all hobby LiPo charging modules).

The "3PDT" (3 pole double throw) manual switch is Adafruit's answer to this problem: you can't use the cells while they are charging.

Given the expensive destruction associated with overcharging and overdischarging Li-based cells, you are much better off with NiMH cells. 3xAA will provide 3.6 V nominal with 2500 mAh capacity, can be trickle charged continuously, and are far more tolerant of abuse.

Thank you, that's very helpful.

Can you share any reference to modules that charge NiMH array of 3 batteries, also is there a step up module that can cope with up to 5A draw ?

Cheers

Everything you need to know about batteries can be found at http://batteryuniversity.com/learn/

Pololu has a great selection of voltage step up or down modules.

jremington: Everything you need to know about batteries can be found at http://batteryuniversity.com/learn/

Pololu has a great selection of voltage step up or down modules.

Wow looks like a great resource of information - it would help me a lot, thanks.

Any idea regarding the common battery selection and modules though ? would it be better to use step up or step down module (1 cell vs. 2 cell pack)

Do you really need 5v?

An Uno or Mega will happily run on 4.5v from 3 x AA alkaline cells connected to the 5v pin. I have not tried it with 3 x AA NiMh cells which would only be 3.6v. Nor have I tried it on 4 x AA NiMh cells which produce 4.8v and should be OK. However I don't know if there is a risk of exceeding 5v while charging 4 x AA NiMh cells.

Another option is to build a breadboard Atmega 328 using its internal 8MHz oscillator - that will run happily on 2 x AA alkaline cells or a 1s LiPo. It should also be quite happy with 3 x AA NiMh cells.

...R

Robin2: Do you really need 5v?

An Uno or Mega will happily run on 4.5v from 3 x AA alkaline cells connected to the 5v pin. I have not tried it with 3 x AA NiMh cells which would only be 3.6v. Nor have I tried it on 4 x AA NiMh cells which produce 4.8v and should be OK. However I don't know if there is a risk of exceeding 5v while charging 4 x AA NiMh cells.

Another option is to build a breadboard Atmega 328 using its internal 8MHz oscillator - that will run happily on 2 x AA alkaline cells or a 1s LiPo. It should also be quite happy with 3 x AA NiMh cells.

...R

Hi,

Yes the LED array that is attached to the project requires 5V, you think I should choose step up or step down module ?

nitbeat: Yes the LED array that is attached to the project requires 5V,

Have you tried it with 4.5v?

I don't have any suggestions for step-up / down modules. None of my project has required anything other than a 7805, LM317 or an LD1117. None of those is efficient. The attraction for me of using batteries directly is avoiding the need for any step- module.

...R

Yes the LED array that is attached to the project requires 5V,

It most likely does not. Post a link to the data sheet.

jremington: It most likely does not. Post a link to the data sheet.

mmm you're right https://cdn-shop.adafruit.com/datasheets/WS2812B.pdf

That's very interesting...

It opens up some doors for sure

Robin2: Do you really need 5v?

An Uno or Mega will happily run on 4.5v from 3 x AA alkaline cells connected to the 5v pin. I have not tried it with 3 x AA NiMh cells which would only be 3.6v. Nor have I tried it on 4 x AA NiMh cells which produce 4.8v and should be OK. However I don't know if there is a risk of exceeding 5v while charging 4 x AA NiMh cells.

Another option is to build a breadboard Atmega 328 using its internal 8MHz oscillator - that will run happily on 2 x AA alkaline cells or a 1s LiPo. It should also be quite happy with 3 x AA NiMh cells.

...R

Thanks for the idea, I think I'm going to try: https://www.aliexpress.com/item/4-8v-ni-mh-battery-2400mAh-high-quality-batteries-aa-nimh-rechargeable-battery-for-Remote-control/32819556648.html

jremington, made me recheck the datasheet of the LEDs input voltage, and its appears they can work as low as 4.5

Cheers