Author Topic: Acceptable batteries?  (Read 204 times)

dalbert

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Acceptable batteries?
« on: April 22, 2020, 06:29:43 PM »
I am a long-time uCurrent Gold user and I just received my CurrentRanger (thank you!) and am excited to try it.  Unfortunately, I realized my lithium polymer batteries are at the (closed due to COVID) office.  I have several 18650 LiIon cells at home; is there any reason not to use them (other than that the case is slightly too shallow)?  The MCP73831 battery charger seems to handle both Li-Ion and Li-Poly and I see nothing in the schematic to suggest problems; is there any reason not to do this?

Also, a suggestion for a future spin, please consider adding another ORing diode and a couple of pads or a pin header to allow connecting a 3x AA alkaline or 4x AAA NiMH battery holder.  Making the enclosure slightly deeper would also fit many more types of cylindrical cells.  That would make the out-of-box experience a lot easier for many users.  Thanks!
« Last Edit: April 22, 2020, 06:49:17 PM by dalbert »

TomWS

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Re: Acceptable batteries?
« Reply #1 on: April 23, 2020, 06:24:47 PM »
I have several 18650 LiIon cells at home; is there any reason not to use them (other than that the case is slightly too shallow)?  The MCP73831 battery charger seems to handle both Li-Ion and Li-Poly and I see nothing in the schematic to suggest problems; is there any reason not to do this?
You are correct, the MCP73831 will be able to charge the battery and you'll be able to use is (as a side-car of course) but the 18650 battery will take a LOT longer to reach full charge than a 500mAH battery with the charge current the MCP73831 is probably set for.

Update: Fixed typo on charger chip part number.
« Last Edit: April 24, 2020, 06:11:28 PM by TomWS »

Felix

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Re: Acceptable batteries?
« Reply #2 on: April 24, 2020, 09:27:32 AM »
dalbert,
Thanks for the suggestions. I will consider a schottky separated AA(A) battery power.
That means the CR wont charge the batteries, and you have to supply enough voltage to stay above 3.3V+LDO-dropout ~3.5V.

If I implement that in a future CR, I can post a deeper box for folks to print if they prefer AA(A)s.
But the default will stay as is for now, each case already takes around 50 minutes to print ;-)

Thanks Tom for answering the other question!

FWIW the CR power/battery use/guide page is posted here.

dalbert

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Re: Acceptable batteries?
« Reply #3 on: April 25, 2020, 08:19:47 AM »
Thank you TomWS and Felix!

@TomWS: with respect to the 18650 (or any higher capacity battery) taking longer to charge, while that's true, it certainly seems like a net positive since the battery will last that much longer.  I eventually sacked an ancient PDA from my junk box for its rectangular 2600mAh battery pack which fit the case perfectly.

@Felix: thank you for considering adding the ORing diode.  As I look at this more, it's probably better to put a bridged solder jumper (like the jumper used for Auto-Off) on pin 3 of U1 so you can disconnect the LiPo charger if using non-LiPo batteries; there are very few use cases where you'd want to hook up both a LiPo battery *and* another battery.   The user could cut the jumper and then safely connect an AA or AAA battery pack to the existing JST connector without worrying about something bad happening if the USB connector is plugged in.  Also, thanks for posting an enclosure model in F360!

TomWS

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Re: Acceptable batteries?
« Reply #4 on: April 25, 2020, 06:50:19 PM »
Thank you TomWS and Felix!
I eventually sacked an ancient PDA from my junk box for its rectangular 2600mAh battery pack which fit the case perfectly.
Does that battery have a built-in protection circuit?  It may not be an issue WRT overcharging because the charger circuit is good enough to protect it, and you probably won't short it out, so that's not a problem, but it could over discharge if you're not careful...