nRF52840 + 500mAh LiPo = 30 minute drain

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CYMotorsport
 
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nRF52840 + 500mAh LiPo = 30 minute drain

Post by CYMotorsport »

Attached is my pin out of my Feather nRF52840 Express using a 3.7v 500mAh LiPo and mini boost. I'm noticing on both boards, one with a boost and without, both the 500mAh LiPo are draining to 0% when my battery is plugged in but my EN pin switched off. This can take inside an hour at a 75% charge.

Maybe this is just a fundamental brain fart, but should the battery be draining? or with this information only in front of you is there an issue with the EN pin being grounded? Did I integrate these two incorrectly? Apologies if this is a dumb question I just can't seem to find anything in other questions and I've been staring at this for some time now to no avail.

Nick
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Feather lipo drain.png
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mikeysklar
 
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Re: nRF52840 + 500mAh LiPo = 30 minute drain

Post by mikeysklar »

Your wiring looks correct.

When you have the EN pin pulled low with your switch can you take a voltage measurement with a multimeter?

Check the 5v Out and GND on the TPS61023. Is there any output?

You can also break the Vin connection on the TPS61023 and check for how much current is being pulled into the TPS61023.

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CYMotorsport
 
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Re: nRF52840 + 500mAh LiPo = 30 minute drain

Post by CYMotorsport »

Hey Mike/team,


Sorry just saw this response - I've turned on notifications for the post now.

As I went to test this, I did notice one thing that I wasn't sure was correct. if it is, please let me know as i could just be saying something perfectly normal. But I have a feeling it's playing a part in the issue:

So based on the diagram I made to show the wiring, when the EN is turned "on", the Nextion screen powers up. I imagine this is a physical sign the 5V is active and thus correctly, the boost is activated. which is consistent with the wiring.

BUT when i turn it off, wireless function still works. and if you reference the diagram, you'll see the BAT pin on the NRF board is wired to the VIN on the boost. So maybe because the EN pin is wired to the EN on the boost, it won't 'pull from the boost when switched "OFF" but it seems obviously it's still drawing power. There's no other way wireless should be working if a lipo is plugged in, no USB power, but it's not turning on the nextion with the EN switched "off". Seems like it's pulling enough to dimly light my LED buttons on my wheel (very ultra bright when EN pin ON) but not enough for bigger tech like an HMI.

Is this normal? I'm wondering if I just cut the BAT trace on the boost, will a lipo still charge?

EDIT: also can confirm on my second wheel the battery drains (and won't charge) when one is plugged in despite EN being "off". worth noting that the BAT pin isn't wired to anything as there is no boost board. Just the EN pin wired in the same fashion as the previous diagram. the difference with it in my hand is that when EN is "OFF" on this board without a boost, bluetooth no longer works. when switched on, bluetooth buttons function perfectly.

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CYMotorsport
 
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Re: nRF52840 + 500mAh LiPo = 30 minute drain

Post by CYMotorsport »

After some brain storming, could I be overthinking this? my original plan may be the best option to limit power leaks as I originally planned on using your JST extension with onboard on/off switch below:

https://www.adafruit.com/product/3064

Could it be this simple as a work around?

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alpierce
 
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Re: nRF52840 + 500mAh LiPo = 30 minute drain

Post by alpierce »

Yep, using the switch in the JST extender is the right way to go.
The EN pin only disables the on board regulator generating 3.3 volts for the feather. If you were using the 3.3 v output to boost it would work, but since you are boosting the battery voltage it simply turns off the feather and leaves your display running off the battery. Switching off the battery removes power from both the feather and the display.

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CYMotorsport
 
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Re: nRF52840 + 500mAh LiPo = 30 minute drain

Post by CYMotorsport »

but since you are boosting the battery voltage it simply turns off the feather and leaves your display running off the battery.
This is probably why the lights are dimmed and there's not enough juice to turn on the nextion which requires 5 volts. makes perfect sense.

I imagine this means that on the NRF board without a boost, that's just a plain old power leak? that seems like a mighty leak. One follow up to this - I have that 2nd NRF board that currently is without a screen and without a boost programmed to run a healthy amount of switches - see attached for the sake of convenience that diagram. Though now that I have it built, I genuinely will only run 2 buttons , 3 max.

Do you think removing all the unused pins will slow any leaks? or is this just a function of the board itself being run on bluetooth? Either way, as per this chat I'm going to build in a jst extender to kill power on this 2nd wheel as well.
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alpierce
 
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Re: nRF52840 + 500mAh LiPo = 30 minute drain

Post by alpierce »

If you are constantly using the Bluetooth it uses a good amount of power. Running on battery requires a lot of attention to power management. Read the spec sheets on the processor carefully and find out about sleep modes and other methods of saving power.
500mAh is not a lot of battery capacity when you’re powering any sort of radio equipped board, be it Bluetooth, WiFi, Lora, etc.

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CYMotorsport
 
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Re: nRF52840 + 500mAh LiPo = 30 minute drain

Post by CYMotorsport »

much appreciated - I'll be more intentional about management of idle modes as I think that'll be the key along with intentional cut off extenders. cheers

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