I charged this case thing overnight, next day put a battery in it in the morning, by the end of the day it was still flat with a red light showing. Does this thing not charge unless it is plugged in via USB C like a regular charger?

It is more like a battery-hub so it need batteries to charge. It is NOT a powerbank that you thought.

Think of it more like a three position charger.  The case itself has no battery in it.  With Action 3 batteries in the case, they will charge in sequence when the case is plugged in.  With batteries in the case the case could also be used as a portable power bank, but it will draw its power from whatever action 3 batteries are stored inside.  

So the case itself doesn't "charge up" and then charge the batteries when they are inside.  It's not like a portable earbud case where it acts like a charger and they you charge the case.  It's just a charger that can charge three batteries at once, can store up to three batteries and can proved some power out when there are batteries inside.  Hopefully that makes sense.
Edit:  And actually, I don't think it actually charges all the batteries at once.  It charges them one at a time, but will eventually charge all three.

Thanks for the replies.

Hi there. Thank you for reaching out and we're sorry for the confusion. The DJI Osmo Action 3 Multifunctional Battery case can only charge the batteries by plugging in the USB-C cable. In addition, Osmo Action 3 Multifunctional Battery Case enhances efficiency by charging batteries in sequence according to their remaining power level, with more fully-charged batteries receiving power first. When charging three batteries simultaneously, the battery with the most remaining power will be charged first, and when it is 80% charged, trickle charging is triggered. At the same time, the battery with the second-highest power will be fast charged, and the charging logic of the third battery is the same. When charging an external device, batteries with the least remaining power level will discharge first, with more fully-charged batteries discharging later. Hope this helps. Thank you for your valued support.

DJI Paladin Posted at 2022-11-5 01:58
Hi there. Thank you for reaching out and we're sorry for the confusion. The DJI Osmo Action 3 Multifunctional Battery case can only charge the batteries by plugging in the USB-C cable. In addition, Osmo Action 3 Multifunctional Battery Case enhances efficiency by charging batteries in sequence according to their remaining power level, with more fully-charged batteries receiving power first. When charging three batteries simultaneously, the battery with the most remaining power will be charged first, and when it is 80% charged, trickle charging is triggered. At the same time, the battery with the second-highest power will be fast charged, and the charging logic of the third battery is the same. When charging an external device, batteries with the least remaining power level will discharge first, with more fully-charged batteries discharging later. Hope this helps. Thank you for your valued support.

Really dropped the ball on this one. Was really hoping it would charge the batteries when placed in the case. Finding out it's just a holder is very disappointing.....should have made it a charging case.

Sporttster Posted at 6-2 20:50
Really dropped the ball on this one. Was really hoping it would charge the batteries when placed in the case. Finding out it's just a holder is very disappointing.....should have made it a charging case.

We appreciate your understanding on this one. Please let us know if you have other inquiries. Thank you for your valued support.

Telesin Accu selfie stick?

DJI Paladin Posted at 2022-11-5 01:58
Hi there. Thank you for reaching out and we're sorry for the confusion. The DJI Osmo Action 3 Multifunctional Battery case can only charge the batteries by plugging in the USB-C cable. In addition, Osmo Action 3 Multifunctional Battery Case enhances efficiency by charging batteries in sequence according to their remaining power level, with more fully-charged batteries receiving power first. When charging three batteries simultaneously, the battery with the most remaining power will be charged first, and when it is 80% charged, trickle charging is triggered. At the same time, the battery with the second-highest power will be fast charged, and the charging logic of the third battery is the same. When charging an external device, batteries with the least remaining power level will discharge first, with more fully-charged batteries discharging later. Hope this helps. Thank you for your valued support.

I just bought Osmo action 4 adventurer combo and it came with the multifunctional charger case. When I charge batteries inside the charger case, it only charges up to 83% and it remains at 83% no matter how long I have it in charging. Why is that? Also, the third spot only charges up to 54% and remains at 54% no matter how long I keep it charging.

Please help me understand.

djiuser_iuMckmJNkdgd Posted at 9-12 21:58
I just bought Osmo action 4 adventurer combo and it came with the multifunctional charger case. When I charge batteries inside the charger case, it only charges up to 83% and it remains at 83% no matter how long I have it in charging. Why is that? Also, the third spot only charges up to 54% and remains at 54% no matter how long I keep it charging.

Please help me understand.

I literally have the same "issue". Like Two of the batteries charge till green but one remains yellow.. is ist supposed to be like that or is the case or battiers broken ?

djiuser_iuMckmJNkdgd Posted at 9-12 21:58
I just bought Osmo action 4 adventurer combo and it came with the multifunctional charger case. When I charge batteries inside the charger case, it only charges up to 83% and it remains at 83% no matter how long I have it in charging. Why is that? Also, the third spot only charges up to 54% and remains at 54% no matter how long I keep it charging.

Please help me understand.

Hi there. Thank you for reaching out and we're sorry for the trouble. Can you please confirm what USB-C charger are you using? We recommend using the DJI 30W USB-C Charger to charge your batteries using the Multifunctional Battery Case. When using the specific charger, 3 batteries will take 58 minutes to charge them all to 80%, and 120 minutes to fully charge them. Please note that after a battery is charged to 80%, it will then be fully charged by trickle charging. Hope this helps. Have a nice day ahead!

Note: Trickle charging means charging a device using a tiny current, thus ensuring that the battery is truly saturated and thereby extend the battery life.

djiuser_CLimnAlWeSuJ Posted at 9-14 09:37
I literally have the same "issue". Like Two of the batteries charge till green but one remains yellow.. is ist supposed to be like that or is the case or battiers broken ?

Hi there. Thank you for reaching out and we do apologize for the trouble. Can you please confirm what specific DJI product are you using? Please keep us posted. Thank you.

My battery hub for my Action 3 got wet.. Now it won't charge batteries, but the lights stay on when batteries are inside. Can this be fixed? I dried everything out carefully.. But it's still not working. Are these able to be fixed, or do I just order another one

djiuser_SHkyWLsbGEv7 Posted at 10-8 07:07
My battery hub for my Action 3 got wet.. Now it won't charge batteries, but the lights stay on when batteries are inside. Can this be fixed? I dried everything out carefully.. But it's still not working. Are these able to be fixed, or do I just order another one

Hello there. Sorry about what happened to your charging case. We suggest sending the device for repair. You can submit a repair request from the DJI official website to get it fixed. Here is the link: https://www.dji.com/support. Have a great day ahead.

I have a similar issue as others described when it comes to plugging all three batteries in.  All three were Yellow last night and woke up to only 1 being green.  I have been using the provided cable that came with the case.  I a 30 watt charger as well, not branded DJI but that should not matter in this scenario.  Kind of feel like I have a defective unit. I like the concept of having extra batteries available for that opportune time but not being fully charged is a shame.

I am facing a similar issue of slow charging of the batteries using the battery case. I am using a 45W fast charging plug. I have been charging for 24 hours but only 2 of the batteries are charged fully and one battery is still showing yellow. I am worried if the batteries or the case have a defect.

Similar issue. Using the included USB cable. Batteries will not charge beyond yellow in case. Last attempt, battery remains red. Having to charge through camera =( About to return this thing.