What is the energy rating (Watt Hours capacity) of a fully charged hub? Just the station, without batteries. Thanks.

If you are asking about the DJI Portable charging station, then here you go.
Actual capacity: 4200 m Ah (built-in 5000 mAh battery), 54 Wh.

Hi, good day David 2. Thank you for reaching us your concern. For this concern, post #2 is correct that the actual capacity of the Spark Portable Charging Station is 4200mAh with built-in 5000mAh battery, 54Wh. You may try to refer to the photo below about the specification of the Portable Charging Station. Thank you for your continued support and have a safe and happy flying always!

nilanjan118 Posted at 4-15 03:43
If you are asking about the DJI Portable charging station, then here you go.
Actual capacity: 4200 m Ah (built-in 5000 mAh battery), 54 Wh.

Thanks so much. Then even with 3 charged batteries and the station fully charged the energy level is well below travel guideline limits. Hmmmmm....if I were flying with the 4 batteries and teh portable charging station I reckon it would be a good idea to have them dicharged some, anyway...? What do you think? Say 50%???

DJI Gamora Posted at 4-15 09:52
Hi, good day David 2. Thank you for reaching us your concern. For this concern, post #2 is correct that the actual capacity of the Spark Portable Charging Station is 4200mAh with built-in 5000mAh battery, 54Wh. You may try to refer to the photo below about the specification of the Portable Charging Station. Thank you for your continued support and have a safe and happy flying always!

[view_image]

SO OK, 4200mAh... But what does it mean 5000 mAH "built in"?

David 2 Posted at 4-23 14:25
Thanks so much. Then even with 3 charged batteries and the station fully charged the energy level is well below travel guideline limits. Hmmmmm....if I were flying with the 4 batteries and teh portable charging station I reckon it would be a good idea to have them dicharged some, anyway...? What do you think? Say 50%???

Well travel guidelines vary from country to country and airline to airline. I think you have to check with individual airlines to know what's the allowed limit. There are also rules pertaining to batteries which are removable and non-removable. For example: the AC battery is removable and many airlines say that you should carry them in lipo bags. On the other hand, the battery on the portable charging station is non-removable and doesn't have to be stored in a lipo bag.

David 2 Posted at 4-23 14:28
SO OK, 4200mAh... But what does it mean 5000 mAH "built in"?

4200mAH is the output energy, 5000mAH is the input energy. But there is a catch here. We all know that ampere is the unit of current, whereas watt is the unit of energy. So, mAH (milli ampere hours) is a unit of energy which is dependent on voltage. You have to multiply it with voltage to get the energy in mWH (milli watt hour) or WH, which is voltage independent. So there is always a difference in the input and output energy rating in case of mAH when the charging voltage of the charging station and the batteries it charges are different. I have to check what are the exact voltages but just for the sake of example let us assume that the charging voltage of the charging station is 4V and that of the Spark batteries is 5V. So, the energy of the charging station in mWH will be 5000x4=20000mWH. And the output energy (in mAH) you can get out of it to charge batteries at 5V is 20000/5=4000mAH.

nilanjan118 Posted at 4-23 15:46
Well travel guidelines vary from country to country and airline to airline. I think you have to check with individual airlines to know what's the allowed limit. There are also rules pertaining to batteries which are removable and non-removable. For example: the AC battery is removable and many airlines say that you should carry them in lipo bags. On the other hand, the battery on the portable charging station is non-removable and doesn't have to be stored in a lipo bag.

Thanks again. Yes, I have Lipo bags... Will check with carrier and country as I get ready to travel. cheers

nilanjan118 Posted at 4-23 16:04
4200mAH is the output energy, 5000mAH is the input energy. But there is a catch here. We all know that ampere is the unit of current, whereas watt is the unit of energy. So, mAH (milli ampere hours) is a unit of energy which is dependent on voltage. You have to multiply it with voltage to get the energy in mWH (milli watt hour) or WH, which is voltage independent. So there is always a difference in the input and output energy rating in case of mAH when the charging voltage of the charging station and the batteries it charges are different. I have to check what are the exact voltages but just for the sake of example let us assume that the charging voltage of the charging station is 4V and that of the Spark batteries is 5V. So, the energy of the charging station in mWH will be 5000x4=20000mWH. And the output energy (in mAH) you can get out of it to charge batteries at 5V is 20000/5=4000mWH.

I see....Thanks. It's been MANY years...but I did a first year electrical engineering course...so I have some better sense of what you mean. cheers

David 2 Posted at 4-23 20:19
I see....Thanks. It's been MANY years...but I did a first year electrical engineering course...so I have some better sense of what you mean. cheers

You are welcome mate. Glad I could clear your confusion. It is similar to how internet service providers share their bandwidth or speed details. They would always specify in terms of Mbps (mega bits per sec) whereas we are more familiar with MB/s (mega byte per second) because that's the unit which is displayed in our download managers. So if any service provider says they are giving you a 16mbps connection, it actually means the max. speed you will get is 16/8 = 2 MB/s.