Charging Nikon Z9 with power bank - compatibility

I'd like to charge my Z9 using a power bank but I'm not clear about which ones are compatible in terms of brand or output. I have a BatPower 210Wh | 56000mAh Power Bank. Any idea if I could use this to charge the Z9?

I guess the Z9 has a USB-C charging socket?

 

and your PB has a USB-C output?

 

If it's anything like my Z6ii, the camera limits the charging current to avoid any camera heating, so it's probably OK for a slow top-up or to actually power the camera, but don't expect any speedy charging.

The Z 9 does have a USB charging port so its battery can be charged without removing it from the Z9. I just got my Z9 and am charging the battery with the battery charger for the first time.

 

Read the Z9 Reference Guide for more info especially page 76 as it specifies that a special USB cable will be needed if you do not use the supplied EH-7P charger. The special cables are listed on page 843 of the Reference Guide. However it was not clear to me what power source is needed so I would be extremely cautious in doing something not specifically described in Nikon Z9 manuals.

 

I hope others with more knowledge can help you out.

In-body charging my Z6ii from a USB-C PB is limited to 460mA by the camera.

 

So, that's nominally USB @ 5v internally boosted to ~8.4v to charge the 2280mA capacity 7.2v EnEl15c. So, 5hrs to fully charge in body.

 

The EnEl15's battery charger, the MH-25a output is 8.4v at 1200mA, so less than 2hrs from flat to full.

 

I'm sure someone must have a Z9 and a USB power meter to see what the Z9 can suck up during in-body charging.

Most powerbanks have a standard USB A type socket as power output - so no compatibility issue - you just use the lead supplied with the camera. And since the voltage on a USB line is limited to a nominal 5 volts there's no electrical incompatibilty issue either.

 

Basically any powerbank with a USB socket will be useable, with the only difference being the amount of charge available. This should be at least 1.5 times* the camera battery capacity (in mAH) to be able to fully charge the camera battery from flat.

 

*The LIon cells used in powerbanks are only about 50% efficient, and some makers 'cheat' on the stated capacity. I.e. they quote the energy input required to fully charge the Powerbank, rather than the amount of energy available at the output. Minus, of course, the overall efficiency quotient of the device.

 

Anyway, a Powerbank rated at 5600mAH ought to be able to fully charge a battery rated at 2280mAH, even allowing for some exaggeration and inefficiency.

I am kind of curious. The EN-EL 18D battery pack for the Z9 is rated at 10.8V so internal to the camera there is boost converter to boost the voltage from 5V to at least 10.8 for charging?

there is boost converter to boost the voltage from 5V to at least 10.8 for charging?

Yup, just like the Z6ii, except higher voltage.

 

I'd guess USB 5v >12v to charge a 10.8v cell.

so internal to the camera there is boost converter to boost the voltage from 5V to at least 10.8 for charging?

Yep. There's also a boost converter in cheap Powerbanks as well. Some use 2x 3.7 v cells in series, and so the 5v USB input needs to be boosted to 7.4 volts, and then regulated back down to 5v for the USB output socket.

 

In the case of single Li-ion cell devices, the reverse is the case, with the 5v charging voltage being dropped to 3.7v, and the output voltage being boosted back up to 5v.

 

It's no big deal. A single chip can provide the chopper oscillator and driver devices for a small auto-transformer and associated rectifier. Using a high chopper frequency for maximum efficiency.

It's risky to use any USB-C power bank unless you know for sure that it is regulated to 7.2 vdc or less. You can use a 5 vdc power bank, but it will only supply about 80% of the power needed by the camera, there rest by the camera battery.

 

The best use of an USB power supply is to extend the shooting time for a fixed setup, such as event portraits, or video. If you want to charge on the go, consider using the AC charger with a convertor for the car, one with pure sine wave output. Switching converters play havoc with universal chargers and computers. There are also portable power banks with pure AC outputs

It's risky to use any USB-C power bank unless you know for sure that it is regulated to 7.2 vdc or less.

Unless they are different where you are, all USB-C power banks are limited to USB Voltage of 5 to 5.5v MAX.

 

The camera limits the ampage. If you look at any of the labels on the bottom of MILCs/DSLRs it seems the system can 'accept' about 12v 2.5A aka about 30W.

 

After a bit of net searching, the current limit for internal battery charging for the Z9 seems to be 1500mA.