Phone won't charge from bike

[Biplaneguy]

My Radster Trail has a USB port for charging a smartphone, but when I plug in my phone (Pixel 7) it initially connects and shows it's charging, the USB indicator on the bike display comes on, but then the phone displays a message warning that it's charging very slowly or not at all, and while the bike display still says it's connected the phone shows that it's not charging. Anybody else seen this?

 

[Gionnirocket]

New'r phones can be finicky.
Try charging another device to be sure the USB is out putting correctly.
You can also try a different cable with the phone.
You may just have a compatibility issue with a finicky phone.

 

[Jeremy McCreary]

Welcome aboard!

May well be normal behavior on your ebike. A forum search on "USB port" brought up this recent post of mine:

2025 - Our Rides in Words, Photos, Maps and Videos

Good news is that my controller display (on left in the pix) has a USB-C port which I think can be used to charge the phone if needed. I even have a cable for that, but I need to get one in black. Depends on how much current your phone needs to charge. My first ebike had 2 USB ports — a 0.5A on...

forums.electricbikereview.com

 

[Biplaneguy]

I've already verified that the cable is good, tried another good cable. The phone has no trouble charging on a variety of other chargers. Sometimes it says, "charging slowly", but it never fails to charge at all, except from the bike.

 

[Gionnirocket]

I've already verified that the cable is good, tried another good cable. The phone has no trouble charging on a variety of other chargers. Sometimes it says, "charging slowly", but it never fails to charge at all, except from the bike.

I'd say the bike is putting out a low current, probably 0.5a and that is below the phones threshold for accepting a charge. Do you have a 0.5a charger to test it with? Most are 1a at a minimum.
The newer phones are geared towards faster charging.
Again try charging something other than the phone on the bike to verify output there.

edit: If you want to know for sure what's going on... You can... get yourself something like this.

 

[Jeremy McCreary]

I've already verified that the cable is good, tried another good cable. The phone has no trouble charging on a variety of other chargers. Sometimes it says, "charging slowly", but it never fails to charge at all, except from the bike.

The thrust of the post I linked was about the current available from your display's USB port. My Note20 phone doesn't even recognize my 0.5A display port as a charging source, but the port charges my battery-powered headlight just fine. Others have had similar experiences.

You might test with a device like my headlight that requires less charging current than your phone.

 

[Biplaneguy]

Hmmm, yes... though it seems strange that they'd put a low current charging port on a new bike these days. Either way, the tester linked above looks like a useful thing to have.

 

[Gionnirocket]

Hmmm, yes... though it seems strange that they'd put a low current charging port on a new bike these days. Either way, the tester linked above looks like a useful thing to have.

I have a much older version that I've had for years. Makes troubleshooting a breeze.
If you search around there's many a version... but you really don't need anything sophisticated.

 

[Gionnirocket]

Ok for giggles I checked mine, and it did work.
Though I never used it for my Pixel 6, I do use it to charge the mp3 speaker you see on the handlebars
Bafang 860c display USB port rated at 5v/0.5a

 

[Biplaneguy]

Interesting... I tried it again just now, with the phone at about 70% charge state... it works fine, and says "charging", not even "charging slowly" as it usually does on low power chargers. Last night when I tried it it was already at around 98% charge so it would have been in "adaptive charging" mode, so perhaps the bike doesn't handle the phone's negotiating the USB charge rate well.

 

[6zfshdb]

The USB ports on all three of my bikes are rated at .5A. I get the same error message when trying to charge my iPhone 16 Pro. No issues with my old iPhone Xs or much older iPhone 5. I also have the same issues when trying to power a GPS receiver. As previously stated, it appears to be a limited current problem. It appears .5A isn't enough for newer electronics but seems to work fine for trickle charging batteries in other devices.

To solve the problem, I use two of these handlebar mounted USB ports:

Amazon.com

They output 5V at 2.1A with an input voltage of 36-100V

 

[6zfshdb]

Interesting... I tried it again just now, with the phone at about 70% charge state... it works fine, and says "charging", not even "charging slowly" as it usually does on low power chargers. Last night when I tried it it was already at around 98% charge so it would have been in "adaptive charging" mode, so perhaps the bike doesn't handle the phone's negotiating the USB charge rate well.

I've noticed on my bikes anyway, that the state of charge of the bike battery will affect the output of these USB ports. You may get better results with a fully charged bike battery.