USB fast-charger powered by e-bike battery

[mrbill]

Hi Folks:

Does anyone know of a USB charger that will push at least 1 Amp when its input is hooked to a typical e-bike battery, say 20-100 VDC (or if that's asking too much, then 44-60 VDC)?

For the last few years I've been using some cheap 120/240 VAC USB chargers that function as a charger with as low as 44Vdc input. One of them will even "fast-charge" (~700 mA), but the others only slow-charge (200-500mA).

Finding one of these that is sufficiently out of spec to fast-charge with a lower DC input voltage vs. the intended 120/240 VAC is a crap-shoot of buying a bunch of different units on ebay/Amazon and testing to see what works. Yes, they're cheap, but I'm interested in saving some time and hassle.

So, I thought I'd ask if anyone had gone through this and discovered one that does the job.

Btw, Grin's USB DC-DC chargers are not in stock, and I'd prefer to find something compact that works in one package rather than to construct a two-step system: <e-bike battery voltage> ==> 12VDC ==> 5VDC USB, with the attendant complexity and inefficiency.

Thanks.

 

[E-HP]

These will get you to 12V, so any 12V USB charger can work off of it. They have ones with USB ports, but using one of these and a 12V aux power outlet makes it more versatile.

 

[amberwolf]

Does anyone know of a USB charger that will push at least 1 Amp when its input is hooked to a typical e-bike battery, say 20-100 VDC (or if that's asking too much, then 44-60 VDC)?

AFAICR, my old 2A Samsung unit will do this, as well as an ASUS, on my 14s 52v battery on the trike, which is in your latter range. But I haven't actually measured the current, just found that recharging a tablet or phone / etc on it is as quick on that as when its' plugged into the wall.

In a couple of months I should have a USB wattmeter (slowboat shipping) and can verify actual charging current. I'd have to go out to the trike to find out the exact models on those USB wallwarts.


Other than that, I'm sure I've seen small DC-DCs that will do over 1A at 5Vdc output regardless of input voltage. I can look those up for you; you'd have to build them into something and add your own output USB socket (off an old cable, computer motherboard, computer case, etc) and input connector from your battery, as they just come as unenclosed electronics with no wires attached.


There are a number of devices like this
https://www.aliexpress.com/item/4001031081283.html
that can probably do what you want...if they are based on the LT8631 (and it's not a counterfeit!) then it can do up to 100v input and still do 1a at 5v output (but I don't know what that specific one is based on; was just the first hit in a search).

 

[mrbill]

Hi Amberwolf:

Thanks for your reply.

I've built a USB charger using an old USB socket and a QST 3A DC converter of the type sold by EM3EV and others a few years back, but that only produced at most about 300 mA, and that was after following the instructions to short the data wires or whatever I needed to do to tell my phone at the time that it was on a fast charger, and then the problem is that the next generation of devices will require a complicated voltage divider set to a specific ratio or some other obscure logic.

I'm currently using these:

https://www.ebay.com/itm/Wall-Charger-2-Port-Wall-Charger-USB-Plug-Charger-Wall-Plug-2-1-Amp-Red/174369890339?hash=item2899416023:g:B-oAAOSw2kZfIfAY

They work as well as I described in my opening message, and they are unlikely to get fried if I ever increase my system voltage even momentarily (as during a robust regeneration session), a problem with the QST converter that had a hard upper limit of 60 VDC.

I'm looking for something similar in a compact format that doesn't require assembling other than attaching an appropriate connector to the AC input so that I can hook it to my system power. I'm really hoping I can find one of these that operates down to about 40 Vdc input, even though most are rated only down to 90 or 100 VAC.

 

[markz]

I've seen people on youtube disassemble those usb chargers to find out how sketchy in design and safety they can be.

I've had good luck with original, authentic cell phone chargers from the thrift store when I needed to charge up a cell or two.

This wasnt the one I originally saw, but this link was the first video in the yt search.
https://www.youtube.com/watch?v=ehYYoU13i-I

The original video I saw was a small "charger" hooked up to the usb with ONLY one resistor.
This is that video - https://www.youtube.com/watch?v=ejU_97skXCg

Here is a good youtube, crazy australian EEVBLog
https://www.youtube.com/watch?v=wi-b9k-0KfE

I'm currently using these:

https://www.ebay.com/itm/Wall-Charger-2-Port-Wall-Charger-USB-Plug-Charger-Wall-Plug-2-1-Amp-Red/174369890339?hash=item2899416023:g:B-oAAOSw2kZfIfAY

They work as well as I described in my opening message, and they are unlikely to get fried if I ever increase my system voltage even momentarily (as during a robust regeneration session), a problem with the QST converter that had a hard upper limit of 60 VDC.

I'm looking for something similar in a compact format that doesn't require assembling other than attaching an appropriate connector to the AC input so that I can hook it to my system power. I'm really hoping I can find one of these that operates down to about 40 Vdc input, even though most are rated only down to 90 or 100 VAC.

 

[mrbill]

I've had good luck with original, authentic cell phone chargers from the thrift store when I needed to charge up a cell or two.

I know that most cheap USB chargers are of marginal quality. But, since I'm only working with a system voltage of around 50Vdc I figure a failure of the sort anticipated by the makers of those videos is unlikely.

I tried using the "Turbo" charger that came with my phone. Plugged into the wall it charges as 2-3 Amps, but at 50Vdc on the e-bike it doesn't even turn on.

 

[Chalo]

I use one of these to power a chip-on-board LED that I use as a headlight:

https://www.ebay.com/itm/124480545093


There's a trim pot that can be dialed to regulate output voltage from 4.5V to 30V. If all you want is 1 amp at 5 volts, and you don't need a hardware handshake, this thing should do the job. It's supposed to be good for up to 3A.

P.S. - Hi, Bill! It's been a while since I came by your place with Pardo.

 

[mrbill]

I use one of these to power a chip-on-board LED that I use as a headlight:

https://www.ebay.com/itm/124480545093


There's a trim pot that can be dialed to regulate output voltage from 4.5V to 30V. If all you want is 1 amp at 5 volts, and you don't need a hardware handshake, this thing should do the job. It's supposed to be good for up to 3A.

P.S. - Hi, Bill! It's been a while since I came by your place with Pardo.

Hi Chalo, good to hear from (and see) you. That visit was almost six years ago! Time flies.

I haven't been posting much lately to E-S as I've been very happy with my current e-bike systems--current issue excepted--and have been mostly out there enjoying the riding, doing routine maintenance, and not so much building and experimenting.

This looks like the potted innards of the QST (or was it QSK?) regulator of which I still have a few in my cabinet, and a couple of which I accidentally burned out after a creating a brief regeneration voltage peak as might occur when demanding sudden motor braking at high speed on a steep downgrade. The adjustability was nice, but I could never get the phone to recognize it as a "fast" charger. After much online research (shorting the data lines, holding the data lines at fixed voltages, or whatever "magical" state they needed to be held for my then-current phone) I could never get it to fast-charge. Never more than 300mA drawn, and usually only 150-200 mA. That wasn't enough to keep a phone from losing charge on a long ride while (for example) using a GPS tracking app.