Wanted 18650 USB charger/powerbank with pass-through

Hi there.
I am very new to this battery stuff.

My requirements are listed below.
I need a small usb (not mains) powered charger that will -

1. Charge 1 or 2 18650 batteries
2. Must be pass through, so I can charge via USB from bicycle dynamo and simultaneously power a low-load GPS at the same time.
3. Must be also usable as a power-bank for charging duties at the end of the day.
4. It needs also to be 18650 because I can put this batteries in my head-lamp to supplement my dynamo light.

So: 18650/Pass-through/Powerbank/Chargeable via USB.

Is anyone doing this?

I have used one of these, and it IS pass-through, but is very temperamental.
If I rotate the battery or bump it, it stops charging a connected device.
http://www.aliexpress.com/snapshot/6393135512.html?orderId=65002314659067

I have what I THINK is a later version of this, (Enb) in 2x18650.
Its great, but is NOT pass-through. The one in this review supposedly is.
http://lygte-info.dk/review/Review USB battery box 2x18650 enb UK.html

Does anyone know where I can get something like this?

I aplogoise if this is not strictly flash-light, it is in a way, as I used your forums to help me pick the Flash-light that this device will charge!

Thanks for your time.
Cheers
Jeff

I'm not familiar with a product like this, but I haven't been looking either. I do play around with bike dynamos and battery charging, and have some professional experience with the issues of battery charging. As such, there's no reason that something couldn't be designed, but I think it does complicate the battery charging process and there's not a lot of demand for it.

For lithium-ion batteries in particular, the charging process is much more complicated than for nicads or NiMH. Getting the li-ion battery fully charged while there is a load connected to the battery and the power source is turning on and off is nearly impossible.

There are a variety of converters that will produce a 5v USB output from the dynamo, such as the Sinewave Cycles product....
http://www.sinewavecycles.com/products/sinewave-revolution
Perhaps you can plug a battery pack and the GPS into this?

Just get two of them and charge one while using the other one for powering items and when the batteries get low on one of them either swap batteries or chargers. I suppose with some doing you could even wire in a switch or two to swap which one is charging and powering things.

Steve K said:

I'm not familiar with a product like this, but I haven't been looking either. I do play around with bike dynamos and battery charging, and have some professional experience with the issues of battery charging. As such, there's no reason that something couldn't be designed, but I think it does complicate the battery charging process and there's not a lot of demand for it.

For lithium-ion batteries in particular, the charging process is much more complicated than for nicads or NiMH. Getting the li-ion battery fully charged while there is a load connected to the battery and the power source is turning on and off is nearly impossible.

There are a variety of converters that will produce a 5v USB output from the dynamo, such as the Sinewave Cycles product....
http://www.sinewavecycles.com/products/sinewave-revolution
Perhaps you can plug a battery pack and the GPS into this?

Click to expand...

Hey that is a given, I have a sinewave on order, and have even been looking at the much cheaper Biologic Reecharge USB converter. One of those two will fit between my SP dynamo hub and the battery/device I am charging.

ts commonplace today for people to use a "cache-battery" (to stop the device turning off) between the USB converter (Sinewave) and any device being used (usually a GPS). What I am after is effectively a cache battery that does double time as a powerbank.

The cache battery needs to be pass-through tho for this to work. These solutions are very popular today with long distance Bikepacking.

My difficulty is caused by me wanting to use 18650 cells I guess. There are plenty of pass-through enabled power-banks.

Thanks for your feedback.

>> Getting the li-ion battery fully charged while there is a load connected to the battery
>> and the power source is turning on and off is nearly impossible.

Lynx_Arc said:

Just get two of them and charge one while using the other one for powering items and when the batteries get low on one of them either swap batteries or chargers. I suppose with some doing you could even wire in a switch or two to swap which one is charging and powering things.

Click to expand...

Thats not a silly idea.....

The Aili 4x 18650 fits right in with your other requirements except maybe number 1 but if you considered the Enb 2x, the Aili isn't that much bigger.

what output is your dynamo?

potpot said:

The Aili 4x 18650 fits right in with your other requirements except maybe number 1 but if you considered the Enb 2x, the Aili isn't that much bigger.

Click to expand...

Yeah I have an enb x2. It doesn't do pass through.

cousinmosquito said:

Yeah I have an enb x2. It doesn't do pass through.

Click to expand...

I don't think pass through is possible using lithium ion batteries because the charger would be unable to detect when a battery is charged or not if you had a load on it interfering with it that could sag the voltage. Imagine a charger trying to get the battery to about 4.2v and your load drops that 4.2v to 4.1v and the load goes up and down it would drive the charger crazy it may even be dangerous if the charger got confused and overcharged the battery in it. I also don't think the chargers in these power banks have a 100% duty cycle on them they probably aren't meant to operate indefinitely. I think you would be better served to create a circuit that uses an AC power adapter to power things with a USB power bank to back it up.

Lynx_Arc said:

I don't think pass through is possible using lithium ion batteries because the charger would be unable to detect when a battery is charged or not if you had a load on it interfering with it that could sag the voltage. Imagine a charger trying to get the battery to about 4.2v and your load drops that 4.2v to 4.1v and the load goes up and down it would drive the charger crazy it may even be dangerous if the charger got confused and overcharged the battery in it. I also don't think the chargers in these power banks have a 100% duty cycle on them they probably aren't meant to operate indefinitely. I think you would be better served to create a circuit that uses an AC power adapter to power things with a USB power bank to back it up.

Click to expand...

Ive just done a bit more googling, thanks for the help guys. The later model of the EnB 2x does appear to do pass-through, although the guy calls it "simultaneous charging" in his review. I re-tested my earlier model last night and confirmed it didnt. I have been using these guys (link below), and they work really well, but one of them failed on a 280km ride I did in the weekend so thats no good. https://www.fasttech.com/product/1137904 .

Thanks for all your advice. I really dont know about the electronics behind (above) just wanting a solution : )
Cheers
jeff

cousinmosquito said:

Ive just done a bit more googling, thanks for the help guys. The later model of the EnB 2x does appear to do pass-through, although the guy calls it "simultaneous charging" in his review. I re-tested my earlier model last night and confirmed it didnt. I have been using these guys (link below), and they work really well, but one of them failed on a 280km ride I did in the weekend so thats no good. https://www.fasttech.com/product/1137904 .

Thanks for all your advice. I really dont know about the electronics behind (above) just wanting a solution : )
Cheers
jeff

Click to expand...

Doh. Looks like the NEW one doesnt do pass through, the old one did. I must have the new one.

cousinmosquito said:

Doh. Looks like the NEW one doesnt do pass through, the old one did. I must have the new one.

Click to expand...

I finally got a hold of the "other model" and it KIND-OF does pass through charging : ) With one 18650 cell it does, with two, it does not !!
Go figure. I was just wanting to use it as a cache battery between my dynamo and my Garmin etrex 20 so I think one cell should get me through the day in the slow stuff.