my phone has a 3300 mAh battery init and i need a powerbank that will deliver at least a full charge. i have 18650’s lying around so i’m wondering if there is one with a charge indicator so i know if the battery is running low? i can carry an extra battery but i’d like to know when it’s running low so it can be changed. anyone know of anything?
You will need a 1S4P 4x power bank, the singles and double 18650’s do well…but just don’t have enough mAh, with the conversion inefficencies and all
to charge 3300mAh, you will need 4000+
HKJ did several great reviews on 4x18650 power banks
This guy showed a pretty good power bank…not the cheapest but has a really cool display
http://www.amazon.com/Smart-External-Battery-Charger-Display/dp/B00IM3NZ86
The link does not say whether it does. Just because it has a 2A USB port does not nessesarily mean that it will. It needs an Apple compatible 2A port.
This looks really good otherwise.
Good rule of thumb, per HKJ, is about a 65% total efficiency rate in charging (with a decent battery bank). So about 65% of the mah from your 18650’s will wind up in your phone battery.
So look at HKJ’s reviews, pick one he recommends. A 2x18650 bank with reasonably high capacity 18650’s should be enough to give your phone a full charge. A larger bank would of course be able to do more - a 4x18650 should be able to charge your phone twice.
All the reviews I’ve seen, battery banks seem to give (at best) only a very general indication of how charged the batteries inside are. I think your best bet is to use your voltmeter and test the 18650’s to be sure they’re fully charged before you load them into the bank.
Keep in mind that the phone is also draining battery whilst you are charging.
If you want to get it to 100% you need the (100% capacity + drain while charging) / efficiency
Depending on how you use your phone whilst charging (3G/4G, wifi, hotspot, etc), you can easily deplete a 2x18650 NCR18650B bank in one charge.
Not quite sure which bank you are getting that from.
The ruinovos that HKJ test (and personally my favourite) seem to have an efficiency that averages around 85% under heavy USB charging load (2.5ohm or 2.0A)
Don’t forget the charging circuitry inside the phone.
I got a pair of these from fasttech when my wife and I got new iphone 5C’s not sure the mAh capacity of their batteries but off two panna NCR18650B’s we get about a charge and a half, or about 4 days of topping off the battery. Has a built in battery level indicator that works with one or two cells.
I was pretty impressed the other day when I had unknowingly inserted one of the cells backwards and the charger had no issues, kept right on chargin till I caught it with zero damage/issues.
how about QIDIAN
This TOMO charger is also on Fasttech. https://www.fasttech.com/products/1424/10007187/1592501 It looks good, I think price is reasonable if there is really 2A micro USB INPUT/OUTPUT.
Being a flashlight forum, my favorite solution is this:
http://www.kaidomain.com/product/details.S022116
Its 40 bucks and carries 3 18650 batteries in parallel. It has a battery life indicator with 5 LEDs, and a built in charger via micro USB. The flashlight is around 1000 raw lumens, with pretty decent throw due to smooth reflector size.
You can push a button and turn it into Charger Mode and it has 2 USB ports for this, an apple one, and regular. The flashlight head comes off too in case you just want the charger aspect.