Mobile internet, DVD, TV, SatNav, UHF/VHF etc
 #82479  by Mark
 Sat Oct 25, 2014 2:56 pm
I see your point: what's that? 90 hours to recharge the battery pack :o
Maybe at $12-$13 I should just buy one, see how many charges I get and buy a second if needed. Seems that they weigh about 300g each.
I can always get Kathy to carry the second ;) . (Mine will get lighter first if I empty it first :-T )
 #83513  by Neddy
 Sat Nov 15, 2014 6:36 pm
I have run yet another capacity check on the "30,000 mAh" Portable Charger I bought as mentioned on page 3 of this thread. This test was at 5 volts/1 Amp - I figured this to be a fairly common requirement for the "USB" charging of cellphones etc.

The devices 5 volt USB socket was used to power a 5 Ohm resistor giving a load of exactly 1 Amp. The fully charged battery started at 12 volts and the load was automatically disconnected when the battery voltage had fallen to 9.5 volts. It took 3 hours and 12 minutes.
This equates to a capacity of 3,200 mAh - roughly one tenth of the claimed capacity.

There are other easier ways by which users can estimate the capacity of similar devices.
Charge time. The 1 amp charger supplied with the unit takes about 3.5 hours to charge the flattened battery, so 3500mAh have gone in - and you can't take out more than you have put in.
Assuming an efficiency of 90%, that's.... about 3200 mAh!
Torch Run Time. Most of these units incorporate an LED light, typically drawing around 220mA. Time how long the light runs on a fully charged battery (It will switch itself off when the "Low battery" cut-off point is reached). Mine ran for 14 hours. 220mA x 14hours = 3100mAh.

Mark, knowing the true capacity of a portable charger should enable you to calculate the number of cellphone recharges it is able to provide.

 #83539  by Mark
 Sun Nov 16, 2014 4:02 pm
Thanks, Neville. I have ordered, a torch, a 18650 battery (can't remember the "capacity" claimed, and a charger. I'll do the tests.
Then, maybe I'll order a portable charger for my phone once I understand a bit more about all this. Don't think we have any overnight trips planned this summer, so no known urgency for this at this stage.
 #84402  by Neddy
 Sat Dec 06, 2014 9:08 am
I posted the following feedback on the aforementioned "30,000mAh" portable charger that I bought :-
(Two stars) "Very disappointing. This is a well made, well designed unit, spoiled by an inadequate, poor quality battery. I measured the battery capacity and found it to be just 3200mAh - about one tenth of the claimed capacity!"

Since then, I have received several emails from the vendor querying my figures. I have replied to these with supporting data. The latest move from the vendor is to offer me money to change my negative feedback!

hello friend,did you try to use it to charge the phone and check how many time it can work?? i would like to refund you 10$ and please help us change the feedback,is it ok?you know the feedback is very important to our store,if you have paypal,please tell me your paypal,i will refund to your paypal,thank you very much for your understanding.
best regards. happy weekend!

My reply :-
Liang Zhiwen, The unit was able to fully charge my Samsung Galaxie S3 just once, with a little power to spare.
Since the cellphone battery is 2100mAh and the Jump Starter has a capacity of around 3200mAh, that is exactly what you would expect.
I will amend my feedback to include this comment.
 #100552  by Mark
 Wed Sep 30, 2015 6:50 pm
Have just received a Pineng 999 20,000mAH powerbank, purchased through AliExpress.

It is weighty at 451g (a good start) and came fully charged.

It also has an LCD display showing % charge.

I have just charged my Xperia Z1 which has a 3000mAH battery. It was reading 55% charged. The Pineng 100%
2 hours and 20 mins later the Xperia was 100% and the Pineng read 90%.

That means that 45% of 3000mAH used up 10% of the Pineng capacity giving the Pineng a 5V capacity of 13500mAH.

I'm very happy with that (IF both the phone and the Pineng % readings are reasonably accurate) since the 20,000 capacity is quoted at 3.7V.
 #100600  by petercw
 Thu Oct 01, 2015 11:43 am
O Neville, that's just priceless.. Just loved it... :lol: :lol:
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