Hello everyone,

I Have this power bank Remax, Model: RP-V20 | Capacity : 20 Ah | Input : DC 5V / 2A | Output : DC 5V / 2.1 A

It had an accident someone dropped it in a water fountain, anyway I managed to pick it up and found out that the charging circuit is damaged in one component or many,

I extracted the li-ion batteries and charged them separately and they work so fine, The Output of the Batteries is 3.93 Volts

And when i connect them back to the charging circuit they give a reading in the USB output 3.66 Volts

And when I plug a a 5 Volts charger in any in any IN inputs it gives me a reading of 0.4 Volts which means its charging the batteries with this value

Assuming that the charging circuit is unfix-able,
Now the problems is two parts,

Firstly and most important the output way : I need to increase this voltage output from 3.9V to 5V to be able to charge my phone.

Secondly : I need to charge the batteries, so will it be a problem to directly connect them with the IN slot so that they be charged with a 5V, will that affect the battery life on the long term or should i charge them with exactly 3.8 V as written on the battery case ?

I thought about making a Joule Thief Circuit but I don't know how to calculate everything to make the output exactly 5 volts !

I'm counting on you to make this work please tell me every possible solution,

Thanks.

 

hi Teeky,
Welcome to AAC.
Perhaps a simple Boost converter would be OK.
E
https://www.amazon.co.uk/s/ref=nb_sb_noss?url=search-alias=aps&field-keywords=boost+conveter+modules

 

Please make sure you charge the batteries with a proper charger to suit the chemistry else you will have a fire or explosion.
Ebay has some LiPo charger/over discharge protection boards for a couple of dollars.
Also some cheap boost converters to jack the volts up to 5V.
Have you looked at them?

 

first of all thanks Eric for your concern, unfortunately I'm from Egypt it's so hard to get an electric circuit to pass from our custom system and it's expensive too to pay custom fees for it, But I'll look for it in the electronic market in my city and hopefully I'll find it or at least find a DIY tutorial online, you gave me the key word and I have to do a lot of home work

 

Please make sure you charge the batteries with a proper charger to suit the chemistry else you will have a fire or explosion.
Ebay has some LiPo charger/over discharge protection boards for a couple of dollars.
Also some cheap boost converters to jack the volts up to 5V.
Have you looked at them?

I'll make sure it's not over 3.8 volts when charging, btw how do I know it's fully charged?

 

Have you tried repairing the board?
A closer view of the board may help. That part removed next to C3, does that have a board designation? It may just be another capacitor in parallel with C3. So measure to see if C3 is shorted. And try to read anything on C3 and look to see if the damaged part could be the same.
I would not charge a LiPo cell without a charge controller.
This site may help your understanding...
http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries

 

dendad, thanks for your reply, I tried to fix it and when i went to market to look for the booster i showed the burned component to the seller he told me that he will provide it to me tomorrow,

the circuit seems promising and fixable but the problem is the place of the burned component it took the bottom soldering area of the green layer as shown in the images,the top part is clear but idk how to re-connect the bottom part to the new component when i get it tomorrow.

 

On the other hand i found a DC-DC booster with max output of 5V online here in egypt i will get it in few days, i guess that will solve the output problem, but the input (charging the batteries) i'm still looking for the best safe way i will see the link in your comment.

thanks.

 

hi Teeky,
Welcome to AAC.
Perhaps a simple Boost converter would be OK.
E
https://www.amazon.co.uk/s/ref=nb_sb_noss?url=search-alias=aps&field-keywords=boost+conveter+modules

the dc-dc step up (boost) converter which i bought gives an output of 5.1 Volts but it doesn't charge my mobile phone, I think its becuase the current ampere is very low and I don't know how to solve this problem any more :/

 

hi Teeky,
What is the specified output current of that module, it looks a very small module.
Some phones require sensing wires from the charger, is yours that type.
E

 

hi Teeky,
What is the specified output current of that module, it looks a very small module.
Some phones require sensing wires from the charger, is yours that type.
E

this is the specs of the converter
http://ram-e-shop.com/oscmax/catalog/product_info.php?cPath=261&products_id=3637

and my phone is iPhone 7 Plus,

on the other hand where can i find someone who can help me to fix the original chargeing circuit ?

 

Hi T,
I have been searching the web for your RP-V20 and I cannot find any technical information.

E

 

Hi Teeky,
Considering that your new 5.1V will not charge the iPhone battery, is it possible that the RP-V20 was damaged due to a fault in the iPhone internal charge controller.? [ or possibly the reverse, ie: RP fails and damages the iPhone controller]

While looking thru the web for the RP-V20 info, I saw links that showed failures of the iPhones internal controller and how to replace the damaged IC.?

Also some internal charge controllers expect to see voltage levels on the +/-D lines of the USB connector.
There was a Thread on AAC a few weeks ago, showing how to connect resistors to the +/-D lines in order to make the internal charger work.

E

 

Hi Teeky,
Considering that your new 5.1V will not charge the iPhone battery, is it possible that the RP-V20 was damaged due to a fault in the iPhone internal charge controller.? [ or possibly the reverse, ie: RP fails and damages the iPhone controller]

While looking thru the web for the RP-V20 info, I saw links that showed failures of the iPhones internal controller and how to replace the damaged IC.?

Also some internal charge controllers expect to see voltage levels on the +/-D lines of the USB connector.
There was a Thread on AAC a few weeks ago, showing how to connect resistors to the +/-D lines in order to make the internal charger work.

E

I should say that the 5.1 charged for like 30 seconds when connected to the lipo and then to the iPhone, i tried the step up with a Panasonic li ion batteries (4 in parallel - each one fully charged 3.7) it charged the phone from 41% at 8:18 am to 63 % at 9:30 am and stopped charging at this point though the 4 batteries still charged with 3.3 volts.

And to be more sure I'll try it on a different phones and tell you the results

I think it's an ampere thing and i really don't know how to modify the ampere output of the step up converter.

P = V.I
I understand that when boosting the voltage the current drops to keep the power constant all the times but taking In consideration the mAhr capacity of the lipo and li ion batteries,these batteries should at least charge the iPhone up to 50 percent. And that's exactly what the power bank charging circuit do. It boost the voltage with a 1 ampere out put how on earth do they do that?!

I tried a modified joule thief and it gives and output up to 30 voltage but it drops to 2.3 volts as soon as i connect any thing to it also tried putting a 5.1 zener diode and it also drops to 2.3 volts when connecting it to a led or the iPhone

I'm about to try this circuit nowadays

but i have to order this mosfet online it will take 3 days to arrive.