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1151 posts

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#195714 1-May-2016 11:18
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One simple solution which cost me zero $$ and few hours of fun: 

 

Pre-requisite - RC Li charger. I had different models already (e.g. IMAX B6), hence the solution was easy. Imax B6 operates from up to 18DC - hence you can use many sources to power it up - e.g. Car on board power or in my case - old IBM laptop PS (18V).

 

End result: 3-in-1 device: Flash Light + 2xUSB 1A Charger + Battery Power supply for my cordless drill/screwdriver.

 

Components - all recycled from the old obsolete stuff:

 

     

  1. Dolphin Flash Light without the battery. 4.8v Bulb on board. Used as a body for the project and as a Flash Light in the 3-in-1 end product;
  2. 10 x Li-Ion 18650 batteries from failed laptop packs. (note: sometimes one pair in the 2P3S pack fails but the rest 2 pairs are good in my case ~ 3.5 Ah/pair remaining capacity) (Note: I have Professional tools to test laptop packs standalone and see what the condition and the remaining capacity is and Professional Battery Capacity Testing tools, but you can use cheap IMAX or other RC chargers to load test the Li capacity with 10% accuracy); Batteries were reassembled into 5P2S configuration - that is 7.2V nominal output (8.2V Max) with 11Ah capacity if new - in my case - about 9Ah left.
  3. Switch from some toy model - to switch LM7805 off when not in use;
  4. LM7805 Voltage regulator - fixed 5v @ 1A output - to feed USB and 4.8V original bulb; Got it from some old transformer type network power supply;
  5. 2 x USB ports taken from the front of an old PC;
  6. LM35 Temperature sensor (optional and only required if batteries are charged by IMAX charger) - those were a gift from Texas Instruments;
  7. Few wires ending up with 3 small plugs (power; temp sensor, balance charging) sticking out of the flashlight body - to be able to charge batteries without dismantling the flash light, to quickly test the condition of the batteries inside using one of my portable "baterryless quick test Li probe" (you can use voltmenter instead) and to power “cordless” drill which is 7.2V rated.

 

End result:

 

 

One leftover 18650 cell went into the small brother - another flashlight made of broken LED light, another small toy switch and canister from Vitamin C tablets:

 

 

 


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23462 posts

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  #1544781 1-May-2016 11:47
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 I would get a switcher instead of a 7805. 1A will not charge most phones much and I hate to think of how toasty it is making it inside there.

 

Do you have any protection board on the cells to stop them over discharging or going out of ballance when charging it up?





Richard rich.ms



1151 posts

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  #1544789 1-May-2016 12:13
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richms:

 

 I would get a switcher instead of a 7805. 1A will not charge most phones much and I hate to think of how toasty it is making it inside there.

 

Do you have any protection board on the cells to stop them over discharging or going out of ballance when charging it up?

 

 

I have literally about 3 dozens of other types of IC based regulators used in phone charger circuits in New Zealand - they all have limitation - 0.5Amps only. Meaning that you can't charge two phones at once. With this - I can. Tested both of my HTC and HTC + Samsung and HTC + Siemens etc.

 

7805 specifically chosen to provide 1A output.

 

There is no heat as the voltage drop is only from 7.2V to 5V. There will be more heat with more voltage drop - i.e. if you were using 12V input and wanted 5V output.

 

Balancing is done by external balance charger as described.

 

Over discharging could be noticed easily by observing the bulb - which is fed from LM7805 which will stop working as 5V regulator when the 1.25v inside reference will drop. Hence I deliberately did not use extra circuits (have them) and as described I have portable pocket size tool (size of match box) to check the remaining voltage if in doubt. I use the same external battery pack for the drill for more than a year now and had no issues with over discharge...

 

 


 
 
 
 


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  #1544816 1-May-2016 12:35
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RUKI:

 

I have literally about 3 dozens of other types of IC based regulators used in phone charger circuits in New Zealand - they all have limitation - 0.5Amps only. Meaning that you can't charge two phones at once. With this - I can. Tested both of my HTC and HTC + Samsung and HTC + Siemens etc.

 

7805 specifically chosen to provide 1A output.

 

 

1A is barely enough for 1 phone to charge. The problem with 7805 is the output voltage will sag massivly as the the limit is hit (either thermal or the its all it can do limit) and the phone will still indicate it is charging, but the number is not going up at all.

 

Even my small cheap china dual sim phone needs 1.3A when the battery is near low to actually make any gains, otherwise it just hovers around 10% and will switch off after a while. Also the data pins really need one of the smart IC's if you want an iPhone to charge from it as those will only charge at a really low current on a charger with the the pins just shorted together.





Richard rich.ms



1151 posts

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  #1544885 1-May-2016 14:31
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richms

 

1A is barely enough for 1 phone to charge.

 

 

You are right in a sense that more and more power-hungry devices are introduced nowadays...

 

Majority of the car chargers found in New Zealand have 0.5A limit - as the same IC is used in them all.

 

Modification of those to make them providing higher output requires much more components. I have those more powerful ones and could've used one of those if the need be.

 

Everything is possible. This is a simple DIY with minimum components which 100% suits my needs.

 

 


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