Custom DIY 18650 Power Bank for Light and Phone with Recharge Circuit (variable current)

Andrew's picture

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Custom DIY 18650 Power Bank for Light and Phone with Recharge Circuit (variable current)
November 16, 2020 - 2:28am

I recently found and purchased an antique Ray-O-Vac lantern.  For a fun and useful project, I'd like to convert it to a rechargable lantern that doubles as a phone charger. There are a zillion DIY boards available for my type of project.  But since it has been more than 45 years since I have read more than a basic ciruit diagram or done much of anything with electronics, I need some help determining what to get.  I hope I can find some help here.  So, thank you in advance.

Here are some details about the project and the questions I have.

  • The lantern case will easily hold 22 of the 18650 batteries, but I anticipate using less than half that number.
  • I would like to be able to recharge the batteries from different sources (solar, generator, USB charger).
    • So, obviously I will need a charge circuit that is flexible and have over-charge protection.
  • I would like the light to be as bright as reasonbly achievable and be either stepped or dimmable.
    • I do not have any depth of knowledge regarding the modern LED (Cree?) bulbs, so I will certainly need some help with this matter.
    • Are they dimmable?  If not, for stepped illumination, can it be achieved with one bulb or does one use add additional bulbs for additional brightness?
    • In short, I'll need help determinging how best to get optimal brightness that can be varied from low intensity to high.
  • In addition to powering the light(s), I would like to be able to use the battery pack as a USB (phone) charger.
    • Since I have a Samsung Galaxy, a 'smart' charger would be great.
  • Obviously, for the light and charger functions, I'll need circuit(s) that have over-discharge protection (or a separate discharge protection circuit).
  • I would like to have pass-through (?) charging.
    • For example, have a solar panel sending current to the unit while it is simultaneously charging my phone.
  • How do I best accomplish balanced charging?
  • Is it best to have batteries with charge/discharge protection built-in or is it fine just to have it in the boards?

So, that is the project.  I will appreciate all the direction you can provide.  I do not mind doing my own homework, but with all the different options avaiable I really do not know where to start.

Thanks,
Andrew

Sourav Gupta's picture

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Joined: Feb 12, 2018

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You came up with a lot of requirements. Before going directly into the circuitry operations, it is essential to know the load. So, basically what is your load is the LED or the bulb that is the load. Does the load circuit uses any driver or it is directly connected with the battery? If you are not sure could you check it?

Following informations are required -

1. The battery voltage that is being used in the lantern.

2. The load current

3. The load voltage

Using the above spec, we can decide the battery voltage but not the capacity. For the capacity we first require the battery voltage spec that is requires. Without battery spec the charger can not be built. For solar and other things everything can be done afterwards deciding the battery.

Andrew's picture

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Thank you Sourav.  I believe the light bulb(s) chosen may dictate the load.  But this is another area where I am ignorant.  I have a couple of different solid state flashlights.  I know one uses Cree bulbs.  They are all powered by 18650 batteries.  I don't know if a driver is used or not.  With all three I am amazed at the brightness and life of the battery and I'd like to do the same on this project.

Do you know where I can find the information on which bulb or bulbs to select?  (Meanwhile, I'll keep searching.)  As I mentioned, I would like to have adjustable brightness - either dimmable or stepped.

Thanks againm,
Andrew

Andrew's picture

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Update:  I have made a post at candlepowerforums to ask specifically about bulbs.  However, any responses may be slow in coming since I am new there and my post will need to have moderator approval.

Sourav Gupta's picture

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Well those are all white leds. White leds are selected as per the lumen and wattage. For example 5730 White LEDs with 0.5Watt rating will provide 8 Lumen of light. Thus, you need to findout the space whare you want to light the area. You could use a flux meter or lumen meter to get the information how much lumen of light is required for your application. Then find out how many LEDs will require to produce the light depending on the different white leds that you choose. After selecting the LEDs then go to the circuitry. First find out the LEDs. You could use 5730 White leds of 0.5Watt.

Andrew's picture

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Thanks Sourav.  I just wanted to drop a note to let you know that I haven't abandoned the project.  I am learning about the emitters, drivers, and associated equipment.  Once that is determined, we will know the power requirements.  But I'm also going to be otherwise occupied for the next few days.  It may be well into next week before I can pursue the power aspect of this project.

Andrew